Linux v2.6.13

[linux-2.6/next.git] / drivers / ide / ide-tape.c

/*
 * linux/drivers/ide/ide-tape.c         Version 1.19    Nov, 2003
 *
 * Copyright (C) 1995 - 1999 Gadi Oxman <gadio@netvision.net.il>
 *
 * $Header$
 *
 * This driver was constructed as a student project in the software laboratory
 * of the faculty of electrical engineering in the Technion - Israel's
 * Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David.
 *
 * It is hereby placed under the terms of the GNU general public license.
 * (See linux/COPYING).
 */
 
/*
 * IDE ATAPI streaming tape driver.
 *
 * This driver is a part of the Linux ide driver and works in co-operation
 * with linux/drivers/block/ide.c.
 *
 * The driver, in co-operation with ide.c, basically traverses the 
 * request-list for the block device interface. The character device
 * interface, on the other hand, creates new requests, adds them
 * to the request-list of the block device, and waits for their completion.
 *
 * Pipelined operation mode is now supported on both reads and writes.
 *
 * The block device major and minor numbers are determined from the
 * tape's relative position in the ide interfaces, as explained in ide.c.
 *
 * The character device interface consists of the following devices:
 *
 * ht0          major 37, minor 0       first  IDE tape, rewind on close.
 * ht1          major 37, minor 1       second IDE tape, rewind on close.
 * ...
 * nht0         major 37, minor 128     first  IDE tape, no rewind on close.
 * nht1         major 37, minor 129     second IDE tape, no rewind on close.
 * ...
 *
 * Run linux/scripts/MAKEDEV.ide to create the above entries.
 *
 * The general magnetic tape commands compatible interface, as defined by
 * include/linux/mtio.h, is accessible through the character device.
 *
 * General ide driver configuration options, such as the interrupt-unmask
 * flag, can be configured by issuing an ioctl to the block device interface,
 * as any other ide device.
 *
 * Our own ide-tape ioctl's can be issued to either the block device or
 * the character device interface.
 *
 * Maximal throughput with minimal bus load will usually be achieved in the
 * following scenario:
 *
 *      1.      ide-tape is operating in the pipelined operation mode.
 *      2.      No buffering is performed by the user backup program.
 *
 * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
 * 
 * Ver 0.1   Nov  1 95   Pre-working code :-)
 * Ver 0.2   Nov 23 95   A short backup (few megabytes) and restore procedure
 *                        was successful ! (Using tar cvf ... on the block
 *                        device interface).
 *                       A longer backup resulted in major swapping, bad
 *                        overall Linux performance and eventually failed as
 *                        we received non serial read-ahead requests from the
 *                        buffer cache.
 * Ver 0.3   Nov 28 95   Long backups are now possible, thanks to the
 *                        character device interface. Linux's responsiveness
 *                        and performance doesn't seem to be much affected
 *                        from the background backup procedure.
 *                       Some general mtio.h magnetic tape operations are
 *                        now supported by our character device. As a result,
 *                        popular tape utilities are starting to work with
 *                        ide tapes :-)
 *                       The following configurations were tested:
 *                              1. An IDE ATAPI TAPE shares the same interface
 *                                 and irq with an IDE ATAPI CDROM.
 *                              2. An IDE ATAPI TAPE shares the same interface
 *                                 and irq with a normal IDE disk.
 *                        Both configurations seemed to work just fine !
 *                        However, to be on the safe side, it is meanwhile
 *                        recommended to give the IDE TAPE its own interface
 *                        and irq.
 *                       The one thing which needs to be done here is to
 *                        add a "request postpone" feature to ide.c,
 *                        so that we won't have to wait for the tape to finish
 *                        performing a long media access (DSC) request (such
 *                        as a rewind) before we can access the other device
 *                        on the same interface. This effect doesn't disturb
 *                        normal operation most of the time because read/write
 *                        requests are relatively fast, and once we are
 *                        performing one tape r/w request, a lot of requests
 *                        from the other device can be queued and ide.c will
 *                        service all of them after this single tape request.
 * Ver 1.0   Dec 11 95   Integrated into Linux 1.3.46 development tree.
 *                       On each read / write request, we now ask the drive
 *                        if we can transfer a constant number of bytes
 *                        (a parameter of the drive) only to its buffers,
 *                        without causing actual media access. If we can't,
 *                        we just wait until we can by polling the DSC bit.
 *                        This ensures that while we are not transferring
 *                        more bytes than the constant referred to above, the
 *                        interrupt latency will not become too high and
 *                        we won't cause an interrupt timeout, as happened
 *                        occasionally in the previous version.
 *                       While polling for DSC, the current request is
 *                        postponed and ide.c is free to handle requests from
 *                        the other device. This is handled transparently to
 *                        ide.c. The hwgroup locking method which was used
 *                        in the previous version was removed.
 *                       Use of new general features which are provided by
 *                        ide.c for use with atapi devices.
 *                        (Programming done by Mark Lord)
 *                       Few potential bug fixes (Again, suggested by Mark)
 *                       Single character device data transfers are now
 *                        not limited in size, as they were before.
 *                       We are asking the tape about its recommended
 *                        transfer unit and send a larger data transfer
 *                        as several transfers of the above size.
 *                        For best results, use an integral number of this
 *                        basic unit (which is shown during driver
 *                        initialization). I will soon add an ioctl to get
 *                        this important parameter.
 *                       Our data transfer buffer is allocated on startup,
 *                        rather than before each data transfer. This should
 *                        ensure that we will indeed have a data buffer.
 * Ver 1.1   Dec 14 95   Fixed random problems which occurred when the tape
 *                        shared an interface with another device.
 *                        (poll_for_dsc was a complete mess).
 *                       Removed some old (non-active) code which had
 *                        to do with supporting buffer cache originated
 *                        requests.
 *                       The block device interface can now be opened, so
 *                        that general ide driver features like the unmask
 *                        interrupts flag can be selected with an ioctl.
 *                        This is the only use of the block device interface.
 *                       New fast pipelined operation mode (currently only on
 *                        writes). When using the pipelined mode, the
 *                        throughput can potentially reach the maximum
 *                        tape supported throughput, regardless of the
 *                        user backup program. On my tape drive, it sometimes
 *                        boosted performance by a factor of 2. Pipelined
 *                        mode is enabled by default, but since it has a few
 *                        downfalls as well, you may want to disable it.
 *                        A short explanation of the pipelined operation mode
 *                        is available below.
 * Ver 1.2   Jan  1 96   Eliminated pipelined mode race condition.
 *                       Added pipeline read mode. As a result, restores
 *                        are now as fast as backups.
 *                       Optimized shared interface behavior. The new behavior
 *                        typically results in better IDE bus efficiency and
 *                        higher tape throughput.
 *                       Pre-calculation of the expected read/write request
 *                        service time, based on the tape's parameters. In
 *                        the pipelined operation mode, this allows us to
 *                        adjust our polling frequency to a much lower value,
 *                        and thus to dramatically reduce our load on Linux,
 *                        without any decrease in performance.
 *                       Implemented additional mtio.h operations.
 *                       The recommended user block size is returned by
 *                        the MTIOCGET ioctl.
 *                       Additional minor changes.
 * Ver 1.3   Feb  9 96   Fixed pipelined read mode bug which prevented the
 *                        use of some block sizes during a restore procedure.
 *                       The character device interface will now present a
 *                        continuous view of the media - any mix of block sizes
 *                        during a backup/restore procedure is supported. The
 *                        driver will buffer the requests internally and
 *                        convert them to the tape's recommended transfer
 *                        unit, making performance almost independent of the
 *                        chosen user block size.
 *                       Some improvements in error recovery.
 *                       By cooperating with ide-dma.c, bus mastering DMA can
 *                        now sometimes be used with IDE tape drives as well.
 *                        Bus mastering DMA has the potential to dramatically
 *                        reduce the CPU's overhead when accessing the device,
 *                        and can be enabled by using hdparm -d1 on the tape's
 *                        block device interface. For more info, read the
 *                        comments in ide-dma.c.
 * Ver 1.4   Mar 13 96   Fixed serialize support.
 * Ver 1.5   Apr 12 96   Fixed shared interface operation, broken in 1.3.85.
 *                       Fixed pipelined read mode inefficiency.
 *                       Fixed nasty null dereferencing bug.
 * Ver 1.6   Aug 16 96   Fixed FPU usage in the driver.
 *                       Fixed end of media bug.
 * Ver 1.7   Sep 10 96   Minor changes for the CONNER CTT8000-A model.
 * Ver 1.8   Sep 26 96   Attempt to find a better balance between good
 *                        interactive response and high system throughput.
 * Ver 1.9   Nov  5 96   Automatically cross encountered filemarks rather
 *                        than requiring an explicit FSF command.
 *                       Abort pending requests at end of media.
 *                       MTTELL was sometimes returning incorrect results.
 *                       Return the real block size in the MTIOCGET ioctl.
 *                       Some error recovery bug fixes.
 * Ver 1.10  Nov  5 96   Major reorganization.
 *                       Reduced CPU overhead a bit by eliminating internal
 *                        bounce buffers.
 *                       Added module support.
 *                       Added multiple tape drives support.
 *                       Added partition support.
 *                       Rewrote DSC handling.
 *                       Some portability fixes.
 *                       Removed ide-tape.h.
 *                       Additional minor changes.
 * Ver 1.11  Dec  2 96   Bug fix in previous DSC timeout handling.
 *                       Use ide_stall_queue() for DSC overlap.
 *                       Use the maximum speed rather than the current speed
 *                        to compute the request service time.
 * Ver 1.12  Dec  7 97   Fix random memory overwriting and/or last block data
 *                        corruption, which could occur if the total number
 *                        of bytes written to the tape was not an integral
 *                        number of tape blocks.
 *                       Add support for INTERRUPT DRQ devices.
 * Ver 1.13  Jan  2 98   Add "speed == 0" work-around for HP COLORADO 5GB
 * Ver 1.14  Dec 30 98   Partial fixes for the Sony/AIWA tape drives.
 *                       Replace cli()/sti() with hwgroup spinlocks.
 * Ver 1.15  Mar 25 99   Fix SMP race condition by replacing hwgroup
 *                        spinlock with private per-tape spinlock.
 * Ver 1.16  Sep  1 99   Add OnStream tape support.
 *                       Abort read pipeline on EOD.
 *                       Wait for the tape to become ready in case it returns
 *                        "in the process of becoming ready" on open().
 *                       Fix zero padding of the last written block in
 *                        case the tape block size is larger than PAGE_SIZE.
 *                       Decrease the default disconnection time to tn.
 * Ver 1.16e Oct  3 99   Minor fixes.
 * Ver 1.16e1 Oct 13 99  Patches by Arnold Niessen,
 *                          niessen@iae.nl / arnold.niessen@philips.com
 *                   GO-1)  Undefined code in idetape_read_position
 *                              according to Gadi's email
 *                   AJN-1) Minor fix asc == 11 should be asc == 0x11
 *                               in idetape_issue_packet_command (did effect
 *                               debugging output only)
 *                   AJN-2) Added more debugging output, and
 *                              added ide-tape: where missing. I would also
 *                              like to add tape->name where possible
 *                   AJN-3) Added different debug_level's 
 *                              via /proc/ide/hdc/settings
 *                              "debug_level" determines amount of debugging output;
 *                              can be changed using /proc/ide/hdx/settings
 *                              0 : almost no debugging output
 *                              1 : 0+output errors only
 *                              2 : 1+output all sensekey/asc
 *                              3 : 2+follow all chrdev related procedures
 *                              4 : 3+follow all procedures
 *                              5 : 4+include pc_stack rq_stack info
 *                              6 : 5+USE_COUNT updates
 *                   AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
 *                              from 5 to 10 minutes
 *                   AJN-5) Changed maximum number of blocks to skip when
 *                              reading tapes with multiple consecutive write
 *                              errors from 100 to 1000 in idetape_get_logical_blk
 *                   Proposed changes to code:
 *                   1) output "logical_blk_num" via /proc
 *                   2) output "current_operation" via /proc
 *                   3) Either solve or document the fact that `mt rewind' is
 *                      required after reading from /dev/nhtx to be
 *                      able to rmmod the idetape module;
 *                      Also, sometimes an application finishes but the
 *                      device remains `busy' for some time. Same cause ?
 *                   Proposed changes to release-notes:
 *                   4) write a simple `quickstart' section in the
 *                      release notes; I volunteer if you don't want to
 *                   5) include a pointer to video4linux in the doc
 *                      to stimulate video applications
 *                   6) release notes lines 331 and 362: explain what happens
 *                      if the application data rate is higher than 1100 KB/s; 
 *                      similar approach to lower-than-500 kB/s ?
 *                   7) 6.6 Comparison; wouldn't it be better to allow different 
 *                      strategies for read and write ?
 *                      Wouldn't it be better to control the tape buffer
 *                      contents instead of the bandwidth ?
 *                   8) line 536: replace will by would (if I understand
 *                      this section correctly, a hypothetical and unwanted situation
 *                       is being described)
 * Ver 1.16f Dec 15 99   Change place of the secondary OnStream header frames.
 * Ver 1.17  Nov 2000 / Jan 2001  Marcel Mol, marcel@mesa.nl
 *                      - Add idetape_onstream_mode_sense_tape_parameter_page
 *                        function to get tape capacity in frames: tape->capacity.
 *                      - Add support for DI-50 drives( or any DI- drive).
 *                      - 'workaround' for read error/blank block around block 3000.
 *                      - Implement Early warning for end of media for Onstream.
 *                      - Cosmetic code changes for readability.
 *                      - Idetape_position_tape should not use SKIP bit during
 *                        Onstream read recovery.
 *                      - Add capacity, logical_blk_num and first/last_frame_position
 *                        to /proc/ide/hd?/settings.
 *                      - Module use count was gone in the Linux 2.4 driver.
 * Ver 1.17a Apr 2001 Willem Riede osst@riede.org
 *                      - Get drive's actual block size from mode sense block descriptor
 *                      - Limit size of pipeline
 * Ver 1.17b Oct 2002   Alan Stern <stern@rowland.harvard.edu>
 *                      Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
 *                       it in the code!
 *                      Actually removed aborted stages in idetape_abort_pipeline
 *                       instead of just changing the command code.
 *                      Made the transfer byte count for Request Sense equal to the
 *                       actual length of the data transfer.
 *                      Changed handling of partial data transfers: they do not
 *                       cause DMA errors.
 *                      Moved initiation of DMA transfers to the correct place.
 *                      Removed reference to unallocated memory.
 *                      Made __idetape_discard_read_pipeline return the number of
 *                       sectors skipped, not the number of stages.
 *                      Replaced errant kfree() calls with __idetape_kfree_stage().
 *                      Fixed off-by-one error in testing the pipeline length.
 *                      Fixed handling of filemarks in the read pipeline.
 *                      Small code optimization for MTBSF and MTBSFM ioctls.
 *                      Don't try to unlock the door during device close if is
 *                       already unlocked!
 *                      Cosmetic fixes to miscellaneous debugging output messages.
 *                      Set the minimum /proc/ide/hd?/settings values for "pipeline",
 *                       "pipeline_min", and "pipeline_max" to 1.
 *
 * Here are some words from the first releases of hd.c, which are quoted
 * in ide.c and apply here as well:
 *
 * | Special care is recommended.  Have Fun!
 *
 */

/*
 * An overview of the pipelined operation mode.
 *
 * In the pipelined write mode, we will usually just add requests to our
 * pipeline and return immediately, before we even start to service them. The
 * user program will then have enough time to prepare the next request while
 * we are still busy servicing previous requests. In the pipelined read mode,
 * the situation is similar - we add read-ahead requests into the pipeline,
 * before the user even requested them.
 *
 * The pipeline can be viewed as a "safety net" which will be activated when
 * the system load is high and prevents the user backup program from keeping up
 * with the current tape speed. At this point, the pipeline will get
 * shorter and shorter but the tape will still be streaming at the same speed.
 * Assuming we have enough pipeline stages, the system load will hopefully
 * decrease before the pipeline is completely empty, and the backup program
 * will be able to "catch up" and refill the pipeline again.
 * 
 * When using the pipelined mode, it would be best to disable any type of
 * buffering done by the user program, as ide-tape already provides all the
 * benefits in the kernel, where it can be done in a more efficient way.
 * As we will usually not block the user program on a request, the most
 * efficient user code will then be a simple read-write-read-... cycle.
 * Any additional logic will usually just slow down the backup process.
 *
 * Using the pipelined mode, I get a constant over 400 KBps throughput,
 * which seems to be the maximum throughput supported by my tape.
 *
 * However, there are some downfalls:
 *
 *      1.      We use memory (for data buffers) in proportional to the number
 *              of pipeline stages (each stage is about 26 KB with my tape).
 *      2.      In the pipelined write mode, we cheat and postpone error codes
 *              to the user task. In read mode, the actual tape position
 *              will be a bit further than the last requested block.
 *
 * Concerning (1):
 *
 *      1.      We allocate stages dynamically only when we need them. When
 *              we don't need them, we don't consume additional memory. In
 *              case we can't allocate stages, we just manage without them
 *              (at the expense of decreased throughput) so when Linux is
 *              tight in memory, we will not pose additional difficulties.
 *
 *      2.      The maximum number of stages (which is, in fact, the maximum
 *              amount of memory) which we allocate is limited by the compile
 *              time parameter IDETAPE_MAX_PIPELINE_STAGES.
 *
 *      3.      The maximum number of stages is a controlled parameter - We
 *              don't start from the user defined maximum number of stages
 *              but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
 *              will not even allocate this amount of stages if the user
 *              program can't handle the speed). We then implement a feedback
 *              loop which checks if the pipeline is empty, and if it is, we
 *              increase the maximum number of stages as necessary until we
 *              reach the optimum value which just manages to keep the tape
 *              busy with minimum allocated memory or until we reach
 *              IDETAPE_MAX_PIPELINE_STAGES.
 *
 * Concerning (2):
 *
 *      In pipelined write mode, ide-tape can not return accurate error codes
 *      to the user program since we usually just add the request to the
 *      pipeline without waiting for it to be serviced. In case an error
 *      occurs, I will report it on the next user request.
 *
 *      In the pipelined read mode, subsequent read requests or forward
 *      filemark spacing will perform correctly, as we preserve all blocks
 *      and filemarks which we encountered during our excess read-ahead.
 * 
 *      For accurate tape positioning and error reporting, disabling
 *      pipelined mode might be the best option.
 *
 * You can enable/disable/tune the pipelined operation mode by adjusting
 * the compile time parameters below.
 */

/*
 *      Possible improvements.
 *
 *      1.      Support for the ATAPI overlap protocol.
 *
 *              In order to maximize bus throughput, we currently use the DSC
 *              overlap method which enables ide.c to service requests from the
 *              other device while the tape is busy executing a command. The
 *              DSC overlap method involves polling the tape's status register
 *              for the DSC bit, and servicing the other device while the tape
 *              isn't ready.
 *
 *              In the current QIC development standard (December 1995),
 *              it is recommended that new tape drives will *in addition* 
 *              implement the ATAPI overlap protocol, which is used for the
 *              same purpose - efficient use of the IDE bus, but is interrupt
 *              driven and thus has much less CPU overhead.
 *
 *              ATAPI overlap is likely to be supported in most new ATAPI
 *              devices, including new ATAPI cdroms, and thus provides us
 *              a method by which we can achieve higher throughput when
 *              sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
 */

#define IDETAPE_VERSION "1.19"

#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/major.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/ide.h>
#include <linux/smp_lock.h>
#include <linux/completion.h>
#include <linux/bitops.h>

#include <asm/byteorder.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/unaligned.h>

/*
 * partition
 */
typedef struct os_partition_s {
        __u8    partition_num;
        __u8    par_desc_ver;
        __u16   wrt_pass_cntr;
        __u32   first_frame_addr;
        __u32   last_frame_addr;
        __u32   eod_frame_addr;
} os_partition_t;

/*
 * DAT entry
 */
typedef struct os_dat_entry_s {
        __u32   blk_sz;
        __u16   blk_cnt;
        __u8    flags;
        __u8    reserved;
} os_dat_entry_t;

/*
 * DAT
 */
#define OS_DAT_FLAGS_DATA       (0xc)
#define OS_DAT_FLAGS_MARK       (0x1)

typedef struct os_dat_s {
        __u8            dat_sz;
        __u8            reserved1;
        __u8            entry_cnt;
        __u8            reserved3;
        os_dat_entry_t  dat_list[16];
} os_dat_t;

#include <linux/mtio.h>

/**************************** Tunable parameters *****************************/


/*
 *      Pipelined mode parameters.
 *
 *      We try to use the minimum number of stages which is enough to
 *      keep the tape constantly streaming. To accomplish that, we implement
 *      a feedback loop around the maximum number of stages:
 *
 *      We start from MIN maximum stages (we will not even use MIN stages
 *      if we don't need them), increment it by RATE*(MAX-MIN)
 *      whenever we sense that the pipeline is empty, until we reach
 *      the optimum value or until we reach MAX.
 *
 *      Setting the following parameter to 0 is illegal: the pipelined mode
 *      cannot be disabled (calculate_speeds() divides by tape->max_stages.)
 */
#define IDETAPE_MIN_PIPELINE_STAGES       1
#define IDETAPE_MAX_PIPELINE_STAGES     400
#define IDETAPE_INCREASE_STAGES_RATE     20

/*
 *      The following are used to debug the driver:
 *
 *      Setting IDETAPE_DEBUG_INFO to 1 will report device capabilities.
 *      Setting IDETAPE_DEBUG_LOG to 1 will log driver flow control.
 *      Setting IDETAPE_DEBUG_BUGS to 1 will enable self-sanity checks in
 *      some places.
 *
 *      Setting them to 0 will restore normal operation mode:
 *
 *              1.      Disable logging normal successful operations.
 *              2.      Disable self-sanity checks.
 *              3.      Errors will still be logged, of course.
 *
 *      All the #if DEBUG code will be removed some day, when the driver
 *      is verified to be stable enough. This will make it much more
 *      esthetic.
 */
#define IDETAPE_DEBUG_INFO              0
#define IDETAPE_DEBUG_LOG               0
#define IDETAPE_DEBUG_BUGS              1

/*
 *      After each failed packet command we issue a request sense command
 *      and retry the packet command IDETAPE_MAX_PC_RETRIES times.
 *
 *      Setting IDETAPE_MAX_PC_RETRIES to 0 will disable retries.
 */
#define IDETAPE_MAX_PC_RETRIES          3

/*
 *      With each packet command, we allocate a buffer of
 *      IDETAPE_PC_BUFFER_SIZE bytes. This is used for several packet
 *      commands (Not for READ/WRITE commands).
 */
#define IDETAPE_PC_BUFFER_SIZE          256

/*
 *      In various places in the driver, we need to allocate storage
 *      for packet commands and requests, which will remain valid while
 *      we leave the driver to wait for an interrupt or a timeout event.
 */
#define IDETAPE_PC_STACK                (10 + IDETAPE_MAX_PC_RETRIES)

/*
 * Some drives (for example, Seagate STT3401A Travan) require a very long
 * timeout, because they don't return an interrupt or clear their busy bit
 * until after the command completes (even retension commands).
 */
#define IDETAPE_WAIT_CMD                (900*HZ)

/*
 *      The following parameter is used to select the point in the internal
 *      tape fifo in which we will start to refill the buffer. Decreasing
 *      the following parameter will improve the system's latency and
 *      interactive response, while using a high value might improve sytem
 *      throughput.
 */
#define IDETAPE_FIFO_THRESHOLD          2

/*
 *      DSC polling parameters.
 *
 *      Polling for DSC (a single bit in the status register) is a very
 *      important function in ide-tape. There are two cases in which we
 *      poll for DSC:
 *
 *      1.      Before a read/write packet command, to ensure that we
 *              can transfer data from/to the tape's data buffers, without
 *              causing an actual media access. In case the tape is not
 *              ready yet, we take out our request from the device
 *              request queue, so that ide.c will service requests from
 *              the other device on the same interface meanwhile.
 *
 *      2.      After the successful initialization of a "media access
 *              packet command", which is a command which can take a long
 *              time to complete (it can be several seconds or even an hour).
 *
 *              Again, we postpone our request in the middle to free the bus
 *              for the other device. The polling frequency here should be
 *              lower than the read/write frequency since those media access
 *              commands are slow. We start from a "fast" frequency -
 *              IDETAPE_DSC_MA_FAST (one second), and if we don't receive DSC
 *              after IDETAPE_DSC_MA_THRESHOLD (5 minutes), we switch it to a
 *              lower frequency - IDETAPE_DSC_MA_SLOW (1 minute).
 *
 *      We also set a timeout for the timer, in case something goes wrong.
 *      The timeout should be longer then the maximum execution time of a
 *      tape operation.
 */
 
/*
 *      DSC timings.
 */
#define IDETAPE_DSC_RW_MIN              5*HZ/100        /* 50 msec */
#define IDETAPE_DSC_RW_MAX              40*HZ/100       /* 400 msec */
#define IDETAPE_DSC_RW_TIMEOUT          2*60*HZ         /* 2 minutes */
#define IDETAPE_DSC_MA_FAST             2*HZ            /* 2 seconds */
#define IDETAPE_DSC_MA_THRESHOLD        5*60*HZ         /* 5 minutes */
#define IDETAPE_DSC_MA_SLOW             30*HZ           /* 30 seconds */
#define IDETAPE_DSC_MA_TIMEOUT          2*60*60*HZ      /* 2 hours */

/*************************** End of tunable parameters ***********************/

/*
 *      Debugging/Performance analysis
 *
 *      I/O trace support
 */
#define USE_IOTRACE     0
#if USE_IOTRACE
#include <linux/io_trace.h>
#define IO_IDETAPE_FIFO 500
#endif

/*
 *      Read/Write error simulation
 */
#define SIMULATE_ERRORS                 0

/*
 *      For general magnetic tape device compatibility.
 */
typedef enum {
        idetape_direction_none,
        idetape_direction_read,
        idetape_direction_write
} idetape_chrdev_direction_t;

struct idetape_bh {
        unsigned short b_size;
        atomic_t b_count;
        struct idetape_bh *b_reqnext;
        char *b_data;
};

/*
 *      Our view of a packet command.
 */
typedef struct idetape_packet_command_s {
        u8 c[12];                               /* Actual packet bytes */
        int retries;                            /* On each retry, we increment retries */
        int error;                              /* Error code */
        int request_transfer;                   /* Bytes to transfer */
        int actually_transferred;               /* Bytes actually transferred */
        int buffer_size;                        /* Size of our data buffer */
        struct idetape_bh *bh;
        char *b_data;
        int b_count;
        u8 *buffer;                             /* Data buffer */
        u8 *current_position;                   /* Pointer into the above buffer */
        ide_startstop_t (*callback) (ide_drive_t *);    /* Called when this packet command is completed */
        u8 pc_buffer[IDETAPE_PC_BUFFER_SIZE];   /* Temporary buffer */
        unsigned long flags;                    /* Status/Action bit flags: long for set_bit */
} idetape_pc_t;

/*
 *      Packet command flag bits.
 */
/* Set when an error is considered normal - We won't retry */
#define PC_ABORT                        0
/* 1 When polling for DSC on a media access command */
#define PC_WAIT_FOR_DSC                 1
/* 1 when we prefer to use DMA if possible */
#define PC_DMA_RECOMMENDED              2
/* 1 while DMA in progress */
#define PC_DMA_IN_PROGRESS              3
/* 1 when encountered problem during DMA */
#define PC_DMA_ERROR                    4
/* Data direction */
#define PC_WRITING                      5

/*
 *      Capabilities and Mechanical Status Page
 */
typedef struct {
        unsigned        page_code       :6;     /* Page code - Should be 0x2a */
        __u8            reserved0_6     :1;
        __u8            ps              :1;     /* parameters saveable */
        __u8            page_length;            /* Page Length - Should be 0x12 */
        __u8            reserved2, reserved3;
        unsigned        ro              :1;     /* Read Only Mode */
        unsigned        reserved4_1234  :4;
        unsigned        sprev           :1;     /* Supports SPACE in the reverse direction */
        unsigned        reserved4_67    :2;
        unsigned        reserved5_012   :3;
        unsigned        efmt            :1;     /* Supports ERASE command initiated formatting */
        unsigned        reserved5_4     :1;
        unsigned        qfa             :1;     /* Supports the QFA two partition formats */
        unsigned        reserved5_67    :2;
        unsigned        lock            :1;     /* Supports locking the volume */
        unsigned        locked          :1;     /* The volume is locked */
        unsigned        prevent         :1;     /* The device defaults in the prevent state after power up */   
        unsigned        eject           :1;     /* The device can eject the volume */
        __u8            disconnect      :1;     /* The device can break request > ctl */        
        __u8            reserved6_5     :1;
        unsigned        ecc             :1;     /* Supports error correction */
        unsigned        cmprs           :1;     /* Supports data compression */
        unsigned        reserved7_0     :1;
        unsigned        blk512          :1;     /* Supports 512 bytes block size */
        unsigned        blk1024         :1;     /* Supports 1024 bytes block size */
        unsigned        reserved7_3_6   :4;
        unsigned        blk32768        :1;     /* slowb - the device restricts the byte count for PIO */
                                                /* transfers for slow buffer memory ??? */
                                                /* Also 32768 block size in some cases */
        __u16           max_speed;              /* Maximum speed supported in KBps */
        __u8            reserved10, reserved11;
        __u16           ctl;                    /* Continuous Transfer Limit in blocks */
        __u16           speed;                  /* Current Speed, in KBps */
        __u16           buffer_size;            /* Buffer Size, in 512 bytes */
        __u8            reserved18, reserved19;
} idetape_capabilities_page_t;

/*
 *      Block Size Page
 */
typedef struct {
        unsigned        page_code       :6;     /* Page code - Should be 0x30 */
        unsigned        reserved1_6     :1;
        unsigned        ps              :1;
        __u8            page_length;            /* Page Length - Should be 2 */
        __u8            reserved2;
        unsigned        play32          :1;
        unsigned        play32_5        :1;
        unsigned        reserved2_23    :2;
        unsigned        record32        :1;
        unsigned        record32_5      :1;
        unsigned        reserved2_6     :1;
        unsigned        one             :1;
} idetape_block_size_page_t;

/*
 *      A pipeline stage.
 */
typedef struct idetape_stage_s {
        struct request rq;                      /* The corresponding request */
        struct idetape_bh *bh;                  /* The data buffers */
        struct idetape_stage_s *next;           /* Pointer to the next stage */
} idetape_stage_t;

/*
 *      REQUEST SENSE packet command result - Data Format.
 */
typedef struct {
        unsigned        error_code      :7;     /* Current of deferred errors */
        unsigned        valid           :1;     /* The information field conforms to QIC-157C */
        __u8            reserved1       :8;     /* Segment Number - Reserved */
        unsigned        sense_key       :4;     /* Sense Key */
        unsigned        reserved2_4     :1;     /* Reserved */
        unsigned        ili             :1;     /* Incorrect Length Indicator */
        unsigned        eom             :1;     /* End Of Medium */
        unsigned        filemark        :1;     /* Filemark */
        __u32           information __attribute__ ((packed));
        __u8            asl;                    /* Additional sense length (n-7) */
        __u32           command_specific;       /* Additional command specific information */
        __u8            asc;                    /* Additional Sense Code */
        __u8            ascq;                   /* Additional Sense Code Qualifier */
        __u8            replaceable_unit_code;  /* Field Replaceable Unit Code */
        unsigned        sk_specific1    :7;     /* Sense Key Specific */
        unsigned        sksv            :1;     /* Sense Key Specific information is valid */
        __u8            sk_specific2;           /* Sense Key Specific */
        __u8            sk_specific3;           /* Sense Key Specific */
        __u8            pad[2];                 /* Padding to 20 bytes */
} idetape_request_sense_result_t;


/*
 *      Most of our global data which we need to save even as we leave the
 *      driver due to an interrupt or a timer event is stored in a variable
 *      of type idetape_tape_t, defined below.
 */
typedef struct ide_tape_obj {
        ide_drive_t     *drive;
        ide_driver_t    *driver;
        struct gendisk  *disk;
        struct kref     kref;

        /*
         *      Since a typical character device operation requires more
         *      than one packet command, we provide here enough memory
         *      for the maximum of interconnected packet commands.
         *      The packet commands are stored in the circular array pc_stack.
         *      pc_stack_index points to the last used entry, and warps around
         *      to the start when we get to the last array entry.
         *
         *      pc points to the current processed packet command.
         *
         *      failed_pc points to the last failed packet command, or contains
         *      NULL if we do not need to retry any packet command. This is
         *      required since an additional packet command is needed before the
         *      retry, to get detailed information on what went wrong.
         */
        /* Current packet command */
        idetape_pc_t *pc;
        /* Last failed packet command */
        idetape_pc_t *failed_pc;
        /* Packet command stack */
        idetape_pc_t pc_stack[IDETAPE_PC_STACK];
        /* Next free packet command storage space */
        int pc_stack_index;
        struct request rq_stack[IDETAPE_PC_STACK];
        /* We implement a circular array */
        int rq_stack_index;

        /*
         *      DSC polling variables.
         *
         *      While polling for DSC we use postponed_rq to postpone the
         *      current request so that ide.c will be able to service
         *      pending requests on the other device. Note that at most
         *      we will have only one DSC (usually data transfer) request
         *      in the device request queue. Additional requests can be
         *      queued in our internal pipeline, but they will be visible
         *      to ide.c only one at a time.
         */
        struct request *postponed_rq;
        /* The time in which we started polling for DSC */
        unsigned long dsc_polling_start;
        /* Timer used to poll for dsc */
        struct timer_list dsc_timer;
        /* Read/Write dsc polling frequency */
        unsigned long best_dsc_rw_frequency;
        /* The current polling frequency */
        unsigned long dsc_polling_frequency;
        /* Maximum waiting time */
        unsigned long dsc_timeout;

        /*
         *      Read position information
         */
        u8 partition;
        /* Current block */
        unsigned int first_frame_position;
        unsigned int last_frame_position;
        unsigned int blocks_in_buffer;

        /*
         *      Last error information
         */
        u8 sense_key, asc, ascq;

        /*
         *      Character device operation
         */
        unsigned int minor;
        /* device name */
        char name[4];
        /* Current character device data transfer direction */
        idetape_chrdev_direction_t chrdev_direction;

        /*
         *      Device information
         */
        /* Usually 512 or 1024 bytes */
        unsigned short tape_block_size;
        int user_bs_factor;
        /* Copy of the tape's Capabilities and Mechanical Page */
        idetape_capabilities_page_t capabilities;

        /*
         *      Active data transfer request parameters.
         *
         *      At most, there is only one ide-tape originated data transfer
         *      request in the device request queue. This allows ide.c to
         *      easily service requests from the other device when we
         *      postpone our active request. In the pipelined operation
         *      mode, we use our internal pipeline structure to hold
         *      more data requests.
         *
         *      The data buffer size is chosen based on the tape's
         *      recommendation.
         */
        /* Pointer to the request which is waiting in the device request queue */
        struct request *active_data_request;
        /* Data buffer size (chosen based on the tape's recommendation */
        int stage_size;
        idetape_stage_t *merge_stage;
        int merge_stage_size;
        struct idetape_bh *bh;
        char *b_data;
        int b_count;
        
        /*
         *      Pipeline parameters.
         *
         *      To accomplish non-pipelined mode, we simply set the following
         *      variables to zero (or NULL, where appropriate).
         */
        /* Number of currently used stages */
        int nr_stages;
        /* Number of pending stages */
        int nr_pending_stages;
        /* We will not allocate more than this number of stages */
        int max_stages, min_pipeline, max_pipeline;
        /* The first stage which will be removed from the pipeline */
        idetape_stage_t *first_stage;
        /* The currently active stage */
        idetape_stage_t *active_stage;
        /* Will be serviced after the currently active request */
        idetape_stage_t *next_stage;
        /* New requests will be added to the pipeline here */
        idetape_stage_t *last_stage;
        /* Optional free stage which we can use */
        idetape_stage_t *cache_stage;
        int pages_per_stage;
        /* Wasted space in each stage */
        int excess_bh_size;

        /* Status/Action flags: long for set_bit */
        unsigned long flags;
        /* protects the ide-tape queue */
        spinlock_t spinlock;

        /*
         * Measures average tape speed
         */
        unsigned long avg_time;
        int avg_size;
        int avg_speed;

        /* last sense information */
        idetape_request_sense_result_t sense;

        char vendor_id[10];
        char product_id[18];
        char firmware_revision[6];
        int firmware_revision_num;

        /* the door is currently locked */
        int door_locked;
        /* the tape hardware is write protected */
        char drv_write_prot;
        /* the tape is write protected (hardware or opened as read-only) */
        char write_prot;

        /*
         * Limit the number of times a request can
         * be postponed, to avoid an infinite postpone
         * deadlock.
         */
        /* request postpone count limit */
        int postpone_cnt;

        /*
         * Measures number of frames:
         *
         * 1. written/read to/from the driver pipeline (pipeline_head).
         * 2. written/read to/from the tape buffers (idetape_bh).
         * 3. written/read by the tape to/from the media (tape_head).
         */
        int pipeline_head;
        int buffer_head;
        int tape_head;
        int last_tape_head;

        /*
         * Speed control at the tape buffers input/output
         */
        unsigned long insert_time;
        int insert_size;
        int insert_speed;
        int max_insert_speed;
        int measure_insert_time;

        /*
         * Measure tape still time, in milliseconds
         */
        unsigned long tape_still_time_begin;
        int tape_still_time;

        /*
         * Speed regulation negative feedback loop
         */
        int speed_control;
        int pipeline_head_speed;
        int controlled_pipeline_head_speed;
        int uncontrolled_pipeline_head_speed;
        int controlled_last_pipeline_head;
        int uncontrolled_last_pipeline_head;
        unsigned long uncontrolled_pipeline_head_time;
        unsigned long controlled_pipeline_head_time;
        int controlled_previous_pipeline_head;
        int uncontrolled_previous_pipeline_head;
        unsigned long controlled_previous_head_time;
        unsigned long uncontrolled_previous_head_time;
        int restart_speed_control_req;

        /*
         * Debug_level determines amount of debugging output;
         * can be changed using /proc/ide/hdx/settings
         * 0 : almost no debugging output
         * 1 : 0+output errors only
         * 2 : 1+output all sensekey/asc
         * 3 : 2+follow all chrdev related procedures
         * 4 : 3+follow all procedures
         * 5 : 4+include pc_stack rq_stack info
         * 6 : 5+USE_COUNT updates
         */
         int debug_level; 
} idetape_tape_t;

static DECLARE_MUTEX(idetape_ref_sem);

#define to_ide_tape(obj) container_of(obj, struct ide_tape_obj, kref)

#define ide_tape_g(disk) \
        container_of((disk)->private_data, struct ide_tape_obj, driver)

static struct ide_tape_obj *ide_tape_get(struct gendisk *disk)
{
        struct ide_tape_obj *tape = NULL;

        down(&idetape_ref_sem);
        tape = ide_tape_g(disk);
        if (tape)
                kref_get(&tape->kref);
        up(&idetape_ref_sem);
        return tape;
}

static void ide_tape_release(struct kref *);

static void ide_tape_put(struct ide_tape_obj *tape)
{
        down(&idetape_ref_sem);
        kref_put(&tape->kref, ide_tape_release);
        up(&idetape_ref_sem);
}

/*
 *      Tape door status
 */
#define DOOR_UNLOCKED                   0
#define DOOR_LOCKED                     1
#define DOOR_EXPLICITLY_LOCKED          2

/*
 *      Tape flag bits values.
 */
#define IDETAPE_IGNORE_DSC              0
#define IDETAPE_ADDRESS_VALID           1       /* 0 When the tape position is unknown */
#define IDETAPE_BUSY                    2       /* Device already opened */
#define IDETAPE_PIPELINE_ERROR          3       /* Error detected in a pipeline stage */
#define IDETAPE_DETECT_BS               4       /* Attempt to auto-detect the current user block size */
#define IDETAPE_FILEMARK                5       /* Currently on a filemark */
#define IDETAPE_DRQ_INTERRUPT           6       /* DRQ interrupt device */
#define IDETAPE_READ_ERROR              7
#define IDETAPE_PIPELINE_ACTIVE         8       /* pipeline active */
/* 0 = no tape is loaded, so we don't rewind after ejecting */
#define IDETAPE_MEDIUM_PRESENT          9

/*
 *      Supported ATAPI tape drives packet commands
 */
#define IDETAPE_TEST_UNIT_READY_CMD     0x00
#define IDETAPE_REWIND_CMD              0x01
#define IDETAPE_REQUEST_SENSE_CMD       0x03
#define IDETAPE_READ_CMD                0x08
#define IDETAPE_WRITE_CMD               0x0a
#define IDETAPE_WRITE_FILEMARK_CMD      0x10
#define IDETAPE_SPACE_CMD               0x11
#define IDETAPE_INQUIRY_CMD             0x12
#define IDETAPE_ERASE_CMD               0x19
#define IDETAPE_MODE_SENSE_CMD          0x1a
#define IDETAPE_MODE_SELECT_CMD         0x15
#define IDETAPE_LOAD_UNLOAD_CMD         0x1b
#define IDETAPE_PREVENT_CMD             0x1e
#define IDETAPE_LOCATE_CMD              0x2b
#define IDETAPE_READ_POSITION_CMD       0x34
#define IDETAPE_READ_BUFFER_CMD         0x3c
#define IDETAPE_SET_SPEED_CMD           0xbb

/*
 *      Some defines for the READ BUFFER command
 */
#define IDETAPE_RETRIEVE_FAULTY_BLOCK   6

/*
 *      Some defines for the SPACE command
 */
#define IDETAPE_SPACE_OVER_FILEMARK     1
#define IDETAPE_SPACE_TO_EOD            3

/*
 *      Some defines for the LOAD UNLOAD command
 */
#define IDETAPE_LU_LOAD_MASK            1
#define IDETAPE_LU_RETENSION_MASK       2
#define IDETAPE_LU_EOT_MASK             4

/*
 *      Special requests for our block device strategy routine.
 *
 *      In order to service a character device command, we add special
 *      requests to the tail of our block device request queue and wait
 *      for their completion.
 */

enum {
        REQ_IDETAPE_PC1         = (1 << 0), /* packet command (first stage) */
        REQ_IDETAPE_PC2         = (1 << 1), /* packet command (second stage) */
        REQ_IDETAPE_READ        = (1 << 2),
        REQ_IDETAPE_WRITE       = (1 << 3),
        REQ_IDETAPE_READ_BUFFER = (1 << 4),
};

/*
 *      Error codes which are returned in rq->errors to the higher part
 *      of the driver.
 */
#define IDETAPE_ERROR_GENERAL           101
#define IDETAPE_ERROR_FILEMARK          102
#define IDETAPE_ERROR_EOD               103

/*
 *      The following is used to format the general configuration word of
 *      the ATAPI IDENTIFY DEVICE command.
 */
struct idetape_id_gcw { 
        unsigned packet_size            :2;     /* Packet Size */
        unsigned reserved234            :3;     /* Reserved */
        unsigned drq_type               :2;     /* Command packet DRQ type */
        unsigned removable              :1;     /* Removable media */
        unsigned device_type            :5;     /* Device type */
        unsigned reserved13             :1;     /* Reserved */
        unsigned protocol               :2;     /* Protocol type */
};

/*
 *      INQUIRY packet command - Data Format (From Table 6-8 of QIC-157C)
 */
typedef struct {
        unsigned        device_type     :5;     /* Peripheral Device Type */
        unsigned        reserved0_765   :3;     /* Peripheral Qualifier - Reserved */
        unsigned        reserved1_6t0   :7;     /* Reserved */
        unsigned        rmb             :1;     /* Removable Medium Bit */
        unsigned        ansi_version    :3;     /* ANSI Version */
        unsigned        ecma_version    :3;     /* ECMA Version */
        unsigned        iso_version     :2;     /* ISO Version */
        unsigned        response_format :4;     /* Response Data Format */
        unsigned        reserved3_45    :2;     /* Reserved */
        unsigned        reserved3_6     :1;     /* TrmIOP - Reserved */
        unsigned        reserved3_7     :1;     /* AENC - Reserved */
        __u8            additional_length;      /* Additional Length (total_length-4) */
        __u8            rsv5, rsv6, rsv7;       /* Reserved */
        __u8            vendor_id[8];           /* Vendor Identification */
        __u8            product_id[16];         /* Product Identification */
        __u8            revision_level[4];      /* Revision Level */
        __u8            vendor_specific[20];    /* Vendor Specific - Optional */
        __u8            reserved56t95[40];      /* Reserved - Optional */
                                                /* Additional information may be returned */
} idetape_inquiry_result_t;

/*
 *      READ POSITION packet command - Data Format (From Table 6-57)
 */
typedef struct {
        unsigned        reserved0_10    :2;     /* Reserved */
        unsigned        bpu             :1;     /* Block Position Unknown */    
        unsigned        reserved0_543   :3;     /* Reserved */
        unsigned        eop             :1;     /* End Of Partition */
        unsigned        bop             :1;     /* Beginning Of Partition */
        u8              partition;              /* Partition Number */
        u8              reserved2, reserved3;   /* Reserved */
        u32             first_block;            /* First Block Location */
        u32             last_block;             /* Last Block Location (Optional) */
        u8              reserved12;             /* Reserved */
        u8              blocks_in_buffer[3];    /* Blocks In Buffer - (Optional) */
        u32             bytes_in_buffer;        /* Bytes In Buffer (Optional) */
} idetape_read_position_result_t;

/*
 *      Follows structures which are related to the SELECT SENSE / MODE SENSE
 *      packet commands. Those packet commands are still not supported
 *      by ide-tape.
 */
#define IDETAPE_BLOCK_DESCRIPTOR        0
#define IDETAPE_CAPABILITIES_PAGE       0x2a
#define IDETAPE_PARAMTR_PAGE            0x2b   /* Onstream DI-x0 only */
#define IDETAPE_BLOCK_SIZE_PAGE         0x30
#define IDETAPE_BUFFER_FILLING_PAGE     0x33

/*
 *      Mode Parameter Header for the MODE SENSE packet command
 */
typedef struct {
        __u8    mode_data_length;       /* Length of the following data transfer */
        __u8    medium_type;            /* Medium Type */
        __u8    dsp;                    /* Device Specific Parameter */
        __u8    bdl;                    /* Block Descriptor Length */
#if 0
        /* data transfer page */
        __u8    page_code       :6;
        __u8    reserved0_6     :1;
        __u8    ps              :1;     /* parameters saveable */
        __u8    page_length;            /* page Length == 0x02 */
        __u8    reserved2;
        __u8    read32k         :1;     /* 32k blk size (data only) */
        __u8    read32k5        :1;     /* 32.5k blk size (data&AUX) */
        __u8    reserved3_23    :2;
        __u8    write32k        :1;     /* 32k blk size (data only) */
        __u8    write32k5       :1;     /* 32.5k blk size (data&AUX) */
        __u8    reserved3_6     :1;
        __u8    streaming       :1;     /* streaming mode enable */
#endif
} idetape_mode_parameter_header_t;

/*
 *      Mode Parameter Block Descriptor the MODE SENSE packet command
 *
 *      Support for block descriptors is optional.
 */
typedef struct {
        __u8            density_code;           /* Medium density code */
        __u8            blocks[3];              /* Number of blocks */
        __u8            reserved4;              /* Reserved */
        __u8            length[3];              /* Block Length */
} idetape_parameter_block_descriptor_t;

/*
 *      The Data Compression Page, as returned by the MODE SENSE packet command.
 */
typedef struct {
        unsigned        page_code       :6;     /* Page Code - Should be 0xf */
        unsigned        reserved0       :1;     /* Reserved */
        unsigned        ps              :1;
        __u8            page_length;            /* Page Length - Should be 14 */
        unsigned        reserved2       :6;     /* Reserved */
        unsigned        dcc             :1;     /* Data Compression Capable */
        unsigned        dce             :1;     /* Data Compression Enable */
        unsigned        reserved3       :5;     /* Reserved */
        unsigned        red             :2;     /* Report Exception on Decompression */
        unsigned        dde             :1;     /* Data Decompression Enable */
        __u32           ca;                     /* Compression Algorithm */
        __u32           da;                     /* Decompression Algorithm */
        __u8            reserved[4];            /* Reserved */
} idetape_data_compression_page_t;

/*
 *      The Medium Partition Page, as returned by the MODE SENSE packet command.
 */
typedef struct {
        unsigned        page_code       :6;     /* Page Code - Should be 0x11 */
        unsigned        reserved1_6     :1;     /* Reserved */
        unsigned        ps              :1;
        __u8            page_length;            /* Page Length - Should be 6 */
        __u8            map;                    /* Maximum Additional Partitions - Should be 0 */
        __u8            apd;                    /* Additional Partitions Defined - Should be 0 */
        unsigned        reserved4_012   :3;     /* Reserved */
        unsigned        psum            :2;     /* Should be 0 */
        unsigned        idp             :1;     /* Should be 0 */
        unsigned        sdp             :1;     /* Should be 0 */
        unsigned        fdp             :1;     /* Fixed Data Partitions */
        __u8            mfr;                    /* Medium Format Recognition */
        __u8            reserved[2];            /* Reserved */
} idetape_medium_partition_page_t;

/*
 *      Run time configurable parameters.
 */
typedef struct {
        int     dsc_rw_frequency;
        int     dsc_media_access_frequency;
        int     nr_stages;
} idetape_config_t;

/*
 *      The variables below are used for the character device interface.
 *      Additional state variables are defined in our ide_drive_t structure.
 */
static struct ide_tape_obj * idetape_devs[MAX_HWIFS * MAX_DRIVES];

#define ide_tape_f(file) ((file)->private_data)

static struct ide_tape_obj *ide_tape_chrdev_get(unsigned int i)
{
        struct ide_tape_obj *tape = NULL;

        down(&idetape_ref_sem);
        tape = idetape_devs[i];
        if (tape)
                kref_get(&tape->kref);
        up(&idetape_ref_sem);
        return tape;
}

/*
 *      Function declarations
 *
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp);
static void idetape_write_release (ide_drive_t *drive, unsigned int minor);

/*
 * Too bad. The drive wants to send us data which we are not ready to accept.
 * Just throw it away.
 */
static void idetape_discard_data (ide_drive_t *drive, unsigned int bcount)
{
        while (bcount--)
                (void) HWIF(drive)->INB(IDE_DATA_REG);
}

static void idetape_input_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
        struct idetape_bh *bh = pc->bh;
        int count;

        while (bcount) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in "
                                "idetape_input_buffers\n");
                        idetape_discard_data(drive, bcount);
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), bcount);
                HWIF(drive)->atapi_input_bytes(drive, bh->b_data + atomic_read(&bh->b_count), count);
                bcount -= count;
                atomic_add(count, &bh->b_count);
                if (atomic_read(&bh->b_count) == bh->b_size) {
                        bh = bh->b_reqnext;
                        if (bh)
                                atomic_set(&bh->b_count, 0);
                }
        }
        pc->bh = bh;
}

static void idetape_output_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
        struct idetape_bh *bh = pc->bh;
        int count;

        while (bcount) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in "
                                "idetape_output_buffers\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = min((unsigned int)pc->b_count, (unsigned int)bcount);
                HWIF(drive)->atapi_output_bytes(drive, pc->b_data, count);
                bcount -= count;
                pc->b_data += count;
                pc->b_count -= count;
                if (!pc->b_count) {
                        pc->bh = bh = bh->b_reqnext;
                        if (bh) {
                                pc->b_data = bh->b_data;
                                pc->b_count = atomic_read(&bh->b_count);
                        }
                }
        }
}

static void idetape_update_buffers (idetape_pc_t *pc)
{
        struct idetape_bh *bh = pc->bh;
        int count;
        unsigned int bcount = pc->actually_transferred;

        if (test_bit(PC_WRITING, &pc->flags))
                return;
        while (bcount) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in "
                                "idetape_update_buffers\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = min((unsigned int)bh->b_size, (unsigned int)bcount);
                atomic_set(&bh->b_count, count);
                if (atomic_read(&bh->b_count) == bh->b_size)
                        bh = bh->b_reqnext;
                bcount -= count;
        }
        pc->bh = bh;
}

/*
 *      idetape_next_pc_storage returns a pointer to a place in which we can
 *      safely store a packet command, even though we intend to leave the
 *      driver. A storage space for a maximum of IDETAPE_PC_STACK packet
 *      commands is allocated at initialization time.
 */
static idetape_pc_t *idetape_next_pc_storage (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 5)
                printk(KERN_INFO "ide-tape: pc_stack_index=%d\n",
                        tape->pc_stack_index);
#endif /* IDETAPE_DEBUG_LOG */
        if (tape->pc_stack_index == IDETAPE_PC_STACK)
                tape->pc_stack_index=0;
        return (&tape->pc_stack[tape->pc_stack_index++]);
}

/*
 *      idetape_next_rq_storage is used along with idetape_next_pc_storage.
 *      Since we queue packet commands in the request queue, we need to
 *      allocate a request, along with the allocation of a packet command.
 */
 
/**************************************************************
 *                                                            *
 *  This should get fixed to use kmalloc(.., GFP_ATOMIC)      *
 *  followed later on by kfree().   -ml                       *
 *                                                            *
 **************************************************************/
 
static struct request *idetape_next_rq_storage (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 5)
                printk(KERN_INFO "ide-tape: rq_stack_index=%d\n",
                        tape->rq_stack_index);
#endif /* IDETAPE_DEBUG_LOG */
        if (tape->rq_stack_index == IDETAPE_PC_STACK)
                tape->rq_stack_index=0;
        return (&tape->rq_stack[tape->rq_stack_index++]);
}

/*
 *      idetape_init_pc initializes a packet command.
 */
static void idetape_init_pc (idetape_pc_t *pc)
{
        memset(pc->c, 0, 12);
        pc->retries = 0;
        pc->flags = 0;
        pc->request_transfer = 0;
        pc->buffer = pc->pc_buffer;
        pc->buffer_size = IDETAPE_PC_BUFFER_SIZE;
        pc->bh = NULL;
        pc->b_data = NULL;
}

/*
 *      idetape_analyze_error is called on each failed packet command retry
 *      to analyze the request sense. We currently do not utilize this
 *      information.
 */
static void idetape_analyze_error (ide_drive_t *drive, idetape_request_sense_result_t *result)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->failed_pc;

        tape->sense     = *result;
        tape->sense_key = result->sense_key;
        tape->asc       = result->asc;
        tape->ascq      = result->ascq;
#if IDETAPE_DEBUG_LOG
        /*
         *      Without debugging, we only log an error if we decided to
         *      give up retrying.
         */
        if (tape->debug_level >= 1)
                printk(KERN_INFO "ide-tape: pc = %x, sense key = %x, "
                        "asc = %x, ascq = %x\n",
                        pc->c[0], result->sense_key,
                        result->asc, result->ascq);
#endif /* IDETAPE_DEBUG_LOG */

        /*
         *      Correct pc->actually_transferred by asking the tape.
         */
        if (test_bit(PC_DMA_ERROR, &pc->flags)) {
                pc->actually_transferred = pc->request_transfer - tape->tape_block_size * ntohl(get_unaligned(&result->information));
                idetape_update_buffers(pc);
        }

        /*
         * If error was the result of a zero-length read or write command,
         * with sense key=5, asc=0x22, ascq=0, let it slide.  Some drives
         * (i.e. Seagate STT3401A Travan) don't support 0-length read/writes.
         */
        if ((pc->c[0] == IDETAPE_READ_CMD || pc->c[0] == IDETAPE_WRITE_CMD)
            && pc->c[4] == 0 && pc->c[3] == 0 && pc->c[2] == 0) { /* length==0 */
                if (result->sense_key == 5) {
                        /* don't report an error, everything's ok */
                        pc->error = 0;
                        /* don't retry read/write */
                        set_bit(PC_ABORT, &pc->flags);
                }
        }
        if (pc->c[0] == IDETAPE_READ_CMD && result->filemark) {
                pc->error = IDETAPE_ERROR_FILEMARK;
                set_bit(PC_ABORT, &pc->flags);
        }
        if (pc->c[0] == IDETAPE_WRITE_CMD) {
                if (result->eom ||
                    (result->sense_key == 0xd && result->asc == 0x0 &&
                     result->ascq == 0x2)) {
                        pc->error = IDETAPE_ERROR_EOD;
                        set_bit(PC_ABORT, &pc->flags);
                }
        }
        if (pc->c[0] == IDETAPE_READ_CMD || pc->c[0] == IDETAPE_WRITE_CMD) {
                if (result->sense_key == 8) {
                        pc->error = IDETAPE_ERROR_EOD;
                        set_bit(PC_ABORT, &pc->flags);
                }
                if (!test_bit(PC_ABORT, &pc->flags) &&
                    pc->actually_transferred)
                        pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
        }
}

/*
 * idetape_active_next_stage will declare the next stage as "active".
 */
static void idetape_active_next_stage (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage = tape->next_stage;
        struct request *rq = &stage->rq;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_active_next_stage\n");
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
        if (stage == NULL) {
                printk(KERN_ERR "ide-tape: bug: Trying to activate a non existing stage\n");
                return;
        }
#endif /* IDETAPE_DEBUG_BUGS */ 

        rq->rq_disk = tape->disk;
        rq->buffer = NULL;
        rq->special = (void *)stage->bh;
        tape->active_data_request = rq;
        tape->active_stage = stage;
        tape->next_stage = stage->next;
}

/*
 *      idetape_increase_max_pipeline_stages is a part of the feedback
 *      loop which tries to find the optimum number of stages. In the
 *      feedback loop, we are starting from a minimum maximum number of
 *      stages, and if we sense that the pipeline is empty, we try to
 *      increase it, until we reach the user compile time memory limit.
 */
static void idetape_increase_max_pipeline_stages (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int increase = (tape->max_pipeline - tape->min_pipeline) / 10;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk (KERN_INFO "ide-tape: Reached idetape_increase_max_pipeline_stages\n");
#endif /* IDETAPE_DEBUG_LOG */

        tape->max_stages += max(increase, 1);
        tape->max_stages = max(tape->max_stages, tape->min_pipeline);
        tape->max_stages = min(tape->max_stages, tape->max_pipeline);
}

/*
 *      idetape_kfree_stage calls kfree to completely free a stage, along with
 *      its related buffers.
 */
static void __idetape_kfree_stage (idetape_stage_t *stage)
{
        struct idetape_bh *prev_bh, *bh = stage->bh;
        int size;

        while (bh != NULL) {
                if (bh->b_data != NULL) {
                        size = (int) bh->b_size;
                        while (size > 0) {
                                free_page((unsigned long) bh->b_data);
                                size -= PAGE_SIZE;
                                bh->b_data += PAGE_SIZE;
                        }
                }
                prev_bh = bh;
                bh = bh->b_reqnext;
                kfree(prev_bh);
        }
        kfree(stage);
}

static void idetape_kfree_stage (idetape_tape_t *tape, idetape_stage_t *stage)
{
        __idetape_kfree_stage(stage);
}

/*
 *      idetape_remove_stage_head removes tape->first_stage from the pipeline.
 *      The caller should avoid race conditions.
 */
static void idetape_remove_stage_head (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_remove_stage_head\n");
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
        if (tape->first_stage == NULL) {
                printk(KERN_ERR "ide-tape: bug: tape->first_stage is NULL\n");
                return;         
        }
        if (tape->active_stage == tape->first_stage) {
                printk(KERN_ERR "ide-tape: bug: Trying to free our active pipeline stage\n");
                return;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        stage = tape->first_stage;
        tape->first_stage = stage->next;
        idetape_kfree_stage(tape, stage);
        tape->nr_stages--;
        if (tape->first_stage == NULL) {
                tape->last_stage = NULL;
#if IDETAPE_DEBUG_BUGS
                if (tape->next_stage != NULL)
                        printk(KERN_ERR "ide-tape: bug: tape->next_stage != NULL\n");
                if (tape->nr_stages)
                        printk(KERN_ERR "ide-tape: bug: nr_stages should be 0 now\n");
#endif /* IDETAPE_DEBUG_BUGS */
        }
}

/*
 * This will free all the pipeline stages starting from new_last_stage->next
 * to the end of the list, and point tape->last_stage to new_last_stage.
 */
static void idetape_abort_pipeline(ide_drive_t *drive,
                                   idetape_stage_t *new_last_stage)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage = new_last_stage->next;
        idetape_stage_t *nstage;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: %s: idetape_abort_pipeline called\n", tape->name);
#endif
        while (stage) {
                nstage = stage->next;
                idetape_kfree_stage(tape, stage);
                --tape->nr_stages;
                --tape->nr_pending_stages;
                stage = nstage;
        }
        if (new_last_stage)
                new_last_stage->next = NULL;
        tape->last_stage = new_last_stage;
        tape->next_stage = NULL;
}

/*
 *      idetape_end_request is used to finish servicing a request, and to
 *      insert a pending pipeline request into the main device queue.
 */
static int idetape_end_request(ide_drive_t *drive, int uptodate, int nr_sects)
{
        struct request *rq = HWGROUP(drive)->rq;
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;
        int error;
        int remove_stage = 0;
        idetape_stage_t *active_stage;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
        printk(KERN_INFO "ide-tape: Reached idetape_end_request\n");
#endif /* IDETAPE_DEBUG_LOG */

        switch (uptodate) {
                case 0: error = IDETAPE_ERROR_GENERAL; break;
                case 1: error = 0; break;
                default: error = uptodate;
        }
        rq->errors = error;
        if (error)
                tape->failed_pc = NULL;

        spin_lock_irqsave(&tape->spinlock, flags);

        /* The request was a pipelined data transfer request */
        if (tape->active_data_request == rq) {
                active_stage = tape->active_stage;
                tape->active_stage = NULL;
                tape->active_data_request = NULL;
                tape->nr_pending_stages--;
                if (rq->cmd[0] & REQ_IDETAPE_WRITE) {
                        remove_stage = 1;
                        if (error) {
                                set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
                                if (error == IDETAPE_ERROR_EOD)
                                        idetape_abort_pipeline(drive, active_stage);
                        }
                } else if (rq->cmd[0] & REQ_IDETAPE_READ) {
                        if (error == IDETAPE_ERROR_EOD) {
                                set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
                                idetape_abort_pipeline(drive, active_stage);
                        }
                }
                if (tape->next_stage != NULL) {
                        idetape_active_next_stage(drive);

                        /*
                         * Insert the next request into the request queue.
                         */
                        (void) ide_do_drive_cmd(drive, tape->active_data_request, ide_end);
                } else if (!error) {
                                idetape_increase_max_pipeline_stages(drive);
                }
        }
        ide_end_drive_cmd(drive, 0, 0);
//      blkdev_dequeue_request(rq);
//      drive->rq = NULL;
//      end_that_request_last(rq);

        if (remove_stage)
                idetape_remove_stage_head(drive);
        if (tape->active_data_request == NULL)
                clear_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
        spin_unlock_irqrestore(&tape->spinlock, flags);
        return 0;
}

static ide_startstop_t idetape_request_sense_callback (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_request_sense_callback\n");
#endif /* IDETAPE_DEBUG_LOG */
        if (!tape->pc->error) {
                idetape_analyze_error(drive, (idetape_request_sense_result_t *) tape->pc->buffer);
                idetape_end_request(drive, 1, 0);
        } else {
                printk(KERN_ERR "ide-tape: Error in REQUEST SENSE itself - Aborting request!\n");
                idetape_end_request(drive, 0, 0);
        }
        return ide_stopped;
}

static void idetape_create_request_sense_cmd (idetape_pc_t *pc)
{
        idetape_init_pc(pc);    
        pc->c[0] = IDETAPE_REQUEST_SENSE_CMD;
        pc->c[4] = 20;
        pc->request_transfer = 20;
        pc->callback = &idetape_request_sense_callback;
}

static void idetape_init_rq(struct request *rq, u8 cmd)
{
        memset(rq, 0, sizeof(*rq));
        rq->flags = REQ_SPECIAL;
        rq->cmd[0] = cmd;
}

/*
 *      idetape_queue_pc_head generates a new packet command request in front
 *      of the request queue, before the current request, so that it will be
 *      processed immediately, on the next pass through the driver.
 *
 *      idetape_queue_pc_head is called from the request handling part of
 *      the driver (the "bottom" part). Safe storage for the request should
 *      be allocated with idetape_next_pc_storage and idetape_next_rq_storage
 *      before calling idetape_queue_pc_head.
 *
 *      Memory for those requests is pre-allocated at initialization time, and
 *      is limited to IDETAPE_PC_STACK requests. We assume that we have enough
 *      space for the maximum possible number of inter-dependent packet commands.
 *
 *      The higher level of the driver - The ioctl handler and the character
 *      device handling functions should queue request to the lower level part
 *      and wait for their completion using idetape_queue_pc_tail or
 *      idetape_queue_rw_tail.
 */
static void idetape_queue_pc_head (ide_drive_t *drive, idetape_pc_t *pc,struct request *rq)
{
        struct ide_tape_obj *tape = drive->driver_data;

        idetape_init_rq(rq, REQ_IDETAPE_PC1);
        rq->buffer = (char *) pc;
        rq->rq_disk = tape->disk;
        (void) ide_do_drive_cmd(drive, rq, ide_preempt);
}

/*
 *      idetape_retry_pc is called when an error was detected during the
 *      last packet command. We queue a request sense packet command in
 *      the head of the request list.
 */
static ide_startstop_t idetape_retry_pc (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc;
        struct request *rq;
        atapi_error_t error;

        error.all = HWIF(drive)->INB(IDE_ERROR_REG);
        pc = idetape_next_pc_storage(drive);
        rq = idetape_next_rq_storage(drive);
        idetape_create_request_sense_cmd(pc);
        set_bit(IDETAPE_IGNORE_DSC, &tape->flags);
        idetape_queue_pc_head(drive, pc, rq);
        return ide_stopped;
}

/*
 *      idetape_postpone_request postpones the current request so that
 *      ide.c will be able to service requests from another device on
 *      the same hwgroup while we are polling for DSC.
 */
static void idetape_postpone_request (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: idetape_postpone_request\n");
#endif
        tape->postponed_rq = HWGROUP(drive)->rq;
        ide_stall_queue(drive, tape->dsc_polling_frequency);
}

/*
 *      idetape_pc_intr is the usual interrupt handler which will be called
 *      during a packet command. We will transfer some of the data (as
 *      requested by the drive) and will re-point interrupt handler to us.
 *      When data transfer is finished, we will act according to the
 *      algorithm described before idetape_issue_packet_command.
 *
 */
static ide_startstop_t idetape_pc_intr (ide_drive_t *drive)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        atapi_status_t status;
        atapi_bcount_t bcount;
        atapi_ireason_t ireason;
        idetape_pc_t *pc = tape->pc;

        unsigned int temp;
#if SIMULATE_ERRORS
        static int error_sim_count = 0;
#endif

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_pc_intr "
                                "interrupt handler\n");
#endif /* IDETAPE_DEBUG_LOG */  

        /* Clear the interrupt */
        status.all = HWIF(drive)->INB(IDE_STATUS_REG);

        if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
                if (HWIF(drive)->ide_dma_end(drive) || status.b.check) {
                        /*
                         * A DMA error is sometimes expected. For example,
                         * if the tape is crossing a filemark during a
                         * READ command, it will issue an irq and position
                         * itself before the filemark, so that only a partial
                         * data transfer will occur (which causes the DMA
                         * error). In that case, we will later ask the tape
                         * how much bytes of the original request were
                         * actually transferred (we can't receive that
                         * information from the DMA engine on most chipsets).
                         */

                        /*
                         * On the contrary, a DMA error is never expected;
                         * it usually indicates a hardware error or abort.
                         * If the tape crosses a filemark during a READ
                         * command, it will issue an irq and position itself
                         * after the filemark (not before). Only a partial
                         * data transfer will occur, but no DMA error.
                         * (AS, 19 Apr 2001)
                         */
                        set_bit(PC_DMA_ERROR, &pc->flags);
                } else {
                        pc->actually_transferred = pc->request_transfer;
                        idetape_update_buffers(pc);
                }
#if IDETAPE_DEBUG_LOG
                if (tape->debug_level >= 4)
                        printk(KERN_INFO "ide-tape: DMA finished\n");
#endif /* IDETAPE_DEBUG_LOG */
        }

        /* No more interrupts */
        if (!status.b.drq) {
#if IDETAPE_DEBUG_LOG
                if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: Packet command completed, %d bytes transferred\n", pc->actually_transferred);
#endif /* IDETAPE_DEBUG_LOG */
                clear_bit(PC_DMA_IN_PROGRESS, &pc->flags);

                local_irq_enable();

#if SIMULATE_ERRORS
                if ((pc->c[0] == IDETAPE_WRITE_CMD ||
                     pc->c[0] == IDETAPE_READ_CMD) &&
                    (++error_sim_count % 100) == 0) {
                        printk(KERN_INFO "ide-tape: %s: simulating error\n",
                                tape->name);
                        status.b.check = 1;
                }
#endif
                if (status.b.check && pc->c[0] == IDETAPE_REQUEST_SENSE_CMD)
                        status.b.check = 0;
                if (status.b.check || test_bit(PC_DMA_ERROR, &pc->flags)) {     /* Error detected */
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 1)
                                printk(KERN_INFO "ide-tape: %s: I/O error\n",
                                        tape->name);
#endif /* IDETAPE_DEBUG_LOG */
                        if (pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
                                printk(KERN_ERR "ide-tape: I/O error in request sense command\n");
                                return ide_do_reset(drive);
                        }
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 1)
                                printk(KERN_INFO "ide-tape: [cmd %x]: check condition\n", pc->c[0]);
#endif
                        /* Retry operation */
                        return idetape_retry_pc(drive);
                }
                pc->error = 0;
                if (test_bit(PC_WAIT_FOR_DSC, &pc->flags) &&
                    !status.b.dsc) {
                        /* Media access command */
                        tape->dsc_polling_start = jiffies;
                        tape->dsc_polling_frequency = IDETAPE_DSC_MA_FAST;
                        tape->dsc_timeout = jiffies + IDETAPE_DSC_MA_TIMEOUT;
                        /* Allow ide.c to handle other requests */
                        idetape_postpone_request(drive);
                        return ide_stopped;
                }
                if (tape->failed_pc == pc)
                        tape->failed_pc = NULL;
                /* Command finished - Call the callback function */
                return pc->callback(drive);
        }
        if (test_and_clear_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
                printk(KERN_ERR "ide-tape: The tape wants to issue more "
                                "interrupts in DMA mode\n");
                printk(KERN_ERR "ide-tape: DMA disabled, reverting to PIO\n");
                (void)__ide_dma_off(drive);
                return ide_do_reset(drive);
        }
        /* Get the number of bytes to transfer on this interrupt. */
        bcount.b.high = hwif->INB(IDE_BCOUNTH_REG);
        bcount.b.low = hwif->INB(IDE_BCOUNTL_REG);

        ireason.all = hwif->INB(IDE_IREASON_REG);

        if (ireason.b.cod) {
                printk(KERN_ERR "ide-tape: CoD != 0 in idetape_pc_intr\n");
                return ide_do_reset(drive);
        }
        if (ireason.b.io == test_bit(PC_WRITING, &pc->flags)) {
                /* Hopefully, we will never get here */
                printk(KERN_ERR "ide-tape: We wanted to %s, ",
                        ireason.b.io ? "Write":"Read");
                printk(KERN_ERR "ide-tape: but the tape wants us to %s !\n",
                        ireason.b.io ? "Read":"Write");
                return ide_do_reset(drive);
        }
        if (!test_bit(PC_WRITING, &pc->flags)) {
                /* Reading - Check that we have enough space */
                temp = pc->actually_transferred + bcount.all;
                if (temp > pc->request_transfer) {
                        if (temp > pc->buffer_size) {
                                printk(KERN_ERR "ide-tape: The tape wants to send us more data than expected - discarding data\n");
                                idetape_discard_data(drive, bcount.all);
                                ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
                                return ide_started;
                        }
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 2)
                                printk(KERN_NOTICE "ide-tape: The tape wants to send us more data than expected - allowing transfer\n");
#endif /* IDETAPE_DEBUG_LOG */
                }
        }
        if (test_bit(PC_WRITING, &pc->flags)) {
                if (pc->bh != NULL)
                        idetape_output_buffers(drive, pc, bcount.all);
                else
                        /* Write the current buffer */
                        HWIF(drive)->atapi_output_bytes(drive, pc->current_position, bcount.all);
        } else {
                if (pc->bh != NULL)
                        idetape_input_buffers(drive, pc, bcount.all);
                else
                        /* Read the current buffer */
                        HWIF(drive)->atapi_input_bytes(drive, pc->current_position, bcount.all);
        }
        /* Update the current position */
        pc->actually_transferred += bcount.all;
        pc->current_position += bcount.all;
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: [cmd %x] transferred %d bytes on that interrupt\n", pc->c[0], bcount.all);
#endif
        /* And set the interrupt handler again */
        ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
        return ide_started;
}

/*
 *      Packet Command Interface
 *
 *      The current Packet Command is available in tape->pc, and will not
 *      change until we finish handling it. Each packet command is associated
 *      with a callback function that will be called when the command is
 *      finished.
 *
 *      The handling will be done in three stages:
 *
 *      1.      idetape_issue_packet_command will send the packet command to the
 *              drive, and will set the interrupt handler to idetape_pc_intr.
 *
 *      2.      On each interrupt, idetape_pc_intr will be called. This step
 *              will be repeated until the device signals us that no more
 *              interrupts will be issued.
 *
 *      3.      ATAPI Tape media access commands have immediate status with a
 *              delayed process. In case of a successful initiation of a
 *              media access packet command, the DSC bit will be set when the
 *              actual execution of the command is finished. 
 *              Since the tape drive will not issue an interrupt, we have to
 *              poll for this event. In this case, we define the request as
 *              "low priority request" by setting rq_status to
 *              IDETAPE_RQ_POSTPONED,   set a timer to poll for DSC and exit
 *              the driver.
 *
 *              ide.c will then give higher priority to requests which
 *              originate from the other device, until will change rq_status
 *              to RQ_ACTIVE.
 *
 *      4.      When the packet command is finished, it will be checked for errors.
 *
 *      5.      In case an error was found, we queue a request sense packet
 *              command in front of the request queue and retry the operation
 *              up to IDETAPE_MAX_PC_RETRIES times.
 *
 *      6.      In case no error was found, or we decided to give up and not
 *              to retry again, the callback function will be called and then
 *              we will handle the next request.
 *
 */
static ide_startstop_t idetape_transfer_pc(ide_drive_t *drive)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        atapi_ireason_t ireason;
        int retries = 100;
        ide_startstop_t startstop;

        if (ide_wait_stat(&startstop,drive,DRQ_STAT,BUSY_STAT,WAIT_READY)) {
                printk(KERN_ERR "ide-tape: Strange, packet command initiated yet DRQ isn't asserted\n");
                return startstop;
        }
        ireason.all = hwif->INB(IDE_IREASON_REG);
        while (retries-- && (!ireason.b.cod || ireason.b.io)) {
                printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while issuing "
                                "a packet command, retrying\n");
                udelay(100);
                ireason.all = hwif->INB(IDE_IREASON_REG);
                if (retries == 0) {
                        printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while "
                                        "issuing a packet command, ignoring\n");
                        ireason.b.cod = 1;
                        ireason.b.io = 0;
                }
        }
        if (!ireason.b.cod || ireason.b.io) {
                printk(KERN_ERR "ide-tape: (IO,CoD) != (0,1) while issuing "
                                "a packet command\n");
                return ide_do_reset(drive);
        }
        /* Set the interrupt routine */
        ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
#ifdef CONFIG_BLK_DEV_IDEDMA
        /* Begin DMA, if necessary */
        if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags))
                hwif->dma_start(drive);
#endif
        /* Send the actual packet */
        HWIF(drive)->atapi_output_bytes(drive, pc->c, 12);
        return ide_started;
}

static ide_startstop_t idetape_issue_packet_command (ide_drive_t *drive, idetape_pc_t *pc)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        atapi_bcount_t bcount;
        int dma_ok = 0;

#if IDETAPE_DEBUG_BUGS
        if (tape->pc->c[0] == IDETAPE_REQUEST_SENSE_CMD &&
            pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
                printk(KERN_ERR "ide-tape: possible ide-tape.c bug - "
                        "Two request sense in serial were issued\n");
        }
#endif /* IDETAPE_DEBUG_BUGS */

        if (tape->failed_pc == NULL && pc->c[0] != IDETAPE_REQUEST_SENSE_CMD)
                tape->failed_pc = pc;
        /* Set the current packet command */
        tape->pc = pc;

        if (pc->retries > IDETAPE_MAX_PC_RETRIES ||
            test_bit(PC_ABORT, &pc->flags)) {
                /*
                 *      We will "abort" retrying a packet command in case
                 *      a legitimate error code was received (crossing a
                 *      filemark, or end of the media, for example).
                 */
                if (!test_bit(PC_ABORT, &pc->flags)) {
                        if (!(pc->c[0] == IDETAPE_TEST_UNIT_READY_CMD &&
                              tape->sense_key == 2 && tape->asc == 4 &&
                             (tape->ascq == 1 || tape->ascq == 8))) {
                                printk(KERN_ERR "ide-tape: %s: I/O error, "
                                                "pc = %2x, key = %2x, "
                                                "asc = %2x, ascq = %2x\n",
                                                tape->name, pc->c[0],
                                                tape->sense_key, tape->asc,
                                                tape->ascq);
                        }
                        /* Giving up */
                        pc->error = IDETAPE_ERROR_GENERAL;
                }
                tape->failed_pc = NULL;
                return pc->callback(drive);
        }
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: Retry number - %d, cmd = %02X\n", pc->retries, pc->c[0]);
#endif /* IDETAPE_DEBUG_LOG */

        pc->retries++;
        /* We haven't transferred any data yet */
        pc->actually_transferred = 0;
        pc->current_position = pc->buffer;
        /* Request to transfer the entire buffer at once */
        bcount.all = pc->request_transfer;

        if (test_and_clear_bit(PC_DMA_ERROR, &pc->flags)) {
                printk(KERN_WARNING "ide-tape: DMA disabled, "
                                "reverting to PIO\n");
                (void)__ide_dma_off(drive);
        }
        if (test_bit(PC_DMA_RECOMMENDED, &pc->flags) && drive->using_dma)
                dma_ok = !hwif->dma_setup(drive);

        if (IDE_CONTROL_REG)
                hwif->OUTB(drive->ctl, IDE_CONTROL_REG);
        hwif->OUTB(dma_ok ? 1 : 0, IDE_FEATURE_REG);    /* Use PIO/DMA */
        hwif->OUTB(bcount.b.high, IDE_BCOUNTH_REG);
        hwif->OUTB(bcount.b.low, IDE_BCOUNTL_REG);
        hwif->OUTB(drive->select.all, IDE_SELECT_REG);
        if (dma_ok)                     /* Will begin DMA later */
                set_bit(PC_DMA_IN_PROGRESS, &pc->flags);
        if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
                ide_set_handler(drive, &idetape_transfer_pc, IDETAPE_WAIT_CMD, NULL);
                hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
                return ide_started;
        } else {
                hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
                return idetape_transfer_pc(drive);
        }
}

/*
 *      General packet command callback function.
 */
static ide_startstop_t idetape_pc_callback (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_pc_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

        idetape_end_request(drive, tape->pc->error ? 0 : 1, 0);
        return ide_stopped;
}

/*
 *      A mode sense command is used to "sense" tape parameters.
 */
static void idetape_create_mode_sense_cmd (idetape_pc_t *pc, u8 page_code)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_MODE_SENSE_CMD;
        if (page_code != IDETAPE_BLOCK_DESCRIPTOR)
                pc->c[1] = 8;   /* DBD = 1 - Don't return block descriptors */
        pc->c[2] = page_code;
        /*
         * Changed pc->c[3] to 0 (255 will at best return unused info).
         *
         * For SCSI this byte is defined as subpage instead of high byte
         * of length and some IDE drives seem to interpret it this way
         * and return an error when 255 is used.
         */
        pc->c[3] = 0;
        pc->c[4] = 255;         /* (We will just discard data in that case) */
        if (page_code == IDETAPE_BLOCK_DESCRIPTOR)
                pc->request_transfer = 12;
        else if (page_code == IDETAPE_CAPABILITIES_PAGE)
                pc->request_transfer = 24;
        else
                pc->request_transfer = 50;
        pc->callback = &idetape_pc_callback;
}

static void calculate_speeds(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int full = 125, empty = 75;

        if (time_after(jiffies, tape->controlled_pipeline_head_time + 120 * HZ)) {
                tape->controlled_previous_pipeline_head = tape->controlled_last_pipeline_head;
                tape->controlled_previous_head_time = tape->controlled_pipeline_head_time;
                tape->controlled_last_pipeline_head = tape->pipeline_head;
                tape->controlled_pipeline_head_time = jiffies;
        }
        if (time_after(jiffies, tape->controlled_pipeline_head_time + 60 * HZ))
                tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_last_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_pipeline_head_time);
        else if (time_after(jiffies, tape->controlled_previous_head_time))
                tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_previous_head_time);

        if (tape->nr_pending_stages < tape->max_stages /*- 1 */) {
                /* -1 for read mode error recovery */
                if (time_after(jiffies, tape->uncontrolled_previous_head_time + 10 * HZ)) {
                        tape->uncontrolled_pipeline_head_time = jiffies;
                        tape->uncontrolled_pipeline_head_speed = (tape->pipeline_head - tape->uncontrolled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->uncontrolled_previous_head_time);
                }
        } else {
                tape->uncontrolled_previous_head_time = jiffies;
                tape->uncontrolled_previous_pipeline_head = tape->pipeline_head;
                if (time_after(jiffies, tape->uncontrolled_pipeline_head_time + 30 * HZ)) {
                        tape->uncontrolled_pipeline_head_time = jiffies;
                }
        }
        tape->pipeline_head_speed = max(tape->uncontrolled_pipeline_head_speed, tape->controlled_pipeline_head_speed);
        if (tape->speed_control == 0) {
                tape->max_insert_speed = 5000;
        } else if (tape->speed_control == 1) {
                if (tape->nr_pending_stages >= tape->max_stages / 2)
                        tape->max_insert_speed = tape->pipeline_head_speed +
                                (1100 - tape->pipeline_head_speed) * 2 * (tape->nr_pending_stages - tape->max_stages / 2) / tape->max_stages;
                else
                        tape->max_insert_speed = 500 +
                                (tape->pipeline_head_speed - 500) * 2 * tape->nr_pending_stages / tape->max_stages;
                if (tape->nr_pending_stages >= tape->max_stages * 99 / 100)
                        tape->max_insert_speed = 5000;
        } else if (tape->speed_control == 2) {
                tape->max_insert_speed = tape->pipeline_head_speed * empty / 100 +
                        (tape->pipeline_head_speed * full / 100 - tape->pipeline_head_speed * empty / 100) * tape->nr_pending_stages / tape->max_stages;
        } else
                tape->max_insert_speed = tape->speed_control;
        tape->max_insert_speed = max(tape->max_insert_speed, 500);
}

static ide_startstop_t idetape_media_access_finished (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        atapi_status_t status;

        status.all = HWIF(drive)->INB(IDE_STATUS_REG);
        if (status.b.dsc) {
                if (status.b.check) {
                        /* Error detected */
                        if (pc->c[0] != IDETAPE_TEST_UNIT_READY_CMD)
                                printk(KERN_ERR "ide-tape: %s: I/O error, ",
                                                tape->name);
                        /* Retry operation */
                        return idetape_retry_pc(drive);
                }
                pc->error = 0;
                if (tape->failed_pc == pc)
                        tape->failed_pc = NULL;
        } else {
                pc->error = IDETAPE_ERROR_GENERAL;
                tape->failed_pc = NULL;
        }
        return pc->callback(drive);
}

static ide_startstop_t idetape_rw_callback (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        struct request *rq = HWGROUP(drive)->rq;
        int blocks = tape->pc->actually_transferred / tape->tape_block_size;

        tape->avg_size += blocks * tape->tape_block_size;
        tape->insert_size += blocks * tape->tape_block_size;
        if (tape->insert_size > 1024 * 1024)
                tape->measure_insert_time = 1;
        if (tape->measure_insert_time) {
                tape->measure_insert_time = 0;
                tape->insert_time = jiffies;
                tape->insert_size = 0;
        }
        if (time_after(jiffies, tape->insert_time))
                tape->insert_speed = tape->insert_size / 1024 * HZ / (jiffies - tape->insert_time);
        if (jiffies - tape->avg_time >= HZ) {
                tape->avg_speed = tape->avg_size * HZ / (jiffies - tape->avg_time) / 1024;
                tape->avg_size = 0;
                tape->avg_time = jiffies;
        }

#if IDETAPE_DEBUG_LOG   
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_rw_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

        tape->first_frame_position += blocks;
        rq->current_nr_sectors -= blocks;

        if (!tape->pc->error)
                idetape_end_request(drive, 1, 0);
        else
                idetape_end_request(drive, tape->pc->error, 0);
        return ide_stopped;
}

static void idetape_create_read_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_READ_CMD;
        put_unaligned(htonl(length), (unsigned int *) &pc->c[1]);
        pc->c[1] = 1;
        pc->callback = &idetape_rw_callback;
        pc->bh = bh;
        atomic_set(&bh->b_count, 0);
        pc->buffer = NULL;
        pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
        if (pc->request_transfer == tape->stage_size)
                set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

static void idetape_create_read_buffer_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
        int size = 32768;
        struct idetape_bh *p = bh;

        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_READ_BUFFER_CMD;
        pc->c[1] = IDETAPE_RETRIEVE_FAULTY_BLOCK;
        pc->c[7] = size >> 8;
        pc->c[8] = size & 0xff;
        pc->callback = &idetape_pc_callback;
        pc->bh = bh;
        atomic_set(&bh->b_count, 0);
        pc->buffer = NULL;
        while (p) {
                atomic_set(&p->b_count, 0);
                p = p->b_reqnext;
        }
        pc->request_transfer = pc->buffer_size = size;
}

static void idetape_create_write_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_WRITE_CMD;
        put_unaligned(htonl(length), (unsigned int *) &pc->c[1]);
        pc->c[1] = 1;
        pc->callback = &idetape_rw_callback;
        set_bit(PC_WRITING, &pc->flags);
        pc->bh = bh;
        pc->b_data = bh->b_data;
        pc->b_count = atomic_read(&bh->b_count);
        pc->buffer = NULL;
        pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
        if (pc->request_transfer == tape->stage_size)
                set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

/*
 * idetape_do_request is our request handling function. 
 */
static ide_startstop_t idetape_do_request(ide_drive_t *drive,
                                          struct request *rq, sector_t block)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = NULL;
        struct request *postponed_rq = tape->postponed_rq;
        atapi_status_t status;

#if IDETAPE_DEBUG_LOG
#if 0
        if (tape->debug_level >= 5)
                printk(KERN_INFO "ide-tape: rq_status: %d, "
                        "dev: %s, cmd: %ld, errors: %d\n", rq->rq_status,
                         rq->rq_disk->disk_name, rq->cmd[0], rq->errors);
#endif
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: sector: %ld, "
                        "nr_sectors: %ld, current_nr_sectors: %d\n",
                        rq->sector, rq->nr_sectors, rq->current_nr_sectors);
#endif /* IDETAPE_DEBUG_LOG */

        if ((rq->flags & REQ_SPECIAL) == 0) {
                /*
                 * We do not support buffer cache originated requests.
                 */
                printk(KERN_NOTICE "ide-tape: %s: Unsupported request in "
                        "request queue (%ld)\n", drive->name, rq->flags);
                ide_end_request(drive, 0, 0);
                return ide_stopped;
        }

        /*
         *      Retry a failed packet command
         */
        if (tape->failed_pc != NULL &&
            tape->pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
                return idetape_issue_packet_command(drive, tape->failed_pc);
        }
#if IDETAPE_DEBUG_BUGS
        if (postponed_rq != NULL)
                if (rq != postponed_rq) {
                        printk(KERN_ERR "ide-tape: ide-tape.c bug - "
                                        "Two DSC requests were queued\n");
                        idetape_end_request(drive, 0, 0);
                        return ide_stopped;
                }
#endif /* IDETAPE_DEBUG_BUGS */

        tape->postponed_rq = NULL;

        /*
         * If the tape is still busy, postpone our request and service
         * the other device meanwhile.
         */
        status.all = HWIF(drive)->INB(IDE_STATUS_REG);

        if (!drive->dsc_overlap && !(rq->cmd[0] & REQ_IDETAPE_PC2))
                set_bit(IDETAPE_IGNORE_DSC, &tape->flags);

        if (drive->post_reset == 1) {
                set_bit(IDETAPE_IGNORE_DSC, &tape->flags);
                drive->post_reset = 0;
        }

        if (tape->tape_still_time > 100 && tape->tape_still_time < 200)
                tape->measure_insert_time = 1;
        if (time_after(jiffies, tape->insert_time))
                tape->insert_speed = tape->insert_size / 1024 * HZ / (jiffies - tape->insert_time);
        calculate_speeds(drive);
        if (!test_and_clear_bit(IDETAPE_IGNORE_DSC, &tape->flags) &&
            !status.b.dsc) {
                if (postponed_rq == NULL) {
                        tape->dsc_polling_start = jiffies;
                        tape->dsc_polling_frequency = tape->best_dsc_rw_frequency;
                        tape->dsc_timeout = jiffies + IDETAPE_DSC_RW_TIMEOUT;
                } else if (time_after(jiffies, tape->dsc_timeout)) {
                        printk(KERN_ERR "ide-tape: %s: DSC timeout\n",
                                tape->name);
                        if (rq->cmd[0] & REQ_IDETAPE_PC2) {
                                idetape_media_access_finished(drive);
                                return ide_stopped;
                        } else {
                                return ide_do_reset(drive);
                        }
                } else if (jiffies - tape->dsc_polling_start > IDETAPE_DSC_MA_THRESHOLD)
                        tape->dsc_polling_frequency = IDETAPE_DSC_MA_SLOW;
                idetape_postpone_request(drive);
                return ide_stopped;
        }
        if (rq->cmd[0] & REQ_IDETAPE_READ) {
                tape->buffer_head++;
#if USE_IOTRACE
                IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
                tape->postpone_cnt = 0;
                pc = idetape_next_pc_storage(drive);
                idetape_create_read_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
                goto out;
        }
        if (rq->cmd[0] & REQ_IDETAPE_WRITE) {
                tape->buffer_head++;
#if USE_IOTRACE
                IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
                tape->postpone_cnt = 0;
                pc = idetape_next_pc_storage(drive);
                idetape_create_write_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
                goto out;
        }
        if (rq->cmd[0] & REQ_IDETAPE_READ_BUFFER) {
                tape->postpone_cnt = 0;
                pc = idetape_next_pc_storage(drive);
                idetape_create_read_buffer_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
                goto out;
        }
        if (rq->cmd[0] & REQ_IDETAPE_PC1) {
                pc = (idetape_pc_t *) rq->buffer;
                rq->cmd[0] &= ~(REQ_IDETAPE_PC1);
                rq->cmd[0] |= REQ_IDETAPE_PC2;
                goto out;
        }
        if (rq->cmd[0] & REQ_IDETAPE_PC2) {
                idetape_media_access_finished(drive);
                return ide_stopped;
        }
        BUG();
out:
        return idetape_issue_packet_command(drive, pc);
}

/*
 *      Pipeline related functions
 */
static inline int idetape_pipeline_active (idetape_tape_t *tape)
{
        int rc1, rc2;

        rc1 = test_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
        rc2 = (tape->active_data_request != NULL);
        return rc1;
}

/*
 *      idetape_kmalloc_stage uses __get_free_page to allocate a pipeline
 *      stage, along with all the necessary small buffers which together make
 *      a buffer of size tape->stage_size (or a bit more). We attempt to
 *      combine sequential pages as much as possible.
 *
 *      Returns a pointer to the new allocated stage, or NULL if we
 *      can't (or don't want to) allocate a stage.
 *
 *      Pipeline stages are optional and are used to increase performance.
 *      If we can't allocate them, we'll manage without them.
 */
static idetape_stage_t *__idetape_kmalloc_stage (idetape_tape_t *tape, int full, int clear)
{
        idetape_stage_t *stage;
        struct idetape_bh *prev_bh, *bh;
        int pages = tape->pages_per_stage;
        char *b_data = NULL;

        if ((stage = (idetape_stage_t *) kmalloc (sizeof (idetape_stage_t),GFP_KERNEL)) == NULL)
                return NULL;
        stage->next = NULL;

        bh = stage->bh = (struct idetape_bh *)kmalloc(sizeof(struct idetape_bh), GFP_KERNEL);
        if (bh == NULL)
                goto abort;
        bh->b_reqnext = NULL;
        if ((bh->b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
                goto abort;
        if (clear)
                memset(bh->b_data, 0, PAGE_SIZE);
        bh->b_size = PAGE_SIZE;
        atomic_set(&bh->b_count, full ? bh->b_size : 0);

        while (--pages) {
                if ((b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
                        goto abort;
                if (clear)
                        memset(b_data, 0, PAGE_SIZE);
                if (bh->b_data == b_data + PAGE_SIZE) {
                        bh->b_size += PAGE_SIZE;
                        bh->b_data -= PAGE_SIZE;
                        if (full)
                                atomic_add(PAGE_SIZE, &bh->b_count);
                        continue;
                }
                if (b_data == bh->b_data + bh->b_size) {
                        bh->b_size += PAGE_SIZE;
                        if (full)
                                atomic_add(PAGE_SIZE, &bh->b_count);
                        continue;
                }
                prev_bh = bh;
                if ((bh = (struct idetape_bh *)kmalloc(sizeof(struct idetape_bh), GFP_KERNEL)) == NULL) {
                        free_page((unsigned long) b_data);
                        goto abort;
                }
                bh->b_reqnext = NULL;
                bh->b_data = b_data;
                bh->b_size = PAGE_SIZE;
                atomic_set(&bh->b_count, full ? bh->b_size : 0);
                prev_bh->b_reqnext = bh;
        }
        bh->b_size -= tape->excess_bh_size;
        if (full)
                atomic_sub(tape->excess_bh_size, &bh->b_count);
        return stage;
abort:
        __idetape_kfree_stage(stage);
        return NULL;
}

static idetape_stage_t *idetape_kmalloc_stage (idetape_tape_t *tape)
{
        idetape_stage_t *cache_stage = tape->cache_stage;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_kmalloc_stage\n");
#endif /* IDETAPE_DEBUG_LOG */

        if (tape->nr_stages >= tape->max_stages)
                return NULL;
        if (cache_stage != NULL) {
                tape->cache_stage = NULL;
                return cache_stage;
        }
        return __idetape_kmalloc_stage(tape, 0, 0);
}

static void idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
{
        struct idetape_bh *bh = tape->bh;
        int count;

        while (n) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in "
                                "idetape_copy_stage_from_user\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
                copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count);
                n -= count;
                atomic_add(count, &bh->b_count);
                buf += count;
                if (atomic_read(&bh->b_count) == bh->b_size) {
                        bh = bh->b_reqnext;
                        if (bh)
                                atomic_set(&bh->b_count, 0);
                }
        }
        tape->bh = bh;
}

static void idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
{
        struct idetape_bh *bh = tape->bh;
        int count;

        while (n) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in "
                                "idetape_copy_stage_to_user\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = min(tape->b_count, n);
                copy_to_user(buf, tape->b_data, count);
                n -= count;
                tape->b_data += count;
                tape->b_count -= count;
                buf += count;
                if (!tape->b_count) {
                        tape->bh = bh = bh->b_reqnext;
                        if (bh) {
                                tape->b_data = bh->b_data;
                                tape->b_count = atomic_read(&bh->b_count);
                        }
                }
        }
}

static void idetape_init_merge_stage (idetape_tape_t *tape)
{
        struct idetape_bh *bh = tape->merge_stage->bh;
        
        tape->bh = bh;
        if (tape->chrdev_direction == idetape_direction_write)
                atomic_set(&bh->b_count, 0);
        else {
                tape->b_data = bh->b_data;
                tape->b_count = atomic_read(&bh->b_count);
        }
}

static void idetape_switch_buffers (idetape_tape_t *tape, idetape_stage_t *stage)
{
        struct idetape_bh *tmp;

        tmp = stage->bh;
        stage->bh = tape->merge_stage->bh;
        tape->merge_stage->bh = tmp;
        idetape_init_merge_stage(tape);
}

/*
 *      idetape_add_stage_tail adds a new stage at the end of the pipeline.
 */
static void idetape_add_stage_tail (ide_drive_t *drive,idetape_stage_t *stage)
{
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk (KERN_INFO "ide-tape: Reached idetape_add_stage_tail\n");
#endif /* IDETAPE_DEBUG_LOG */
        spin_lock_irqsave(&tape->spinlock, flags);
        stage->next = NULL;
        if (tape->last_stage != NULL)
                tape->last_stage->next=stage;
        else
                tape->first_stage = tape->next_stage=stage;
        tape->last_stage = stage;
        if (tape->next_stage == NULL)
                tape->next_stage = tape->last_stage;
        tape->nr_stages++;
        tape->nr_pending_stages++;
        spin_unlock_irqrestore(&tape->spinlock, flags);
}

/*
 *      idetape_wait_for_request installs a completion in a pending request
 *      and sleeps until it is serviced.
 *
 *      The caller should ensure that the request will not be serviced
 *      before we install the completion (usually by disabling interrupts).
 */
static void idetape_wait_for_request (ide_drive_t *drive, struct request *rq)
{
        DECLARE_COMPLETION(wait);
        idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_BUGS
        if (rq == NULL || (rq->flags & REQ_SPECIAL) == 0) {
                printk (KERN_ERR "ide-tape: bug: Trying to sleep on non-valid request\n");
                return;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        rq->waiting = &wait;
        rq->end_io = blk_end_sync_rq;
        spin_unlock_irq(&tape->spinlock);
        wait_for_completion(&wait);
        /* The stage and its struct request have been deallocated */
        spin_lock_irq(&tape->spinlock);
}

static ide_startstop_t idetape_read_position_callback (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_read_position_result_t *result;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_read_position_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

        if (!tape->pc->error) {
                result = (idetape_read_position_result_t *) tape->pc->buffer;
#if IDETAPE_DEBUG_LOG
                if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: BOP - %s\n",result->bop ? "Yes":"No");
                if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: EOP - %s\n",result->eop ? "Yes":"No");
#endif /* IDETAPE_DEBUG_LOG */
                if (result->bpu) {
                        printk(KERN_INFO "ide-tape: Block location is unknown to the tape\n");
                        clear_bit(IDETAPE_ADDRESS_VALID, &tape->flags);
                        idetape_end_request(drive, 0, 0);
                } else {
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 2)
                                printk(KERN_INFO "ide-tape: Block Location - %u\n", ntohl(result->first_block));
#endif /* IDETAPE_DEBUG_LOG */
                        tape->partition = result->partition;
                        tape->first_frame_position = ntohl(result->first_block);
                        tape->last_frame_position = ntohl(result->last_block);
                        tape->blocks_in_buffer = result->blocks_in_buffer[2];
                        set_bit(IDETAPE_ADDRESS_VALID, &tape->flags);
                        idetape_end_request(drive, 1, 0);
                }
        } else {
                idetape_end_request(drive, 0, 0);
        }
        return ide_stopped;
}

/*
 *      idetape_create_write_filemark_cmd will:
 *
 *              1.      Write a filemark if write_filemark=1.
 *              2.      Flush the device buffers without writing a filemark
 *                      if write_filemark=0.
 *
 */
static void idetape_create_write_filemark_cmd (ide_drive_t *drive, idetape_pc_t *pc,int write_filemark)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_WRITE_FILEMARK_CMD;
        pc->c[4] = write_filemark;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static void idetape_create_test_unit_ready_cmd(idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_TEST_UNIT_READY_CMD;
        pc->callback = &idetape_pc_callback;
}

/*
 *      idetape_queue_pc_tail is based on the following functions:
 *
 *      ide_do_drive_cmd from ide.c
 *      cdrom_queue_request and cdrom_queue_packet_command from ide-cd.c
 *
 *      We add a special packet command request to the tail of the request
 *      queue, and wait for it to be serviced.
 *
 *      This is not to be called from within the request handling part
 *      of the driver ! We allocate here data in the stack, and it is valid
 *      until the request is finished. This is not the case for the bottom
 *      part of the driver, where we are always leaving the functions to wait
 *      for an interrupt or a timer event.
 *
 *      From the bottom part of the driver, we should allocate safe memory
 *      using idetape_next_pc_storage and idetape_next_rq_storage, and add
 *      the request to the request list without waiting for it to be serviced !
 *      In that case, we usually use idetape_queue_pc_head.
 */
static int __idetape_queue_pc_tail (ide_drive_t *drive, idetape_pc_t *pc)
{
        struct ide_tape_obj *tape = drive->driver_data;
        struct request rq;

        idetape_init_rq(&rq, REQ_IDETAPE_PC1);
        rq.buffer = (char *) pc;
        rq.rq_disk = tape->disk;
        return ide_do_drive_cmd(drive, &rq, ide_wait);
}

static void idetape_create_load_unload_cmd (ide_drive_t *drive, idetape_pc_t *pc,int cmd)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_LOAD_UNLOAD_CMD;
        pc->c[4] = cmd;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static int idetape_wait_ready(ide_drive_t *drive, unsigned long timeout)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        int load_attempted = 0;

        /*
         * Wait for the tape to become ready
         */
        set_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags);
        timeout += jiffies;
        while (time_before(jiffies, timeout)) {
                idetape_create_test_unit_ready_cmd(&pc);
                if (!__idetape_queue_pc_tail(drive, &pc))
                        return 0;
                if ((tape->sense_key == 2 && tape->asc == 4 && tape->ascq == 2)
                    || (tape->asc == 0x3A)) {   /* no media */
                        if (load_attempted)
                                return -ENOMEDIUM;
                        idetape_create_load_unload_cmd(drive, &pc, IDETAPE_LU_LOAD_MASK);
                        __idetape_queue_pc_tail(drive, &pc);
                        load_attempted = 1;
                /* not about to be ready */
                } else if (!(tape->sense_key == 2 && tape->asc == 4 &&
                             (tape->ascq == 1 || tape->ascq == 8)))
                        return -EIO;
                current->state = TASK_INTERRUPTIBLE;
                schedule_timeout(HZ / 10);
        }
        return -EIO;
}

static int idetape_queue_pc_tail (ide_drive_t *drive,idetape_pc_t *pc)
{
        return __idetape_queue_pc_tail(drive, pc);
}

static int idetape_flush_tape_buffers (ide_drive_t *drive)
{
        idetape_pc_t pc;
        int rc;

        idetape_create_write_filemark_cmd(drive, &pc, 0);
        if ((rc = idetape_queue_pc_tail(drive, &pc)))
                return rc;
        idetape_wait_ready(drive, 60 * 5 * HZ);
        return 0;
}

static void idetape_create_read_position_cmd (idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_READ_POSITION_CMD;
        pc->request_transfer = 20;
        pc->callback = &idetape_read_position_callback;
}

static int idetape_read_position (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        int position;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_read_position\n");
#endif /* IDETAPE_DEBUG_LOG */

        idetape_create_read_position_cmd(&pc);
        if (idetape_queue_pc_tail(drive, &pc))
                return -1;
        position = tape->first_frame_position;
        return position;
}

static void idetape_create_locate_cmd (ide_drive_t *drive, idetape_pc_t *pc, unsigned int block, u8 partition, int skip)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_LOCATE_CMD;
        pc->c[1] = 2;
        put_unaligned(htonl(block), (unsigned int *) &pc->c[3]);
        pc->c[8] = partition;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static int idetape_create_prevent_cmd (ide_drive_t *drive, idetape_pc_t *pc, int prevent)
{
        idetape_tape_t *tape = drive->driver_data;

        if (!tape->capabilities.lock)
                return 0;

        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_PREVENT_CMD;
        pc->c[4] = prevent;
        pc->callback = &idetape_pc_callback;
        return 1;
}

static int __idetape_discard_read_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;
        int cnt;

        if (tape->chrdev_direction != idetape_direction_read)
                return 0;

        /* Remove merge stage. */
        cnt = tape->merge_stage_size / tape->tape_block_size;
        if (test_and_clear_bit(IDETAPE_FILEMARK, &tape->flags))
                ++cnt;          /* Filemarks count as 1 sector */
        tape->merge_stage_size = 0;
        if (tape->merge_stage != NULL) {
                __idetape_kfree_stage(tape->merge_stage);
                tape->merge_stage = NULL;
        }

        /* Clear pipeline flags. */
        clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
        tape->chrdev_direction = idetape_direction_none;

        /* Remove pipeline stages. */
        if (tape->first_stage == NULL)
                return 0;

        spin_lock_irqsave(&tape->spinlock, flags);
        tape->next_stage = NULL;
        if (idetape_pipeline_active(tape))
                idetape_wait_for_request(drive, tape->active_data_request);
        spin_unlock_irqrestore(&tape->spinlock, flags);

        while (tape->first_stage != NULL) {
                struct request *rq_ptr = &tape->first_stage->rq;

                cnt += rq_ptr->nr_sectors - rq_ptr->current_nr_sectors; 
                if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
                        ++cnt;
                idetape_remove_stage_head(drive);
        }
        tape->nr_pending_stages = 0;
        tape->max_stages = tape->min_pipeline;
        return cnt;
}

/*
 *      idetape_position_tape positions the tape to the requested block
 *      using the LOCATE packet command. A READ POSITION command is then
 *      issued to check where we are positioned.
 *
 *      Like all higher level operations, we queue the commands at the tail
 *      of the request queue and wait for their completion.
 *      
 */
static int idetape_position_tape (ide_drive_t *drive, unsigned int block, u8 partition, int skip)
{
        idetape_tape_t *tape = drive->driver_data;
        int retval;
        idetape_pc_t pc;

        if (tape->chrdev_direction == idetape_direction_read)
                __idetape_discard_read_pipeline(drive);
        idetape_wait_ready(drive, 60 * 5 * HZ);
        idetape_create_locate_cmd(drive, &pc, block, partition, skip);
        retval = idetape_queue_pc_tail(drive, &pc);
        if (retval)
                return (retval);

        idetape_create_read_position_cmd(&pc);
        return (idetape_queue_pc_tail(drive, &pc));
}

static void idetape_discard_read_pipeline (ide_drive_t *drive, int restore_position)
{
        idetape_tape_t *tape = drive->driver_data;
        int cnt;
        int seek, position;

        cnt = __idetape_discard_read_pipeline(drive);
        if (restore_position) {
                position = idetape_read_position(drive);
                seek = position > cnt ? position - cnt : 0;
                if (idetape_position_tape(drive, seek, 0, 0)) {
                        printk(KERN_INFO "ide-tape: %s: position_tape failed in discard_pipeline()\n", tape->name);
                        return;
                }
        }
}

/*
 * idetape_queue_rw_tail generates a read/write request for the block
 * device interface and wait for it to be serviced.
 */
static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks, struct idetape_bh *bh)
{
        idetape_tape_t *tape = drive->driver_data;
        struct request rq;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: idetape_queue_rw_tail: cmd=%d\n",cmd);
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
        if (idetape_pipeline_active(tape)) {
                printk(KERN_ERR "ide-tape: bug: the pipeline is active in idetape_queue_rw_tail\n");
                return (0);
        }
#endif /* IDETAPE_DEBUG_BUGS */ 

        idetape_init_rq(&rq, cmd);
        rq.rq_disk = tape->disk;
        rq.special = (void *)bh;
        rq.sector = tape->first_frame_position;
        rq.nr_sectors = rq.current_nr_sectors = blocks;
        (void) ide_do_drive_cmd(drive, &rq, ide_wait);

        if ((cmd & (REQ_IDETAPE_READ | REQ_IDETAPE_WRITE)) == 0)
                return 0;

        if (tape->merge_stage)
                idetape_init_merge_stage(tape);
        if (rq.errors == IDETAPE_ERROR_GENERAL)
                return -EIO;
        return (tape->tape_block_size * (blocks-rq.current_nr_sectors));
}

/*
 *      idetape_insert_pipeline_into_queue is used to start servicing the
 *      pipeline stages, starting from tape->next_stage.
 */
static void idetape_insert_pipeline_into_queue (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

        if (tape->next_stage == NULL)
                return;
        if (!idetape_pipeline_active(tape)) {
                set_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
                idetape_active_next_stage(drive);
                (void) ide_do_drive_cmd(drive, tape->active_data_request, ide_end);
        }
}

static void idetape_create_inquiry_cmd (idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_INQUIRY_CMD;
        pc->c[4] = pc->request_transfer = 254;
        pc->callback = &idetape_pc_callback;
}

static void idetape_create_rewind_cmd (ide_drive_t *drive, idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_REWIND_CMD;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

#if 0
static void idetape_create_mode_select_cmd (idetape_pc_t *pc, int length)
{
        idetape_init_pc(pc);
        set_bit(PC_WRITING, &pc->flags);
        pc->c[0] = IDETAPE_MODE_SELECT_CMD;
        pc->c[1] = 0x10;
        put_unaligned(htons(length), (unsigned short *) &pc->c[3]);
        pc->request_transfer = 255;
        pc->callback = &idetape_pc_callback;
}
#endif

static void idetape_create_erase_cmd (idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_ERASE_CMD;
        pc->c[1] = 1;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static void idetape_create_space_cmd (idetape_pc_t *pc,int count, u8 cmd)
{
        idetape_init_pc(pc);
        pc->c[0] = IDETAPE_SPACE_CMD;
        put_unaligned(htonl(count), (unsigned int *) &pc->c[1]);
        pc->c[1] = cmd;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static void idetape_wait_first_stage (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;

        if (tape->first_stage == NULL)
                return;
        spin_lock_irqsave(&tape->spinlock, flags);
        if (tape->active_stage == tape->first_stage)
                idetape_wait_for_request(drive, tape->active_data_request);
        spin_unlock_irqrestore(&tape->spinlock, flags);
}

/*
 *      idetape_add_chrdev_write_request tries to add a character device
 *      originated write request to our pipeline. In case we don't succeed,
 *      we revert to non-pipelined operation mode for this request.
 *
 *      1.      Try to allocate a new pipeline stage.
 *      2.      If we can't, wait for more and more requests to be serviced
 *              and try again each time.
 *      3.      If we still can't allocate a stage, fallback to
 *              non-pipelined operation mode for this request.
 */
static int idetape_add_chrdev_write_request (ide_drive_t *drive, int blocks)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *new_stage;
        unsigned long flags;
        struct request *rq;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 3)
                printk(KERN_INFO "ide-tape: Reached idetape_add_chrdev_write_request\n");
#endif /* IDETAPE_DEBUG_LOG */

        /*
         *      Attempt to allocate a new stage.
         *      Pay special attention to possible race conditions.
         */
        while ((new_stage = idetape_kmalloc_stage(tape)) == NULL) {
                spin_lock_irqsave(&tape->spinlock, flags);
                if (idetape_pipeline_active(tape)) {
                        idetape_wait_for_request(drive, tape->active_data_request);
                        spin_unlock_irqrestore(&tape->spinlock, flags);
                } else {
                        spin_unlock_irqrestore(&tape->spinlock, flags);
                        idetape_insert_pipeline_into_queue(drive);
                        if (idetape_pipeline_active(tape))
                                continue;
                        /*
                         *      Linux is short on memory. Fallback to
                         *      non-pipelined operation mode for this request.
                         */
                        return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, blocks, tape->merge_stage->bh);
                }
        }
        rq = &new_stage->rq;
        idetape_init_rq(rq, REQ_IDETAPE_WRITE);
        /* Doesn't actually matter - We always assume sequential access */
        rq->sector = tape->first_frame_position;
        rq->nr_sectors = rq->current_nr_sectors = blocks;

        idetape_switch_buffers(tape, new_stage);
        idetape_add_stage_tail(drive, new_stage);
        tape->pipeline_head++;
#if USE_IOTRACE
        IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
        calculate_speeds(drive);

        /*
         *      Estimate whether the tape has stopped writing by checking
         *      if our write pipeline is currently empty. If we are not
         *      writing anymore, wait for the pipeline to be full enough
         *      (90%) before starting to service requests, so that we will
         *      be able to keep up with the higher speeds of the tape.
         */
        if (!idetape_pipeline_active(tape)) {
                if (tape->nr_stages >= tape->max_stages * 9 / 10 ||
                    tape->nr_stages >= tape->max_stages - tape->uncontrolled_pipeline_head_speed * 3 * 1024 / tape->tape_block_size) {
                        tape->measure_insert_time = 1;
                        tape->insert_time = jiffies;
                        tape->insert_size = 0;
                        tape->insert_speed = 0;
                        idetape_insert_pipeline_into_queue(drive);
                }
        }
        if (test_and_clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags))
                /* Return a deferred error */
                return -EIO;
        return blocks;
}

/*
 *      idetape_wait_for_pipeline will wait until all pending pipeline
 *      requests are serviced. Typically called on device close.
 */
static void idetape_wait_for_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;

        while (tape->next_stage || idetape_pipeline_active(tape)) {
                idetape_insert_pipeline_into_queue(drive);
                spin_lock_irqsave(&tape->spinlock, flags);
                if (idetape_pipeline_active(tape))
                        idetape_wait_for_request(drive, tape->active_data_request);
                spin_unlock_irqrestore(&tape->spinlock, flags);
        }
}

static void idetape_empty_write_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int blocks, min;
        struct idetape_bh *bh;
        
#if IDETAPE_DEBUG_BUGS
        if (tape->chrdev_direction != idetape_direction_write) {
                printk(KERN_ERR "ide-tape: bug: Trying to empty write pipeline, but we are not writing.\n");
                return;
        }
        if (tape->merge_stage_size > tape->stage_size) {
                printk(KERN_ERR "ide-tape: bug: merge_buffer too big\n");
                tape->merge_stage_size = tape->stage_size;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        if (tape->merge_stage_size) {
                blocks = tape->merge_stage_size / tape->tape_block_size;
                if (tape->merge_stage_size % tape->tape_block_size) {
                        unsigned int i;

                        blocks++;
                        i = tape->tape_block_size - tape->merge_stage_size % tape->tape_block_size;
                        bh = tape->bh->b_reqnext;
                        while (bh) {
                                atomic_set(&bh->b_count, 0);
                                bh = bh->b_reqnext;
                        }
                        bh = tape->bh;
                        while (i) {
                                if (bh == NULL) {

                                        printk(KERN_INFO "ide-tape: bug, bh NULL\n");
                                        break;
                                }
                                min = min(i, (unsigned int)(bh->b_size - atomic_read(&bh->b_count)));
                                memset(bh->b_data + atomic_read(&bh->b_count), 0, min);
                                atomic_add(min, &bh->b_count);
                                i -= min;
                                bh = bh->b_reqnext;
                        }
                }
                (void) idetape_add_chrdev_write_request(drive, blocks);
                tape->merge_stage_size = 0;
        }
        idetape_wait_for_pipeline(drive);
        if (tape->merge_stage != NULL) {
                __idetape_kfree_stage(tape->merge_stage);
                tape->merge_stage = NULL;
        }
        clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
        tape->chrdev_direction = idetape_direction_none;

        /*
         *      On the next backup, perform the feedback loop again.
         *      (I don't want to keep sense information between backups,
         *       as some systems are constantly on, and the system load
         *       can be totally different on the next backup).
         */
        tape->max_stages = tape->min_pipeline;
#if IDETAPE_DEBUG_BUGS
        if (tape->first_stage != NULL ||
            tape->next_stage != NULL ||
            tape->last_stage != NULL ||
            tape->nr_stages != 0) {
                printk(KERN_ERR "ide-tape: ide-tape pipeline bug, "
                        "first_stage %p, next_stage %p, "
                        "last_stage %p, nr_stages %d\n",
                        tape->first_stage, tape->next_stage,
                        tape->last_stage, tape->nr_stages);
        }
#endif /* IDETAPE_DEBUG_BUGS */
}

static void idetape_restart_speed_control (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

        tape->restart_speed_control_req = 0;
        tape->pipeline_head = 0;
        tape->controlled_last_pipeline_head = tape->uncontrolled_last_pipeline_head = 0;
        tape->controlled_previous_pipeline_head = tape->uncontrolled_previous_pipeline_head = 0;
        tape->pipeline_head_speed = tape->controlled_pipeline_head_speed = 5000;
        tape->uncontrolled_pipeline_head_speed = 0;
        tape->controlled_pipeline_head_time = tape->uncontrolled_pipeline_head_time = jiffies;
        tape->controlled_previous_head_time = tape->uncontrolled_previous_head_time = jiffies;
}

static int idetape_initiate_read (ide_drive_t *drive, int max_stages)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *new_stage;
        struct request rq;
        int bytes_read;
        int blocks = tape->capabilities.ctl;

        /* Initialize read operation */
        if (tape->chrdev_direction != idetape_direction_read) {
                if (tape->chrdev_direction == idetape_direction_write) {
                        idetape_empty_write_pipeline(drive);
                        idetape_flush_tape_buffers(drive);
                }
#if IDETAPE_DEBUG_BUGS
                if (tape->merge_stage || tape->merge_stage_size) {
                        printk (KERN_ERR "ide-tape: merge_stage_size should be 0 now\n");
                        tape->merge_stage_size = 0;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                        return -ENOMEM;
                tape->chrdev_direction = idetape_direction_read;

                /*
                 *      Issue a read 0 command to ensure that DSC handshake
                 *      is switched from completion mode to buffer available
                 *      mode.
                 *      No point in issuing this if DSC overlap isn't supported,
                 *      some drives (Seagate STT3401A) will return an error.
                 */
                if (drive->dsc_overlap) {
                        bytes_read = idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, 0, tape->merge_stage->bh);
                        if (bytes_read < 0) {
                                __idetape_kfree_stage(tape->merge_stage);
                                tape->merge_stage = NULL;
                                tape->chrdev_direction = idetape_direction_none;
                                return bytes_read;
                        }
                }
        }
        if (tape->restart_speed_control_req)
                idetape_restart_speed_control(drive);
        idetape_init_rq(&rq, REQ_IDETAPE_READ);
        rq.sector = tape->first_frame_position;
        rq.nr_sectors = rq.current_nr_sectors = blocks;
        if (!test_bit(IDETAPE_PIPELINE_ERROR, &tape->flags) &&
            tape->nr_stages < max_stages) {
                new_stage = idetape_kmalloc_stage(tape);
                while (new_stage != NULL) {
                        new_stage->rq = rq;
                        idetape_add_stage_tail(drive, new_stage);
                        if (tape->nr_stages >= max_stages)
                                break;
                        new_stage = idetape_kmalloc_stage(tape);
                }
        }
        if (!idetape_pipeline_active(tape)) {
                if (tape->nr_pending_stages >= 3 * max_stages / 4) {
                        tape->measure_insert_time = 1;
                        tape->insert_time = jiffies;
                        tape->insert_size = 0;
                        tape->insert_speed = 0;
                        idetape_insert_pipeline_into_queue(drive);
                }
        }
        return 0;
}

/*
 *      idetape_add_chrdev_read_request is called from idetape_chrdev_read
 *      to service a character device read request and add read-ahead
 *      requests to our pipeline.
 */
static int idetape_add_chrdev_read_request (ide_drive_t *drive,int blocks)
{
        idetape_tape_t *tape = drive->driver_data;
        unsigned long flags;
        struct request *rq_ptr;
        int bytes_read;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_add_chrdev_read_request, %d blocks\n", blocks);
#endif /* IDETAPE_DEBUG_LOG */

        /*
         * If we are at a filemark, return a read length of 0
         */
        if (test_bit(IDETAPE_FILEMARK, &tape->flags))
                return 0;

        /*
         * Wait for the next block to be available at the head
         * of the pipeline
         */
        idetape_initiate_read(drive, tape->max_stages);
        if (tape->first_stage == NULL) {
                if (test_bit(IDETAPE_PIPELINE_ERROR, &tape->flags))
                        return 0;
                return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks, tape->merge_stage->bh);
        }
        idetape_wait_first_stage(drive);
        rq_ptr = &tape->first_stage->rq;
        bytes_read = tape->tape_block_size * (rq_ptr->nr_sectors - rq_ptr->current_nr_sectors);
        rq_ptr->nr_sectors = rq_ptr->current_nr_sectors = 0;


        if (rq_ptr->errors == IDETAPE_ERROR_EOD)
                return 0;
        else {
                idetape_switch_buffers(tape, tape->first_stage);
                if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
                        set_bit(IDETAPE_FILEMARK, &tape->flags);
                spin_lock_irqsave(&tape->spinlock, flags);
                idetape_remove_stage_head(drive);
                spin_unlock_irqrestore(&tape->spinlock, flags);
                tape->pipeline_head++;
#if USE_IOTRACE
                IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
                calculate_speeds(drive);
        }
#if IDETAPE_DEBUG_BUGS
        if (bytes_read > blocks * tape->tape_block_size) {
                printk(KERN_ERR "ide-tape: bug: trying to return more bytes than requested\n");
                bytes_read = blocks * tape->tape_block_size;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        return (bytes_read);
}

static void idetape_pad_zeros (ide_drive_t *drive, int bcount)
{
        idetape_tape_t *tape = drive->driver_data;
        struct idetape_bh *bh;
        int blocks;
        
        while (bcount) {
                unsigned int count;

                bh = tape->merge_stage->bh;
                count = min(tape->stage_size, bcount);
                bcount -= count;
                blocks = count / tape->tape_block_size;
                while (count) {
                        atomic_set(&bh->b_count, min(count, (unsigned int)bh->b_size));
                        memset(bh->b_data, 0, atomic_read(&bh->b_count));
                        count -= atomic_read(&bh->b_count);
                        bh = bh->b_reqnext;
                }
                idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, blocks, tape->merge_stage->bh);
        }
}

static int idetape_pipeline_size (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage;
        struct request *rq;
        int size = 0;

        idetape_wait_for_pipeline(drive);
        stage = tape->first_stage;
        while (stage != NULL) {
                rq = &stage->rq;
                size += tape->tape_block_size * (rq->nr_sectors-rq->current_nr_sectors);
                if (rq->errors == IDETAPE_ERROR_FILEMARK)
                        size += tape->tape_block_size;
                stage = stage->next;
        }
        size += tape->merge_stage_size;
        return size;
}

/*
 *      Rewinds the tape to the Beginning Of the current Partition (BOP).
 *
 *      We currently support only one partition.
 */ 
static int idetape_rewind_tape (ide_drive_t *drive)
{
        int retval;
        idetape_pc_t pc;
#if IDETAPE_DEBUG_LOG
        idetape_tape_t *tape = drive->driver_data;
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: Reached idetape_rewind_tape\n");
#endif /* IDETAPE_DEBUG_LOG */  
        
        idetape_create_rewind_cmd(drive, &pc);
        retval = idetape_queue_pc_tail(drive, &pc);
        if (retval)
                return retval;

        idetape_create_read_position_cmd(&pc);
        retval = idetape_queue_pc_tail(drive, &pc);
        if (retval)
                return retval;
        return 0;
}

/*
 *      Our special ide-tape ioctl's.
 *
 *      Currently there aren't any ioctl's.
 *      mtio.h compatible commands should be issued to the character device
 *      interface.
 */
static int idetape_blkdev_ioctl(ide_drive_t *drive, unsigned int cmd, unsigned long arg)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_config_t config;
        void __user *argp = (void __user *)arg;

#if IDETAPE_DEBUG_LOG   
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_blkdev_ioctl\n");
#endif /* IDETAPE_DEBUG_LOG */
        switch (cmd) {
                case 0x0340:
                        if (copy_from_user(&config, argp, sizeof (idetape_config_t)))
                                return -EFAULT;
                        tape->best_dsc_rw_frequency = config.dsc_rw_frequency;
                        tape->max_stages = config.nr_stages;
                        break;
                case 0x0350:
                        config.dsc_rw_frequency = (int) tape->best_dsc_rw_frequency;
                        config.nr_stages = tape->max_stages; 
                        if (copy_to_user(argp, &config, sizeof (idetape_config_t)))
                                return -EFAULT;
                        break;
                default:
                        return -EIO;
        }
        return 0;
}

/*
 *      idetape_space_over_filemarks is now a bit more complicated than just
 *      passing the command to the tape since we may have crossed some
 *      filemarks during our pipelined read-ahead mode.
 *
 *      As a minor side effect, the pipeline enables us to support MTFSFM when
 *      the filemark is in our internal pipeline even if the tape doesn't
 *      support spacing over filemarks in the reverse direction.
 */
static int idetape_space_over_filemarks (ide_drive_t *drive,short mt_op,int mt_count)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        unsigned long flags;
        int retval,count=0;

        if (mt_count == 0)
                return 0;
        if (MTBSF == mt_op || MTBSFM == mt_op) {
                if (!tape->capabilities.sprev)
                        return -EIO;
                mt_count = - mt_count;
        }

        if (tape->chrdev_direction == idetape_direction_read) {
                /*
                 *      We have a read-ahead buffer. Scan it for crossed
                 *      filemarks.
                 */
                tape->merge_stage_size = 0;
                if (test_and_clear_bit(IDETAPE_FILEMARK, &tape->flags))
                        ++count;
                while (tape->first_stage != NULL) {
                        if (count == mt_count) {
                                if (mt_op == MTFSFM)
                                        set_bit(IDETAPE_FILEMARK, &tape->flags);
                                return 0;
                        }
                        spin_lock_irqsave(&tape->spinlock, flags);
                        if (tape->first_stage == tape->active_stage) {
                                /*
                                 *      We have reached the active stage in the read pipeline.
                                 *      There is no point in allowing the drive to continue
                                 *      reading any farther, so we stop the pipeline.
                                 *
                                 *      This section should be moved to a separate subroutine,
                                 *      because a similar function is performed in
                                 *      __idetape_discard_read_pipeline(), for example.
                                 */
                                tape->next_stage = NULL;
                                spin_unlock_irqrestore(&tape->spinlock, flags);
                                idetape_wait_first_stage(drive);
                                tape->next_stage = tape->first_stage->next;
                        } else
                                spin_unlock_irqrestore(&tape->spinlock, flags);
                        if (tape->first_stage->rq.errors == IDETAPE_ERROR_FILEMARK)
                                ++count;
                        idetape_remove_stage_head(drive);
                }
                idetape_discard_read_pipeline(drive, 0);
        }

        /*
         *      The filemark was not found in our internal pipeline.
         *      Now we can issue the space command.
         */
        switch (mt_op) {
                case MTFSF:
                case MTBSF:
                        idetape_create_space_cmd(&pc,mt_count-count,IDETAPE_SPACE_OVER_FILEMARK);
                        return (idetape_queue_pc_tail(drive, &pc));
                case MTFSFM:
                case MTBSFM:
                        if (!tape->capabilities.sprev)
                                return (-EIO);
                        retval = idetape_space_over_filemarks(drive, MTFSF, mt_count-count);
                        if (retval) return (retval);
                        count = (MTBSFM == mt_op ? 1 : -1);
                        return (idetape_space_over_filemarks(drive, MTFSF, count));
                default:
                        printk(KERN_ERR "ide-tape: MTIO operation %d not supported\n",mt_op);
                        return (-EIO);
        }
}


/*
 *      Our character device read / write functions.
 *
 *      The tape is optimized to maximize throughput when it is transferring
 *      an integral number of the "continuous transfer limit", which is
 *      a parameter of the specific tape (26 KB on my particular tape).
 *      (32 kB for Onstream)
 *
 *      As of version 1.3 of the driver, the character device provides an
 *      abstract continuous view of the media - any mix of block sizes (even 1
 *      byte) on the same backup/restore procedure is supported. The driver
 *      will internally convert the requests to the recommended transfer unit,
 *      so that an unmatch between the user's block size to the recommended
 *      size will only result in a (slightly) increased driver overhead, but
 *      will no longer hit performance.
 *      This is not applicable to Onstream.
 */
static ssize_t idetape_chrdev_read (struct file *file, char __user *buf,
                                    size_t count, loff_t *ppos)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        ssize_t bytes_read,temp, actually_read = 0, rc;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 3)
                printk(KERN_INFO "ide-tape: Reached idetape_chrdev_read, count %Zd\n", count);
#endif /* IDETAPE_DEBUG_LOG */

        if (tape->chrdev_direction != idetape_direction_read) {
                if (test_bit(IDETAPE_DETECT_BS, &tape->flags))
                        if (count > tape->tape_block_size &&
                            (count % tape->tape_block_size) == 0)
                                tape->user_bs_factor = count / tape->tape_block_size;
        }
        if ((rc = idetape_initiate_read(drive, tape->max_stages)) < 0)
                return rc;
        if (count == 0)
                return (0);
        if (tape->merge_stage_size) {
                actually_read = min((unsigned int)(tape->merge_stage_size), (unsigned int)count);
                idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read);
                buf += actually_read;
                tape->merge_stage_size -= actually_read;
                count -= actually_read;
        }
        while (count >= tape->stage_size) {
                bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
                if (bytes_read <= 0)
                        goto finish;
                idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read);
                buf += bytes_read;
                count -= bytes_read;
                actually_read += bytes_read;
        }
        if (count) {
                bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
                if (bytes_read <= 0)
                        goto finish;
                temp = min((unsigned long)count, (unsigned long)bytes_read);
                idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp);
                actually_read += temp;
                tape->merge_stage_size = bytes_read-temp;
        }
finish:
        if (!actually_read && test_bit(IDETAPE_FILEMARK, &tape->flags)) {
#if IDETAPE_DEBUG_LOG
                if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: %s: spacing over filemark\n", tape->name);
#endif
                idetape_space_over_filemarks(drive, MTFSF, 1);
                return 0;
        }
        return actually_read;
}

static ssize_t idetape_chrdev_write (struct file *file, const char __user *buf,
                                     size_t count, loff_t *ppos)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        ssize_t retval, actually_written = 0;

        /* The drive is write protected. */
        if (tape->write_prot)
                return -EACCES;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 3)
                printk(KERN_INFO "ide-tape: Reached idetape_chrdev_write, "
                        "count %Zd\n", count);
#endif /* IDETAPE_DEBUG_LOG */

        /* Initialize write operation */
        if (tape->chrdev_direction != idetape_direction_write) {
                if (tape->chrdev_direction == idetape_direction_read)
                        idetape_discard_read_pipeline(drive, 1);
#if IDETAPE_DEBUG_BUGS
                if (tape->merge_stage || tape->merge_stage_size) {
                        printk(KERN_ERR "ide-tape: merge_stage_size "
                                "should be 0 now\n");
                        tape->merge_stage_size = 0;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                        return -ENOMEM;
                tape->chrdev_direction = idetape_direction_write;
                idetape_init_merge_stage(tape);

                /*
                 *      Issue a write 0 command to ensure that DSC handshake
                 *      is switched from completion mode to buffer available
                 *      mode.
                 *      No point in issuing this if DSC overlap isn't supported,
                 *      some drives (Seagate STT3401A) will return an error.
                 */
                if (drive->dsc_overlap) {
                        retval = idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, 0, tape->merge_stage->bh);
                        if (retval < 0) {
                                __idetape_kfree_stage(tape->merge_stage);
                                tape->merge_stage = NULL;
                                tape->chrdev_direction = idetape_direction_none;
                                return retval;
                        }
                }
        }
        if (count == 0)
                return (0);
        if (tape->restart_speed_control_req)
                idetape_restart_speed_control(drive);
        if (tape->merge_stage_size) {
#if IDETAPE_DEBUG_BUGS
                if (tape->merge_stage_size >= tape->stage_size) {
                        printk(KERN_ERR "ide-tape: bug: merge buffer too big\n");
                        tape->merge_stage_size = 0;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                actually_written = min((unsigned int)(tape->stage_size - tape->merge_stage_size), (unsigned int)count);
                idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written);
                buf += actually_written;
                tape->merge_stage_size += actually_written;
                count -= actually_written;

                if (tape->merge_stage_size == tape->stage_size) {
                        tape->merge_stage_size = 0;
                        retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
                        if (retval <= 0)
                                return (retval);
                }
        }
        while (count >= tape->stage_size) {
                idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size);
                buf += tape->stage_size;
                count -= tape->stage_size;
                retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
                actually_written += tape->stage_size;
                if (retval <= 0)
                        return (retval);
        }
        if (count) {
                actually_written += count;
                idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count);
                tape->merge_stage_size += count;
        }
        return (actually_written);
}

static int idetape_write_filemark (ide_drive_t *drive)
{
        idetape_pc_t pc;

        /* Write a filemark */
        idetape_create_write_filemark_cmd(drive, &pc, 1);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: Couldn't write a filemark\n");
                return -EIO;
        }
        return 0;
}

/*
 *      idetape_mtioctop is called from idetape_chrdev_ioctl when
 *      the general mtio MTIOCTOP ioctl is requested.
 *
 *      We currently support the following mtio.h operations:
 *
 *      MTFSF   -       Space over mt_count filemarks in the positive direction.
 *                      The tape is positioned after the last spaced filemark.
 *
 *      MTFSFM  -       Same as MTFSF, but the tape is positioned before the
 *                      last filemark.
 *
 *      MTBSF   -       Steps background over mt_count filemarks, tape is
 *                      positioned before the last filemark.
 *
 *      MTBSFM  -       Like MTBSF, only tape is positioned after the last filemark.
 *
 *      Note:
 *
 *              MTBSF and MTBSFM are not supported when the tape doesn't
 *              support spacing over filemarks in the reverse direction.
 *              In this case, MTFSFM is also usually not supported (it is
 *              supported in the rare case in which we crossed the filemark
 *              during our read-ahead pipelined operation mode).
 *              
 *      MTWEOF  -       Writes mt_count filemarks. Tape is positioned after
 *                      the last written filemark.
 *
 *      MTREW   -       Rewinds tape.
 *
 *      MTLOAD  -       Loads the tape.
 *
 *      MTOFFL  -       Puts the tape drive "Offline": Rewinds the tape and
 *      MTUNLOAD        prevents further access until the media is replaced.
 *
 *      MTNOP   -       Flushes tape buffers.
 *
 *      MTRETEN -       Retension media. This typically consists of one end
 *                      to end pass on the media.
 *
 *      MTEOM   -       Moves to the end of recorded data.
 *
 *      MTERASE -       Erases tape.
 *
 *      MTSETBLK -      Sets the user block size to mt_count bytes. If
 *                      mt_count is 0, we will attempt to autodetect
 *                      the block size.
 *
 *      MTSEEK  -       Positions the tape in a specific block number, where
 *                      each block is assumed to contain which user_block_size
 *                      bytes.
 *
 *      MTSETPART -     Switches to another tape partition.
 *
 *      MTLOCK -        Locks the tape door.
 *
 *      MTUNLOCK -      Unlocks the tape door.
 *
 *      The following commands are currently not supported:
 *
 *      MTFSS, MTBSS, MTWSM, MTSETDENSITY,
 *      MTSETDRVBUFFER, MT_ST_BOOLEANS, MT_ST_WRITE_THRESHOLD.
 */
static int idetape_mtioctop (ide_drive_t *drive,short mt_op,int mt_count)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        int i,retval;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 1)
                printk(KERN_INFO "ide-tape: Handling MTIOCTOP ioctl: "
                        "mt_op=%d, mt_count=%d\n", mt_op, mt_count);
#endif /* IDETAPE_DEBUG_LOG */
        /*
         *      Commands which need our pipelined read-ahead stages.
         */
        switch (mt_op) {
                case MTFSF:
                case MTFSFM:
                case MTBSF:
                case MTBSFM:
                        if (!mt_count)
                                return (0);
                        return (idetape_space_over_filemarks(drive,mt_op,mt_count));
                default:
                        break;
        }
        switch (mt_op) {
                case MTWEOF:
                        if (tape->write_prot)
                                return -EACCES;
                        idetape_discard_read_pipeline(drive, 1);
                        for (i = 0; i < mt_count; i++) {
                                retval = idetape_write_filemark(drive);
                                if (retval)
                                        return retval;
                        }
                        return (0);
                case MTREW:
                        idetape_discard_read_pipeline(drive, 0);
                        if (idetape_rewind_tape(drive))
                                return -EIO;
                        return 0;
                case MTLOAD:
                        idetape_discard_read_pipeline(drive, 0);
                        idetape_create_load_unload_cmd(drive, &pc, IDETAPE_LU_LOAD_MASK);
                        return (idetape_queue_pc_tail(drive, &pc));
                case MTUNLOAD:
                case MTOFFL:
                        /*
                         * If door is locked, attempt to unlock before
                         * attempting to eject.
                         */
                        if (tape->door_locked) {
                                if (idetape_create_prevent_cmd(drive, &pc, 0))
                                        if (!idetape_queue_pc_tail(drive, &pc))
                                                tape->door_locked = DOOR_UNLOCKED;
                        }
                        idetape_discard_read_pipeline(drive, 0);
                        idetape_create_load_unload_cmd(drive, &pc,!IDETAPE_LU_LOAD_MASK);
                        retval = idetape_queue_pc_tail(drive, &pc);
                        if (!retval)
                                clear_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags);
                        return retval;
                case MTNOP:
                        idetape_discard_read_pipeline(drive, 0);
                        return (idetape_flush_tape_buffers(drive));
                case MTRETEN:
                        idetape_discard_read_pipeline(drive, 0);
                        idetape_create_load_unload_cmd(drive, &pc,IDETAPE_LU_RETENSION_MASK | IDETAPE_LU_LOAD_MASK);
                        return (idetape_queue_pc_tail(drive, &pc));
                case MTEOM:
                        idetape_create_space_cmd(&pc, 0, IDETAPE_SPACE_TO_EOD);
                        return (idetape_queue_pc_tail(drive, &pc));
                case MTERASE:
                        (void) idetape_rewind_tape(drive);
                        idetape_create_erase_cmd(&pc);
                        return (idetape_queue_pc_tail(drive, &pc));
                case MTSETBLK:
                        if (mt_count) {
                                if (mt_count < tape->tape_block_size || mt_count % tape->tape_block_size)
                                        return -EIO;
                                tape->user_bs_factor = mt_count / tape->tape_block_size;
                                clear_bit(IDETAPE_DETECT_BS, &tape->flags);
                        } else
                                set_bit(IDETAPE_DETECT_BS, &tape->flags);
                        return 0;
                case MTSEEK:
                        idetape_discard_read_pipeline(drive, 0);
                        return idetape_position_tape(drive, mt_count * tape->user_bs_factor, tape->partition, 0);
                case MTSETPART:
                        idetape_discard_read_pipeline(drive, 0);
                        return (idetape_position_tape(drive, 0, mt_count, 0));
                case MTFSR:
                case MTBSR:
                case MTLOCK:
                        if (!idetape_create_prevent_cmd(drive, &pc, 1))
                                return 0;
                        retval = idetape_queue_pc_tail(drive, &pc);
                        if (retval) return retval;
                        tape->door_locked = DOOR_EXPLICITLY_LOCKED;
                        return 0;
                case MTUNLOCK:
                        if (!idetape_create_prevent_cmd(drive, &pc, 0))
                                return 0;
                        retval = idetape_queue_pc_tail(drive, &pc);
                        if (retval) return retval;
                        tape->door_locked = DOOR_UNLOCKED;
                        return 0;
                default:
                        printk(KERN_ERR "ide-tape: MTIO operation %d not "
                                "supported\n", mt_op);
                        return (-EIO);
        }
}

/*
 *      Our character device ioctls.
 *
 *      General mtio.h magnetic io commands are supported here, and not in
 *      the corresponding block interface.
 *
 *      The following ioctls are supported:
 *
 *      MTIOCTOP -      Refer to idetape_mtioctop for detailed description.
 *
 *      MTIOCGET -      The mt_dsreg field in the returned mtget structure
 *                      will be set to (user block size in bytes <<
 *                      MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK.
 *
 *                      The mt_blkno is set to the current user block number.
 *                      The other mtget fields are not supported.
 *
 *      MTIOCPOS -      The current tape "block position" is returned. We
 *                      assume that each block contains user_block_size
 *                      bytes.
 *
 *      Our own ide-tape ioctls are supported on both interfaces.
 */
static int idetape_chrdev_ioctl (struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        struct mtop mtop;
        struct mtget mtget;
        struct mtpos mtpos;
        int block_offset = 0, position = tape->first_frame_position;
        void __user *argp = (void __user *)arg;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 3)
                printk(KERN_INFO "ide-tape: Reached idetape_chrdev_ioctl, "
                        "cmd=%u\n", cmd);
#endif /* IDETAPE_DEBUG_LOG */

        tape->restart_speed_control_req = 1;
        if (tape->chrdev_direction == idetape_direction_write) {
                idetape_empty_write_pipeline(drive);
                idetape_flush_tape_buffers(drive);
        }
        if (cmd == MTIOCGET || cmd == MTIOCPOS) {
                block_offset = idetape_pipeline_size(drive) / (tape->tape_block_size * tape->user_bs_factor);
                if ((position = idetape_read_position(drive)) < 0)
                        return -EIO;
        }
        switch (cmd) {
                case MTIOCTOP:
                        if (copy_from_user(&mtop, argp, sizeof (struct mtop)))
                                return -EFAULT;
                        return (idetape_mtioctop(drive,mtop.mt_op,mtop.mt_count));
                case MTIOCGET:
                        memset(&mtget, 0, sizeof (struct mtget));
                        mtget.mt_type = MT_ISSCSI2;
                        mtget.mt_blkno = position / tape->user_bs_factor - block_offset;
                        mtget.mt_dsreg = ((tape->tape_block_size * tape->user_bs_factor) << MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK;
                        if (tape->drv_write_prot) {
                                mtget.mt_gstat |= GMT_WR_PROT(0xffffffff);
                        }
                        if (copy_to_user(argp, &mtget, sizeof(struct mtget)))
                                return -EFAULT;
                        return 0;
                case MTIOCPOS:
                        mtpos.mt_blkno = position / tape->user_bs_factor - block_offset;
                        if (copy_to_user(argp, &mtpos, sizeof(struct mtpos)))
                                return -EFAULT;
                        return 0;
                default:
                        if (tape->chrdev_direction == idetape_direction_read)
                                idetape_discard_read_pipeline(drive, 1);
                        return idetape_blkdev_ioctl(drive, cmd, arg);
        }
}

static void idetape_get_blocksize_from_block_descriptor(ide_drive_t *drive);

/*
 *      Our character device open function.
 */
static int idetape_chrdev_open (struct inode *inode, struct file *filp)
{
        unsigned int minor = iminor(inode), i = minor & ~0xc0;
        ide_drive_t *drive;
        idetape_tape_t *tape;
        idetape_pc_t pc;
        int retval;

        /*
         * We really want to do nonseekable_open(inode, filp); here, but some
         * versions of tar incorrectly call lseek on tapes and bail out if that
         * fails.  So we disallow pread() and pwrite(), but permit lseeks.
         */
        filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);

#if IDETAPE_DEBUG_LOG
        printk(KERN_INFO "ide-tape: Reached idetape_chrdev_open\n");
#endif /* IDETAPE_DEBUG_LOG */
        
        if (i >= MAX_HWIFS * MAX_DRIVES)
                return -ENXIO;

        if (!(tape = ide_tape_chrdev_get(i)))
                return -ENXIO;

        drive = tape->drive;

        filp->private_data = tape;

        if (test_and_set_bit(IDETAPE_BUSY, &tape->flags)) {
                retval = -EBUSY;
                goto out_put_tape;
        }

        retval = idetape_wait_ready(drive, 60 * HZ);
        if (retval) {
                clear_bit(IDETAPE_BUSY, &tape->flags);
                printk(KERN_ERR "ide-tape: %s: drive not ready\n", tape->name);
                goto out_put_tape;
        }

        idetape_read_position(drive);
        if (!test_bit(IDETAPE_ADDRESS_VALID, &tape->flags))
                (void)idetape_rewind_tape(drive);

        if (tape->chrdev_direction != idetape_direction_read)
                clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);

        /* Read block size and write protect status from drive. */
        idetape_get_blocksize_from_block_descriptor(drive);

        /* Set write protect flag if device is opened as read-only. */
        if ((filp->f_flags & O_ACCMODE) == O_RDONLY)
                tape->write_prot = 1;
        else
                tape->write_prot = tape->drv_write_prot;

        /* Make sure drive isn't write protected if user wants to write. */
        if (tape->write_prot) {
                if ((filp->f_flags & O_ACCMODE) == O_WRONLY ||
                    (filp->f_flags & O_ACCMODE) == O_RDWR) {
                        clear_bit(IDETAPE_BUSY, &tape->flags);
                        retval = -EROFS;
                        goto out_put_tape;
                }
        }

        /*
         * Lock the tape drive door so user can't eject.
         */
        if (tape->chrdev_direction == idetape_direction_none) {
                if (idetape_create_prevent_cmd(drive, &pc, 1)) {
                        if (!idetape_queue_pc_tail(drive, &pc)) {
                                if (tape->door_locked != DOOR_EXPLICITLY_LOCKED)
                                        tape->door_locked = DOOR_LOCKED;
                        }
                }
        }
        idetape_restart_speed_control(drive);
        tape->restart_speed_control_req = 0;
        return 0;

out_put_tape:
        ide_tape_put(tape);
        return retval;
}

static void idetape_write_release (ide_drive_t *drive, unsigned int minor)
{
        idetape_tape_t *tape = drive->driver_data;

        idetape_empty_write_pipeline(drive);
        tape->merge_stage = __idetape_kmalloc_stage(tape, 1, 0);
        if (tape->merge_stage != NULL) {
                idetape_pad_zeros(drive, tape->tape_block_size * (tape->user_bs_factor - 1));
                __idetape_kfree_stage(tape->merge_stage);
                tape->merge_stage = NULL;
        }
        idetape_write_filemark(drive);
        idetape_flush_tape_buffers(drive);
        idetape_flush_tape_buffers(drive);
}

/*
 *      Our character device release function.
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp)
{
        struct ide_tape_obj *tape = ide_tape_f(filp);
        ide_drive_t *drive = tape->drive;
        idetape_pc_t pc;
        unsigned int minor = iminor(inode);

        lock_kernel();
        tape = drive->driver_data;
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 3)
                printk(KERN_INFO "ide-tape: Reached idetape_chrdev_release\n");
#endif /* IDETAPE_DEBUG_LOG */

        if (tape->chrdev_direction == idetape_direction_write)
                idetape_write_release(drive, minor);
        if (tape->chrdev_direction == idetape_direction_read) {
                if (minor < 128)
                        idetape_discard_read_pipeline(drive, 1);
                else
                        idetape_wait_for_pipeline(drive);
        }
        if (tape->cache_stage != NULL) {
                __idetape_kfree_stage(tape->cache_stage);
                tape->cache_stage = NULL;
        }
        if (minor < 128 && test_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags))
                (void) idetape_rewind_tape(drive);
        if (tape->chrdev_direction == idetape_direction_none) {
                if (tape->door_locked == DOOR_LOCKED) {
                        if (idetape_create_prevent_cmd(drive, &pc, 0)) {
                                if (!idetape_queue_pc_tail(drive, &pc))
                                        tape->door_locked = DOOR_UNLOCKED;
                        }
                }
        }
        clear_bit(IDETAPE_BUSY, &tape->flags);
        ide_tape_put(tape);
        unlock_kernel();
        return 0;
}

/*
 *      idetape_identify_device is called to check the contents of the
 *      ATAPI IDENTIFY command results. We return:
 *
 *      1       If the tape can be supported by us, based on the information
 *              we have so far.
 *
 *      0       If this tape driver is not currently supported by us.
 */
static int idetape_identify_device (ide_drive_t *drive)
{
        struct idetape_id_gcw gcw;
        struct hd_driveid *id = drive->id;
#if IDETAPE_DEBUG_INFO
        unsigned short mask,i;
#endif /* IDETAPE_DEBUG_INFO */

        if (drive->id_read == 0)
                return 1;

        *((unsigned short *) &gcw) = id->config;

#if IDETAPE_DEBUG_INFO
        printk(KERN_INFO "ide-tape: Dumping ATAPI Identify Device tape parameters\n");
        printk(KERN_INFO "ide-tape: Protocol Type: ");
        switch (gcw.protocol) {
                case 0: case 1: printk("ATA\n");break;
                case 2: printk("ATAPI\n");break;
                case 3: printk("Reserved (Unknown to ide-tape)\n");break;
        }
        printk(KERN_INFO "ide-tape: Device Type: %x - ",gcw.device_type);       
        switch (gcw.device_type) {
                case 0: printk("Direct-access Device\n");break;
                case 1: printk("Streaming Tape Device\n");break;
                case 2: case 3: case 4: printk("Reserved\n");break;
                case 5: printk("CD-ROM Device\n");break;
                case 6: printk("Reserved\n");
                case 7: printk("Optical memory Device\n");break;
                case 0x1f: printk("Unknown or no Device type\n");break;
                default: printk("Reserved\n");
        }
        printk(KERN_INFO "ide-tape: Removable: %s",gcw.removable ? "Yes\n":"No\n");     
        printk(KERN_INFO "ide-tape: Command Packet DRQ Type: ");
        switch (gcw.drq_type) {
                case 0: printk("Microprocessor DRQ\n");break;
                case 1: printk("Interrupt DRQ\n");break;
                case 2: printk("Accelerated DRQ\n");break;
                case 3: printk("Reserved\n");break;
        }
        printk(KERN_INFO "ide-tape: Command Packet Size: ");
        switch (gcw.packet_size) {
                case 0: printk("12 bytes\n");break;
                case 1: printk("16 bytes\n");break;
                default: printk("Reserved\n");break;
        }
        printk(KERN_INFO "ide-tape: Model: %.40s\n",id->model);
        printk(KERN_INFO "ide-tape: Firmware Revision: %.8s\n",id->fw_rev);
        printk(KERN_INFO "ide-tape: Serial Number: %.20s\n",id->serial_no);
        printk(KERN_INFO "ide-tape: Write buffer size: %d bytes\n",id->buf_size*512);
        printk(KERN_INFO "ide-tape: DMA: %s",id->capability & 0x01 ? "Yes\n":"No\n");
        printk(KERN_INFO "ide-tape: LBA: %s",id->capability & 0x02 ? "Yes\n":"No\n");
        printk(KERN_INFO "ide-tape: IORDY can be disabled: %s",id->capability & 0x04 ? "Yes\n":"No\n");
        printk(KERN_INFO "ide-tape: IORDY supported: %s",id->capability & 0x08 ? "Yes\n":"Unknown\n");
        printk(KERN_INFO "ide-tape: ATAPI overlap supported: %s",id->capability & 0x20 ? "Yes\n":"No\n");
        printk(KERN_INFO "ide-tape: PIO Cycle Timing Category: %d\n",id->tPIO);
        printk(KERN_INFO "ide-tape: DMA Cycle Timing Category: %d\n",id->tDMA);
        printk(KERN_INFO "ide-tape: Single Word DMA supported modes: ");
        for (i=0,mask=1;i<8;i++,mask=mask << 1) {
                if (id->dma_1word & mask)
                        printk("%d ",i);
                if (id->dma_1word & (mask << 8))
                        printk("(active) ");
        }
        printk("\n");
        printk(KERN_INFO "ide-tape: Multi Word DMA supported modes: ");
        for (i=0,mask=1;i<8;i++,mask=mask << 1) {
                if (id->dma_mword & mask)
                        printk("%d ",i);
                if (id->dma_mword & (mask << 8))
                        printk("(active) ");
        }
        printk("\n");
        if (id->field_valid & 0x0002) {
                printk(KERN_INFO "ide-tape: Enhanced PIO Modes: %s\n",
                        id->eide_pio_modes & 1 ? "Mode 3":"None");
                printk(KERN_INFO "ide-tape: Minimum Multi-word DMA cycle per word: ");
                if (id->eide_dma_min == 0)
                        printk("Not supported\n");
                else
                        printk("%d ns\n",id->eide_dma_min);

                printk(KERN_INFO "ide-tape: Manufacturer\'s Recommended Multi-word cycle: ");
                if (id->eide_dma_time == 0)
                        printk("Not supported\n");
                else
                        printk("%d ns\n",id->eide_dma_time);

                printk(KERN_INFO "ide-tape: Minimum PIO cycle without IORDY: ");
                if (id->eide_pio == 0)
                        printk("Not supported\n");
                else
                        printk("%d ns\n",id->eide_pio);

                printk(KERN_INFO "ide-tape: Minimum PIO cycle with IORDY: ");
                if (id->eide_pio_iordy == 0)
                        printk("Not supported\n");
                else
                        printk("%d ns\n",id->eide_pio_iordy);
                
        } else
                printk(KERN_INFO "ide-tape: According to the device, fields 64-70 are not valid.\n");
#endif /* IDETAPE_DEBUG_INFO */

        /* Check that we can support this device */

        if (gcw.protocol !=2 )
                printk(KERN_ERR "ide-tape: Protocol is not ATAPI\n");
        else if (gcw.device_type != 1)
                printk(KERN_ERR "ide-tape: Device type is not set to tape\n");
        else if (!gcw.removable)
                printk(KERN_ERR "ide-tape: The removable flag is not set\n");
        else if (gcw.packet_size != 0) {
                printk(KERN_ERR "ide-tape: Packet size is not 12 bytes long\n");
                if (gcw.packet_size == 1)
                        printk(KERN_ERR "ide-tape: Sorry, padding to 16 bytes is still not supported\n");
        } else
                return 1;
        return 0;
}

/*
 * Use INQUIRY to get the firmware revision
 */
static void idetape_get_inquiry_results (ide_drive_t *drive)
{
        char *r;
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        idetape_inquiry_result_t *inquiry;
        
        idetape_create_inquiry_cmd(&pc);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: %s: can't get INQUIRY results\n", tape->name);
                return;
        }
        inquiry = (idetape_inquiry_result_t *) pc.buffer;
        memcpy(tape->vendor_id, inquiry->vendor_id, 8);
        memcpy(tape->product_id, inquiry->product_id, 16);
        memcpy(tape->firmware_revision, inquiry->revision_level, 4);
        ide_fixstring(tape->vendor_id, 10, 0);
        ide_fixstring(tape->product_id, 18, 0);
        ide_fixstring(tape->firmware_revision, 6, 0);
        r = tape->firmware_revision;
        if (*(r + 1) == '.')
                tape->firmware_revision_num = (*r - '0') * 100 + (*(r + 2) - '0') * 10 + *(r + 3) - '0';
        printk(KERN_INFO "ide-tape: %s <-> %s: %s %s rev %s\n", drive->name, tape->name, tape->vendor_id, tape->product_id, tape->firmware_revision);
}

/*
 *      idetape_get_mode_sense_results asks the tape about its various
 *      parameters. In particular, we will adjust our data transfer buffer
 *      size to the recommended value as returned by the tape.
 */
static void idetape_get_mode_sense_results (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        idetape_mode_parameter_header_t *header;
        idetape_capabilities_page_t *capabilities;
        
        idetape_create_mode_sense_cmd(&pc, IDETAPE_CAPABILITIES_PAGE);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: Can't get tape parameters - assuming some default values\n");
                tape->tape_block_size = 512;
                tape->capabilities.ctl = 52;
                tape->capabilities.speed = 450;
                tape->capabilities.buffer_size = 6 * 52;
                return;
        }
        header = (idetape_mode_parameter_header_t *) pc.buffer;
        capabilities = (idetape_capabilities_page_t *) (pc.buffer + sizeof(idetape_mode_parameter_header_t) + header->bdl);

        capabilities->max_speed = ntohs(capabilities->max_speed);
        capabilities->ctl = ntohs(capabilities->ctl);
        capabilities->speed = ntohs(capabilities->speed);
        capabilities->buffer_size = ntohs(capabilities->buffer_size);

        if (!capabilities->speed) {
                printk(KERN_INFO "ide-tape: %s: overriding capabilities->speed (assuming 650KB/sec)\n", drive->name);
                capabilities->speed = 650;
        }
        if (!capabilities->max_speed) {
                printk(KERN_INFO "ide-tape: %s: overriding capabilities->max_speed (assuming 650KB/sec)\n", drive->name);
                capabilities->max_speed = 650;
        }

        tape->capabilities = *capabilities;             /* Save us a copy */
        if (capabilities->blk512)
                tape->tape_block_size = 512;
        else if (capabilities->blk1024)
                tape->tape_block_size = 1024;

#if IDETAPE_DEBUG_INFO
        printk(KERN_INFO "ide-tape: Dumping the results of the MODE SENSE packet command\n");
        printk(KERN_INFO "ide-tape: Mode Parameter Header:\n");
        printk(KERN_INFO "ide-tape: Mode Data Length - %d\n",header->mode_data_length);
        printk(KERN_INFO "ide-tape: Medium Type - %d\n",header->medium_type);
        printk(KERN_INFO "ide-tape: Device Specific Parameter - %d\n",header->dsp);
        printk(KERN_INFO "ide-tape: Block Descriptor Length - %d\n",header->bdl);
        
        printk(KERN_INFO "ide-tape: Capabilities and Mechanical Status Page:\n");
        printk(KERN_INFO "ide-tape: Page code - %d\n",capabilities->page_code);
        printk(KERN_INFO "ide-tape: Page length - %d\n",capabilities->page_length);
        printk(KERN_INFO "ide-tape: Read only - %s\n",capabilities->ro ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports reverse space - %s\n",capabilities->sprev ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports erase initiated formatting - %s\n",capabilities->efmt ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports QFA two Partition format - %s\n",capabilities->qfa ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports locking the medium - %s\n",capabilities->lock ? "Yes":"No");
        printk(KERN_INFO "ide-tape: The volume is currently locked - %s\n",capabilities->locked ? "Yes":"No");
        printk(KERN_INFO "ide-tape: The device defaults in the prevent state - %s\n",capabilities->prevent ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports ejecting the medium - %s\n",capabilities->eject ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports error correction - %s\n",capabilities->ecc ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports data compression - %s\n",capabilities->cmprs ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports 512 bytes block size - %s\n",capabilities->blk512 ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports 1024 bytes block size - %s\n",capabilities->blk1024 ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Supports 32768 bytes block size / Restricted byte count for PIO transfers - %s\n",capabilities->blk32768 ? "Yes":"No");
        printk(KERN_INFO "ide-tape: Maximum supported speed in KBps - %d\n",capabilities->max_speed);
        printk(KERN_INFO "ide-tape: Continuous transfer limits in blocks - %d\n",capabilities->ctl);
        printk(KERN_INFO "ide-tape: Current speed in KBps - %d\n",capabilities->speed); 
        printk(KERN_INFO "ide-tape: Buffer size - %d\n",capabilities->buffer_size*512);
#endif /* IDETAPE_DEBUG_INFO */
}

/*
 *      ide_get_blocksize_from_block_descriptor does a mode sense page 0 with block descriptor
 *      and if it succeeds sets the tape block size with the reported value
 */
static void idetape_get_blocksize_from_block_descriptor(ide_drive_t *drive)
{

        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        idetape_mode_parameter_header_t *header;
        idetape_parameter_block_descriptor_t *block_descrp;
        
        idetape_create_mode_sense_cmd(&pc, IDETAPE_BLOCK_DESCRIPTOR);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: Can't get block descriptor\n");
                if (tape->tape_block_size == 0) {
                        printk(KERN_WARNING "ide-tape: Cannot deal with zero block size, assume 32k\n");
                        tape->tape_block_size =  32768;
                }
                return;
        }
        header = (idetape_mode_parameter_header_t *) pc.buffer;
        block_descrp = (idetape_parameter_block_descriptor_t *) (pc.buffer + sizeof(idetape_mode_parameter_header_t));
        tape->tape_block_size =( block_descrp->length[0]<<16) + (block_descrp->length[1]<<8) + block_descrp->length[2];
        tape->drv_write_prot = (header->dsp & 0x80) >> 7;

#if IDETAPE_DEBUG_INFO
        printk(KERN_INFO "ide-tape: Adjusted block size - %d\n", tape->tape_block_size);
#endif /* IDETAPE_DEBUG_INFO */
}
static void idetape_add_settings (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

/*
 *                      drive   setting name    read/write      ioctl   ioctl           data type       min                     max                     mul_factor                      div_factor                      data pointer                            set function
 */
        ide_add_setting(drive,  "buffer",       SETTING_READ,   -1,     -1,             TYPE_SHORT,     0,                      0xffff,                 1,                              2,                              &tape->capabilities.buffer_size,        NULL);
        ide_add_setting(drive,  "pipeline_min", SETTING_RW,     -1,     -1,             TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->min_pipeline,                    NULL);
        ide_add_setting(drive,  "pipeline",     SETTING_RW,     -1,     -1,             TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->max_stages,                      NULL);
        ide_add_setting(drive,  "pipeline_max", SETTING_RW,     -1,     -1,             TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->max_pipeline,                    NULL);
        ide_add_setting(drive,  "pipeline_used",SETTING_READ,   -1,     -1,             TYPE_INT,       0,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->nr_stages,                       NULL);
        ide_add_setting(drive,  "pipeline_pending",SETTING_READ,-1,     -1,             TYPE_INT,       0,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->nr_pending_stages,               NULL);
        ide_add_setting(drive,  "speed",        SETTING_READ,   -1,     -1,             TYPE_SHORT,     0,                      0xffff,                 1,                              1,                              &tape->capabilities.speed,              NULL);
        ide_add_setting(drive,  "stage",        SETTING_READ,   -1,     -1,             TYPE_INT,       0,                      0xffff,                 1,                              1024,                           &tape->stage_size,                      NULL);
        ide_add_setting(drive,  "tdsc",         SETTING_RW,     -1,     -1,             TYPE_INT,       IDETAPE_DSC_RW_MIN,     IDETAPE_DSC_RW_MAX,     1000,                           HZ,                             &tape->best_dsc_rw_frequency,           NULL);
        ide_add_setting(drive,  "dsc_overlap",  SETTING_RW,     -1,     -1,             TYPE_BYTE,      0,                      1,                      1,                              1,                              &drive->dsc_overlap,                    NULL);
        ide_add_setting(drive,  "pipeline_head_speed_c",SETTING_READ,   -1,     -1,     TYPE_INT,       0,                      0xffff,                 1,                              1,                              &tape->controlled_pipeline_head_speed,  NULL);
        ide_add_setting(drive,  "pipeline_head_speed_u",SETTING_READ,   -1,     -1,     TYPE_INT,       0,                      0xffff,                 1,                              1,                              &tape->uncontrolled_pipeline_head_speed,        NULL);
        ide_add_setting(drive,  "avg_speed",    SETTING_READ,   -1,     -1,             TYPE_INT,       0,                      0xffff,                 1,                              1,                              &tape->avg_speed,               NULL);
        ide_add_setting(drive,  "debug_level",SETTING_RW,       -1,     -1,             TYPE_INT,       0,                      0xffff,                 1,                              1,                              &tape->debug_level,             NULL);
}

/*
 *      ide_setup is called to:
 *
 *              1.      Initialize our various state variables.
 *              2.      Ask the tape for its capabilities.
 *              3.      Allocate a buffer which will be used for data
 *                      transfer. The buffer size is chosen based on
 *                      the recommendation which we received in step (2).
 *
 *      Note that at this point ide.c already assigned us an irq, so that
 *      we can queue requests here and wait for their completion.
 */
static void idetape_setup (ide_drive_t *drive, idetape_tape_t *tape, int minor)
{
        unsigned long t1, tmid, tn, t;
        int speed;
        struct idetape_id_gcw gcw;
        int stage_size;
        struct sysinfo si;

        spin_lock_init(&tape->spinlock);
        drive->dsc_overlap = 1;
#ifdef CONFIG_BLK_DEV_IDEPCI
        if (HWIF(drive)->pci_dev != NULL) {
                /*
                 * These two ide-pci host adapters appear to need DSC overlap disabled.
                 * This probably needs further analysis.
                 */
                if ((HWIF(drive)->pci_dev->device == PCI_DEVICE_ID_ARTOP_ATP850UF) ||
                    (HWIF(drive)->pci_dev->device == PCI_DEVICE_ID_TTI_HPT343)) {
                        printk(KERN_INFO "ide-tape: %s: disabling DSC overlap\n", tape->name);
                        drive->dsc_overlap = 0;
                }
        }
#endif /* CONFIG_BLK_DEV_IDEPCI */
        /* Seagate Travan drives do not support DSC overlap. */
        if (strstr(drive->id->model, "Seagate STT3401"))
                drive->dsc_overlap = 0;
        tape->minor = minor;
        tape->name[0] = 'h';
        tape->name[1] = 't';
        tape->name[2] = '0' + minor;
        tape->chrdev_direction = idetape_direction_none;
        tape->pc = tape->pc_stack;
        tape->max_insert_speed = 10000;
        tape->speed_control = 1;
        *((unsigned short *) &gcw) = drive->id->config;
        if (gcw.drq_type == 1)
                set_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags);

        tape->min_pipeline = tape->max_pipeline = tape->max_stages = 10;
        
        idetape_get_inquiry_results(drive);
        idetape_get_mode_sense_results(drive);
        idetape_get_blocksize_from_block_descriptor(drive);
        tape->user_bs_factor = 1;
        tape->stage_size = tape->capabilities.ctl * tape->tape_block_size;
        while (tape->stage_size > 0xffff) {
                printk(KERN_NOTICE "ide-tape: decreasing stage size\n");
                tape->capabilities.ctl /= 2;
                tape->stage_size = tape->capabilities.ctl * tape->tape_block_size;
        }
        stage_size = tape->stage_size;
        tape->pages_per_stage = stage_size / PAGE_SIZE;
        if (stage_size % PAGE_SIZE) {
                tape->pages_per_stage++;
                tape->excess_bh_size = PAGE_SIZE - stage_size % PAGE_SIZE;
        }

        /*
         *      Select the "best" DSC read/write polling frequency
         *      and pipeline size.
         */
        speed = max(tape->capabilities.speed, tape->capabilities.max_speed);

        tape->max_stages = speed * 1000 * 10 / tape->stage_size;

        /*
         *      Limit memory use for pipeline to 10% of physical memory
         */
        si_meminfo(&si);
        if (tape->max_stages * tape->stage_size > si.totalram * si.mem_unit / 10)
                tape->max_stages = si.totalram * si.mem_unit / (10 * tape->stage_size);
        tape->max_stages   = min(tape->max_stages, IDETAPE_MAX_PIPELINE_STAGES);
        tape->min_pipeline = min(tape->max_stages, IDETAPE_MIN_PIPELINE_STAGES);
        tape->max_pipeline = min(tape->max_stages * 2, IDETAPE_MAX_PIPELINE_STAGES);
        if (tape->max_stages == 0)
                tape->max_stages = tape->min_pipeline = tape->max_pipeline = 1;

        t1 = (tape->stage_size * HZ) / (speed * 1000);
        tmid = (tape->capabilities.buffer_size * 32 * HZ) / (speed * 125);
        tn = (IDETAPE_FIFO_THRESHOLD * tape->stage_size * HZ) / (speed * 1000);

        if (tape->max_stages)
                t = tn;
        else
                t = t1;

        /*
         *      Ensure that the number we got makes sense; limit
         *      it within IDETAPE_DSC_RW_MIN and IDETAPE_DSC_RW_MAX.
         */
        tape->best_dsc_rw_frequency = max_t(unsigned long, min_t(unsigned long, t, IDETAPE_DSC_RW_MAX), IDETAPE_DSC_RW_MIN);
        printk(KERN_INFO "ide-tape: %s <-> %s: %dKBps, %d*%dkB buffer, "
                "%dkB pipeline, %lums tDSC%s\n",
                drive->name, tape->name, tape->capabilities.speed,
                (tape->capabilities.buffer_size * 512) / tape->stage_size,
                tape->stage_size / 1024,
                tape->max_stages * tape->stage_size / 1024,
                tape->best_dsc_rw_frequency * 1000 / HZ,
                drive->using_dma ? ", DMA":"");

        idetape_add_settings(drive);
}

static int ide_tape_remove(struct device *dev)
{
        ide_drive_t *drive = to_ide_device(dev);
        idetape_tape_t *tape = drive->driver_data;

        ide_unregister_subdriver(drive, tape->driver);

        ide_unregister_region(tape->disk);

        ide_tape_put(tape);

        return 0;
}

static void ide_tape_release(struct kref *kref)
{
        struct ide_tape_obj *tape = to_ide_tape(kref);
        ide_drive_t *drive = tape->drive;
        struct gendisk *g = tape->disk;

        BUG_ON(tape->first_stage != NULL || tape->merge_stage_size);

        drive->dsc_overlap = 0;
        drive->driver_data = NULL;
        devfs_remove("%s/mt", drive->devfs_name);
        devfs_remove("%s/mtn", drive->devfs_name);
        devfs_unregister_tape(g->number);
        idetape_devs[tape->minor] = NULL;
        g->private_data = NULL;
        put_disk(g);
        kfree(tape);
}

#ifdef CONFIG_PROC_FS

static int proc_idetape_read_name
        (char *page, char **start, off_t off, int count, int *eof, void *data)
{
        ide_drive_t     *drive = (ide_drive_t *) data;
        idetape_tape_t  *tape = drive->driver_data;
        char            *out = page;
        int             len;

        len = sprintf(out, "%s\n", tape->name);
        PROC_IDE_READ_RETURN(page, start, off, count, eof, len);
}

static ide_proc_entry_t idetape_proc[] = {
        { "capacity",   S_IFREG|S_IRUGO,        proc_ide_read_capacity, NULL },
        { "name",       S_IFREG|S_IRUGO,        proc_idetape_read_name, NULL },
        { NULL, 0, NULL, NULL }
};

#else

#define idetape_proc    NULL

#endif

static int ide_tape_probe(struct device *);

static ide_driver_t idetape_driver = {
        .owner                  = THIS_MODULE,
        .gen_driver = {
                .name           = "ide-tape",
                .bus            = &ide_bus_type,
                .probe          = ide_tape_probe,
                .remove         = ide_tape_remove,
        },
        .version                = IDETAPE_VERSION,
        .media                  = ide_tape,
        .supports_dsc_overlap   = 1,
        .do_request             = idetape_do_request,
        .end_request            = idetape_end_request,
        .error                  = __ide_error,
        .abort                  = __ide_abort,
        .proc                   = idetape_proc,
};

/*
 *      Our character device supporting functions, passed to register_chrdev.
 */
static struct file_operations idetape_fops = {
        .owner          = THIS_MODULE,
        .read           = idetape_chrdev_read,
        .write          = idetape_chrdev_write,
        .ioctl          = idetape_chrdev_ioctl,
        .open           = idetape_chrdev_open,
        .release        = idetape_chrdev_release,
};

static int idetape_open(struct inode *inode, struct file *filp)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ide_tape_obj *tape;
        ide_drive_t *drive;

        if (!(tape = ide_tape_get(disk)))
                return -ENXIO;

        drive = tape->drive;

        drive->usage++;

        return 0;
}

static int idetape_release(struct inode *inode, struct file *filp)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ide_tape_obj *tape = ide_tape_g(disk);
        ide_drive_t *drive = tape->drive;

        drive->usage--;

        ide_tape_put(tape);

        return 0;
}

static int idetape_ioctl(struct inode *inode, struct file *file,
                        unsigned int cmd, unsigned long arg)
{
        struct block_device *bdev = inode->i_bdev;
        struct ide_tape_obj *tape = ide_tape_g(bdev->bd_disk);
        ide_drive_t *drive = tape->drive;
        int err = generic_ide_ioctl(drive, file, bdev, cmd, arg);
        if (err == -EINVAL)
                err = idetape_blkdev_ioctl(drive, cmd, arg);
        return err;
}

static struct block_device_operations idetape_block_ops = {
        .owner          = THIS_MODULE,
        .open           = idetape_open,
        .release        = idetape_release,
        .ioctl          = idetape_ioctl,
};

static int ide_tape_probe(struct device *dev)
{
        ide_drive_t *drive = to_ide_device(dev);
        idetape_tape_t *tape;
        struct gendisk *g;
        int minor;

        if (!strstr("ide-tape", drive->driver_req))
                goto failed;
        if (!drive->present)
                goto failed;
        if (drive->media != ide_tape)
                goto failed;
        if (!idetape_identify_device (drive)) {
                printk(KERN_ERR "ide-tape: %s: not supported by this version of ide-tape\n", drive->name);
                goto failed;
        }
        if (drive->scsi) {
                printk("ide-tape: passing drive %s to ide-scsi emulation.\n", drive->name);
                goto failed;
        }
        if (strstr(drive->id->model, "OnStream DI-")) {
                printk(KERN_WARNING "ide-tape: Use drive %s with ide-scsi emulation and osst.\n", drive->name);
                printk(KERN_WARNING "ide-tape: OnStream support will be removed soon from ide-tape!\n");
        }
        tape = (idetape_tape_t *) kmalloc (sizeof (idetape_tape_t), GFP_KERNEL);
        if (tape == NULL) {
                printk(KERN_ERR "ide-tape: %s: Can't allocate a tape structure\n", drive->name);
                goto failed;
        }

        g = alloc_disk(1 << PARTN_BITS);
        if (!g)
                goto out_free_tape;

        ide_init_disk(g, drive);

        ide_register_subdriver(drive, &idetape_driver);

        memset(tape, 0, sizeof(*tape));

        kref_init(&tape->kref);

        tape->drive = drive;
        tape->driver = &idetape_driver;
        tape->disk = g;

        g->private_data = &tape->driver;

        drive->driver_data = tape;

        down(&idetape_ref_sem);
        for (minor = 0; idetape_devs[minor]; minor++)
                ;
        idetape_devs[minor] = tape;
        up(&idetape_ref_sem);

        idetape_setup(drive, tape, minor);

        devfs_mk_cdev(MKDEV(HWIF(drive)->major, minor),
                        S_IFCHR | S_IRUGO | S_IWUGO,
                        "%s/mt", drive->devfs_name);
        devfs_mk_cdev(MKDEV(HWIF(drive)->major, minor + 128),
                        S_IFCHR | S_IRUGO | S_IWUGO,
                        "%s/mtn", drive->devfs_name);

        g->number = devfs_register_tape(drive->devfs_name);
        g->fops = &idetape_block_ops;
        ide_register_region(g);

        return 0;

out_free_tape:
        kfree(tape);
failed:
        return -ENODEV;
}

MODULE_DESCRIPTION("ATAPI Streaming TAPE Driver");
MODULE_LICENSE("GPL");

static void __exit idetape_exit (void)
{
        driver_unregister(&idetape_driver.gen_driver);
        unregister_chrdev(IDETAPE_MAJOR, "ht");
}

/*
 *      idetape_init will register the driver for each tape.
 */
static int idetape_init (void)
{
        if (register_chrdev(IDETAPE_MAJOR, "ht", &idetape_fops)) {
                printk(KERN_ERR "ide-tape: Failed to register character device interface\n");
                return -EBUSY;
        }
        return driver_register(&idetape_driver.gen_driver);
}

module_init(idetape_init);
module_exit(idetape_exit);
MODULE_ALIAS_CHARDEV_MAJOR(IDETAPE_MAJOR);