x86, mrst: use a temporary variable for SFI irq

[linux-btrfs-devel.git] / drivers / usb / storage / transport.c

/* Driver for USB Mass Storage compliant devices
 *
 * Current development and maintenance by:
 *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
 *
 * Developed with the assistance of:
 *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
 *   (c) 2000 Stephen J. Gowdy (SGowdy@lbl.gov)
 *   (c) 2002 Alan Stern <stern@rowland.org>
 *
 * Initial work by:
 *   (c) 1999 Michael Gee (michael@linuxspecific.com)
 *
 * This driver is based on the 'USB Mass Storage Class' document. This
 * describes in detail the protocol used to communicate with such
 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 * mind when they created this document.  The commands are all very
 * similar to commands in the SCSI-II and ATAPI specifications.
 *
 * It is important to note that in a number of cases this class
 * exhibits class-specific exemptions from the USB specification.
 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 * that they are used to communicate wait, failed and OK on commands.
 *
 * Also, for certain devices, the interrupt endpoint is used to convey
 * status of a command.
 *
 * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
 * information about this driver.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/sched.h>
#include <linux/gfp.h>
#include <linux/errno.h>

#include <linux/usb/quirks.h>

#include <scsi/scsi.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_device.h>

#include "usb.h"
#include "transport.h"
#include "protocol.h"
#include "scsiglue.h"
#include "debug.h"

#include <linux/blkdev.h>
#include "../../scsi/sd.h"


/***********************************************************************
 * Data transfer routines
 ***********************************************************************/

/*
 * This is subtle, so pay attention:
 * ---------------------------------
 * We're very concerned about races with a command abort.  Hanging this code
 * is a sure fire way to hang the kernel.  (Note that this discussion applies
 * only to transactions resulting from a scsi queued-command, since only
 * these transactions are subject to a scsi abort.  Other transactions, such
 * as those occurring during device-specific initialization, must be handled
 * by a separate code path.)
 *
 * The abort function (usb_storage_command_abort() in scsiglue.c) first
 * sets the machine state and the ABORTING bit in us->dflags to prevent
 * new URBs from being submitted.  It then calls usb_stor_stop_transport()
 * below, which atomically tests-and-clears the URB_ACTIVE bit in us->dflags
 * to see if the current_urb needs to be stopped.  Likewise, the SG_ACTIVE
 * bit is tested to see if the current_sg scatter-gather request needs to be
 * stopped.  The timeout callback routine does much the same thing.
 *
 * When a disconnect occurs, the DISCONNECTING bit in us->dflags is set to
 * prevent new URBs from being submitted, and usb_stor_stop_transport() is
 * called to stop any ongoing requests.
 *
 * The submit function first verifies that the submitting is allowed
 * (neither ABORTING nor DISCONNECTING bits are set) and that the submit
 * completes without errors, and only then sets the URB_ACTIVE bit.  This
 * prevents the stop_transport() function from trying to cancel the URB
 * while the submit call is underway.  Next, the submit function must test
 * the flags to see if an abort or disconnect occurred during the submission
 * or before the URB_ACTIVE bit was set.  If so, it's essential to cancel
 * the URB if it hasn't been cancelled already (i.e., if the URB_ACTIVE bit
 * is still set).  Either way, the function must then wait for the URB to
 * finish.  Note that the URB can still be in progress even after a call to
 * usb_unlink_urb() returns.
 *
 * The idea is that (1) once the ABORTING or DISCONNECTING bit is set,
 * either the stop_transport() function or the submitting function
 * is guaranteed to call usb_unlink_urb() for an active URB,
 * and (2) test_and_clear_bit() prevents usb_unlink_urb() from being
 * called more than once or from being called during usb_submit_urb().
 */

/* This is the completion handler which will wake us up when an URB
 * completes.
 */
static void usb_stor_blocking_completion(struct urb *urb)
{
        struct completion *urb_done_ptr = urb->context;

        complete(urb_done_ptr);
}

/* This is the common part of the URB message submission code
 *
 * All URBs from the usb-storage driver involved in handling a queued scsi
 * command _must_ pass through this function (or something like it) for the
 * abort mechanisms to work properly.
 */
static int usb_stor_msg_common(struct us_data *us, int timeout)
{
        struct completion urb_done;
        long timeleft;
        int status;

        /* don't submit URBs during abort processing */
        if (test_bit(US_FLIDX_ABORTING, &us->dflags))
                return -EIO;

        /* set up data structures for the wakeup system */
        init_completion(&urb_done);

        /* fill the common fields in the URB */
        us->current_urb->context = &urb_done;
        us->current_urb->transfer_flags = 0;

        /* we assume that if transfer_buffer isn't us->iobuf then it
         * hasn't been mapped for DMA.  Yes, this is clunky, but it's
         * easier than always having the caller tell us whether the
         * transfer buffer has already been mapped. */
        if (us->current_urb->transfer_buffer == us->iobuf)
                us->current_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
        us->current_urb->transfer_dma = us->iobuf_dma;

        /* submit the URB */
        status = usb_submit_urb(us->current_urb, GFP_NOIO);
        if (status) {
                /* something went wrong */
                return status;
        }

        /* since the URB has been submitted successfully, it's now okay
         * to cancel it */
        set_bit(US_FLIDX_URB_ACTIVE, &us->dflags);

        /* did an abort occur during the submission? */
        if (test_bit(US_FLIDX_ABORTING, &us->dflags)) {

                /* cancel the URB, if it hasn't been cancelled already */
                if (test_and_clear_bit(US_FLIDX_URB_ACTIVE, &us->dflags)) {
                        US_DEBUGP("-- cancelling URB\n");
                        usb_unlink_urb(us->current_urb);
                }
        }
 
        /* wait for the completion of the URB */
        timeleft = wait_for_completion_interruptible_timeout(
                        &urb_done, timeout ? : MAX_SCHEDULE_TIMEOUT);
 
        clear_bit(US_FLIDX_URB_ACTIVE, &us->dflags);

        if (timeleft <= 0) {
                US_DEBUGP("%s -- cancelling URB\n",
                          timeleft == 0 ? "Timeout" : "Signal");
                usb_kill_urb(us->current_urb);
        }

        /* return the URB status */
        return us->current_urb->status;
}

/*
 * Transfer one control message, with timeouts, and allowing early
 * termination.  Return codes are usual -Exxx, *not* USB_STOR_XFER_xxx.
 */
int usb_stor_control_msg(struct us_data *us, unsigned int pipe,
                 u8 request, u8 requesttype, u16 value, u16 index, 
                 void *data, u16 size, int timeout)
{
        int status;

        US_DEBUGP("%s: rq=%02x rqtype=%02x value=%04x index=%02x len=%u\n",
                        __func__, request, requesttype,
                        value, index, size);

        /* fill in the devrequest structure */
        us->cr->bRequestType = requesttype;
        us->cr->bRequest = request;
        us->cr->wValue = cpu_to_le16(value);
        us->cr->wIndex = cpu_to_le16(index);
        us->cr->wLength = cpu_to_le16(size);

        /* fill and submit the URB */
        usb_fill_control_urb(us->current_urb, us->pusb_dev, pipe, 
                         (unsigned char*) us->cr, data, size, 
                         usb_stor_blocking_completion, NULL);
        status = usb_stor_msg_common(us, timeout);

        /* return the actual length of the data transferred if no error */
        if (status == 0)
                status = us->current_urb->actual_length;
        return status;
}
EXPORT_SYMBOL_GPL(usb_stor_control_msg);

/* This is a version of usb_clear_halt() that allows early termination and
 * doesn't read the status from the device -- this is because some devices
 * crash their internal firmware when the status is requested after a halt.
 *
 * A definitive list of these 'bad' devices is too difficult to maintain or
 * make complete enough to be useful.  This problem was first observed on the
 * Hagiwara FlashGate DUAL unit.  However, bus traces reveal that neither
 * MacOS nor Windows checks the status after clearing a halt.
 *
 * Since many vendors in this space limit their testing to interoperability
 * with these two OSes, specification violations like this one are common.
 */
int usb_stor_clear_halt(struct us_data *us, unsigned int pipe)
{
        int result;
        int endp = usb_pipeendpoint(pipe);

        if (usb_pipein (pipe))
                endp |= USB_DIR_IN;

        result = usb_stor_control_msg(us, us->send_ctrl_pipe,
                USB_REQ_CLEAR_FEATURE, USB_RECIP_ENDPOINT,
                USB_ENDPOINT_HALT, endp,
                NULL, 0, 3*HZ);

        if (result >= 0)
                usb_reset_endpoint(us->pusb_dev, endp);

        US_DEBUGP("%s: result = %d\n", __func__, result);
        return result;
}
EXPORT_SYMBOL_GPL(usb_stor_clear_halt);


/*
 * Interpret the results of a URB transfer
 *
 * This function prints appropriate debugging messages, clears halts on
 * non-control endpoints, and translates the status to the corresponding
 * USB_STOR_XFER_xxx return code.
 */
static int interpret_urb_result(struct us_data *us, unsigned int pipe,
                unsigned int length, int result, unsigned int partial)
{
        US_DEBUGP("Status code %d; transferred %u/%u\n",
                        result, partial, length);
        switch (result) {

        /* no error code; did we send all the data? */
        case 0:
                if (partial != length) {
                        US_DEBUGP("-- short transfer\n");
                        return USB_STOR_XFER_SHORT;
                }

                US_DEBUGP("-- transfer complete\n");
                return USB_STOR_XFER_GOOD;

        /* stalled */
        case -EPIPE:
                /* for control endpoints, (used by CB[I]) a stall indicates
                 * a failed command */
                if (usb_pipecontrol(pipe)) {
                        US_DEBUGP("-- stall on control pipe\n");
                        return USB_STOR_XFER_STALLED;
                }

                /* for other sorts of endpoint, clear the stall */
                US_DEBUGP("clearing endpoint halt for pipe 0x%x\n", pipe);
                if (usb_stor_clear_halt(us, pipe) < 0)
                        return USB_STOR_XFER_ERROR;
                return USB_STOR_XFER_STALLED;

        /* babble - the device tried to send more than we wanted to read */
        case -EOVERFLOW:
                US_DEBUGP("-- babble\n");
                return USB_STOR_XFER_LONG;

        /* the transfer was cancelled by abort, disconnect, or timeout */
        case -ECONNRESET:
                US_DEBUGP("-- transfer cancelled\n");
                return USB_STOR_XFER_ERROR;

        /* short scatter-gather read transfer */
        case -EREMOTEIO:
                US_DEBUGP("-- short read transfer\n");
                return USB_STOR_XFER_SHORT;

        /* abort or disconnect in progress */
        case -EIO:
                US_DEBUGP("-- abort or disconnect in progress\n");
                return USB_STOR_XFER_ERROR;

        /* the catch-all error case */
        default:
                US_DEBUGP("-- unknown error\n");
                return USB_STOR_XFER_ERROR;
        }
}

/*
 * Transfer one control message, without timeouts, but allowing early
 * termination.  Return codes are USB_STOR_XFER_xxx.
 */
int usb_stor_ctrl_transfer(struct us_data *us, unsigned int pipe,
                u8 request, u8 requesttype, u16 value, u16 index,
                void *data, u16 size)
{
        int result;

        US_DEBUGP("%s: rq=%02x rqtype=%02x value=%04x index=%02x len=%u\n",
                        __func__, request, requesttype,
                        value, index, size);

        /* fill in the devrequest structure */
        us->cr->bRequestType = requesttype;
        us->cr->bRequest = request;
        us->cr->wValue = cpu_to_le16(value);
        us->cr->wIndex = cpu_to_le16(index);
        us->cr->wLength = cpu_to_le16(size);

        /* fill and submit the URB */
        usb_fill_control_urb(us->current_urb, us->pusb_dev, pipe, 
                         (unsigned char*) us->cr, data, size, 
                         usb_stor_blocking_completion, NULL);
        result = usb_stor_msg_common(us, 0);

        return interpret_urb_result(us, pipe, size, result,
                        us->current_urb->actual_length);
}
EXPORT_SYMBOL_GPL(usb_stor_ctrl_transfer);

/*
 * Receive one interrupt buffer, without timeouts, but allowing early
 * termination.  Return codes are USB_STOR_XFER_xxx.
 *
 * This routine always uses us->recv_intr_pipe as the pipe and
 * us->ep_bInterval as the interrupt interval.
 */
static int usb_stor_intr_transfer(struct us_data *us, void *buf,
                                  unsigned int length)
{
        int result;
        unsigned int pipe = us->recv_intr_pipe;
        unsigned int maxp;

        US_DEBUGP("%s: xfer %u bytes\n", __func__, length);

        /* calculate the max packet size */
        maxp = usb_maxpacket(us->pusb_dev, pipe, usb_pipeout(pipe));
        if (maxp > length)
                maxp = length;

        /* fill and submit the URB */
        usb_fill_int_urb(us->current_urb, us->pusb_dev, pipe, buf,
                        maxp, usb_stor_blocking_completion, NULL,
                        us->ep_bInterval);
        result = usb_stor_msg_common(us, 0);

        return interpret_urb_result(us, pipe, length, result,
                        us->current_urb->actual_length);
}

/*
 * Transfer one buffer via bulk pipe, without timeouts, but allowing early
 * termination.  Return codes are USB_STOR_XFER_xxx.  If the bulk pipe
 * stalls during the transfer, the halt is automatically cleared.
 */
int usb_stor_bulk_transfer_buf(struct us_data *us, unsigned int pipe,
        void *buf, unsigned int length, unsigned int *act_len)
{
        int result;

        US_DEBUGP("%s: xfer %u bytes\n", __func__, length);

        /* fill and submit the URB */
        usb_fill_bulk_urb(us->current_urb, us->pusb_dev, pipe, buf, length,
                      usb_stor_blocking_completion, NULL);
        result = usb_stor_msg_common(us, 0);

        /* store the actual length of the data transferred */
        if (act_len)
                *act_len = us->current_urb->actual_length;
        return interpret_urb_result(us, pipe, length, result, 
                        us->current_urb->actual_length);
}
EXPORT_SYMBOL_GPL(usb_stor_bulk_transfer_buf);

/*
 * Transfer a scatter-gather list via bulk transfer
 *
 * This function does basically the same thing as usb_stor_bulk_transfer_buf()
 * above, but it uses the usbcore scatter-gather library.
 */
static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe,
                struct scatterlist *sg, int num_sg, unsigned int length,
                unsigned int *act_len)
{
        int result;

        /* don't submit s-g requests during abort processing */
        if (test_bit(US_FLIDX_ABORTING, &us->dflags))
                return USB_STOR_XFER_ERROR;

        /* initialize the scatter-gather request block */
        US_DEBUGP("%s: xfer %u bytes, %d entries\n", __func__,
                        length, num_sg);
        result = usb_sg_init(&us->current_sg, us->pusb_dev, pipe, 0,
                        sg, num_sg, length, GFP_NOIO);
        if (result) {
                US_DEBUGP("usb_sg_init returned %d\n", result);
                return USB_STOR_XFER_ERROR;
        }

        /* since the block has been initialized successfully, it's now
         * okay to cancel it */
        set_bit(US_FLIDX_SG_ACTIVE, &us->dflags);

        /* did an abort occur during the submission? */
        if (test_bit(US_FLIDX_ABORTING, &us->dflags)) {

                /* cancel the request, if it hasn't been cancelled already */
                if (test_and_clear_bit(US_FLIDX_SG_ACTIVE, &us->dflags)) {
                        US_DEBUGP("-- cancelling sg request\n");
                        usb_sg_cancel(&us->current_sg);
                }
        }

        /* wait for the completion of the transfer */
        usb_sg_wait(&us->current_sg);
        clear_bit(US_FLIDX_SG_ACTIVE, &us->dflags);

        result = us->current_sg.status;
        if (act_len)
                *act_len = us->current_sg.bytes;
        return interpret_urb_result(us, pipe, length, result,
                        us->current_sg.bytes);
}

/*
 * Common used function. Transfer a complete command
 * via usb_stor_bulk_transfer_sglist() above. Set cmnd resid
 */
int usb_stor_bulk_srb(struct us_data* us, unsigned int pipe,
                      struct scsi_cmnd* srb)
{
        unsigned int partial;
        int result = usb_stor_bulk_transfer_sglist(us, pipe, scsi_sglist(srb),
                                      scsi_sg_count(srb), scsi_bufflen(srb),
                                      &partial);

        scsi_set_resid(srb, scsi_bufflen(srb) - partial);
        return result;
}
EXPORT_SYMBOL_GPL(usb_stor_bulk_srb);

/*
 * Transfer an entire SCSI command's worth of data payload over the bulk
 * pipe.
 *
 * Note that this uses usb_stor_bulk_transfer_buf() and
 * usb_stor_bulk_transfer_sglist() to achieve its goals --
 * this function simply determines whether we're going to use
 * scatter-gather or not, and acts appropriately.
 */
int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe,
                void *buf, unsigned int length_left, int use_sg, int *residual)
{
        int result;
        unsigned int partial;

        /* are we scatter-gathering? */
        if (use_sg) {
                /* use the usb core scatter-gather primitives */
                result = usb_stor_bulk_transfer_sglist(us, pipe,
                                (struct scatterlist *) buf, use_sg,
                                length_left, &partial);
                length_left -= partial;
        } else {
                /* no scatter-gather, just make the request */
                result = usb_stor_bulk_transfer_buf(us, pipe, buf, 
                                length_left, &partial);
                length_left -= partial;
        }

        /* store the residual and return the error code */
        if (residual)
                *residual = length_left;
        return result;
}
EXPORT_SYMBOL_GPL(usb_stor_bulk_transfer_sg);

/***********************************************************************
 * Transport routines
 ***********************************************************************/

/* There are so many devices that report the capacity incorrectly,
 * this routine was written to counteract some of the resulting
 * problems.
 */
static void last_sector_hacks(struct us_data *us, struct scsi_cmnd *srb)
{
        struct gendisk *disk;
        struct scsi_disk *sdkp;
        u32 sector;

        /* To Report "Medium Error: Record Not Found */
        static unsigned char record_not_found[18] = {
                [0]     = 0x70,                 /* current error */
                [2]     = MEDIUM_ERROR,         /* = 0x03 */
                [7]     = 0x0a,                 /* additional length */
                [12]    = 0x14                  /* Record Not Found */
        };

        /* If last-sector problems can't occur, whether because the
         * capacity was already decremented or because the device is
         * known to report the correct capacity, then we don't need
         * to do anything.
         */
        if (!us->use_last_sector_hacks)
                return;

        /* Was this command a READ(10) or a WRITE(10)? */
        if (srb->cmnd[0] != READ_10 && srb->cmnd[0] != WRITE_10)
                goto done;

        /* Did this command access the last sector? */
        sector = (srb->cmnd[2] << 24) | (srb->cmnd[3] << 16) |
                        (srb->cmnd[4] << 8) | (srb->cmnd[5]);
        disk = srb->request->rq_disk;
        if (!disk)
                goto done;
        sdkp = scsi_disk(disk);
        if (!sdkp)
                goto done;
        if (sector + 1 != sdkp->capacity)
                goto done;

        if (srb->result == SAM_STAT_GOOD && scsi_get_resid(srb) == 0) {

                /* The command succeeded.  We know this device doesn't
                 * have the last-sector bug, so stop checking it.
                 */
                us->use_last_sector_hacks = 0;

        } else {
                /* The command failed.  Allow up to 3 retries in case this
                 * is some normal sort of failure.  After that, assume the
                 * capacity is wrong and we're trying to access the sector
                 * beyond the end.  Replace the result code and sense data
                 * with values that will cause the SCSI core to fail the
                 * command immediately, instead of going into an infinite
                 * (or even just a very long) retry loop.
                 */
                if (++us->last_sector_retries < 3)
                        return;
                srb->result = SAM_STAT_CHECK_CONDITION;
                memcpy(srb->sense_buffer, record_not_found,
                                sizeof(record_not_found));
        }

 done:
        /* Don't reset the retry counter for TEST UNIT READY commands,
         * because they get issued after device resets which might be
         * caused by a failed last-sector access.
         */
        if (srb->cmnd[0] != TEST_UNIT_READY)
                us->last_sector_retries = 0;
}

/* Invoke the transport and basic error-handling/recovery methods
 *
 * This is used by the protocol layers to actually send the message to
 * the device and receive the response.
 */
void usb_stor_invoke_transport(struct scsi_cmnd *srb, struct us_data *us)
{
        int need_auto_sense;
        int result;

        /* send the command to the transport layer */
        scsi_set_resid(srb, 0);
        result = us->transport(srb, us);

        /* if the command gets aborted by the higher layers, we need to
         * short-circuit all other processing
         */
        if (test_bit(US_FLIDX_TIMED_OUT, &us->dflags)) {
                US_DEBUGP("-- command was aborted\n");
                srb->result = DID_ABORT << 16;
                goto Handle_Errors;
        }

        /* if there is a transport error, reset and don't auto-sense */
        if (result == USB_STOR_TRANSPORT_ERROR) {
                US_DEBUGP("-- transport indicates error, resetting\n");
                srb->result = DID_ERROR << 16;
                goto Handle_Errors;
        }

        /* if the transport provided its own sense data, don't auto-sense */
        if (result == USB_STOR_TRANSPORT_NO_SENSE) {
                srb->result = SAM_STAT_CHECK_CONDITION;
                last_sector_hacks(us, srb);
                return;
        }

        srb->result = SAM_STAT_GOOD;

        /* Determine if we need to auto-sense
         *
         * I normally don't use a flag like this, but it's almost impossible
         * to understand what's going on here if I don't.
         */
        need_auto_sense = 0;

        /*
         * If we're running the CB transport, which is incapable
         * of determining status on its own, we will auto-sense
         * unless the operation involved a data-in transfer.  Devices
         * can signal most data-in errors by stalling the bulk-in pipe.
         */
        if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_DPCM_USB) &&
                        srb->sc_data_direction != DMA_FROM_DEVICE) {
                US_DEBUGP("-- CB transport device requiring auto-sense\n");
                need_auto_sense = 1;
        }

        /*
         * If we have a failure, we're going to do a REQUEST_SENSE 
         * automatically.  Note that we differentiate between a command
         * "failure" and an "error" in the transport mechanism.
         */
        if (result == USB_STOR_TRANSPORT_FAILED) {
                US_DEBUGP("-- transport indicates command failure\n");
                need_auto_sense = 1;
        }

        /*
         * Determine if this device is SAT by seeing if the
         * command executed successfully.  Otherwise we'll have
         * to wait for at least one CHECK_CONDITION to determine
         * SANE_SENSE support
         */
        if (unlikely((srb->cmnd[0] == ATA_16 || srb->cmnd[0] == ATA_12) &&
            result == USB_STOR_TRANSPORT_GOOD &&
            !(us->fflags & US_FL_SANE_SENSE) &&
            !(us->fflags & US_FL_BAD_SENSE) &&
            !(srb->cmnd[2] & 0x20))) {
                US_DEBUGP("-- SAT supported, increasing auto-sense\n");
                us->fflags |= US_FL_SANE_SENSE;
        }

        /*
         * A short transfer on a command where we don't expect it
         * is unusual, but it doesn't mean we need to auto-sense.
         */
        if ((scsi_get_resid(srb) > 0) &&
            !((srb->cmnd[0] == REQUEST_SENSE) ||
              (srb->cmnd[0] == INQUIRY) ||
              (srb->cmnd[0] == MODE_SENSE) ||
              (srb->cmnd[0] == LOG_SENSE) ||
              (srb->cmnd[0] == MODE_SENSE_10))) {
                US_DEBUGP("-- unexpectedly short transfer\n");
        }

        /* Now, if we need to do the auto-sense, let's do it */
        if (need_auto_sense) {
                int temp_result;
                struct scsi_eh_save ses;
                int sense_size = US_SENSE_SIZE;

                /* device supports and needs bigger sense buffer */
                if (us->fflags & US_FL_SANE_SENSE)
                        sense_size = ~0;
Retry_Sense:
                US_DEBUGP("Issuing auto-REQUEST_SENSE\n");

                scsi_eh_prep_cmnd(srb, &ses, NULL, 0, sense_size);

                /* FIXME: we must do the protocol translation here */
                if (us->subclass == USB_SC_RBC || us->subclass == USB_SC_SCSI ||
                                us->subclass == USB_SC_CYP_ATACB)
                        srb->cmd_len = 6;
                else
                        srb->cmd_len = 12;

                /* issue the auto-sense command */
                scsi_set_resid(srb, 0);
                temp_result = us->transport(us->srb, us);

                /* let's clean up right away */
                scsi_eh_restore_cmnd(srb, &ses);

                if (test_bit(US_FLIDX_TIMED_OUT, &us->dflags)) {
                        US_DEBUGP("-- auto-sense aborted\n");
                        srb->result = DID_ABORT << 16;

                        /* If SANE_SENSE caused this problem, disable it */
                        if (sense_size != US_SENSE_SIZE) {
                                us->fflags &= ~US_FL_SANE_SENSE;
                                us->fflags |= US_FL_BAD_SENSE;
                        }
                        goto Handle_Errors;
                }

                /* Some devices claim to support larger sense but fail when
                 * trying to request it. When a transport failure happens
                 * using US_FS_SANE_SENSE, we always retry with a standard
                 * (small) sense request. This fixes some USB GSM modems
                 */
                if (temp_result == USB_STOR_TRANSPORT_FAILED &&
                                sense_size != US_SENSE_SIZE) {
                        US_DEBUGP("-- auto-sense failure, retry small sense\n");
                        sense_size = US_SENSE_SIZE;
                        us->fflags &= ~US_FL_SANE_SENSE;
                        us->fflags |= US_FL_BAD_SENSE;
                        goto Retry_Sense;
                }

                /* Other failures */
                if (temp_result != USB_STOR_TRANSPORT_GOOD) {
                        US_DEBUGP("-- auto-sense failure\n");

                        /* we skip the reset if this happens to be a
                         * multi-target device, since failure of an
                         * auto-sense is perfectly valid
                         */
                        srb->result = DID_ERROR << 16;
                        if (!(us->fflags & US_FL_SCM_MULT_TARG))
                                goto Handle_Errors;
                        return;
                }

                /* If the sense data returned is larger than 18-bytes then we
                 * assume this device supports requesting more in the future.
                 * The response code must be 70h through 73h inclusive.
                 */
                if (srb->sense_buffer[7] > (US_SENSE_SIZE - 8) &&
                    !(us->fflags & US_FL_SANE_SENSE) &&
                    !(us->fflags & US_FL_BAD_SENSE) &&
                    (srb->sense_buffer[0] & 0x7C) == 0x70) {
                        US_DEBUGP("-- SANE_SENSE support enabled\n");
                        us->fflags |= US_FL_SANE_SENSE;

                        /* Indicate to the user that we truncated their sense
                         * because we didn't know it supported larger sense.
                         */
                        US_DEBUGP("-- Sense data truncated to %i from %i\n",
                                  US_SENSE_SIZE,
                                  srb->sense_buffer[7] + 8);
                        srb->sense_buffer[7] = (US_SENSE_SIZE - 8);
                }

                US_DEBUGP("-- Result from auto-sense is %d\n", temp_result);
                US_DEBUGP("-- code: 0x%x, key: 0x%x, ASC: 0x%x, ASCQ: 0x%x\n",
                          srb->sense_buffer[0],
                          srb->sense_buffer[2] & 0xf,
                          srb->sense_buffer[12], 
                          srb->sense_buffer[13]);
#ifdef CONFIG_USB_STORAGE_DEBUG
                usb_stor_show_sense(
                          srb->sense_buffer[2] & 0xf,
                          srb->sense_buffer[12], 
                          srb->sense_buffer[13]);
#endif

                /* set the result so the higher layers expect this data */
                srb->result = SAM_STAT_CHECK_CONDITION;

                /* We often get empty sense data.  This could indicate that
                 * everything worked or that there was an unspecified
                 * problem.  We have to decide which.
                 */
                if (    /* Filemark 0, ignore EOM, ILI 0, no sense */
                                (srb->sense_buffer[2] & 0xaf) == 0 &&
                        /* No ASC or ASCQ */
                                srb->sense_buffer[12] == 0 &&
                                srb->sense_buffer[13] == 0) {

                        /* If things are really okay, then let's show that.
                         * Zero out the sense buffer so the higher layers
                         * won't realize we did an unsolicited auto-sense.
                         */
                        if (result == USB_STOR_TRANSPORT_GOOD) {
                                srb->result = SAM_STAT_GOOD;
                                srb->sense_buffer[0] = 0x0;

                        /* If there was a problem, report an unspecified
                         * hardware error to prevent the higher layers from
                         * entering an infinite retry loop.
                         */
                        } else {
                                srb->result = DID_ERROR << 16;
                                srb->sense_buffer[2] = HARDWARE_ERROR;
                        }
                }
        }

        /*
         * Some devices don't work or return incorrect data the first
         * time they get a READ(10) command, or for the first READ(10)
         * after a media change.  If the INITIAL_READ10 flag is set,
         * keep track of whether READ(10) commands succeed.  If the
         * previous one succeeded and this one failed, set the REDO_READ10
         * flag to force a retry.
         */
        if (unlikely((us->fflags & US_FL_INITIAL_READ10) &&
                        srb->cmnd[0] == READ_10)) {
                if (srb->result == SAM_STAT_GOOD) {
                        set_bit(US_FLIDX_READ10_WORKED, &us->dflags);
                } else if (test_bit(US_FLIDX_READ10_WORKED, &us->dflags)) {
                        clear_bit(US_FLIDX_READ10_WORKED, &us->dflags);
                        set_bit(US_FLIDX_REDO_READ10, &us->dflags);
                }

                /*
                 * Next, if the REDO_READ10 flag is set, return a result
                 * code that will cause the SCSI core to retry the READ(10)
                 * command immediately.
                 */
                if (test_bit(US_FLIDX_REDO_READ10, &us->dflags)) {
                        clear_bit(US_FLIDX_REDO_READ10, &us->dflags);
                        srb->result = DID_IMM_RETRY << 16;
                        srb->sense_buffer[0] = 0;
                }
        }

        /* Did we transfer less than the minimum amount required? */
        if ((srb->result == SAM_STAT_GOOD || srb->sense_buffer[2] == 0) &&
                        scsi_bufflen(srb) - scsi_get_resid(srb) < srb->underflow)
                srb->result = DID_ERROR << 16;

        last_sector_hacks(us, srb);
        return;

        /* Error and abort processing: try to resynchronize with the device
         * by issuing a port reset.  If that fails, try a class-specific
         * device reset. */
  Handle_Errors:

        /* Set the RESETTING bit, and clear the ABORTING bit so that
         * the reset may proceed. */
        scsi_lock(us_to_host(us));
        set_bit(US_FLIDX_RESETTING, &us->dflags);
        clear_bit(US_FLIDX_ABORTING, &us->dflags);
        scsi_unlock(us_to_host(us));

        /* We must release the device lock because the pre_reset routine
         * will want to acquire it. */
        mutex_unlock(&us->dev_mutex);
        result = usb_stor_port_reset(us);
        mutex_lock(&us->dev_mutex);

        if (result < 0) {
                scsi_lock(us_to_host(us));
                usb_stor_report_device_reset(us);
                scsi_unlock(us_to_host(us));
                us->transport_reset(us);
        }
        clear_bit(US_FLIDX_RESETTING, &us->dflags);
        last_sector_hacks(us, srb);
}

/* Stop the current URB transfer */
void usb_stor_stop_transport(struct us_data *us)
{
        US_DEBUGP("%s called\n", __func__);

        /* If the state machine is blocked waiting for an URB,
         * let's wake it up.  The test_and_clear_bit() call
         * guarantees that if a URB has just been submitted,
         * it won't be cancelled more than once. */
        if (test_and_clear_bit(US_FLIDX_URB_ACTIVE, &us->dflags)) {
                US_DEBUGP("-- cancelling URB\n");
                usb_unlink_urb(us->current_urb);
        }

        /* If we are waiting for a scatter-gather operation, cancel it. */
        if (test_and_clear_bit(US_FLIDX_SG_ACTIVE, &us->dflags)) {
                US_DEBUGP("-- cancelling sg request\n");
                usb_sg_cancel(&us->current_sg);
        }
}

/*
 * Control/Bulk and Control/Bulk/Interrupt transport
 */

int usb_stor_CB_transport(struct scsi_cmnd *srb, struct us_data *us)
{
        unsigned int transfer_length = scsi_bufflen(srb);
        unsigned int pipe = 0;
        int result;

        /* COMMAND STAGE */
        /* let's send the command via the control pipe */
        result = usb_stor_ctrl_transfer(us, us->send_ctrl_pipe,
                                      US_CBI_ADSC, 
                                      USB_TYPE_CLASS | USB_RECIP_INTERFACE, 0, 
                                      us->ifnum, srb->cmnd, srb->cmd_len);

        /* check the return code for the command */
        US_DEBUGP("Call to usb_stor_ctrl_transfer() returned %d\n", result);

        /* if we stalled the command, it means command failed */
        if (result == USB_STOR_XFER_STALLED) {
                return USB_STOR_TRANSPORT_FAILED;
        }

        /* Uh oh... serious problem here */
        if (result != USB_STOR_XFER_GOOD) {
                return USB_STOR_TRANSPORT_ERROR;
        }

        /* DATA STAGE */
        /* transfer the data payload for this command, if one exists*/
        if (transfer_length) {
                pipe = srb->sc_data_direction == DMA_FROM_DEVICE ? 
                                us->recv_bulk_pipe : us->send_bulk_pipe;
                result = usb_stor_bulk_srb(us, pipe, srb);
                US_DEBUGP("CBI data stage result is 0x%x\n", result);

                /* if we stalled the data transfer it means command failed */
                if (result == USB_STOR_XFER_STALLED)
                        return USB_STOR_TRANSPORT_FAILED;
                if (result > USB_STOR_XFER_STALLED)
                        return USB_STOR_TRANSPORT_ERROR;
        }

        /* STATUS STAGE */

        /* NOTE: CB does not have a status stage.  Silly, I know.  So
         * we have to catch this at a higher level.
         */
        if (us->protocol != USB_PR_CBI)
                return USB_STOR_TRANSPORT_GOOD;

        result = usb_stor_intr_transfer(us, us->iobuf, 2);
        US_DEBUGP("Got interrupt data (0x%x, 0x%x)\n", 
                        us->iobuf[0], us->iobuf[1]);
        if (result != USB_STOR_XFER_GOOD)
                return USB_STOR_TRANSPORT_ERROR;

        /* UFI gives us ASC and ASCQ, like a request sense
         *
         * REQUEST_SENSE and INQUIRY don't affect the sense data on UFI
         * devices, so we ignore the information for those commands.  Note
         * that this means we could be ignoring a real error on these
         * commands, but that can't be helped.
         */
        if (us->subclass == USB_SC_UFI) {
                if (srb->cmnd[0] == REQUEST_SENSE ||
                    srb->cmnd[0] == INQUIRY)
                        return USB_STOR_TRANSPORT_GOOD;
                if (us->iobuf[0])
                        goto Failed;
                return USB_STOR_TRANSPORT_GOOD;
        }

        /* If not UFI, we interpret the data as a result code 
         * The first byte should always be a 0x0.
         *
         * Some bogus devices don't follow that rule.  They stuff the ASC
         * into the first byte -- so if it's non-zero, call it a failure.
         */
        if (us->iobuf[0]) {
                US_DEBUGP("CBI IRQ data showed reserved bType 0x%x\n",
                                us->iobuf[0]);
                goto Failed;

        }

        /* The second byte & 0x0F should be 0x0 for good, otherwise error */
        switch (us->iobuf[1] & 0x0F) {
                case 0x00: 
                        return USB_STOR_TRANSPORT_GOOD;
                case 0x01: 
                        goto Failed;
        }
        return USB_STOR_TRANSPORT_ERROR;

        /* the CBI spec requires that the bulk pipe must be cleared
         * following any data-in/out command failure (section 2.4.3.1.3)
         */
  Failed:
        if (pipe)
                usb_stor_clear_halt(us, pipe);
        return USB_STOR_TRANSPORT_FAILED;
}
EXPORT_SYMBOL_GPL(usb_stor_CB_transport);

/*
 * Bulk only transport
 */

/* Determine what the maximum LUN supported is */
int usb_stor_Bulk_max_lun(struct us_data *us)
{
        int result;

        /* issue the command */
        us->iobuf[0] = 0;
        result = usb_stor_control_msg(us, us->recv_ctrl_pipe,
                                 US_BULK_GET_MAX_LUN, 
                                 USB_DIR_IN | USB_TYPE_CLASS | 
                                 USB_RECIP_INTERFACE,
                                 0, us->ifnum, us->iobuf, 1, 10*HZ);

        US_DEBUGP("GetMaxLUN command result is %d, data is %d\n", 
                  result, us->iobuf[0]);

        /* if we have a successful request, return the result */
        if (result > 0)
                return us->iobuf[0];

        /*
         * Some devices don't like GetMaxLUN.  They may STALL the control
         * pipe, they may return a zero-length result, they may do nothing at
         * all and timeout, or they may fail in even more bizarrely creative
         * ways.  In these cases the best approach is to use the default
         * value: only one LUN.
         */
        return 0;
}

int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us)
{
        struct bulk_cb_wrap *bcb = (struct bulk_cb_wrap *) us->iobuf;
        struct bulk_cs_wrap *bcs = (struct bulk_cs_wrap *) us->iobuf;
        unsigned int transfer_length = scsi_bufflen(srb);
        unsigned int residue;
        int result;
        int fake_sense = 0;
        unsigned int cswlen;
        unsigned int cbwlen = US_BULK_CB_WRAP_LEN;

        /* Take care of BULK32 devices; set extra byte to 0 */
        if (unlikely(us->fflags & US_FL_BULK32)) {
                cbwlen = 32;
                us->iobuf[31] = 0;
        }

        /* set up the command wrapper */
        bcb->Signature = cpu_to_le32(US_BULK_CB_SIGN);
        bcb->DataTransferLength = cpu_to_le32(transfer_length);
        bcb->Flags = srb->sc_data_direction == DMA_FROM_DEVICE ? 1 << 7 : 0;
        bcb->Tag = ++us->tag;
        bcb->Lun = srb->device->lun;
        if (us->fflags & US_FL_SCM_MULT_TARG)
                bcb->Lun |= srb->device->id << 4;
        bcb->Length = srb->cmd_len;

        /* copy the command payload */
        memset(bcb->CDB, 0, sizeof(bcb->CDB));
        memcpy(bcb->CDB, srb->cmnd, bcb->Length);

        /* send it to out endpoint */
        US_DEBUGP("Bulk Command S 0x%x T 0x%x L %d F %d Trg %d LUN %d CL %d\n",
                        le32_to_cpu(bcb->Signature), bcb->Tag,
                        le32_to_cpu(bcb->DataTransferLength), bcb->Flags,
                        (bcb->Lun >> 4), (bcb->Lun & 0x0F), 
                        bcb->Length);
        result = usb_stor_bulk_transfer_buf(us, us->send_bulk_pipe,
                                bcb, cbwlen, NULL);
        US_DEBUGP("Bulk command transfer result=%d\n", result);
        if (result != USB_STOR_XFER_GOOD)
                return USB_STOR_TRANSPORT_ERROR;

        /* DATA STAGE */
        /* send/receive data payload, if there is any */

        /* Some USB-IDE converter chips need a 100us delay between the
         * command phase and the data phase.  Some devices need a little
         * more than that, probably because of clock rate inaccuracies. */
        if (unlikely(us->fflags & US_FL_GO_SLOW))
                udelay(125);

        if (transfer_length) {
                unsigned int pipe = srb->sc_data_direction == DMA_FROM_DEVICE ? 
                                us->recv_bulk_pipe : us->send_bulk_pipe;
                result = usb_stor_bulk_srb(us, pipe, srb);
                US_DEBUGP("Bulk data transfer result 0x%x\n", result);
                if (result == USB_STOR_XFER_ERROR)
                        return USB_STOR_TRANSPORT_ERROR;

                /* If the device tried to send back more data than the
                 * amount requested, the spec requires us to transfer
                 * the CSW anyway.  Since there's no point retrying the
                 * the command, we'll return fake sense data indicating
                 * Illegal Request, Invalid Field in CDB.
                 */
                if (result == USB_STOR_XFER_LONG)
                        fake_sense = 1;
        }

        /* See flow chart on pg 15 of the Bulk Only Transport spec for
         * an explanation of how this code works.
         */

        /* get CSW for device status */
        US_DEBUGP("Attempting to get CSW...\n");
        result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe,
                                bcs, US_BULK_CS_WRAP_LEN, &cswlen);

        /* Some broken devices add unnecessary zero-length packets to the
         * end of their data transfers.  Such packets show up as 0-length
         * CSWs.  If we encounter such a thing, try to read the CSW again.
         */
        if (result == USB_STOR_XFER_SHORT && cswlen == 0) {
                US_DEBUGP("Received 0-length CSW; retrying...\n");
                result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe,
                                bcs, US_BULK_CS_WRAP_LEN, &cswlen);
        }

        /* did the attempt to read the CSW fail? */
        if (result == USB_STOR_XFER_STALLED) {

                /* get the status again */
                US_DEBUGP("Attempting to get CSW (2nd try)...\n");
                result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe,
                                bcs, US_BULK_CS_WRAP_LEN, NULL);
        }

        /* if we still have a failure at this point, we're in trouble */
        US_DEBUGP("Bulk status result = %d\n", result);
        if (result != USB_STOR_XFER_GOOD)
                return USB_STOR_TRANSPORT_ERROR;

        /* check bulk status */
        residue = le32_to_cpu(bcs->Residue);
        US_DEBUGP("Bulk Status S 0x%x T 0x%x R %u Stat 0x%x\n",
                        le32_to_cpu(bcs->Signature), bcs->Tag, 
                        residue, bcs->Status);
        if (!(bcs->Tag == us->tag || (us->fflags & US_FL_BULK_IGNORE_TAG)) ||
                bcs->Status > US_BULK_STAT_PHASE) {
                US_DEBUGP("Bulk logical error\n");
                return USB_STOR_TRANSPORT_ERROR;
        }

        /* Some broken devices report odd signatures, so we do not check them
         * for validity against the spec. We store the first one we see,
         * and check subsequent transfers for validity against this signature.
         */
        if (!us->bcs_signature) {
                us->bcs_signature = bcs->Signature;
                if (us->bcs_signature != cpu_to_le32(US_BULK_CS_SIGN))
                        US_DEBUGP("Learnt BCS signature 0x%08X\n",
                                        le32_to_cpu(us->bcs_signature));
        } else if (bcs->Signature != us->bcs_signature) {
                US_DEBUGP("Signature mismatch: got %08X, expecting %08X\n",
                          le32_to_cpu(bcs->Signature),
                          le32_to_cpu(us->bcs_signature));
                return USB_STOR_TRANSPORT_ERROR;
        }

        /* try to compute the actual residue, based on how much data
         * was really transferred and what the device tells us */
        if (residue && !(us->fflags & US_FL_IGNORE_RESIDUE)) {

                /* Heuristically detect devices that generate bogus residues
                 * by seeing what happens with INQUIRY and READ CAPACITY
                 * commands.
                 */
                if (bcs->Status == US_BULK_STAT_OK &&
                                scsi_get_resid(srb) == 0 &&
                                        ((srb->cmnd[0] == INQUIRY &&
                                                transfer_length == 36) ||
                                        (srb->cmnd[0] == READ_CAPACITY &&
                                                transfer_length == 8))) {
                        us->fflags |= US_FL_IGNORE_RESIDUE;

                } else {
                        residue = min(residue, transfer_length);
                        scsi_set_resid(srb, max(scsi_get_resid(srb),
                                                               (int) residue));
                }
        }

        /* based on the status code, we report good or bad */
        switch (bcs->Status) {
                case US_BULK_STAT_OK:
                        /* device babbled -- return fake sense data */
                        if (fake_sense) {
                                memcpy(srb->sense_buffer, 
                                       usb_stor_sense_invalidCDB, 
                                       sizeof(usb_stor_sense_invalidCDB));
                                return USB_STOR_TRANSPORT_NO_SENSE;
                        }

                        /* command good -- note that data could be short */
                        return USB_STOR_TRANSPORT_GOOD;

                case US_BULK_STAT_FAIL:
                        /* command failed */
                        return USB_STOR_TRANSPORT_FAILED;

                case US_BULK_STAT_PHASE:
                        /* phase error -- note that a transport reset will be
                         * invoked by the invoke_transport() function
                         */
                        return USB_STOR_TRANSPORT_ERROR;
        }

        /* we should never get here, but if we do, we're in trouble */
        return USB_STOR_TRANSPORT_ERROR;
}
EXPORT_SYMBOL_GPL(usb_stor_Bulk_transport);

/***********************************************************************
 * Reset routines
 ***********************************************************************/

/* This is the common part of the device reset code.
 *
 * It's handy that every transport mechanism uses the control endpoint for
 * resets.
 *
 * Basically, we send a reset with a 5-second timeout, so we don't get
 * jammed attempting to do the reset.
 */
static int usb_stor_reset_common(struct us_data *us,
                u8 request, u8 requesttype,
                u16 value, u16 index, void *data, u16 size)
{
        int result;
        int result2;

        if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
                US_DEBUGP("No reset during disconnect\n");
                return -EIO;
        }

        result = usb_stor_control_msg(us, us->send_ctrl_pipe,
                        request, requesttype, value, index, data, size,
                        5*HZ);
        if (result < 0) {
                US_DEBUGP("Soft reset failed: %d\n", result);
                return result;
        }

        /* Give the device some time to recover from the reset,
         * but don't delay disconnect processing. */
        wait_event_interruptible_timeout(us->delay_wait,
                        test_bit(US_FLIDX_DISCONNECTING, &us->dflags),
                        HZ*6);
        if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
                US_DEBUGP("Reset interrupted by disconnect\n");
                return -EIO;
        }

        US_DEBUGP("Soft reset: clearing bulk-in endpoint halt\n");
        result = usb_stor_clear_halt(us, us->recv_bulk_pipe);

        US_DEBUGP("Soft reset: clearing bulk-out endpoint halt\n");
        result2 = usb_stor_clear_halt(us, us->send_bulk_pipe);

        /* return a result code based on the result of the clear-halts */
        if (result >= 0)
                result = result2;
        if (result < 0)
                US_DEBUGP("Soft reset failed\n");
        else
                US_DEBUGP("Soft reset done\n");
        return result;
}

/* This issues a CB[I] Reset to the device in question
 */
#define CB_RESET_CMD_SIZE       12

int usb_stor_CB_reset(struct us_data *us)
{
        US_DEBUGP("%s called\n", __func__);

        memset(us->iobuf, 0xFF, CB_RESET_CMD_SIZE);
        us->iobuf[0] = SEND_DIAGNOSTIC;
        us->iobuf[1] = 4;
        return usb_stor_reset_common(us, US_CBI_ADSC, 
                                 USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                                 0, us->ifnum, us->iobuf, CB_RESET_CMD_SIZE);
}
EXPORT_SYMBOL_GPL(usb_stor_CB_reset);

/* This issues a Bulk-only Reset to the device in question, including
 * clearing the subsequent endpoint halts that may occur.
 */
int usb_stor_Bulk_reset(struct us_data *us)
{
        US_DEBUGP("%s called\n", __func__);

        return usb_stor_reset_common(us, US_BULK_RESET_REQUEST, 
                                 USB_TYPE_CLASS | USB_RECIP_INTERFACE,
                                 0, us->ifnum, NULL, 0);
}
EXPORT_SYMBOL_GPL(usb_stor_Bulk_reset);

/* Issue a USB port reset to the device.  The caller must not hold
 * us->dev_mutex.
 */
int usb_stor_port_reset(struct us_data *us)
{
        int result;

        /*for these devices we must use the class specific method */
        if (us->pusb_dev->quirks & USB_QUIRK_RESET_MORPHS)
                return -EPERM;

        result = usb_lock_device_for_reset(us->pusb_dev, us->pusb_intf);
        if (result < 0)
                US_DEBUGP("unable to lock device for reset: %d\n", result);
        else {
                /* Were we disconnected while waiting for the lock? */
                if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags)) {
                        result = -EIO;
                        US_DEBUGP("No reset during disconnect\n");
                } else {
                        result = usb_reset_device(us->pusb_dev);
                        US_DEBUGP("usb_reset_device returns %d\n",
                                        result);
                }
                usb_unlock_device(us->pusb_dev);
        }
        return result;
}