inet: frag: enforce memory limits earlier

[linux/fpc-iii.git] / drivers / scsi / sr.c

/*
 *  sr.c Copyright (C) 1992 David Giller
 *           Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
 *
 *  adapted from:
 *      sd.c Copyright (C) 1992 Drew Eckhardt
 *      Linux scsi disk driver by
 *              Drew Eckhardt <drew@colorado.edu>
 *
 *      Modified by Eric Youngdale ericy@andante.org to
 *      add scatter-gather, multiple outstanding request, and other
 *      enhancements.
 *
 *      Modified by Eric Youngdale eric@andante.org to support loadable
 *      low-level scsi drivers.
 *
 *      Modified by Thomas Quinot thomas@melchior.cuivre.fdn.fr to
 *      provide auto-eject.
 *
 *      Modified by Gerd Knorr <kraxel@cs.tu-berlin.de> to support the
 *      generic cdrom interface
 *
 *      Modified by Jens Axboe <axboe@suse.de> - Uniform sr_packet()
 *      interface, capabilities probe additions, ioctl cleanups, etc.
 *
 *      Modified by Richard Gooch <rgooch@atnf.csiro.au> to support devfs
 *
 *      Modified by Jens Axboe <axboe@suse.de> - support DVD-RAM
 *      transparently and lose the GHOST hack
 *
 *      Modified by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *      check resource allocation in sr_init and some cleanups
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/bio.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/cdrom.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>
#include <asm/uaccess.h>

#include <scsi/scsi.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_ioctl.h>    /* For the door lock/unlock commands */

#include "scsi_logging.h"
#include "sr.h"


MODULE_DESCRIPTION("SCSI cdrom (sr) driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_CDROM_MAJOR);
MODULE_ALIAS_SCSI_DEVICE(TYPE_ROM);
MODULE_ALIAS_SCSI_DEVICE(TYPE_WORM);

#define SR_DISKS        256

#define SR_CAPABILITIES \
        (CDC_CLOSE_TRAY|CDC_OPEN_TRAY|CDC_LOCK|CDC_SELECT_SPEED| \
         CDC_SELECT_DISC|CDC_MULTI_SESSION|CDC_MCN|CDC_MEDIA_CHANGED| \
         CDC_PLAY_AUDIO|CDC_RESET|CDC_DRIVE_STATUS| \
         CDC_CD_R|CDC_CD_RW|CDC_DVD|CDC_DVD_R|CDC_DVD_RAM|CDC_GENERIC_PACKET| \
         CDC_MRW|CDC_MRW_W|CDC_RAM)

static DEFINE_MUTEX(sr_mutex);
static int sr_probe(struct device *);
static int sr_remove(struct device *);
static int sr_init_command(struct scsi_cmnd *SCpnt);
static int sr_done(struct scsi_cmnd *);
static int sr_runtime_suspend(struct device *dev);

static const struct dev_pm_ops sr_pm_ops = {
        .runtime_suspend        = sr_runtime_suspend,
};

static struct scsi_driver sr_template = {
        .gendrv = {
                .name           = "sr",
                .owner          = THIS_MODULE,
                .probe          = sr_probe,
                .remove         = sr_remove,
                .pm             = &sr_pm_ops,
        },
        .init_command           = sr_init_command,
        .done                   = sr_done,
};

static unsigned long sr_index_bits[SR_DISKS / BITS_PER_LONG];
static DEFINE_SPINLOCK(sr_index_lock);

/* This semaphore is used to mediate the 0->1 reference get in the
 * face of object destruction (i.e. we can't allow a get on an
 * object after last put) */
static DEFINE_MUTEX(sr_ref_mutex);

static int sr_open(struct cdrom_device_info *, int);
static void sr_release(struct cdrom_device_info *);

static void get_sectorsize(struct scsi_cd *);
static void get_capabilities(struct scsi_cd *);

static unsigned int sr_check_events(struct cdrom_device_info *cdi,
                                    unsigned int clearing, int slot);
static int sr_packet(struct cdrom_device_info *, struct packet_command *);

static struct cdrom_device_ops sr_dops = {
        .open                   = sr_open,
        .release                = sr_release,
        .drive_status           = sr_drive_status,
        .check_events           = sr_check_events,
        .tray_move              = sr_tray_move,
        .lock_door              = sr_lock_door,
        .select_speed           = sr_select_speed,
        .get_last_session       = sr_get_last_session,
        .get_mcn                = sr_get_mcn,
        .reset                  = sr_reset,
        .audio_ioctl            = sr_audio_ioctl,
        .capability             = SR_CAPABILITIES,
        .generic_packet         = sr_packet,
};

static void sr_kref_release(struct kref *kref);

static inline struct scsi_cd *scsi_cd(struct gendisk *disk)
{
        return container_of(disk->private_data, struct scsi_cd, driver);
}

static int sr_runtime_suspend(struct device *dev)
{
        struct scsi_cd *cd = dev_get_drvdata(dev);

        if (!cd)        /* E.g.: runtime suspend following sr_remove() */
                return 0;

        if (cd->media_present)
                return -EBUSY;
        else
                return 0;
}

/*
 * The get and put routines for the struct scsi_cd.  Note this entity
 * has a scsi_device pointer and owns a reference to this.
 */
static inline struct scsi_cd *scsi_cd_get(struct gendisk *disk)
{
        struct scsi_cd *cd = NULL;

        mutex_lock(&sr_ref_mutex);
        if (disk->private_data == NULL)
                goto out;
        cd = scsi_cd(disk);
        kref_get(&cd->kref);
        if (scsi_device_get(cd->device)) {
                kref_put(&cd->kref, sr_kref_release);
                cd = NULL;
        }
 out:
        mutex_unlock(&sr_ref_mutex);
        return cd;
}

static void scsi_cd_put(struct scsi_cd *cd)
{
        struct scsi_device *sdev = cd->device;

        mutex_lock(&sr_ref_mutex);
        kref_put(&cd->kref, sr_kref_release);
        scsi_device_put(sdev);
        mutex_unlock(&sr_ref_mutex);
}

static unsigned int sr_get_events(struct scsi_device *sdev)
{
        u8 buf[8];
        u8 cmd[] = { GET_EVENT_STATUS_NOTIFICATION,
                     1,                 /* polled */
                     0, 0,              /* reserved */
                     1 << 4,            /* notification class: media */
                     0, 0,              /* reserved */
                     0, sizeof(buf),    /* allocation length */
                     0,                 /* control */
        };
        struct event_header *eh = (void *)buf;
        struct media_event_desc *med = (void *)(buf + 4);
        struct scsi_sense_hdr sshdr;
        int result;

        result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buf, sizeof(buf),
                                  &sshdr, SR_TIMEOUT, MAX_RETRIES, NULL);
        if (scsi_sense_valid(&sshdr) && sshdr.sense_key == UNIT_ATTENTION)
                return DISK_EVENT_MEDIA_CHANGE;

        if (result || be16_to_cpu(eh->data_len) < sizeof(*med))
                return 0;

        if (eh->nea || eh->notification_class != 0x4)
                return 0;

        if (med->media_event_code == 1)
                return DISK_EVENT_EJECT_REQUEST;
        else if (med->media_event_code == 2)
                return DISK_EVENT_MEDIA_CHANGE;
        return 0;
}

/*
 * This function checks to see if the media has been changed or eject
 * button has been pressed.  It is possible that we have already
 * sensed a change, or the drive may have sensed one and not yet
 * reported it.  The past events are accumulated in sdev->changed and
 * returned together with the current state.
 */
static unsigned int sr_check_events(struct cdrom_device_info *cdi,
                                    unsigned int clearing, int slot)
{
        struct scsi_cd *cd = cdi->handle;
        bool last_present;
        struct scsi_sense_hdr sshdr;
        unsigned int events;
        int ret;

        /* no changer support */
        if (CDSL_CURRENT != slot)
                return 0;

        events = sr_get_events(cd->device);
        cd->get_event_changed |= events & DISK_EVENT_MEDIA_CHANGE;

        /*
         * If earlier GET_EVENT_STATUS_NOTIFICATION and TUR did not agree
         * for several times in a row.  We rely on TUR only for this likely
         * broken device, to prevent generating incorrect media changed
         * events for every open().
         */
        if (cd->ignore_get_event) {
                events &= ~DISK_EVENT_MEDIA_CHANGE;
                goto do_tur;
        }

        /*
         * GET_EVENT_STATUS_NOTIFICATION is enough unless MEDIA_CHANGE
         * is being cleared.  Note that there are devices which hang
         * if asked to execute TUR repeatedly.
         */
        if (cd->device->changed) {
                events |= DISK_EVENT_MEDIA_CHANGE;
                cd->device->changed = 0;
                cd->tur_changed = true;
        }

        if (!(clearing & DISK_EVENT_MEDIA_CHANGE))
                return events;
do_tur:
        /* let's see whether the media is there with TUR */
        last_present = cd->media_present;
        ret = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);

        /*
         * Media is considered to be present if TUR succeeds or fails with
         * sense data indicating something other than media-not-present
         * (ASC 0x3a).
         */
        cd->media_present = scsi_status_is_good(ret) ||
                (scsi_sense_valid(&sshdr) && sshdr.asc != 0x3a);

        if (last_present != cd->media_present)
                cd->device->changed = 1;

        if (cd->device->changed) {
                events |= DISK_EVENT_MEDIA_CHANGE;
                cd->device->changed = 0;
                cd->tur_changed = true;
        }

        if (cd->ignore_get_event)
                return events;

        /* check whether GET_EVENT is reporting spurious MEDIA_CHANGE */
        if (!cd->tur_changed) {
                if (cd->get_event_changed) {
                        if (cd->tur_mismatch++ > 8) {
                                sr_printk(KERN_WARNING, cd,
                                          "GET_EVENT and TUR disagree continuously, suppress GET_EVENT events\n");
                                cd->ignore_get_event = true;
                        }
                } else {
                        cd->tur_mismatch = 0;
                }
        }
        cd->tur_changed = false;
        cd->get_event_changed = false;

        return events;
}

/*
 * sr_done is the interrupt routine for the device driver.
 *
 * It will be notified on the end of a SCSI read / write, and will take one
 * of several actions based on success or failure.
 */
static int sr_done(struct scsi_cmnd *SCpnt)
{
        int result = SCpnt->result;
        int this_count = scsi_bufflen(SCpnt);
        int good_bytes = (result == 0 ? this_count : 0);
        int block_sectors = 0;
        long error_sector;
        struct scsi_cd *cd = scsi_cd(SCpnt->request->rq_disk);

#ifdef DEBUG
        scmd_printk(KERN_INFO, SCpnt, "done: %x\n", result);
#endif

        /*
         * Handle MEDIUM ERRORs or VOLUME OVERFLOWs that indicate partial
         * success.  Since this is a relatively rare error condition, no
         * care is taken to avoid unnecessary additional work such as
         * memcpy's that could be avoided.
         */
        if (driver_byte(result) != 0 &&         /* An error occurred */
            (SCpnt->sense_buffer[0] & 0x7f) == 0x70) { /* Sense current */
                switch (SCpnt->sense_buffer[2]) {
                case MEDIUM_ERROR:
                case VOLUME_OVERFLOW:
                case ILLEGAL_REQUEST:
                        if (!(SCpnt->sense_buffer[0] & 0x90))
                                break;
                        error_sector = (SCpnt->sense_buffer[3] << 24) |
                                (SCpnt->sense_buffer[4] << 16) |
                                (SCpnt->sense_buffer[5] << 8) |
                                SCpnt->sense_buffer[6];
                        if (SCpnt->request->bio != NULL)
                                block_sectors =
                                        bio_sectors(SCpnt->request->bio);
                        if (block_sectors < 4)
                                block_sectors = 4;
                        if (cd->device->sector_size == 2048)
                                error_sector <<= 2;
                        error_sector &= ~(block_sectors - 1);
                        good_bytes = (error_sector -
                                      blk_rq_pos(SCpnt->request)) << 9;
                        if (good_bytes < 0 || good_bytes >= this_count)
                                good_bytes = 0;
                        /*
                         * The SCSI specification allows for the value
                         * returned by READ CAPACITY to be up to 75 2K
                         * sectors past the last readable block.
                         * Therefore, if we hit a medium error within the
                         * last 75 2K sectors, we decrease the saved size
                         * value.
                         */
                        if (error_sector < get_capacity(cd->disk) &&
                            cd->capacity - error_sector < 4 * 75)
                                set_capacity(cd->disk, error_sector);
                        break;

                case RECOVERED_ERROR:
                        good_bytes = this_count;
                        break;

                default:
                        break;
                }
        }

        return good_bytes;
}

static int sr_init_command(struct scsi_cmnd *SCpnt)
{
        int block = 0, this_count, s_size;
        struct scsi_cd *cd;
        struct request *rq = SCpnt->request;
        int ret;

        ret = scsi_init_io(SCpnt);
        if (ret != BLKPREP_OK)
                goto out;
        SCpnt = rq->special;
        cd = scsi_cd(rq->rq_disk);

        /* from here on until we're complete, any goto out
         * is used for a killable error condition */
        ret = BLKPREP_KILL;

        SCSI_LOG_HLQUEUE(1, scmd_printk(KERN_INFO, SCpnt,
                "Doing sr request, block = %d\n", block));

        if (!cd->device || !scsi_device_online(cd->device)) {
                SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt,
                        "Finishing %u sectors\n", blk_rq_sectors(rq)));
                SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt,
                        "Retry with 0x%p\n", SCpnt));
                goto out;
        }

        if (cd->device->changed) {
                /*
                 * quietly refuse to do anything to a changed disc until the
                 * changed bit has been reset
                 */
                goto out;
        }

        /*
         * we do lazy blocksize switching (when reading XA sectors,
         * see CDROMREADMODE2 ioctl) 
         */
        s_size = cd->device->sector_size;
        if (s_size > 2048) {
                if (!in_interrupt())
                        sr_set_blocklength(cd, 2048);
                else
                        scmd_printk(KERN_INFO, SCpnt,
                                    "can't switch blocksize: in interrupt\n");
        }

        if (s_size != 512 && s_size != 1024 && s_size != 2048) {
                scmd_printk(KERN_ERR, SCpnt, "bad sector size %d\n", s_size);
                goto out;
        }

        if (rq_data_dir(rq) == WRITE) {
                if (!cd->writeable)
                        goto out;
                SCpnt->cmnd[0] = WRITE_10;
                cd->cdi.media_written = 1;
        } else if (rq_data_dir(rq) == READ) {
                SCpnt->cmnd[0] = READ_10;
        } else {
                blk_dump_rq_flags(rq, "Unknown sr command");
                goto out;
        }

        {
                struct scatterlist *sg;
                int i, size = 0, sg_count = scsi_sg_count(SCpnt);

                scsi_for_each_sg(SCpnt, sg, sg_count, i)
                        size += sg->length;

                if (size != scsi_bufflen(SCpnt)) {
                        scmd_printk(KERN_ERR, SCpnt,
                                "mismatch count %d, bytes %d\n",
                                size, scsi_bufflen(SCpnt));
                        if (scsi_bufflen(SCpnt) > size)
                                SCpnt->sdb.length = size;
                }
        }

        /*
         * request doesn't start on hw block boundary, add scatter pads
         */
        if (((unsigned int)blk_rq_pos(rq) % (s_size >> 9)) ||
            (scsi_bufflen(SCpnt) % s_size)) {
                scmd_printk(KERN_NOTICE, SCpnt, "unaligned transfer\n");
                goto out;
        }

        this_count = (scsi_bufflen(SCpnt) >> 9) / (s_size >> 9);


        SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt,
                                        "%s %d/%u 512 byte blocks.\n",
                                        (rq_data_dir(rq) == WRITE) ?
                                        "writing" : "reading",
                                        this_count, blk_rq_sectors(rq)));

        SCpnt->cmnd[1] = 0;
        block = (unsigned int)blk_rq_pos(rq) / (s_size >> 9);

        if (this_count > 0xffff) {
                this_count = 0xffff;
                SCpnt->sdb.length = this_count * s_size;
        }

        SCpnt->cmnd[2] = (unsigned char) (block >> 24) & 0xff;
        SCpnt->cmnd[3] = (unsigned char) (block >> 16) & 0xff;
        SCpnt->cmnd[4] = (unsigned char) (block >> 8) & 0xff;
        SCpnt->cmnd[5] = (unsigned char) block & 0xff;
        SCpnt->cmnd[6] = SCpnt->cmnd[9] = 0;
        SCpnt->cmnd[7] = (unsigned char) (this_count >> 8) & 0xff;
        SCpnt->cmnd[8] = (unsigned char) this_count & 0xff;

        /*
         * We shouldn't disconnect in the middle of a sector, so with a dumb
         * host adapter, it's safe to assume that we can at least transfer
         * this many bytes between each connect / disconnect.
         */
        SCpnt->transfersize = cd->device->sector_size;
        SCpnt->underflow = this_count << 9;
        SCpnt->allowed = MAX_RETRIES;

        /*
         * This indicates that the command is ready from our end to be
         * queued.
         */
        ret = BLKPREP_OK;
 out:
        return ret;
}

static int sr_block_open(struct block_device *bdev, fmode_t mode)
{
        struct scsi_cd *cd;
        int ret = -ENXIO;

        check_disk_change(bdev);

        mutex_lock(&sr_mutex);
        cd = scsi_cd_get(bdev->bd_disk);
        if (cd) {
                ret = cdrom_open(&cd->cdi, bdev, mode);
                if (ret)
                        scsi_cd_put(cd);
        }
        mutex_unlock(&sr_mutex);
        return ret;
}

static void sr_block_release(struct gendisk *disk, fmode_t mode)
{
        struct scsi_cd *cd = scsi_cd(disk);
        mutex_lock(&sr_mutex);
        cdrom_release(&cd->cdi, mode);
        scsi_cd_put(cd);
        mutex_unlock(&sr_mutex);
}

static int sr_block_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
                          unsigned long arg)
{
        struct scsi_cd *cd = scsi_cd(bdev->bd_disk);
        struct scsi_device *sdev = cd->device;
        void __user *argp = (void __user *)arg;
        int ret;

        mutex_lock(&sr_mutex);

        ret = scsi_ioctl_block_when_processing_errors(sdev, cmd,
                        (mode & FMODE_NDELAY) != 0);
        if (ret)
                goto out;

        /*
         * Send SCSI addressing ioctls directly to mid level, send other
         * ioctls to cdrom/block level.
         */
        switch (cmd) {
        case SCSI_IOCTL_GET_IDLUN:
        case SCSI_IOCTL_GET_BUS_NUMBER:
                ret = scsi_ioctl(sdev, cmd, argp);
                goto out;
        }

        ret = cdrom_ioctl(&cd->cdi, bdev, mode, cmd, arg);
        if (ret != -ENOSYS)
                goto out;

        ret = scsi_ioctl(sdev, cmd, argp);

out:
        mutex_unlock(&sr_mutex);
        return ret;
}

static unsigned int sr_block_check_events(struct gendisk *disk,
                                          unsigned int clearing)
{
        unsigned int ret = 0;
        struct scsi_cd *cd;

        cd = scsi_cd_get(disk);
        if (!cd)
                return 0;

        if (!atomic_read(&cd->device->disk_events_disable_depth))
                ret = cdrom_check_events(&cd->cdi, clearing);

        scsi_cd_put(cd);
        return ret;
}

static int sr_block_revalidate_disk(struct gendisk *disk)
{
        struct scsi_sense_hdr sshdr;
        struct scsi_cd *cd;

        cd = scsi_cd_get(disk);
        if (!cd)
                return -ENXIO;

        /* if the unit is not ready, nothing more to do */
        if (scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr))
                goto out;

        sr_cd_check(&cd->cdi);
        get_sectorsize(cd);
out:
        scsi_cd_put(cd);
        return 0;
}

static const struct block_device_operations sr_bdops =
{
        .owner          = THIS_MODULE,
        .open           = sr_block_open,
        .release        = sr_block_release,
        .ioctl          = sr_block_ioctl,
        .check_events   = sr_block_check_events,
        .revalidate_disk = sr_block_revalidate_disk,
        /* 
         * No compat_ioctl for now because sr_block_ioctl never
         * seems to pass arbitrary ioctls down to host drivers.
         */
};

static int sr_open(struct cdrom_device_info *cdi, int purpose)
{
        struct scsi_cd *cd = cdi->handle;
        struct scsi_device *sdev = cd->device;
        int retval;

        /*
         * If the device is in error recovery, wait until it is done.
         * If the device is offline, then disallow any access to it.
         */
        retval = -ENXIO;
        if (!scsi_block_when_processing_errors(sdev))
                goto error_out;

        return 0;

error_out:
        return retval;  
}

static void sr_release(struct cdrom_device_info *cdi)
{
        struct scsi_cd *cd = cdi->handle;

        if (cd->device->sector_size > 2048)
                sr_set_blocklength(cd, 2048);

}

static int sr_probe(struct device *dev)
{
        struct scsi_device *sdev = to_scsi_device(dev);
        struct gendisk *disk;
        struct scsi_cd *cd;
        int minor, error;

        scsi_autopm_get_device(sdev);
        error = -ENODEV;
        if (sdev->type != TYPE_ROM && sdev->type != TYPE_WORM)
                goto fail;

        error = -ENOMEM;
        cd = kzalloc(sizeof(*cd), GFP_KERNEL);
        if (!cd)
                goto fail;

        kref_init(&cd->kref);

        disk = alloc_disk(1);
        if (!disk)
                goto fail_free;

        spin_lock(&sr_index_lock);
        minor = find_first_zero_bit(sr_index_bits, SR_DISKS);
        if (minor == SR_DISKS) {
                spin_unlock(&sr_index_lock);
                error = -EBUSY;
                goto fail_put;
        }
        __set_bit(minor, sr_index_bits);
        spin_unlock(&sr_index_lock);

        disk->major = SCSI_CDROM_MAJOR;
        disk->first_minor = minor;
        sprintf(disk->disk_name, "sr%d", minor);
        disk->fops = &sr_bdops;
        disk->flags = GENHD_FL_CD | GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE;
        disk->events = DISK_EVENT_MEDIA_CHANGE | DISK_EVENT_EJECT_REQUEST;

        blk_queue_rq_timeout(sdev->request_queue, SR_TIMEOUT);

        cd->device = sdev;
        cd->disk = disk;
        cd->driver = &sr_template;
        cd->disk = disk;
        cd->capacity = 0x1fffff;
        cd->device->changed = 1;        /* force recheck CD type */
        cd->media_present = 1;
        cd->use = 1;
        cd->readcd_known = 0;
        cd->readcd_cdda = 0;

        cd->cdi.ops = &sr_dops;
        cd->cdi.handle = cd;
        cd->cdi.mask = 0;
        cd->cdi.capacity = 1;
        sprintf(cd->cdi.name, "sr%d", minor);

        sdev->sector_size = 2048;       /* A guess, just in case */

        /* FIXME: need to handle a get_capabilities failure properly ?? */
        get_capabilities(cd);
        sr_vendor_init(cd);

        set_capacity(disk, cd->capacity);
        disk->private_data = &cd->driver;
        disk->queue = sdev->request_queue;
        cd->cdi.disk = disk;

        if (register_cdrom(&cd->cdi))
                goto fail_put;

        /*
         * Initialize block layer runtime PM stuffs before the
         * periodic event checking request gets started in add_disk.
         */
        blk_pm_runtime_init(sdev->request_queue, dev);

        dev_set_drvdata(dev, cd);
        disk->flags |= GENHD_FL_REMOVABLE;
        device_add_disk(&sdev->sdev_gendev, disk);

        sdev_printk(KERN_DEBUG, sdev,
                    "Attached scsi CD-ROM %s\n", cd->cdi.name);
        scsi_autopm_put_device(cd->device);

        return 0;

fail_put:
        put_disk(disk);
fail_free:
        kfree(cd);
fail:
        scsi_autopm_put_device(sdev);
        return error;
}


static void get_sectorsize(struct scsi_cd *cd)
{
        unsigned char cmd[10];
        unsigned char buffer[8];
        int the_result, retries = 3;
        int sector_size;
        struct request_queue *queue;

        do {
                cmd[0] = READ_CAPACITY;
                memset((void *) &cmd[1], 0, 9);
                memset(buffer, 0, sizeof(buffer));

                /* Do the command and wait.. */
                the_result = scsi_execute_req(cd->device, cmd, DMA_FROM_DEVICE,
                                              buffer, sizeof(buffer), NULL,
                                              SR_TIMEOUT, MAX_RETRIES, NULL);

                retries--;

        } while (the_result && retries);


        if (the_result) {
                cd->capacity = 0x1fffff;
                sector_size = 2048;     /* A guess, just in case */
        } else {
                long last_written;

                cd->capacity = 1 + ((buffer[0] << 24) | (buffer[1] << 16) |
                                    (buffer[2] << 8) | buffer[3]);
                /*
                 * READ_CAPACITY doesn't return the correct size on
                 * certain UDF media.  If last_written is larger, use
                 * it instead.
                 *
                 * http://bugzilla.kernel.org/show_bug.cgi?id=9668
                 */
                if (!cdrom_get_last_written(&cd->cdi, &last_written))
                        cd->capacity = max_t(long, cd->capacity, last_written);

                sector_size = (buffer[4] << 24) |
                    (buffer[5] << 16) | (buffer[6] << 8) | buffer[7];
                switch (sector_size) {
                        /*
                         * HP 4020i CD-Recorder reports 2340 byte sectors
                         * Philips CD-Writers report 2352 byte sectors
                         *
                         * Use 2k sectors for them..
                         */
                case 0:
                case 2340:
                case 2352:
                        sector_size = 2048;
                        /* fall through */
                case 2048:
                        cd->capacity *= 4;
                        /* fall through */
                case 512:
                        break;
                default:
                        sr_printk(KERN_INFO, cd,
                                  "unsupported sector size %d.", sector_size);
                        cd->capacity = 0;
                }

                cd->device->sector_size = sector_size;

                /*
                 * Add this so that we have the ability to correctly gauge
                 * what the device is capable of.
                 */
                set_capacity(cd->disk, cd->capacity);
        }

        queue = cd->device->request_queue;
        blk_queue_logical_block_size(queue, sector_size);

        return;
}

static void get_capabilities(struct scsi_cd *cd)
{
        unsigned char *buffer;
        struct scsi_mode_data data;
        struct scsi_sense_hdr sshdr;
        unsigned int ms_len = 128;
        int rc, n;

        static const char *loadmech[] =
        {
                "caddy",
                "tray",
                "pop-up",
                "",
                "changer",
                "cartridge changer",
                "",
                ""
        };


        /* allocate transfer buffer */
        buffer = kmalloc(512, GFP_KERNEL | GFP_DMA);
        if (!buffer) {
                sr_printk(KERN_ERR, cd, "out of memory.\n");
                return;
        }

        /* eat unit attentions */
        scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);

        /* ask for mode page 0x2a */
        rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, ms_len,
                             SR_TIMEOUT, 3, &data, NULL);

        if (!scsi_status_is_good(rc) || data.length > ms_len ||
            data.header_length + data.block_descriptor_length > data.length) {
                /* failed, drive doesn't have capabilities mode page */
                cd->cdi.speed = 1;
                cd->cdi.mask |= (CDC_CD_R | CDC_CD_RW | CDC_DVD_R |
                                 CDC_DVD | CDC_DVD_RAM |
                                 CDC_SELECT_DISC | CDC_SELECT_SPEED |
                                 CDC_MRW | CDC_MRW_W | CDC_RAM);
                kfree(buffer);
                sr_printk(KERN_INFO, cd, "scsi-1 drive");
                return;
        }

        n = data.header_length + data.block_descriptor_length;
        cd->cdi.speed = ((buffer[n + 8] << 8) + buffer[n + 9]) / 176;
        cd->readcd_known = 1;
        cd->readcd_cdda = buffer[n + 5] & 0x01;
        /* print some capability bits */
        sr_printk(KERN_INFO, cd,
                  "scsi3-mmc drive: %dx/%dx %s%s%s%s%s%s\n",
                  ((buffer[n + 14] << 8) + buffer[n + 15]) / 176,
                  cd->cdi.speed,
                  buffer[n + 3] & 0x01 ? "writer " : "", /* CD Writer */
                  buffer[n + 3] & 0x20 ? "dvd-ram " : "",
                  buffer[n + 2] & 0x02 ? "cd/rw " : "", /* can read rewriteable */
                  buffer[n + 4] & 0x20 ? "xa/form2 " : "",      /* can read xa/from2 */
                  buffer[n + 5] & 0x01 ? "cdda " : "", /* can read audio data */
                  loadmech[buffer[n + 6] >> 5]);
        if ((buffer[n + 6] >> 5) == 0)
                /* caddy drives can't close tray... */
                cd->cdi.mask |= CDC_CLOSE_TRAY;
        if ((buffer[n + 2] & 0x8) == 0)
                /* not a DVD drive */
                cd->cdi.mask |= CDC_DVD;
        if ((buffer[n + 3] & 0x20) == 0)
                /* can't write DVD-RAM media */
                cd->cdi.mask |= CDC_DVD_RAM;
        if ((buffer[n + 3] & 0x10) == 0)
                /* can't write DVD-R media */
                cd->cdi.mask |= CDC_DVD_R;
        if ((buffer[n + 3] & 0x2) == 0)
                /* can't write CD-RW media */
                cd->cdi.mask |= CDC_CD_RW;
        if ((buffer[n + 3] & 0x1) == 0)
                /* can't write CD-R media */
                cd->cdi.mask |= CDC_CD_R;
        if ((buffer[n + 6] & 0x8) == 0)
                /* can't eject */
                cd->cdi.mask |= CDC_OPEN_TRAY;

        if ((buffer[n + 6] >> 5) == mechtype_individual_changer ||
            (buffer[n + 6] >> 5) == mechtype_cartridge_changer)
                cd->cdi.capacity =
                    cdrom_number_of_slots(&cd->cdi);
        if (cd->cdi.capacity <= 1)
                /* not a changer */
                cd->cdi.mask |= CDC_SELECT_DISC;
        /*else    I don't think it can close its tray
                cd->cdi.mask |= CDC_CLOSE_TRAY; */

        /*
         * if DVD-RAM, MRW-W or CD-RW, we are randomly writable
         */
        if ((cd->cdi.mask & (CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW)) !=
                        (CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW)) {
                cd->writeable = 1;
        }

        kfree(buffer);
}

/*
 * sr_packet() is the entry point for the generic commands generated
 * by the Uniform CD-ROM layer.
 */
static int sr_packet(struct cdrom_device_info *cdi,
                struct packet_command *cgc)
{
        struct scsi_cd *cd = cdi->handle;
        struct scsi_device *sdev = cd->device;

        if (cgc->cmd[0] == GPCMD_READ_DISC_INFO && sdev->no_read_disc_info)
                return -EDRIVE_CANT_DO_THIS;

        if (cgc->timeout <= 0)
                cgc->timeout = IOCTL_TIMEOUT;

        sr_do_ioctl(cd, cgc);

        return cgc->stat;
}

/**
 *      sr_kref_release - Called to free the scsi_cd structure
 *      @kref: pointer to embedded kref
 *
 *      sr_ref_mutex must be held entering this routine.  Because it is
 *      called on last put, you should always use the scsi_cd_get()
 *      scsi_cd_put() helpers which manipulate the semaphore directly
 *      and never do a direct kref_put().
 **/
static void sr_kref_release(struct kref *kref)
{
        struct scsi_cd *cd = container_of(kref, struct scsi_cd, kref);
        struct gendisk *disk = cd->disk;

        spin_lock(&sr_index_lock);
        clear_bit(MINOR(disk_devt(disk)), sr_index_bits);
        spin_unlock(&sr_index_lock);

        unregister_cdrom(&cd->cdi);

        disk->private_data = NULL;

        put_disk(disk);

        kfree(cd);
}

static int sr_remove(struct device *dev)
{
        struct scsi_cd *cd = dev_get_drvdata(dev);

        scsi_autopm_get_device(cd->device);

        del_gendisk(cd->disk);
        dev_set_drvdata(dev, NULL);

        mutex_lock(&sr_ref_mutex);
        kref_put(&cd->kref, sr_kref_release);
        mutex_unlock(&sr_ref_mutex);

        return 0;
}

static int __init init_sr(void)
{
        int rc;

        rc = register_blkdev(SCSI_CDROM_MAJOR, "sr");
        if (rc)
                return rc;
        rc = scsi_register_driver(&sr_template.gendrv);
        if (rc)
                unregister_blkdev(SCSI_CDROM_MAJOR, "sr");

        return rc;
}

static void __exit exit_sr(void)
{
        scsi_unregister_driver(&sr_template.gendrv);
        unregister_blkdev(SCSI_CDROM_MAJOR, "sr");
}

module_init(init_sr);
module_exit(exit_sr);
MODULE_LICENSE("GPL");