Merge remote-tracking branch 'scsi-queue/drivers-for-3.16' into for-linus

[firefly-linux-kernel-4.4.55.git] / drivers / scsi / sd.c

/*
 *      sd.c Copyright (C) 1992 Drew Eckhardt
 *           Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
 *
 *      Linux scsi disk driver
 *              Initial versions: Drew Eckhardt
 *              Subsequent revisions: Eric Youngdale
 *      Modification history:
 *       - Drew Eckhardt <drew@colorado.edu> original
 *       - Eric Youngdale <eric@andante.org> add scatter-gather, multiple 
 *         outstanding request, and other enhancements.
 *         Support loadable low-level scsi drivers.
 *       - Jirka Hanika <geo@ff.cuni.cz> support more scsi disks using 
 *         eight major numbers.
 *       - Richard Gooch <rgooch@atnf.csiro.au> support devfs.
 *       - Torben Mathiasen <tmm@image.dk> Resource allocation fixes in 
 *         sd_init and cleanups.
 *       - Alex Davis <letmein@erols.com> Fix problem where partition info
 *         not being read in sd_open. Fix problem where removable media 
 *         could be ejected after sd_open.
 *       - Douglas Gilbert <dgilbert@interlog.com> cleanup for lk 2.5.x
 *       - Badari Pulavarty <pbadari@us.ibm.com>, Matthew Wilcox 
 *         <willy@debian.org>, Kurt Garloff <garloff@suse.de>: 
 *         Support 32k/1M disks.
 *
 *      Logging policy (needs CONFIG_SCSI_LOGGING defined):
 *       - setting up transfer: SCSI_LOG_HLQUEUE levels 1 and 2
 *       - end of transfer (bh + scsi_lib): SCSI_LOG_HLCOMPLETE level 1
 *       - entering sd_ioctl: SCSI_LOG_IOCTL level 1
 *       - entering other commands: SCSI_LOG_HLQUEUE level 3
 *      Note: when the logging level is set by the user, it must be greater
 *      than the level indicated above to trigger output.       
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/bio.h>
#include <linux/genhd.h>
#include <linux/hdreg.h>
#include <linux/errno.h>
#include <linux/idr.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/string_helpers.h>
#include <linux/async.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsicam.h>

#include "sd.h"
#include "scsi_priv.h"
#include "scsi_logging.h"

MODULE_AUTHOR("Eric Youngdale");
MODULE_DESCRIPTION("SCSI disk (sd) driver");
MODULE_LICENSE("GPL");

MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK0_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK1_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK2_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK3_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK4_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK5_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK6_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK7_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK8_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK9_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK10_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK11_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK12_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK13_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK14_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(SCSI_DISK15_MAJOR);
MODULE_ALIAS_SCSI_DEVICE(TYPE_DISK);
MODULE_ALIAS_SCSI_DEVICE(TYPE_MOD);
MODULE_ALIAS_SCSI_DEVICE(TYPE_RBC);

#if !defined(CONFIG_DEBUG_BLOCK_EXT_DEVT)
#define SD_MINORS       16
#else
#define SD_MINORS       0
#endif

static void sd_config_discard(struct scsi_disk *, unsigned int);
static void sd_config_write_same(struct scsi_disk *);
static int  sd_revalidate_disk(struct gendisk *);
static void sd_unlock_native_capacity(struct gendisk *disk);
static int  sd_probe(struct device *);
static int  sd_remove(struct device *);
static void sd_shutdown(struct device *);
static int sd_suspend_system(struct device *);
static int sd_suspend_runtime(struct device *);
static int sd_resume(struct device *);
static void sd_rescan(struct device *);
static int sd_init_command(struct scsi_cmnd *SCpnt);
static void sd_uninit_command(struct scsi_cmnd *SCpnt);
static int sd_done(struct scsi_cmnd *);
static int sd_eh_action(struct scsi_cmnd *, int);
static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
static void scsi_disk_release(struct device *cdev);
static void sd_print_sense_hdr(struct scsi_disk *, struct scsi_sense_hdr *);
static void sd_print_result(struct scsi_disk *, int);

static DEFINE_SPINLOCK(sd_index_lock);
static DEFINE_IDA(sd_index_ida);

/* 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(sd_ref_mutex);

static struct kmem_cache *sd_cdb_cache;
static mempool_t *sd_cdb_pool;

static const char *sd_cache_types[] = {
        "write through", "none", "write back",
        "write back, no read (daft)"
};

static ssize_t
cache_type_store(struct device *dev, struct device_attribute *attr,
                 const char *buf, size_t count)
{
        int i, ct = -1, rcd, wce, sp;
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;
        char buffer[64];
        char *buffer_data;
        struct scsi_mode_data data;
        struct scsi_sense_hdr sshdr;
        static const char temp[] = "temporary ";
        int len;

        if (sdp->type != TYPE_DISK)
                /* no cache control on RBC devices; theoretically they
                 * can do it, but there's probably so many exceptions
                 * it's not worth the risk */
                return -EINVAL;

        if (strncmp(buf, temp, sizeof(temp) - 1) == 0) {
                buf += sizeof(temp) - 1;
                sdkp->cache_override = 1;
        } else {
                sdkp->cache_override = 0;
        }

        for (i = 0; i < ARRAY_SIZE(sd_cache_types); i++) {
                len = strlen(sd_cache_types[i]);
                if (strncmp(sd_cache_types[i], buf, len) == 0 &&
                    buf[len] == '\n') {
                        ct = i;
                        break;
                }
        }
        if (ct < 0)
                return -EINVAL;
        rcd = ct & 0x01 ? 1 : 0;
        wce = ct & 0x02 ? 1 : 0;

        if (sdkp->cache_override) {
                sdkp->WCE = wce;
                sdkp->RCD = rcd;
                return count;
        }

        if (scsi_mode_sense(sdp, 0x08, 8, buffer, sizeof(buffer), SD_TIMEOUT,
                            SD_MAX_RETRIES, &data, NULL))
                return -EINVAL;
        len = min_t(size_t, sizeof(buffer), data.length - data.header_length -
                  data.block_descriptor_length);
        buffer_data = buffer + data.header_length +
                data.block_descriptor_length;
        buffer_data[2] &= ~0x05;
        buffer_data[2] |= wce << 2 | rcd;
        sp = buffer_data[0] & 0x80 ? 1 : 0;

        if (scsi_mode_select(sdp, 1, sp, 8, buffer_data, len, SD_TIMEOUT,
                             SD_MAX_RETRIES, &data, &sshdr)) {
                if (scsi_sense_valid(&sshdr))
                        sd_print_sense_hdr(sdkp, &sshdr);
                return -EINVAL;
        }
        revalidate_disk(sdkp->disk);
        return count;
}

static ssize_t
manage_start_stop_show(struct device *dev, struct device_attribute *attr,
                       char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;

        return snprintf(buf, 20, "%u\n", sdp->manage_start_stop);
}

static ssize_t
manage_start_stop_store(struct device *dev, struct device_attribute *attr,
                        const char *buf, size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        sdp->manage_start_stop = simple_strtoul(buf, NULL, 10);

        return count;
}
static DEVICE_ATTR_RW(manage_start_stop);

static ssize_t
allow_restart_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 40, "%d\n", sdkp->device->allow_restart);
}

static ssize_t
allow_restart_store(struct device *dev, struct device_attribute *attr,
                    const char *buf, size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (sdp->type != TYPE_DISK)
                return -EINVAL;

        sdp->allow_restart = simple_strtoul(buf, NULL, 10);

        return count;
}
static DEVICE_ATTR_RW(allow_restart);

static ssize_t
cache_type_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        int ct = sdkp->RCD + 2*sdkp->WCE;

        return snprintf(buf, 40, "%s\n", sd_cache_types[ct]);
}
static DEVICE_ATTR_RW(cache_type);

static ssize_t
FUA_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->DPOFUA);
}
static DEVICE_ATTR_RO(FUA);

static ssize_t
protection_type_show(struct device *dev, struct device_attribute *attr,
                     char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->protection_type);
}

static ssize_t
protection_type_store(struct device *dev, struct device_attribute *attr,
                      const char *buf, size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        unsigned int val;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        err = kstrtouint(buf, 10, &val);

        if (err)
                return err;

        if (val >= 0 && val <= SD_DIF_TYPE3_PROTECTION)
                sdkp->protection_type = val;

        return count;
}
static DEVICE_ATTR_RW(protection_type);

static ssize_t
protection_mode_show(struct device *dev, struct device_attribute *attr,
                     char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;
        unsigned int dif, dix;

        dif = scsi_host_dif_capable(sdp->host, sdkp->protection_type);
        dix = scsi_host_dix_capable(sdp->host, sdkp->protection_type);

        if (!dix && scsi_host_dix_capable(sdp->host, SD_DIF_TYPE0_PROTECTION)) {
                dif = 0;
                dix = 1;
        }

        if (!dif && !dix)
                return snprintf(buf, 20, "none\n");

        return snprintf(buf, 20, "%s%u\n", dix ? "dix" : "dif", dif);
}
static DEVICE_ATTR_RO(protection_mode);

static ssize_t
app_tag_own_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->ATO);
}
static DEVICE_ATTR_RO(app_tag_own);

static ssize_t
thin_provisioning_show(struct device *dev, struct device_attribute *attr,
                       char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->lbpme);
}
static DEVICE_ATTR_RO(thin_provisioning);

static const char *lbp_mode[] = {
        [SD_LBP_FULL]           = "full",
        [SD_LBP_UNMAP]          = "unmap",
        [SD_LBP_WS16]           = "writesame_16",
        [SD_LBP_WS10]           = "writesame_10",
        [SD_LBP_ZERO]           = "writesame_zero",
        [SD_LBP_DISABLE]        = "disabled",
};

static ssize_t
provisioning_mode_show(struct device *dev, struct device_attribute *attr,
                       char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%s\n", lbp_mode[sdkp->provisioning_mode]);
}

static ssize_t
provisioning_mode_store(struct device *dev, struct device_attribute *attr,
                        const char *buf, size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (sdp->type != TYPE_DISK)
                return -EINVAL;

        if (!strncmp(buf, lbp_mode[SD_LBP_UNMAP], 20))
                sd_config_discard(sdkp, SD_LBP_UNMAP);
        else if (!strncmp(buf, lbp_mode[SD_LBP_WS16], 20))
                sd_config_discard(sdkp, SD_LBP_WS16);
        else if (!strncmp(buf, lbp_mode[SD_LBP_WS10], 20))
                sd_config_discard(sdkp, SD_LBP_WS10);
        else if (!strncmp(buf, lbp_mode[SD_LBP_ZERO], 20))
                sd_config_discard(sdkp, SD_LBP_ZERO);
        else if (!strncmp(buf, lbp_mode[SD_LBP_DISABLE], 20))
                sd_config_discard(sdkp, SD_LBP_DISABLE);
        else
                return -EINVAL;

        return count;
}
static DEVICE_ATTR_RW(provisioning_mode);

static ssize_t
max_medium_access_timeouts_show(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->max_medium_access_timeouts);
}

static ssize_t
max_medium_access_timeouts_store(struct device *dev,
                                 struct device_attribute *attr, const char *buf,
                                 size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        err = kstrtouint(buf, 10, &sdkp->max_medium_access_timeouts);

        return err ? err : count;
}
static DEVICE_ATTR_RW(max_medium_access_timeouts);

static ssize_t
max_write_same_blocks_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);

        return snprintf(buf, 20, "%u\n", sdkp->max_ws_blocks);
}

static ssize_t
max_write_same_blocks_store(struct device *dev, struct device_attribute *attr,
                            const char *buf, size_t count)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct scsi_device *sdp = sdkp->device;
        unsigned long max;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (sdp->type != TYPE_DISK)
                return -EINVAL;

        err = kstrtoul(buf, 10, &max);

        if (err)
                return err;

        if (max == 0)
                sdp->no_write_same = 1;
        else if (max <= SD_MAX_WS16_BLOCKS) {
                sdp->no_write_same = 0;
                sdkp->max_ws_blocks = max;
        }

        sd_config_write_same(sdkp);

        return count;
}
static DEVICE_ATTR_RW(max_write_same_blocks);

static struct attribute *sd_disk_attrs[] = {
        &dev_attr_cache_type.attr,
        &dev_attr_FUA.attr,
        &dev_attr_allow_restart.attr,
        &dev_attr_manage_start_stop.attr,
        &dev_attr_protection_type.attr,
        &dev_attr_protection_mode.attr,
        &dev_attr_app_tag_own.attr,
        &dev_attr_thin_provisioning.attr,
        &dev_attr_provisioning_mode.attr,
        &dev_attr_max_write_same_blocks.attr,
        &dev_attr_max_medium_access_timeouts.attr,
        NULL,
};
ATTRIBUTE_GROUPS(sd_disk);

static struct class sd_disk_class = {
        .name           = "scsi_disk",
        .owner          = THIS_MODULE,
        .dev_release    = scsi_disk_release,
        .dev_groups     = sd_disk_groups,
};

static const struct dev_pm_ops sd_pm_ops = {
        .suspend                = sd_suspend_system,
        .resume                 = sd_resume,
        .poweroff               = sd_suspend_system,
        .restore                = sd_resume,
        .runtime_suspend        = sd_suspend_runtime,
        .runtime_resume         = sd_resume,
};

static struct scsi_driver sd_template = {
        .owner                  = THIS_MODULE,
        .gendrv = {
                .name           = "sd",
                .probe          = sd_probe,
                .remove         = sd_remove,
                .shutdown       = sd_shutdown,
                .pm             = &sd_pm_ops,
        },
        .rescan                 = sd_rescan,
        .init_command           = sd_init_command,
        .uninit_command         = sd_uninit_command,
        .done                   = sd_done,
        .eh_action              = sd_eh_action,
};

/*
 * Dummy kobj_map->probe function.
 * The default ->probe function will call modprobe, which is
 * pointless as this module is already loaded.
 */
static struct kobject *sd_default_probe(dev_t devt, int *partno, void *data)
{
        return NULL;
}

/*
 * Device no to disk mapping:
 * 
 *       major         disc2     disc  p1
 *   |............|.............|....|....| <- dev_t
 *    31        20 19          8 7  4 3  0
 * 
 * Inside a major, we have 16k disks, however mapped non-
 * contiguously. The first 16 disks are for major0, the next
 * ones with major1, ... Disk 256 is for major0 again, disk 272 
 * for major1, ... 
 * As we stay compatible with our numbering scheme, we can reuse 
 * the well-know SCSI majors 8, 65--71, 136--143.
 */
static int sd_major(int major_idx)
{
        switch (major_idx) {
        case 0:
                return SCSI_DISK0_MAJOR;
        case 1 ... 7:
                return SCSI_DISK1_MAJOR + major_idx - 1;
        case 8 ... 15:
                return SCSI_DISK8_MAJOR + major_idx - 8;
        default:
                BUG();
                return 0;       /* shut up gcc */
        }
}

static struct scsi_disk *__scsi_disk_get(struct gendisk *disk)
{
        struct scsi_disk *sdkp = NULL;

        if (disk->private_data) {
                sdkp = scsi_disk(disk);
                if (scsi_device_get(sdkp->device) == 0)
                        get_device(&sdkp->dev);
                else
                        sdkp = NULL;
        }
        return sdkp;
}

static struct scsi_disk *scsi_disk_get(struct gendisk *disk)
{
        struct scsi_disk *sdkp;

        mutex_lock(&sd_ref_mutex);
        sdkp = __scsi_disk_get(disk);
        mutex_unlock(&sd_ref_mutex);
        return sdkp;
}

static struct scsi_disk *scsi_disk_get_from_dev(struct device *dev)
{
        struct scsi_disk *sdkp;

        mutex_lock(&sd_ref_mutex);
        sdkp = dev_get_drvdata(dev);
        if (sdkp)
                sdkp = __scsi_disk_get(sdkp->disk);
        mutex_unlock(&sd_ref_mutex);
        return sdkp;
}

static void scsi_disk_put(struct scsi_disk *sdkp)
{
        struct scsi_device *sdev = sdkp->device;

        mutex_lock(&sd_ref_mutex);
        put_device(&sdkp->dev);
        scsi_device_put(sdev);
        mutex_unlock(&sd_ref_mutex);
}

static void sd_prot_op(struct scsi_cmnd *scmd, unsigned int dif)
{
        unsigned int prot_op = SCSI_PROT_NORMAL;
        unsigned int dix = scsi_prot_sg_count(scmd);

        if (scmd->sc_data_direction == DMA_FROM_DEVICE) {
                if (dif && dix)
                        prot_op = SCSI_PROT_READ_PASS;
                else if (dif && !dix)
                        prot_op = SCSI_PROT_READ_STRIP;
                else if (!dif && dix)
                        prot_op = SCSI_PROT_READ_INSERT;
        } else {
                if (dif && dix)
                        prot_op = SCSI_PROT_WRITE_PASS;
                else if (dif && !dix)
                        prot_op = SCSI_PROT_WRITE_INSERT;
                else if (!dif && dix)
                        prot_op = SCSI_PROT_WRITE_STRIP;
        }

        scsi_set_prot_op(scmd, prot_op);
        scsi_set_prot_type(scmd, dif);
}

static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
{
        struct request_queue *q = sdkp->disk->queue;
        unsigned int logical_block_size = sdkp->device->sector_size;
        unsigned int max_blocks = 0;

        q->limits.discard_zeroes_data = sdkp->lbprz;
        q->limits.discard_alignment = sdkp->unmap_alignment *
                logical_block_size;
        q->limits.discard_granularity =
                max(sdkp->physical_block_size,
                    sdkp->unmap_granularity * logical_block_size);

        sdkp->provisioning_mode = mode;

        switch (mode) {

        case SD_LBP_DISABLE:
                q->limits.max_discard_sectors = 0;
                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
                return;

        case SD_LBP_UNMAP:
                max_blocks = min_not_zero(sdkp->max_unmap_blocks,
                                          (u32)SD_MAX_WS16_BLOCKS);
                break;

        case SD_LBP_WS16:
                max_blocks = min_not_zero(sdkp->max_ws_blocks,
                                          (u32)SD_MAX_WS16_BLOCKS);
                break;

        case SD_LBP_WS10:
                max_blocks = min_not_zero(sdkp->max_ws_blocks,
                                          (u32)SD_MAX_WS10_BLOCKS);
                break;

        case SD_LBP_ZERO:
                max_blocks = min_not_zero(sdkp->max_ws_blocks,
                                          (u32)SD_MAX_WS10_BLOCKS);
                q->limits.discard_zeroes_data = 1;
                break;
        }

        q->limits.max_discard_sectors = max_blocks * (logical_block_size >> 9);
        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
}

/**
 * sd_setup_discard_cmnd - unmap blocks on thinly provisioned device
 * @sdp: scsi device to operate one
 * @rq: Request to prepare
 *
 * Will issue either UNMAP or WRITE SAME(16) depending on preference
 * indicated by target device.
 **/
static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
{
        struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
        sector_t sector = blk_rq_pos(rq);
        unsigned int nr_sectors = blk_rq_sectors(rq);
        unsigned int nr_bytes = blk_rq_bytes(rq);
        unsigned int len;
        int ret;
        char *buf;
        struct page *page;

        sector >>= ilog2(sdp->sector_size) - 9;
        nr_sectors >>= ilog2(sdp->sector_size) - 9;
        rq->timeout = SD_TIMEOUT;

        memset(rq->cmd, 0, rq->cmd_len);

        page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
        if (!page)
                return BLKPREP_DEFER;

        switch (sdkp->provisioning_mode) {
        case SD_LBP_UNMAP:
                buf = page_address(page);

                rq->cmd_len = 10;
                rq->cmd[0] = UNMAP;
                rq->cmd[8] = 24;

                put_unaligned_be16(6 + 16, &buf[0]);
                put_unaligned_be16(16, &buf[2]);
                put_unaligned_be64(sector, &buf[8]);
                put_unaligned_be32(nr_sectors, &buf[16]);

                len = 24;
                break;

        case SD_LBP_WS16:
                rq->cmd_len = 16;
                rq->cmd[0] = WRITE_SAME_16;
                rq->cmd[1] = 0x8; /* UNMAP */
                put_unaligned_be64(sector, &rq->cmd[2]);
                put_unaligned_be32(nr_sectors, &rq->cmd[10]);

                len = sdkp->device->sector_size;
                break;

        case SD_LBP_WS10:
        case SD_LBP_ZERO:
                rq->cmd_len = 10;
                rq->cmd[0] = WRITE_SAME;
                if (sdkp->provisioning_mode == SD_LBP_WS10)
                        rq->cmd[1] = 0x8; /* UNMAP */
                put_unaligned_be32(sector, &rq->cmd[2]);
                put_unaligned_be16(nr_sectors, &rq->cmd[7]);

                len = sdkp->device->sector_size;
                break;

        default:
                ret = BLKPREP_KILL;
                goto out;
        }

        blk_add_request_payload(rq, page, len);
        ret = scsi_setup_blk_pc_cmnd(sdp, rq);
        rq->buffer = page_address(page);
        rq->__data_len = nr_bytes;

out:
        if (ret != BLKPREP_OK) {
                __free_page(page);
                rq->buffer = NULL;
        }
        return ret;
}

static void sd_config_write_same(struct scsi_disk *sdkp)
{
        struct request_queue *q = sdkp->disk->queue;
        unsigned int logical_block_size = sdkp->device->sector_size;

        if (sdkp->device->no_write_same) {
                sdkp->max_ws_blocks = 0;
                goto out;
        }

        /* Some devices can not handle block counts above 0xffff despite
         * supporting WRITE SAME(16). Consequently we default to 64k
         * blocks per I/O unless the device explicitly advertises a
         * bigger limit.
         */
        if (sdkp->max_ws_blocks > SD_MAX_WS10_BLOCKS)
                sdkp->max_ws_blocks = min_not_zero(sdkp->max_ws_blocks,
                                                   (u32)SD_MAX_WS16_BLOCKS);
        else if (sdkp->ws16 || sdkp->ws10 || sdkp->device->no_report_opcodes)
                sdkp->max_ws_blocks = min_not_zero(sdkp->max_ws_blocks,
                                                   (u32)SD_MAX_WS10_BLOCKS);
        else {
                sdkp->device->no_write_same = 1;
                sdkp->max_ws_blocks = 0;
        }

out:
        blk_queue_max_write_same_sectors(q, sdkp->max_ws_blocks *
                                         (logical_block_size >> 9));
}

/**
 * sd_setup_write_same_cmnd - write the same data to multiple blocks
 * @sdp: scsi device to operate one
 * @rq: Request to prepare
 *
 * Will issue either WRITE SAME(10) or WRITE SAME(16) depending on
 * preference indicated by target device.
 **/
static int sd_setup_write_same_cmnd(struct scsi_device *sdp, struct request *rq)
{
        struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
        struct bio *bio = rq->bio;
        sector_t sector = blk_rq_pos(rq);
        unsigned int nr_sectors = blk_rq_sectors(rq);
        unsigned int nr_bytes = blk_rq_bytes(rq);
        int ret;

        if (sdkp->device->no_write_same)
                return BLKPREP_KILL;

        BUG_ON(bio_offset(bio) || bio_iovec(bio).bv_len != sdp->sector_size);

        sector >>= ilog2(sdp->sector_size) - 9;
        nr_sectors >>= ilog2(sdp->sector_size) - 9;

        rq->__data_len = sdp->sector_size;
        rq->timeout = SD_WRITE_SAME_TIMEOUT;
        memset(rq->cmd, 0, rq->cmd_len);

        if (sdkp->ws16 || sector > 0xffffffff || nr_sectors > 0xffff) {
                rq->cmd_len = 16;
                rq->cmd[0] = WRITE_SAME_16;
                put_unaligned_be64(sector, &rq->cmd[2]);
                put_unaligned_be32(nr_sectors, &rq->cmd[10]);
        } else {
                rq->cmd_len = 10;
                rq->cmd[0] = WRITE_SAME;
                put_unaligned_be32(sector, &rq->cmd[2]);
                put_unaligned_be16(nr_sectors, &rq->cmd[7]);
        }

        ret = scsi_setup_blk_pc_cmnd(sdp, rq);
        rq->__data_len = nr_bytes;

        return ret;
}

static int scsi_setup_flush_cmnd(struct scsi_device *sdp, struct request *rq)
{
        rq->timeout *= SD_FLUSH_TIMEOUT_MULTIPLIER;
        rq->retries = SD_MAX_RETRIES;
        rq->cmd[0] = SYNCHRONIZE_CACHE;
        rq->cmd_len = 10;

        return scsi_setup_blk_pc_cmnd(sdp, rq);
}

static void sd_uninit_command(struct scsi_cmnd *SCpnt)
{
        struct request *rq = SCpnt->request;

        if (rq->cmd_flags & REQ_DISCARD) {
                free_page((unsigned long)rq->buffer);
                rq->buffer = NULL;
        }
        if (SCpnt->cmnd != rq->cmd) {
                mempool_free(SCpnt->cmnd, sd_cdb_pool);
                SCpnt->cmnd = NULL;
                SCpnt->cmd_len = 0;
        }
}

static int sd_init_command(struct scsi_cmnd *SCpnt)
{
        struct request *rq = SCpnt->request;
        struct scsi_device *sdp = SCpnt->device;
        struct gendisk *disk = rq->rq_disk;
        struct scsi_disk *sdkp;
        sector_t block = blk_rq_pos(rq);
        sector_t threshold;
        unsigned int this_count = blk_rq_sectors(rq);
        int ret, host_dif;
        unsigned char protect;

        /*
         * Discard request come in as REQ_TYPE_FS but we turn them into
         * block PC requests to make life easier.
         */
        if (rq->cmd_flags & REQ_DISCARD) {
                ret = sd_setup_discard_cmnd(sdp, rq);
                goto out;
        } else if (rq->cmd_flags & REQ_WRITE_SAME) {
                ret = sd_setup_write_same_cmnd(sdp, rq);
                goto out;
        } else if (rq->cmd_flags & REQ_FLUSH) {
                ret = scsi_setup_flush_cmnd(sdp, rq);
                goto out;
        }
        ret = scsi_setup_fs_cmnd(sdp, rq);
        if (ret != BLKPREP_OK)
                goto out;
        SCpnt = rq->special;
        sdkp = scsi_disk(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,
                        "%s: block=%llu, count=%d\n",
                        __func__, (unsigned long long)block, this_count));

        if (!sdp || !scsi_device_online(sdp) ||
            block + blk_rq_sectors(rq) > get_capacity(disk)) {
                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 (sdp->changed) {
                /*
                 * quietly refuse to do anything to a changed disc until 
                 * the changed bit has been reset
                 */
                /* printk("SCSI disk has been changed or is not present. Prohibiting further I/O.\n"); */
                goto out;
        }

        /*
         * Some SD card readers can't handle multi-sector accesses which touch
         * the last one or two hardware sectors.  Split accesses as needed.
         */
        threshold = get_capacity(disk) - SD_LAST_BUGGY_SECTORS *
                (sdp->sector_size / 512);

        if (unlikely(sdp->last_sector_bug && block + this_count > threshold)) {
                if (block < threshold) {
                        /* Access up to the threshold but not beyond */
                        this_count = threshold - block;
                } else {
                        /* Access only a single hardware sector */
                        this_count = sdp->sector_size / 512;
                }
        }

        SCSI_LOG_HLQUEUE(2, scmd_printk(KERN_INFO, SCpnt, "block=%llu\n",
                                        (unsigned long long)block));

        /*
         * If we have a 1K hardware sectorsize, prevent access to single
         * 512 byte sectors.  In theory we could handle this - in fact
         * the scsi cdrom driver must be able to handle this because
         * we typically use 1K blocksizes, and cdroms typically have
         * 2K hardware sectorsizes.  Of course, things are simpler
         * with the cdrom, since it is read-only.  For performance
         * reasons, the filesystems should be able to handle this
         * and not force the scsi disk driver to use bounce buffers
         * for this.
         */
        if (sdp->sector_size == 1024) {
                if ((block & 1) || (blk_rq_sectors(rq) & 1)) {
                        scmd_printk(KERN_ERR, SCpnt,
                                    "Bad block number requested\n");
                        goto out;
                } else {
                        block = block >> 1;
                        this_count = this_count >> 1;
                }
        }
        if (sdp->sector_size == 2048) {
                if ((block & 3) || (blk_rq_sectors(rq) & 3)) {
                        scmd_printk(KERN_ERR, SCpnt,
                                    "Bad block number requested\n");
                        goto out;
                } else {
                        block = block >> 2;
                        this_count = this_count >> 2;
                }
        }
        if (sdp->sector_size == 4096) {
                if ((block & 7) || (blk_rq_sectors(rq) & 7)) {
                        scmd_printk(KERN_ERR, SCpnt,
                                    "Bad block number requested\n");
                        goto out;
                } else {
                        block = block >> 3;
                        this_count = this_count >> 3;
                }
        }
        if (rq_data_dir(rq) == WRITE) {
                if (!sdp->writeable) {
                        goto out;
                }
                SCpnt->cmnd[0] = WRITE_6;
                SCpnt->sc_data_direction = DMA_TO_DEVICE;

                if (blk_integrity_rq(rq))
                        sd_dif_prepare(rq, block, sdp->sector_size);

        } else if (rq_data_dir(rq) == READ) {
                SCpnt->cmnd[0] = READ_6;
                SCpnt->sc_data_direction = DMA_FROM_DEVICE;
        } else {
                scmd_printk(KERN_ERR, SCpnt, "Unknown command %llx\n", (unsigned long long) rq->cmd_flags);
                goto out;
        }

        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)));

        /* Set RDPROTECT/WRPROTECT if disk is formatted with DIF */
        host_dif = scsi_host_dif_capable(sdp->host, sdkp->protection_type);
        if (host_dif)
                protect = 1 << 5;
        else
                protect = 0;

        if (host_dif == SD_DIF_TYPE2_PROTECTION) {
                SCpnt->cmnd = mempool_alloc(sd_cdb_pool, GFP_ATOMIC);

                if (unlikely(SCpnt->cmnd == NULL)) {
                        ret = BLKPREP_DEFER;
                        goto out;
                }

                SCpnt->cmd_len = SD_EXT_CDB_SIZE;
                memset(SCpnt->cmnd, 0, SCpnt->cmd_len);
                SCpnt->cmnd[0] = VARIABLE_LENGTH_CMD;
                SCpnt->cmnd[7] = 0x18;
                SCpnt->cmnd[9] = (rq_data_dir(rq) == READ) ? READ_32 : WRITE_32;
                SCpnt->cmnd[10] = protect | ((rq->cmd_flags & REQ_FUA) ? 0x8 : 0);

                /* LBA */
                SCpnt->cmnd[12] = sizeof(block) > 4 ? (unsigned char) (block >> 56) & 0xff : 0;
                SCpnt->cmnd[13] = sizeof(block) > 4 ? (unsigned char) (block >> 48) & 0xff : 0;
                SCpnt->cmnd[14] = sizeof(block) > 4 ? (unsigned char) (block >> 40) & 0xff : 0;
                SCpnt->cmnd[15] = sizeof(block) > 4 ? (unsigned char) (block >> 32) & 0xff : 0;
                SCpnt->cmnd[16] = (unsigned char) (block >> 24) & 0xff;
                SCpnt->cmnd[17] = (unsigned char) (block >> 16) & 0xff;
                SCpnt->cmnd[18] = (unsigned char) (block >> 8) & 0xff;
                SCpnt->cmnd[19] = (unsigned char) block & 0xff;

                /* Expected Indirect LBA */
                SCpnt->cmnd[20] = (unsigned char) (block >> 24) & 0xff;
                SCpnt->cmnd[21] = (unsigned char) (block >> 16) & 0xff;
                SCpnt->cmnd[22] = (unsigned char) (block >> 8) & 0xff;
                SCpnt->cmnd[23] = (unsigned char) block & 0xff;

                /* Transfer length */
                SCpnt->cmnd[28] = (unsigned char) (this_count >> 24) & 0xff;
                SCpnt->cmnd[29] = (unsigned char) (this_count >> 16) & 0xff;
                SCpnt->cmnd[30] = (unsigned char) (this_count >> 8) & 0xff;
                SCpnt->cmnd[31] = (unsigned char) this_count & 0xff;
        } else if (sdp->use_16_for_rw) {
                SCpnt->cmnd[0] += READ_16 - READ_6;
                SCpnt->cmnd[1] = protect | ((rq->cmd_flags & REQ_FUA) ? 0x8 : 0);
                SCpnt->cmnd[2] = sizeof(block) > 4 ? (unsigned char) (block >> 56) & 0xff : 0;
                SCpnt->cmnd[3] = sizeof(block) > 4 ? (unsigned char) (block >> 48) & 0xff : 0;
                SCpnt->cmnd[4] = sizeof(block) > 4 ? (unsigned char) (block >> 40) & 0xff : 0;
                SCpnt->cmnd[5] = sizeof(block) > 4 ? (unsigned char) (block >> 32) & 0xff : 0;
                SCpnt->cmnd[6] = (unsigned char) (block >> 24) & 0xff;
                SCpnt->cmnd[7] = (unsigned char) (block >> 16) & 0xff;
                SCpnt->cmnd[8] = (unsigned char) (block >> 8) & 0xff;
                SCpnt->cmnd[9] = (unsigned char) block & 0xff;
                SCpnt->cmnd[10] = (unsigned char) (this_count >> 24) & 0xff;
                SCpnt->cmnd[11] = (unsigned char) (this_count >> 16) & 0xff;
                SCpnt->cmnd[12] = (unsigned char) (this_count >> 8) & 0xff;
                SCpnt->cmnd[13] = (unsigned char) this_count & 0xff;
                SCpnt->cmnd[14] = SCpnt->cmnd[15] = 0;
        } else if ((this_count > 0xff) || (block > 0x1fffff) ||
                   scsi_device_protection(SCpnt->device) ||
                   SCpnt->device->use_10_for_rw) {
                if (this_count > 0xffff)
                        this_count = 0xffff;

                SCpnt->cmnd[0] += READ_10 - READ_6;
                SCpnt->cmnd[1] = protect | ((rq->cmd_flags & REQ_FUA) ? 0x8 : 0);
                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;
        } else {
                if (unlikely(rq->cmd_flags & REQ_FUA)) {
                        /*
                         * This happens only if this drive failed
                         * 10byte rw command with ILLEGAL_REQUEST
                         * during operation and thus turned off
                         * use_10_for_rw.
                         */
                        scmd_printk(KERN_ERR, SCpnt,
                                    "FUA write on READ/WRITE(6) drive\n");
                        goto out;
                }

                SCpnt->cmnd[1] |= (unsigned char) ((block >> 16) & 0x1f);
                SCpnt->cmnd[2] = (unsigned char) ((block >> 8) & 0xff);
                SCpnt->cmnd[3] = (unsigned char) block & 0xff;
                SCpnt->cmnd[4] = (unsigned char) this_count;
                SCpnt->cmnd[5] = 0;
        }
        SCpnt->sdb.length = this_count * sdp->sector_size;

        /* If DIF or DIX is enabled, tell HBA how to handle request */
        if (host_dif || scsi_prot_sg_count(SCpnt))
                sd_prot_op(SCpnt, host_dif);

        /*
         * 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 = sdp->sector_size;
        SCpnt->underflow = this_count << 9;
        SCpnt->allowed = SD_MAX_RETRIES;

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

/**
 *      sd_open - open a scsi disk device
 *      @inode: only i_rdev member may be used
 *      @filp: only f_mode and f_flags may be used
 *
 *      Returns 0 if successful. Returns a negated errno value in case 
 *      of error.
 *
 *      Note: This can be called from a user context (e.g. fsck(1) )
 *      or from within the kernel (e.g. as a result of a mount(1) ).
 *      In the latter case @inode and @filp carry an abridged amount
 *      of information as noted above.
 *
 *      Locking: called with bdev->bd_mutex held.
 **/
static int sd_open(struct block_device *bdev, fmode_t mode)
{
        struct scsi_disk *sdkp = scsi_disk_get(bdev->bd_disk);
        struct scsi_device *sdev;
        int retval;

        if (!sdkp)
                return -ENXIO;

        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_open\n"));

        sdev = sdkp->device;

        /*
         * 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;

        if (sdev->removable || sdkp->write_prot)
                check_disk_change(bdev);

        /*
         * If the drive is empty, just let the open fail.
         */
        retval = -ENOMEDIUM;
        if (sdev->removable && !sdkp->media_present && !(mode & FMODE_NDELAY))
                goto error_out;

        /*
         * If the device has the write protect tab set, have the open fail
         * if the user expects to be able to write to the thing.
         */
        retval = -EROFS;
        if (sdkp->write_prot && (mode & FMODE_WRITE))
                goto error_out;

        /*
         * It is possible that the disk changing stuff resulted in
         * the device being taken offline.  If this is the case,
         * report this to the user, and don't pretend that the
         * open actually succeeded.
         */
        retval = -ENXIO;
        if (!scsi_device_online(sdev))
                goto error_out;

        if ((atomic_inc_return(&sdkp->openers) == 1) && sdev->removable) {
                if (scsi_block_when_processing_errors(sdev))
                        scsi_set_medium_removal(sdev, SCSI_REMOVAL_PREVENT);
        }

        return 0;

error_out:
        scsi_disk_put(sdkp);
        return retval;  
}

/**
 *      sd_release - invoked when the (last) close(2) is called on this
 *      scsi disk.
 *      @inode: only i_rdev member may be used
 *      @filp: only f_mode and f_flags may be used
 *
 *      Returns 0. 
 *
 *      Note: may block (uninterruptible) if error recovery is underway
 *      on this disk.
 *
 *      Locking: called with bdev->bd_mutex held.
 **/
static void sd_release(struct gendisk *disk, fmode_t mode)
{
        struct scsi_disk *sdkp = scsi_disk(disk);
        struct scsi_device *sdev = sdkp->device;

        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_release\n"));

        if (atomic_dec_return(&sdkp->openers) == 0 && sdev->removable) {
                if (scsi_block_when_processing_errors(sdev))
                        scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);
        }

        /*
         * XXX and what if there are packets in flight and this close()
         * XXX is followed by a "rmmod sd_mod"?
         */

        scsi_disk_put(sdkp);
}

static int sd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
        struct scsi_disk *sdkp = scsi_disk(bdev->bd_disk);
        struct scsi_device *sdp = sdkp->device;
        struct Scsi_Host *host = sdp->host;
        int diskinfo[4];

        /* default to most commonly used values */
        diskinfo[0] = 0x40;     /* 1 << 6 */
        diskinfo[1] = 0x20;     /* 1 << 5 */
        diskinfo[2] = sdkp->capacity >> 11;
        
        /* override with calculated, extended default, or driver values */
        if (host->hostt->bios_param)
                host->hostt->bios_param(sdp, bdev, sdkp->capacity, diskinfo);
        else
                scsicam_bios_param(bdev, sdkp->capacity, diskinfo);

        geo->heads = diskinfo[0];
        geo->sectors = diskinfo[1];
        geo->cylinders = diskinfo[2];
        return 0;
}

/**
 *      sd_ioctl - process an ioctl
 *      @inode: only i_rdev/i_bdev members may be used
 *      @filp: only f_mode and f_flags may be used
 *      @cmd: ioctl command number
 *      @arg: this is third argument given to ioctl(2) system call.
 *      Often contains a pointer.
 *
 *      Returns 0 if successful (some ioctls return positive numbers on
 *      success as well). Returns a negated errno value in case of error.
 *
 *      Note: most ioctls are forward onto the block subsystem or further
 *      down in the scsi subsystem.
 **/
static int sd_ioctl(struct block_device *bdev, fmode_t mode,
                    unsigned int cmd, unsigned long arg)
{
        struct gendisk *disk = bdev->bd_disk;
        struct scsi_disk *sdkp = scsi_disk(disk);
        struct scsi_device *sdp = sdkp->device;
        void __user *p = (void __user *)arg;
        int error;
    
        SCSI_LOG_IOCTL(1, sd_printk(KERN_INFO, sdkp, "sd_ioctl: disk=%s, "
                                    "cmd=0x%x\n", disk->disk_name, cmd));

        error = scsi_verify_blk_ioctl(bdev, cmd);
        if (error < 0)
                return error;

        /*
         * If we are in the middle of error recovery, don't let anyone
         * else try and use this device.  Also, if error recovery fails, it
         * may try and take the device offline, in which case all further
         * access to the device is prohibited.
         */
        error = scsi_nonblockable_ioctl(sdp, cmd, p,
                                        (mode & FMODE_NDELAY) != 0);
        if (!scsi_block_when_processing_errors(sdp) || !error)
                goto out;

        /*
         * Send SCSI addressing ioctls directly to mid level, send other
         * ioctls to block level and then onto mid level if they can't be
         * resolved.
         */
        switch (cmd) {
                case SCSI_IOCTL_GET_IDLUN:
                case SCSI_IOCTL_GET_BUS_NUMBER:
                        error = scsi_ioctl(sdp, cmd, p);
                        break;
                default:
                        error = scsi_cmd_blk_ioctl(bdev, mode, cmd, p);
                        if (error != -ENOTTY)
                                break;
                        error = scsi_ioctl(sdp, cmd, p);
                        break;
        }
out:
        return error;
}

static void set_media_not_present(struct scsi_disk *sdkp)
{
        if (sdkp->media_present)
                sdkp->device->changed = 1;

        if (sdkp->device->removable) {
                sdkp->media_present = 0;
                sdkp->capacity = 0;
        }
}

static int media_not_present(struct scsi_disk *sdkp,
                             struct scsi_sense_hdr *sshdr)
{
        if (!scsi_sense_valid(sshdr))
                return 0;

        /* not invoked for commands that could return deferred errors */
        switch (sshdr->sense_key) {
        case UNIT_ATTENTION:
        case NOT_READY:
                /* medium not present */
                if (sshdr->asc == 0x3A) {
                        set_media_not_present(sdkp);
                        return 1;
                }
        }
        return 0;
}

/**
 *      sd_check_events - check media events
 *      @disk: kernel device descriptor
 *      @clearing: disk events currently being cleared
 *
 *      Returns mask of DISK_EVENT_*.
 *
 *      Note: this function is invoked from the block subsystem.
 **/
static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
{
        struct scsi_disk *sdkp = scsi_disk(disk);
        struct scsi_device *sdp = sdkp->device;
        struct scsi_sense_hdr *sshdr = NULL;
        int retval;

        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));

        /*
         * If the device is offline, don't send any commands - just pretend as
         * if the command failed.  If the device ever comes back online, we
         * can deal with it then.  It is only because of unrecoverable errors
         * that we would ever take a device offline in the first place.
         */
        if (!scsi_device_online(sdp)) {
                set_media_not_present(sdkp);
                goto out;
        }

        /*
         * Using TEST_UNIT_READY enables differentiation between drive with
         * no cartridge loaded - NOT READY, drive with changed cartridge -
         * UNIT ATTENTION, or with same cartridge - GOOD STATUS.
         *
         * Drives that auto spin down. eg iomega jaz 1G, will be started
         * by sd_spinup_disk() from sd_revalidate_disk(), which happens whenever
         * sd_revalidate() is called.
         */
        retval = -ENODEV;

        if (scsi_block_when_processing_errors(sdp)) {
                sshdr  = kzalloc(sizeof(*sshdr), GFP_KERNEL);
                retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES,
                                              sshdr);
        }

        /* failed to execute TUR, assume media not present */
        if (host_byte(retval)) {
                set_media_not_present(sdkp);
                goto out;
        }

        if (media_not_present(sdkp, sshdr))
                goto out;

        /*
         * For removable scsi disk we have to recognise the presence
         * of a disk in the drive.
         */
        if (!sdkp->media_present)
                sdp->changed = 1;
        sdkp->media_present = 1;
out:
        /*
         * sdp->changed is set under the following conditions:
         *
         *      Medium present state has changed in either direction.
         *      Device has indicated UNIT_ATTENTION.
         */
        kfree(sshdr);
        retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
        sdp->changed = 0;
        return retval;
}

static int sd_sync_cache(struct scsi_disk *sdkp)
{
        int retries, res;
        struct scsi_device *sdp = sdkp->device;
        const int timeout = sdp->request_queue->rq_timeout
                * SD_FLUSH_TIMEOUT_MULTIPLIER;
        struct scsi_sense_hdr sshdr;

        if (!scsi_device_online(sdp))
                return -ENODEV;

        for (retries = 3; retries > 0; --retries) {
                unsigned char cmd[10] = { 0 };

                cmd[0] = SYNCHRONIZE_CACHE;
                /*
                 * Leave the rest of the command zero to indicate
                 * flush everything.
                 */
                res = scsi_execute_req_flags(sdp, cmd, DMA_NONE, NULL, 0,
                                             &sshdr, timeout, SD_MAX_RETRIES,
                                             NULL, REQ_PM);
                if (res == 0)
                        break;
        }

        if (res) {
                sd_print_result(sdkp, res);

                if (driver_byte(res) & DRIVER_SENSE)
                        sd_print_sense_hdr(sdkp, &sshdr);
                /* we need to evaluate the error return  */
                if (scsi_sense_valid(&sshdr) &&
                        (sshdr.asc == 0x3a ||   /* medium not present */
                         sshdr.asc == 0x20))    /* invalid command */
                                /* this is no error here */
                                return 0;

                switch (host_byte(res)) {
                /* ignore errors due to racing a disconnection */
                case DID_BAD_TARGET:
                case DID_NO_CONNECT:
                        return 0;
                /* signal the upper layer it might try again */
                case DID_BUS_BUSY:
                case DID_IMM_RETRY:
                case DID_REQUEUE:
                case DID_SOFT_ERROR:
                        return -EBUSY;
                default:
                        return -EIO;
                }
        }
        return 0;
}

static void sd_rescan(struct device *dev)
{
        struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);

        if (sdkp) {
                revalidate_disk(sdkp->disk);
                scsi_disk_put(sdkp);
        }
}


#ifdef CONFIG_COMPAT
/* 
 * This gets directly called from VFS. When the ioctl 
 * is not recognized we go back to the other translation paths. 
 */
static int sd_compat_ioctl(struct block_device *bdev, fmode_t mode,
                           unsigned int cmd, unsigned long arg)
{
        struct scsi_device *sdev = scsi_disk(bdev->bd_disk)->device;
        int ret;

        ret = scsi_verify_blk_ioctl(bdev, cmd);
        if (ret < 0)
                return ret;

        /*
         * If we are in the middle of error recovery, don't let anyone
         * else try and use this device.  Also, if error recovery fails, it
         * may try and take the device offline, in which case all further
         * access to the device is prohibited.
         */
        if (!scsi_block_when_processing_errors(sdev))
                return -ENODEV;
               
        if (sdev->host->hostt->compat_ioctl) {
                ret = sdev->host->hostt->compat_ioctl(sdev, cmd, (void __user *)arg);

                return ret;
        }

        /* 
         * Let the static ioctl translation table take care of it.
         */
        return -ENOIOCTLCMD; 
}
#endif

static const struct block_device_operations sd_fops = {
        .owner                  = THIS_MODULE,
        .open                   = sd_open,
        .release                = sd_release,
        .ioctl                  = sd_ioctl,
        .getgeo                 = sd_getgeo,
#ifdef CONFIG_COMPAT
        .compat_ioctl           = sd_compat_ioctl,
#endif
        .check_events           = sd_check_events,
        .revalidate_disk        = sd_revalidate_disk,
        .unlock_native_capacity = sd_unlock_native_capacity,
};

/**
 *      sd_eh_action - error handling callback
 *      @scmd:          sd-issued command that has failed
 *      @eh_disp:       The recovery disposition suggested by the midlayer
 *
 *      This function is called by the SCSI midlayer upon completion of an
 *      error test command (currently TEST UNIT READY). The result of sending
 *      the eh command is passed in eh_disp.  We're looking for devices that
 *      fail medium access commands but are OK with non access commands like
 *      test unit ready (so wrongly see the device as having a successful
 *      recovery)
 **/
static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
{
        struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);

        if (!scsi_device_online(scmd->device) ||
            !scsi_medium_access_command(scmd) ||
            host_byte(scmd->result) != DID_TIME_OUT ||
            eh_disp != SUCCESS)
                return eh_disp;

        /*
         * The device has timed out executing a medium access command.
         * However, the TEST UNIT READY command sent during error
         * handling completed successfully. Either the device is in the
         * process of recovering or has it suffered an internal failure
         * that prevents access to the storage medium.
         */
        sdkp->medium_access_timed_out++;

        /*
         * If the device keeps failing read/write commands but TEST UNIT
         * READY always completes successfully we assume that medium
         * access is no longer possible and take the device offline.
         */
        if (sdkp->medium_access_timed_out >= sdkp->max_medium_access_timeouts) {
                scmd_printk(KERN_ERR, scmd,
                            "Medium access timeout failure. Offlining disk!\n");
                scsi_device_set_state(scmd->device, SDEV_OFFLINE);

                return FAILED;
        }

        return eh_disp;
}

static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
{
        u64 start_lba = blk_rq_pos(scmd->request);
        u64 end_lba = blk_rq_pos(scmd->request) + (scsi_bufflen(scmd) / 512);
        u64 bad_lba;
        int info_valid;
        /*
         * resid is optional but mostly filled in.  When it's unused,
         * its value is zero, so we assume the whole buffer transferred
         */
        unsigned int transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
        unsigned int good_bytes;

        if (scmd->request->cmd_type != REQ_TYPE_FS)
                return 0;

        info_valid = scsi_get_sense_info_fld(scmd->sense_buffer,
                                             SCSI_SENSE_BUFFERSIZE,
                                             &bad_lba);
        if (!info_valid)
                return 0;

        if (scsi_bufflen(scmd) <= scmd->device->sector_size)
                return 0;

        if (scmd->device->sector_size < 512) {
                /* only legitimate sector_size here is 256 */
                start_lba <<= 1;
                end_lba <<= 1;
        } else {
                /* be careful ... don't want any overflows */
                unsigned int factor = scmd->device->sector_size / 512;
                do_div(start_lba, factor);
                do_div(end_lba, factor);
        }

        /* The bad lba was reported incorrectly, we have no idea where
         * the error is.
         */
        if (bad_lba < start_lba  || bad_lba >= end_lba)
                return 0;

        /* This computation should always be done in terms of
         * the resolution of the device's medium.
         */
        good_bytes = (bad_lba - start_lba) * scmd->device->sector_size;
        return min(good_bytes, transferred);
}

/**
 *      sd_done - bottom half handler: called when the lower level
 *      driver has completed (successfully or otherwise) a scsi command.
 *      @SCpnt: mid-level's per command structure.
 *
 *      Note: potentially run from within an ISR. Must not block.
 **/
static int sd_done(struct scsi_cmnd *SCpnt)
{
        int result = SCpnt->result;
        unsigned int good_bytes = result ? 0 : scsi_bufflen(SCpnt);
        struct scsi_sense_hdr sshdr;
        struct scsi_disk *sdkp = scsi_disk(SCpnt->request->rq_disk);
        struct request *req = SCpnt->request;
        int sense_valid = 0;
        int sense_deferred = 0;
        unsigned char op = SCpnt->cmnd[0];
        unsigned char unmap = SCpnt->cmnd[1] & 8;

        if (req->cmd_flags & REQ_DISCARD || req->cmd_flags & REQ_WRITE_SAME) {
                if (!result) {
                        good_bytes = blk_rq_bytes(req);
                        scsi_set_resid(SCpnt, 0);
                } else {
                        good_bytes = 0;
                        scsi_set_resid(SCpnt, blk_rq_bytes(req));
                }
        }

        if (result) {
                sense_valid = scsi_command_normalize_sense(SCpnt, &sshdr);
                if (sense_valid)
                        sense_deferred = scsi_sense_is_deferred(&sshdr);
        }
#ifdef CONFIG_SCSI_LOGGING
        SCSI_LOG_HLCOMPLETE(1, scsi_print_result(SCpnt));
        if (sense_valid) {
                SCSI_LOG_HLCOMPLETE(1, scmd_printk(KERN_INFO, SCpnt,
                                                   "sd_done: sb[respc,sk,asc,"
                                                   "ascq]=%x,%x,%x,%x\n",
                                                   sshdr.response_code,
                                                   sshdr.sense_key, sshdr.asc,
                                                   sshdr.ascq));
        }
#endif
        sdkp->medium_access_timed_out = 0;

        if (driver_byte(result) != DRIVER_SENSE &&
            (!sense_valid || sense_deferred))
                goto out;

        switch (sshdr.sense_key) {
        case HARDWARE_ERROR:
        case MEDIUM_ERROR:
                good_bytes = sd_completed_bytes(SCpnt);
                break;
        case RECOVERED_ERROR:
                good_bytes = scsi_bufflen(SCpnt);
                break;
        case NO_SENSE:
                /* This indicates a false check condition, so ignore it.  An
                 * unknown amount of data was transferred so treat it as an
                 * error.
                 */
                scsi_print_sense("sd", SCpnt);
                SCpnt->result = 0;
                memset(SCpnt->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
                break;
        case ABORTED_COMMAND:
                if (sshdr.asc == 0x10)  /* DIF: Target detected corruption */
                        good_bytes = sd_completed_bytes(SCpnt);
                break;
        case ILLEGAL_REQUEST:
                if (sshdr.asc == 0x10)  /* DIX: Host detected corruption */
                        good_bytes = sd_completed_bytes(SCpnt);
                /* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
                if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
                        switch (op) {
                        case UNMAP:
                                sd_config_discard(sdkp, SD_LBP_DISABLE);
                                break;
                        case WRITE_SAME_16:
                        case WRITE_SAME:
                                if (unmap)
                                        sd_config_discard(sdkp, SD_LBP_DISABLE);
                                else {
                                        sdkp->device->no_write_same = 1;
                                        sd_config_write_same(sdkp);

                                        good_bytes = 0;
                                        req->__data_len = blk_rq_bytes(req);
                                        req->cmd_flags |= REQ_QUIET;
                                }
                        }
                }
                break;
        default:
                break;
        }
 out:
        if (rq_data_dir(SCpnt->request) == READ && scsi_prot_sg_count(SCpnt))
                sd_dif_complete(SCpnt, good_bytes);

        return good_bytes;
}

/*
 * spinup disk - called only in sd_revalidate_disk()
 */
static void
sd_spinup_disk(struct scsi_disk *sdkp)
{
        unsigned char cmd[10];
        unsigned long spintime_expire = 0;
        int retries, spintime;
        unsigned int the_result;
        struct scsi_sense_hdr sshdr;
        int sense_valid = 0;

        spintime = 0;

        /* Spin up drives, as required.  Only do this at boot time */
        /* Spinup needs to be done for module loads too. */
        do {
                retries = 0;

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

                        the_result = scsi_execute_req(sdkp->device, cmd,
                                                      DMA_NONE, NULL, 0,
                                                      &sshdr, SD_TIMEOUT,
                                                      SD_MAX_RETRIES, NULL);

                        /*
                         * If the drive has indicated to us that it
                         * doesn't have any media in it, don't bother
                         * with any more polling.
                         */
                        if (media_not_present(sdkp, &sshdr))
                                return;

                        if (the_result)
                                sense_valid = scsi_sense_valid(&sshdr);
                        retries++;
                } while (retries < 3 && 
                         (!scsi_status_is_good(the_result) ||
                          ((driver_byte(the_result) & DRIVER_SENSE) &&
                          sense_valid && sshdr.sense_key == UNIT_ATTENTION)));

                if ((driver_byte(the_result) & DRIVER_SENSE) == 0) {
                        /* no sense, TUR either succeeded or failed
                         * with a status error */
                        if(!spintime && !scsi_status_is_good(the_result)) {
                                sd_printk(KERN_NOTICE, sdkp, "Unit Not Ready\n");
                                sd_print_result(sdkp, the_result);
                        }
                        break;
                }
                                        
                /*
                 * The device does not want the automatic start to be issued.
                 */
                if (sdkp->device->no_start_on_add)
                        break;

                if (sense_valid && sshdr.sense_key == NOT_READY) {
                        if (sshdr.asc == 4 && sshdr.ascq == 3)
                                break;  /* manual intervention required */
                        if (sshdr.asc == 4 && sshdr.ascq == 0xb)
                                break;  /* standby */
                        if (sshdr.asc == 4 && sshdr.ascq == 0xc)
                                break;  /* unavailable */
                        /*
                         * Issue command to spin up drive when not ready
                         */
                        if (!spintime) {
                                sd_printk(KERN_NOTICE, sdkp, "Spinning up disk...");
                                cmd[0] = START_STOP;
                                cmd[1] = 1;     /* Return immediately */
                                memset((void *) &cmd[2], 0, 8);
                                cmd[4] = 1;     /* Start spin cycle */
                                if (sdkp->device->start_stop_pwr_cond)
                                        cmd[4] |= 1 << 4;
                                scsi_execute_req(sdkp->device, cmd, DMA_NONE,
                                                 NULL, 0, &sshdr,
                                                 SD_TIMEOUT, SD_MAX_RETRIES,
                                                 NULL);
                                spintime_expire = jiffies + 100 * HZ;
                                spintime = 1;
                        }
                        /* Wait 1 second for next try */
                        msleep(1000);
                        printk(".");

                /*
                 * Wait for USB flash devices with slow firmware.
                 * Yes, this sense key/ASC combination shouldn't
                 * occur here.  It's characteristic of these devices.
                 */
                } else if (sense_valid &&
                                sshdr.sense_key == UNIT_ATTENTION &&
                                sshdr.asc == 0x28) {
                        if (!spintime) {
                                spintime_expire = jiffies + 5 * HZ;
                                spintime = 1;
                        }
                        /* Wait 1 second for next try */
                        msleep(1000);
                } else {
                        /* we don't understand the sense code, so it's
                         * probably pointless to loop */
                        if(!spintime) {
                                sd_printk(KERN_NOTICE, sdkp, "Unit Not Ready\n");
                                sd_print_sense_hdr(sdkp, &sshdr);
                        }
                        break;
                }
                                
        } while (spintime && time_before_eq(jiffies, spintime_expire));

        if (spintime) {
                if (scsi_status_is_good(the_result))
                        printk("ready\n");
                else
                        printk("not responding...\n");
        }
}


/*
 * Determine whether disk supports Data Integrity Field.
 */
static int sd_read_protection_type(struct scsi_disk *sdkp, unsigned char *buffer)
{
        struct scsi_device *sdp = sdkp->device;
        u8 type;
        int ret = 0;

        if (scsi_device_protection(sdp) == 0 || (buffer[12] & 1) == 0)
                return ret;

        type = ((buffer[12] >> 1) & 7) + 1; /* P_TYPE 0 = Type 1 */

        if (type > SD_DIF_TYPE3_PROTECTION)
                ret = -ENODEV;
        else if (scsi_host_dif_capable(sdp->host, type))
                ret = 1;

        if (sdkp->first_scan || type != sdkp->protection_type)
                switch (ret) {
                case -ENODEV:
                        sd_printk(KERN_ERR, sdkp, "formatted with unsupported" \
                                  " protection type %u. Disabling disk!\n",
                                  type);
                        break;
                case 1:
                        sd_printk(KERN_NOTICE, sdkp,
                                  "Enabling DIF Type %u protection\n", type);
                        break;
                case 0:
                        sd_printk(KERN_NOTICE, sdkp,
                                  "Disabling DIF Type %u protection\n", type);
                        break;
                }

        sdkp->protection_type = type;

        return ret;
}

static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
                        struct scsi_sense_hdr *sshdr, int sense_valid,
                        int the_result)
{
        sd_print_result(sdkp, the_result);
        if (driver_byte(the_result) & DRIVER_SENSE)
                sd_print_sense_hdr(sdkp, sshdr);
        else
                sd_printk(KERN_NOTICE, sdkp, "Sense not available.\n");

        /*
         * Set dirty bit for removable devices if not ready -
         * sometimes drives will not report this properly.
         */
        if (sdp->removable &&
            sense_valid && sshdr->sense_key == NOT_READY)
                set_media_not_present(sdkp);

        /*
         * We used to set media_present to 0 here to indicate no media
         * in the drive, but some drives fail read capacity even with
         * media present, so we can't do that.
         */
        sdkp->capacity = 0; /* unknown mapped to zero - as usual */
}

#define RC16_LEN 32
#if RC16_LEN > SD_BUF_SIZE
#error RC16_LEN must not be more than SD_BUF_SIZE
#endif

#define READ_CAPACITY_RETRIES_ON_RESET  10

static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
                                                unsigned char *buffer)
{
        unsigned char cmd[16];
        struct scsi_sense_hdr sshdr;
        int sense_valid = 0;
        int the_result;
        int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
        unsigned int alignment;
        unsigned long long lba;
        unsigned sector_size;

        if (sdp->no_read_capacity_16)
                return -EINVAL;

        do {
                memset(cmd, 0, 16);
                cmd[0] = SERVICE_ACTION_IN;
                cmd[1] = SAI_READ_CAPACITY_16;
                cmd[13] = RC16_LEN;
                memset(buffer, 0, RC16_LEN);

                the_result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
                                        buffer, RC16_LEN, &sshdr,
                                        SD_TIMEOUT, SD_MAX_RETRIES, NULL);

                if (media_not_present(sdkp, &sshdr))
                        return -ENODEV;

                if (the_result) {
                        sense_valid = scsi_sense_valid(&sshdr);
                        if (sense_valid &&
                            sshdr.sense_key == ILLEGAL_REQUEST &&
                            (sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
                            sshdr.ascq == 0x00)
                                /* Invalid Command Operation Code or
                                 * Invalid Field in CDB, just retry
                                 * silently with RC10 */
                                return -EINVAL;
                        if (sense_valid &&
                            sshdr.sense_key == UNIT_ATTENTION &&
                            sshdr.asc == 0x29 && sshdr.ascq == 0x00)
                                /* Device reset might occur several times,
                                 * give it one more chance */
                                if (--reset_retries > 0)
                                        continue;
                }
                retries--;

        } while (the_result && retries);

        if (the_result) {
                sd_printk(KERN_NOTICE, sdkp, "READ CAPACITY(16) failed\n");
                read_capacity_error(sdkp, sdp, &sshdr, sense_valid, the_result);
                return -EINVAL;
        }

        sector_size = get_unaligned_be32(&buffer[8]);
        lba = get_unaligned_be64(&buffer[0]);

        if (sd_read_protection_type(sdkp, buffer) < 0) {
                sdkp->capacity = 0;
                return -ENODEV;
        }

        if ((sizeof(sdkp->capacity) == 4) && (lba >= 0xffffffffULL)) {
                sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
                        "kernel compiled with support for large block "
                        "devices.\n");
                sdkp->capacity = 0;
                return -EOVERFLOW;
        }

        /* Logical blocks per physical block exponent */
        sdkp->physical_block_size = (1 << (buffer[13] & 0xf)) * sector_size;

        /* Lowest aligned logical block */
        alignment = ((buffer[14] & 0x3f) << 8 | buffer[15]) * sector_size;
        blk_queue_alignment_offset(sdp->request_queue, alignment);
        if (alignment && sdkp->first_scan)
                sd_printk(KERN_NOTICE, sdkp,
                          "physical block alignment offset: %u\n", alignment);

        if (buffer[14] & 0x80) { /* LBPME */
                sdkp->lbpme = 1;

                if (buffer[14] & 0x40) /* LBPRZ */
                        sdkp->lbprz = 1;

                sd_config_discard(sdkp, SD_LBP_WS16);
        }

        sdkp->capacity = lba + 1;
        return sector_size;
}

static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
                                                unsigned char *buffer)
{
        unsigned char cmd[16];
        struct scsi_sense_hdr sshdr;
        int sense_valid = 0;
        int the_result;
        int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
        sector_t lba;
        unsigned sector_size;

        do {
                cmd[0] = READ_CAPACITY;
                memset(&cmd[1], 0, 9);
                memset(buffer, 0, 8);

                the_result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
                                        buffer, 8, &sshdr,
                                        SD_TIMEOUT, SD_MAX_RETRIES, NULL);

                if (media_not_present(sdkp, &sshdr))
                        return -ENODEV;

                if (the_result) {
                        sense_valid = scsi_sense_valid(&sshdr);
                        if (sense_valid &&
                            sshdr.sense_key == UNIT_ATTENTION &&
                            sshdr.asc == 0x29 && sshdr.ascq == 0x00)
                                /* Device reset might occur several times,
                                 * give it one more chance */
                                if (--reset_retries > 0)
                                        continue;
                }
                retries--;

        } while (the_result && retries);

        if (the_result) {
                sd_printk(KERN_NOTICE, sdkp, "READ CAPACITY failed\n");
                read_capacity_error(sdkp, sdp, &sshdr, sense_valid, the_result);
                return -EINVAL;
        }

        sector_size = get_unaligned_be32(&buffer[4]);
        lba = get_unaligned_be32(&buffer[0]);

        if (sdp->no_read_capacity_16 && (lba == 0xffffffff)) {
                /* Some buggy (usb cardreader) devices return an lba of
                   0xffffffff when the want to report a size of 0 (with
                   which they really mean no media is present) */
                sdkp->capacity = 0;
                sdkp->physical_block_size = sector_size;
                return sector_size;
        }

        if ((sizeof(sdkp->capacity) == 4) && (lba == 0xffffffff)) {
                sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
                        "kernel compiled with support for large block "
                        "devices.\n");
                sdkp->capacity = 0;
                return -EOVERFLOW;
        }

        sdkp->capacity = lba + 1;
        sdkp->physical_block_size = sector_size;
        return sector_size;
}

static int sd_try_rc16_first(struct scsi_device *sdp)
{
        if (sdp->host->max_cmd_len < 16)
                return 0;
        if (sdp->try_rc_10_first)
                return 0;
        if (sdp->scsi_level > SCSI_SPC_2)
                return 1;
        if (scsi_device_protection(sdp))
                return 1;
        return 0;
}

/*
 * read disk capacity
 */
static void
sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
{
        int sector_size;
        struct scsi_device *sdp = sdkp->device;
        sector_t old_capacity = sdkp->capacity;

        if (sd_try_rc16_first(sdp)) {
                sector_size = read_capacity_16(sdkp, sdp, buffer);
                if (sector_size == -EOVERFLOW)
                        goto got_data;
                if (sector_size == -ENODEV)
                        return;
                if (sector_size < 0)
                        sector_size = read_capacity_10(sdkp, sdp, buffer);
                if (sector_size < 0)
                        return;
        } else {
                sector_size = read_capacity_10(sdkp, sdp, buffer);
                if (sector_size == -EOVERFLOW)
                        goto got_data;
                if (sector_size < 0)
                        return;
                if ((sizeof(sdkp->capacity) > 4) &&
                    (sdkp->capacity > 0xffffffffULL)) {
                        int old_sector_size = sector_size;
                        sd_printk(KERN_NOTICE, sdkp, "Very big device. "
                                        "Trying to use READ CAPACITY(16).\n");
                        sector_size = read_capacity_16(sdkp, sdp, buffer);
                        if (sector_size < 0) {
                                sd_printk(KERN_NOTICE, sdkp,
                                        "Using 0xffffffff as device size\n");
                                sdkp->capacity = 1 + (sector_t) 0xffffffff;
                                sector_size = old_sector_size;
                                goto got_data;
                        }
                }
        }

        /* Some devices are known to return the total number of blocks,
         * not the highest block number.  Some devices have versions
         * which do this and others which do not.  Some devices we might
         * suspect of doing this but we don't know for certain.
         *
         * If we know the reported capacity is wrong, decrement it.  If
         * we can only guess, then assume the number of blocks is even
         * (usually true but not always) and err on the side of lowering
         * the capacity.
         */
        if (sdp->fix_capacity ||
            (sdp->guess_capacity && (sdkp->capacity & 0x01))) {
                sd_printk(KERN_INFO, sdkp, "Adjusting the sector count "
                                "from its reported value: %llu\n",
                                (unsigned long long) sdkp->capacity);
                --sdkp->capacity;
        }

got_data:
        if (sector_size == 0) {
                sector_size = 512;
                sd_printk(KERN_NOTICE, sdkp, "Sector size 0 reported, "
                          "assuming 512.\n");
        }

        if (sector_size != 512 &&
            sector_size != 1024 &&
            sector_size != 2048 &&
            sector_size != 4096 &&
            sector_size != 256) {
                sd_printk(KERN_NOTICE, sdkp, "Unsupported sector size %d.\n",
                          sector_size);
                /*
                 * The user might want to re-format the drive with
                 * a supported sectorsize.  Once this happens, it
                 * would be relatively trivial to set the thing up.
                 * For this reason, we leave the thing in the table.
                 */
                sdkp->capacity = 0;
                /*
                 * set a bogus sector size so the normal read/write
                 * logic in the block layer will eventually refuse any
                 * request on this device without tripping over power
                 * of two sector size assumptions
                 */
                sector_size = 512;
        }
        blk_queue_logical_block_size(sdp->request_queue, sector_size);

        {
                char cap_str_2[10], cap_str_10[10];
                u64 sz = (u64)sdkp->capacity << ilog2(sector_size);

                string_get_size(sz, STRING_UNITS_2, cap_str_2,
                                sizeof(cap_str_2));
                string_get_size(sz, STRING_UNITS_10, cap_str_10,
                                sizeof(cap_str_10));

                if (sdkp->first_scan || old_capacity != sdkp->capacity) {
                        sd_printk(KERN_NOTICE, sdkp,
                                  "%llu %d-byte logical blocks: (%s/%s)\n",
                                  (unsigned long long)sdkp->capacity,
                                  sector_size, cap_str_10, cap_str_2);

                        if (sdkp->physical_block_size != sector_size)
                                sd_printk(KERN_NOTICE, sdkp,
                                          "%u-byte physical blocks\n",
                                          sdkp->physical_block_size);
                }
        }

        sdp->use_16_for_rw = (sdkp->capacity > 0xffffffff);

        /* Rescale capacity to 512-byte units */
        if (sector_size == 4096)
                sdkp->capacity <<= 3;
        else if (sector_size == 2048)
                sdkp->capacity <<= 2;
        else if (sector_size == 1024)
                sdkp->capacity <<= 1;
        else if (sector_size == 256)
                sdkp->capacity >>= 1;

        blk_queue_physical_block_size(sdp->request_queue,
                                      sdkp->physical_block_size);
        sdkp->device->sector_size = sector_size;
}

/* called with buffer of length 512 */
static inline int
sd_do_mode_sense(struct scsi_device *sdp, int dbd, int modepage,
                 unsigned char *buffer, int len, struct scsi_mode_data *data,
                 struct scsi_sense_hdr *sshdr)
{
        return scsi_mode_sense(sdp, dbd, modepage, buffer, len,
                               SD_TIMEOUT, SD_MAX_RETRIES, data,
                               sshdr);
}

/*
 * read write protect setting, if possible - called only in sd_revalidate_disk()
 * called with buffer of length SD_BUF_SIZE
 */
static void
sd_read_write_protect_flag(struct scsi_disk *sdkp, unsigned char *buffer)
{
        int res;
        struct scsi_device *sdp = sdkp->device;
        struct scsi_mode_data data;
        int old_wp = sdkp->write_prot;

        set_disk_ro(sdkp->disk, 0);
        if (sdp->skip_ms_page_3f) {
                sd_first_printk(KERN_NOTICE, sdkp, "Assuming Write Enabled\n");
                return;
        }

        if (sdp->use_192_bytes_for_3f) {
                res = sd_do_mode_sense(sdp, 0, 0x3F, buffer, 192, &data, NULL);
        } else {
                /*
                 * First attempt: ask for all pages (0x3F), but only 4 bytes.
                 * We have to start carefully: some devices hang if we ask
                 * for more than is available.
                 */
                res = sd_do_mode_sense(sdp, 0, 0x3F, buffer, 4, &data, NULL);

                /*
                 * Second attempt: ask for page 0 When only page 0 is
                 * implemented, a request for page 3F may return Sense Key
                 * 5: Illegal Request, Sense Code 24: Invalid field in
                 * CDB.
                 */
                if (!scsi_status_is_good(res))
                        res = sd_do_mode_sense(sdp, 0, 0, buffer, 4, &data, NULL);

                /*
                 * Third attempt: ask 255 bytes, as we did earlier.
                 */
                if (!scsi_status_is_good(res))
                        res = sd_do_mode_sense(sdp, 0, 0x3F, buffer, 255,
                                               &data, NULL);
        }

        if (!scsi_status_is_good(res)) {
                sd_first_printk(KERN_WARNING, sdkp,
                          "Test WP failed, assume Write Enabled\n");
        } else {
                sdkp->write_prot = ((data.device_specific & 0x80) != 0);
                set_disk_ro(sdkp->disk, sdkp->write_prot);
                if (sdkp->first_scan || old_wp != sdkp->write_prot) {
                        sd_printk(KERN_NOTICE, sdkp, "Write Protect is %s\n",
                                  sdkp->write_prot ? "on" : "off");
                        sd_printk(KERN_DEBUG, sdkp,
                                  "Mode Sense: %02x %02x %02x %02x\n",
                                  buffer[0], buffer[1], buffer[2], buffer[3]);
                }
        }
}

/*
 * sd_read_cache_type - called only from sd_revalidate_disk()
 * called with buffer of length SD_BUF_SIZE
 */
static void
sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
{
        int len = 0, res;
        struct scsi_device *sdp = sdkp->device;

        int dbd;
        int modepage;
        int first_len;
        struct scsi_mode_data data;
        struct scsi_sense_hdr sshdr;
        int old_wce = sdkp->WCE;
        int old_rcd = sdkp->RCD;
        int old_dpofua = sdkp->DPOFUA;


        if (sdkp->cache_override)
                return;

        first_len = 4;
        if (sdp->skip_ms_page_8) {
                if (sdp->type == TYPE_RBC)
                        goto defaults;
                else {
                        if (sdp->skip_ms_page_3f)
                                goto defaults;
                        modepage = 0x3F;
                        if (sdp->use_192_bytes_for_3f)
                                first_len = 192;
                        dbd = 0;
                }
        } else if (sdp->type == TYPE_RBC) {
                modepage = 6;
                dbd = 8;
        } else {
                modepage = 8;
                dbd = 0;
        }

        /* cautiously ask */
        res = sd_do_mode_sense(sdp, dbd, modepage, buffer, first_len,
                        &data, &sshdr);

        if (!scsi_status_is_good(res))
                goto bad_sense;

        if (!data.header_length) {
                modepage = 6;
                first_len = 0;
                sd_first_printk(KERN_ERR, sdkp,
                                "Missing header in MODE_SENSE response\n");
        }

        /* that went OK, now ask for the proper length */
        len = data.length;

        /*
         * We're only interested in the first three bytes, actually.
         * But the data cache page is defined for the first 20.
         */
        if (len < 3)
                goto bad_sense;
        else if (len > SD_BUF_SIZE) {
                sd_first_printk(KERN_NOTICE, sdkp, "Truncating mode parameter "
                          "data from %d to %d bytes\n", len, SD_BUF_SIZE);
                len = SD_BUF_SIZE;
        }
        if (modepage == 0x3F && sdp->use_192_bytes_for_3f)
                len = 192;

        /* Get the data */
        if (len > first_len)
                res = sd_do_mode_sense(sdp, dbd, modepage, buffer, len,
                                &data, &sshdr);

        if (scsi_status_is_good(res)) {
                int offset = data.header_length + data.block_descriptor_length;

                while (offset < len) {
                        u8 page_code = buffer[offset] & 0x3F;
                        u8 spf       = buffer[offset] & 0x40;

                        if (page_code == 8 || page_code == 6) {
                                /* We're interested only in the first 3 bytes.
                                 */
                                if (len - offset <= 2) {
                                        sd_first_printk(KERN_ERR, sdkp,
                                                "Incomplete mode parameter "
                                                        "data\n");
                                        goto defaults;
                                } else {
                                        modepage = page_code;
                                        goto Page_found;
                                }
                        } else {
                                /* Go to the next page */
                                if (spf && len - offset > 3)
                                        offset += 4 + (buffer[offset+2] << 8) +
                                                buffer[offset+3];
                                else if (!spf && len - offset > 1)
                                        offset += 2 + buffer[offset+1];
                                else {
                                        sd_first_printk(KERN_ERR, sdkp,
                                                        "Incomplete mode "
                                                        "parameter data\n");
                                        goto defaults;
                                }
                        }
                }

                sd_first_printk(KERN_ERR, sdkp, "No Caching mode page found\n");
                goto defaults;

        Page_found:
                if (modepage == 8) {
                        sdkp->WCE = ((buffer[offset + 2] & 0x04) != 0);
                        sdkp->RCD = ((buffer[offset + 2] & 0x01) != 0);
                } else {
                        sdkp->WCE = ((buffer[offset + 2] & 0x01) == 0);
                        sdkp->RCD = 0;
                }

                sdkp->DPOFUA = (data.device_specific & 0x10) != 0;
                if (sdkp->DPOFUA && !sdkp->device->use_10_for_rw) {
                        sd_first_printk(KERN_NOTICE, sdkp,
                                  "Uses READ/WRITE(6), disabling FUA\n");
                        sdkp->DPOFUA = 0;
                }

                if (sdkp->first_scan || old_wce != sdkp->WCE ||
                    old_rcd != sdkp->RCD || old_dpofua != sdkp->DPOFUA)
                        sd_printk(KERN_NOTICE, sdkp,
                                  "Write cache: %s, read cache: %s, %s\n",
                                  sdkp->WCE ? "enabled" : "disabled",
                                  sdkp->RCD ? "disabled" : "enabled",
                                  sdkp->DPOFUA ? "supports DPO and FUA"
                                  : "doesn't support DPO or FUA");

                return;
        }

bad_sense:
        if (scsi_sense_valid(&sshdr) &&
            sshdr.sense_key == ILLEGAL_REQUEST &&
            sshdr.asc == 0x24 && sshdr.ascq == 0x0)
                /* Invalid field in CDB */
                sd_first_printk(KERN_NOTICE, sdkp, "Cache data unavailable\n");
        else
                sd_first_printk(KERN_ERR, sdkp,
                                "Asking for cache data failed\n");

defaults:
        if (sdp->wce_default_on) {
                sd_first_printk(KERN_NOTICE, sdkp,
                                "Assuming drive cache: write back\n");
                sdkp->WCE = 1;
        } else {
                sd_first_printk(KERN_ERR, sdkp,
                                "Assuming drive cache: write through\n");
                sdkp->WCE = 0;
        }
        sdkp->RCD = 0;
        sdkp->DPOFUA = 0;
}

/*
 * The ATO bit indicates whether the DIF application tag is available
 * for use by the operating system.
 */
static void sd_read_app_tag_own(struct scsi_disk *sdkp, unsigned char *buffer)
{
        int res, offset;
        struct scsi_device *sdp = sdkp->device;
        struct scsi_mode_data data;
        struct scsi_sense_hdr sshdr;

        if (sdp->type != TYPE_DISK)
                return;

        if (sdkp->protection_type == 0)
                return;

        res = scsi_mode_sense(sdp, 1, 0x0a, buffer, 36, SD_TIMEOUT,
                              SD_MAX_RETRIES, &data, &sshdr);

        if (!scsi_status_is_good(res) || !data.header_length ||
            data.length < 6) {
                sd_first_printk(KERN_WARNING, sdkp,
                          "getting Control mode page failed, assume no ATO\n");

                if (scsi_sense_valid(&sshdr))
                        sd_print_sense_hdr(sdkp, &sshdr);

                return;
        }

        offset = data.header_length + data.block_descriptor_length;

        if ((buffer[offset] & 0x3f) != 0x0a) {
                sd_first_printk(KERN_ERR, sdkp, "ATO Got wrong page\n");
                return;
        }

        if ((buffer[offset + 5] & 0x80) == 0)
                return;

        sdkp->ATO = 1;

        return;
}

/**
 * sd_read_block_limits - Query disk device for preferred I/O sizes.
 * @disk: disk to query
 */
static void sd_read_block_limits(struct scsi_disk *sdkp)
{
        unsigned int sector_sz = sdkp->device->sector_size;
        const int vpd_len = 64;
        unsigned char *buffer = kmalloc(vpd_len, GFP_KERNEL);

        if (!buffer ||
            /* Block Limits VPD */
            scsi_get_vpd_page(sdkp->device, 0xb0, buffer, vpd_len))
                goto out;

        blk_queue_io_min(sdkp->disk->queue,
                         get_unaligned_be16(&buffer[6]) * sector_sz);
        blk_queue_io_opt(sdkp->disk->queue,
                         get_unaligned_be32(&buffer[12]) * sector_sz);

        if (buffer[3] == 0x3c) {
                unsigned int lba_count, desc_count;

                sdkp->max_ws_blocks = (u32)get_unaligned_be64(&buffer[36]);

                if (!sdkp->lbpme)
                        goto out;

                lba_count = get_unaligned_be32(&buffer[20]);
                desc_count = get_unaligned_be32(&buffer[24]);

                if (lba_count && desc_count)
                        sdkp->max_unmap_blocks = lba_count;

                sdkp->unmap_granularity = get_unaligned_be32(&buffer[28]);

                if (buffer[32] & 0x80)
                        sdkp->unmap_alignment =
                                get_unaligned_be32(&buffer[32]) & ~(1 << 31);

                if (!sdkp->lbpvpd) { /* LBP VPD page not provided */

                        if (sdkp->max_unmap_blocks)
                                sd_config_discard(sdkp, SD_LBP_UNMAP);
                        else
                                sd_config_discard(sdkp, SD_LBP_WS16);

                } else {        /* LBP VPD page tells us what to use */

                        if (sdkp->lbpu && sdkp->max_unmap_blocks)
                                sd_config_discard(sdkp, SD_LBP_UNMAP);
                        else if (sdkp->lbpws)
                                sd_config_discard(sdkp, SD_LBP_WS16);
                        else if (sdkp->lbpws10)
                                sd_config_discard(sdkp, SD_LBP_WS10);
                        else
                                sd_config_discard(sdkp, SD_LBP_DISABLE);
                }
        }

 out:
        kfree(buffer);
}

/**
 * sd_read_block_characteristics - Query block dev. characteristics
 * @disk: disk to query
 */
static void sd_read_block_characteristics(struct scsi_disk *sdkp)
{
        unsigned char *buffer;
        u16 rot;
        const int vpd_len = 64;

        buffer = kmalloc(vpd_len, GFP_KERNEL);

        if (!buffer ||
            /* Block Device Characteristics VPD */
            scsi_get_vpd_page(sdkp->device, 0xb1, buffer, vpd_len))
                goto out;

        rot = get_unaligned_be16(&buffer[4]);

        if (rot == 1)
                queue_flag_set_unlocked(QUEUE_FLAG_NONROT, sdkp->disk->queue);

 out:
        kfree(buffer);
}

/**
 * sd_read_block_provisioning - Query provisioning VPD page
 * @disk: disk to query
 */
static void sd_read_block_provisioning(struct scsi_disk *sdkp)
{
        unsigned char *buffer;
        const int vpd_len = 8;

        if (sdkp->lbpme == 0)
                return;

        buffer = kmalloc(vpd_len, GFP_KERNEL);

        if (!buffer || scsi_get_vpd_page(sdkp->device, 0xb2, buffer, vpd_len))
                goto out;

        sdkp->lbpvpd    = 1;
        sdkp->lbpu      = (buffer[5] >> 7) & 1; /* UNMAP */
        sdkp->lbpws     = (buffer[5] >> 6) & 1; /* WRITE SAME(16) with UNMAP */
        sdkp->lbpws10   = (buffer[5] >> 5) & 1; /* WRITE SAME(10) with UNMAP */

 out:
        kfree(buffer);
}

static void sd_read_write_same(struct scsi_disk *sdkp, unsigned char *buffer)
{
        struct scsi_device *sdev = sdkp->device;

        if (sdev->host->no_write_same) {
                sdev->no_write_same = 1;

                return;
        }

        if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, INQUIRY) < 0) {
                /* too large values might cause issues with arcmsr */
                int vpd_buf_len = 64;

                sdev->no_report_opcodes = 1;

                /* Disable WRITE SAME if REPORT SUPPORTED OPERATION
                 * CODES is unsupported and the device has an ATA
                 * Information VPD page (SAT).
                 */
                if (!scsi_get_vpd_page(sdev, 0x89, buffer, vpd_buf_len))
                        sdev->no_write_same = 1;
        }

        if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME_16) == 1)
                sdkp->ws16 = 1;

        if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, WRITE_SAME) == 1)
                sdkp->ws10 = 1;
}

static int sd_try_extended_inquiry(struct scsi_device *sdp)
{
        /*
         * Although VPD inquiries can go to SCSI-2 type devices,
         * some USB ones crash on receiving them, and the pages
         * we currently ask for are for SPC-3 and beyond
         */
        if (sdp->scsi_level > SCSI_SPC_2 && !sdp->skip_vpd_pages)
                return 1;
        return 0;
}

/**
 *      sd_revalidate_disk - called the first time a new disk is seen,
 *      performs disk spin up, read_capacity, etc.
 *      @disk: struct gendisk we care about
 **/
static int sd_revalidate_disk(struct gendisk *disk)
{
        struct scsi_disk *sdkp = scsi_disk(disk);
        struct scsi_device *sdp = sdkp->device;
        unsigned char *buffer;
        unsigned flush = 0;

        SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,
                                      "sd_revalidate_disk\n"));

        /*
         * If the device is offline, don't try and read capacity or any
         * of the other niceties.
         */
        if (!scsi_device_online(sdp))
                goto out;

        buffer = kmalloc(SD_BUF_SIZE, GFP_KERNEL);
        if (!buffer) {
                sd_printk(KERN_WARNING, sdkp, "sd_revalidate_disk: Memory "
                          "allocation failure.\n");
                goto out;
        }

        sd_spinup_disk(sdkp);

        /*
         * Without media there is no reason to ask; moreover, some devices
         * react badly if we do.
         */
        if (sdkp->media_present) {
                sd_read_capacity(sdkp, buffer);

                if (sd_try_extended_inquiry(sdp)) {
                        sd_read_block_provisioning(sdkp);
                        sd_read_block_limits(sdkp);
                        sd_read_block_characteristics(sdkp);
                }

                sd_read_write_protect_flag(sdkp, buffer);
                sd_read_cache_type(sdkp, buffer);
                sd_read_app_tag_own(sdkp, buffer);
                sd_read_write_same(sdkp, buffer);
        }

        sdkp->first_scan = 0;

        /*
         * We now have all cache related info, determine how we deal
         * with flush requests.
         */
        if (sdkp->WCE) {
                flush |= REQ_FLUSH;
                if (sdkp->DPOFUA)
                        flush |= REQ_FUA;
        }

        blk_queue_flush(sdkp->disk->queue, flush);

        set_capacity(disk, sdkp->capacity);
        sd_config_write_same(sdkp);
        kfree(buffer);

 out:
        return 0;
}

/**
 *      sd_unlock_native_capacity - unlock native capacity
 *      @disk: struct gendisk to set capacity for
 *
 *      Block layer calls this function if it detects that partitions
 *      on @disk reach beyond the end of the device.  If the SCSI host
 *      implements ->unlock_native_capacity() method, it's invoked to
 *      give it a chance to adjust the device capacity.
 *
 *      CONTEXT:
 *      Defined by block layer.  Might sleep.
 */
static void sd_unlock_native_capacity(struct gendisk *disk)
{
        struct scsi_device *sdev = scsi_disk(disk)->device;

        if (sdev->host->hostt->unlock_native_capacity)
                sdev->host->hostt->unlock_native_capacity(sdev);
}

/**
 *      sd_format_disk_name - format disk name
 *      @prefix: name prefix - ie. "sd" for SCSI disks
 *      @index: index of the disk to format name for
 *      @buf: output buffer
 *      @buflen: length of the output buffer
 *
 *      SCSI disk names starts at sda.  The 26th device is sdz and the
 *      27th is sdaa.  The last one for two lettered suffix is sdzz
 *      which is followed by sdaaa.
 *
 *      This is basically 26 base counting with one extra 'nil' entry
 *      at the beginning from the second digit on and can be
 *      determined using similar method as 26 base conversion with the
 *      index shifted -1 after each digit is computed.
 *
 *      CONTEXT:
 *      Don't care.
 *
 *      RETURNS:
 *      0 on success, -errno on failure.
 */
static int sd_format_disk_name(char *prefix, int index, char *buf, int buflen)
{
        const int base = 'z' - 'a' + 1;
        char *begin = buf + strlen(prefix);
        char *end = buf + buflen;
        char *p;
        int unit;

        p = end - 1;
        *p = '\0';
        unit = base;
        do {
                if (p == begin)
                        return -EINVAL;
                *--p = 'a' + (index % unit);
                index = (index / unit) - 1;
        } while (index >= 0);

        memmove(begin, p, end - p);
        memcpy(buf, prefix, strlen(prefix));

        return 0;
}

/*
 * The asynchronous part of sd_probe
 */
static void sd_probe_async(void *data, async_cookie_t cookie)
{
        struct scsi_disk *sdkp = data;
        struct scsi_device *sdp;
        struct gendisk *gd;
        u32 index;
        struct device *dev;

        sdp = sdkp->device;
        gd = sdkp->disk;
        index = sdkp->index;
        dev = &sdp->sdev_gendev;

        gd->major = sd_major((index & 0xf0) >> 4);
        gd->first_minor = ((index & 0xf) << 4) | (index & 0xfff00);
        gd->minors = SD_MINORS;

        gd->fops = &sd_fops;
        gd->private_data = &sdkp->driver;
        gd->queue = sdkp->device->request_queue;

        /* defaults, until the device tells us otherwise */
        sdp->sector_size = 512;
        sdkp->capacity = 0;
        sdkp->media_present = 1;
        sdkp->write_prot = 0;
        sdkp->cache_override = 0;
        sdkp->WCE = 0;
        sdkp->RCD = 0;
        sdkp->ATO = 0;
        sdkp->first_scan = 1;
        sdkp->max_medium_access_timeouts = SD_MAX_MEDIUM_TIMEOUTS;

        sd_revalidate_disk(gd);

        gd->driverfs_dev = &sdp->sdev_gendev;
        gd->flags = GENHD_FL_EXT_DEVT;
        if (sdp->removable) {
                gd->flags |= GENHD_FL_REMOVABLE;
                gd->events |= DISK_EVENT_MEDIA_CHANGE;
        }

        blk_pm_runtime_init(sdp->request_queue, dev);
        add_disk(gd);
        if (sdkp->capacity)
                sd_dif_config_host(sdkp);

        sd_revalidate_disk(gd);

        sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n",
                  sdp->removable ? "removable " : "");
        scsi_autopm_put_device(sdp);
        put_device(&sdkp->dev);
}

/**
 *      sd_probe - called during driver initialization and whenever a
 *      new scsi device is attached to the system. It is called once
 *      for each scsi device (not just disks) present.
 *      @dev: pointer to device object
 *
 *      Returns 0 if successful (or not interested in this scsi device 
 *      (e.g. scanner)); 1 when there is an error.
 *
 *      Note: this function is invoked from the scsi mid-level.
 *      This function sets up the mapping between a given 
 *      <host,channel,id,lun> (found in sdp) and new device name 
 *      (e.g. /dev/sda). More precisely it is the block device major 
 *      and minor number that is chosen here.
 *
 *      Assume sd_probe is not re-entrant (for time being)
 *      Also think about sd_probe() and sd_remove() running coincidentally.
 **/
static int sd_probe(struct device *dev)
{
        struct scsi_device *sdp = to_scsi_device(dev);
        struct scsi_disk *sdkp;
        struct gendisk *gd;
        int index;
        int error;

        error = -ENODEV;
        if (sdp->type != TYPE_DISK && sdp->type != TYPE_MOD && sdp->type != TYPE_RBC)
                goto out;

        SCSI_LOG_HLQUEUE(3, sdev_printk(KERN_INFO, sdp,
                                        "sd_probe\n"));

        error = -ENOMEM;
        sdkp = kzalloc(sizeof(*sdkp), GFP_KERNEL);
        if (!sdkp)
                goto out;

        gd = alloc_disk(SD_MINORS);
        if (!gd)
                goto out_free;

        do {
                if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))
                        goto out_put;

                spin_lock(&sd_index_lock);
                error = ida_get_new(&sd_index_ida, &index);
                spin_unlock(&sd_index_lock);
        } while (error == -EAGAIN);

        if (error) {
                sdev_printk(KERN_WARNING, sdp, "sd_probe: memory exhausted.\n");
                goto out_put;
        }

        error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);
        if (error) {
                sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name length exceeded.\n");
                goto out_free_index;
        }

        sdkp->device = sdp;
        sdkp->driver = &sd_template;
        sdkp->disk = gd;
        sdkp->index = index;
        atomic_set(&sdkp->openers, 0);
        atomic_set(&sdkp->device->ioerr_cnt, 0);

        if (!sdp->request_queue->rq_timeout) {
                if (sdp->type != TYPE_MOD)
                        blk_queue_rq_timeout(sdp->request_queue, SD_TIMEOUT);
                else
                        blk_queue_rq_timeout(sdp->request_queue,
                                             SD_MOD_TIMEOUT);
        }

        device_initialize(&sdkp->dev);
        sdkp->dev.parent = dev;
        sdkp->dev.class = &sd_disk_class;
        dev_set_name(&sdkp->dev, "%s", dev_name(dev));

        if (device_add(&sdkp->dev))
                goto out_free_index;

        get_device(dev);
        dev_set_drvdata(dev, sdkp);

        get_device(&sdkp->dev); /* prevent release before async_schedule */
        async_schedule_domain(sd_probe_async, sdkp, &scsi_sd_probe_domain);

        return 0;

 out_free_index:
        spin_lock(&sd_index_lock);
        ida_remove(&sd_index_ida, index);
        spin_unlock(&sd_index_lock);
 out_put:
        put_disk(gd);
 out_free:
        kfree(sdkp);
 out:
        return error;
}

/**
 *      sd_remove - called whenever a scsi disk (previously recognized by
 *      sd_probe) is detached from the system. It is called (potentially
 *      multiple times) during sd module unload.
 *      @sdp: pointer to mid level scsi device object
 *
 *      Note: this function is invoked from the scsi mid-level.
 *      This function potentially frees up a device name (e.g. /dev/sdc)
 *      that could be re-used by a subsequent sd_probe().
 *      This function is not called when the built-in sd driver is "exit-ed".
 **/
static int sd_remove(struct device *dev)
{
        struct scsi_disk *sdkp;
        dev_t devt;

        sdkp = dev_get_drvdata(dev);
        devt = disk_devt(sdkp->disk);
        scsi_autopm_get_device(sdkp->device);

        async_synchronize_full_domain(&scsi_sd_pm_domain);
        async_synchronize_full_domain(&scsi_sd_probe_domain);
        device_del(&sdkp->dev);
        del_gendisk(sdkp->disk);
        sd_shutdown(dev);

        blk_register_region(devt, SD_MINORS, NULL,
                            sd_default_probe, NULL, NULL);

        mutex_lock(&sd_ref_mutex);
        dev_set_drvdata(dev, NULL);
        put_device(&sdkp->dev);
        mutex_unlock(&sd_ref_mutex);

        return 0;
}

/**
 *      scsi_disk_release - Called to free the scsi_disk structure
 *      @dev: pointer to embedded class device
 *
 *      sd_ref_mutex must be held entering this routine.  Because it is
 *      called on last put, you should always use the scsi_disk_get()
 *      scsi_disk_put() helpers which manipulate the semaphore directly
 *      and never do a direct put_device.
 **/
static void scsi_disk_release(struct device *dev)
{
        struct scsi_disk *sdkp = to_scsi_disk(dev);
        struct gendisk *disk = sdkp->disk;
        
        spin_lock(&sd_index_lock);
        ida_remove(&sd_index_ida, sdkp->index);
        spin_unlock(&sd_index_lock);

        disk->private_data = NULL;
        put_disk(disk);
        put_device(&sdkp->device->sdev_gendev);

        kfree(sdkp);
}

static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
{
        unsigned char cmd[6] = { START_STOP };  /* START_VALID */
        struct scsi_sense_hdr sshdr;
        struct scsi_device *sdp = sdkp->device;
        int res;

        if (start)
                cmd[4] |= 1;    /* START */

        if (sdp->start_stop_pwr_cond)
                cmd[4] |= start ? 1 << 4 : 3 << 4;      /* Active or Standby */

        if (!scsi_device_online(sdp))
                return -ENODEV;

        res = scsi_execute_req_flags(sdp, cmd, DMA_NONE, NULL, 0, &sshdr,
                               SD_TIMEOUT, SD_MAX_RETRIES, NULL, REQ_PM);
        if (res) {
                sd_printk(KERN_WARNING, sdkp, "START_STOP FAILED\n");
                sd_print_result(sdkp, res);
                if (driver_byte(res) & DRIVER_SENSE)
                        sd_print_sense_hdr(sdkp, &sshdr);
                if (scsi_sense_valid(&sshdr) &&
                        /* 0x3a is medium not present */
                        sshdr.asc == 0x3a)
                        res = 0;
        }

        /* SCSI error codes must not go to the generic layer */
        if (res)
                return -EIO;

        return 0;
}

/*
 * Send a SYNCHRONIZE CACHE instruction down to the device through
 * the normal SCSI command structure.  Wait for the command to
 * complete.
 */
static void sd_shutdown(struct device *dev)
{
        struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);

        if (!sdkp)
                return;         /* this can happen */

        if (pm_runtime_suspended(dev))
                goto exit;

        if (sdkp->WCE && sdkp->media_present) {
                sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
                sd_sync_cache(sdkp);
        }

        if (system_state != SYSTEM_RESTART && sdkp->device->manage_start_stop) {
                sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
                sd_start_stop_device(sdkp, 0);
        }

exit:
        scsi_disk_put(sdkp);
}

static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
{
        struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);
        int ret = 0;

        if (!sdkp)
                return 0;       /* this can happen */

        if (sdkp->WCE && sdkp->media_present) {
                sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
                ret = sd_sync_cache(sdkp);
                if (ret) {
                        /* ignore OFFLINE device */
                        if (ret == -ENODEV)
                                ret = 0;
                        goto done;
                }
        }

        if (sdkp->device->manage_start_stop) {
                sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
                /* an error is not worth aborting a system sleep */
                ret = sd_start_stop_device(sdkp, 0);
                if (ignore_stop_errors)
                        ret = 0;
        }

done:
        scsi_disk_put(sdkp);
        return ret;
}

static int sd_suspend_system(struct device *dev)
{
        return sd_suspend_common(dev, true);
}

static int sd_suspend_runtime(struct device *dev)
{
        return sd_suspend_common(dev, false);
}

static int sd_resume(struct device *dev)
{
        struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);
        int ret = 0;

        if (!sdkp->device->manage_start_stop)
                goto done;

        sd_printk(KERN_NOTICE, sdkp, "Starting disk\n");
        ret = sd_start_stop_device(sdkp, 1);

done:
        scsi_disk_put(sdkp);
        return ret;
}

/**
 *      init_sd - entry point for this driver (both when built in or when
 *      a module).
 *
 *      Note: this function registers this driver with the scsi mid-level.
 **/
static int __init init_sd(void)
{
        int majors = 0, i, err;

        SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));

        for (i = 0; i < SD_MAJORS; i++) {
                if (register_blkdev(sd_major(i), "sd") != 0)
                        continue;
                majors++;
                blk_register_region(sd_major(i), SD_MINORS, NULL,
                                    sd_default_probe, NULL, NULL);
        }

        if (!majors)
                return -ENODEV;

        err = class_register(&sd_disk_class);
        if (err)
                goto err_out;

        sd_cdb_cache = kmem_cache_create("sd_ext_cdb", SD_EXT_CDB_SIZE,
                                         0, 0, NULL);
        if (!sd_cdb_cache) {
                printk(KERN_ERR "sd: can't init extended cdb cache\n");
                goto err_out_class;
        }

        sd_cdb_pool = mempool_create_slab_pool(SD_MEMPOOL_SIZE, sd_cdb_cache);
        if (!sd_cdb_pool) {
                printk(KERN_ERR "sd: can't init extended cdb pool\n");
                goto err_out_cache;
        }

        err = scsi_register_driver(&sd_template.gendrv);
        if (err)
                goto err_out_driver;

        return 0;

err_out_driver:
        mempool_destroy(sd_cdb_pool);

err_out_cache:
        kmem_cache_destroy(sd_cdb_cache);

err_out_class:
        class_unregister(&sd_disk_class);
err_out:
        for (i = 0; i < SD_MAJORS; i++)
                unregister_blkdev(sd_major(i), "sd");
        return err;
}

/**
 *      exit_sd - exit point for this driver (when it is a module).
 *
 *      Note: this function unregisters this driver from the scsi mid-level.
 **/
static void __exit exit_sd(void)
{
        int i;

        SCSI_LOG_HLQUEUE(3, printk("exit_sd: exiting sd driver\n"));

        scsi_unregister_driver(&sd_template.gendrv);
        mempool_destroy(sd_cdb_pool);
        kmem_cache_destroy(sd_cdb_cache);

        class_unregister(&sd_disk_class);

        for (i = 0; i < SD_MAJORS; i++) {
                blk_unregister_region(sd_major(i), SD_MINORS);
                unregister_blkdev(sd_major(i), "sd");
        }
}

module_init(init_sd);
module_exit(exit_sd);

static void sd_print_sense_hdr(struct scsi_disk *sdkp,
                               struct scsi_sense_hdr *sshdr)
{
        sd_printk(KERN_INFO, sdkp, " ");
        scsi_show_sense_hdr(sshdr);
        sd_printk(KERN_INFO, sdkp, " ");
        scsi_show_extd_sense(sshdr->asc, sshdr->ascq);
}

static void sd_print_result(struct scsi_disk *sdkp, int result)
{
        sd_printk(KERN_INFO, sdkp, " ");
        scsi_show_result(result);
}