[libata] ATA passthru (arbitrary ATA command execution)

[linux-2.6] / drivers / scsi / libata-scsi.c

/*
   libata-scsi.c - helper library for ATA

   Copyright 2003-2004 Red Hat, Inc.  All rights reserved.
   Copyright 2003-2004 Jeff Garzik

   The contents of this file are subject to the Open
   Software License version 1.1 that can be found at
   http://www.opensource.org/licenses/osl-1.1.txt and is included herein
   by reference.

   Alternatively, the contents of this file may be used under the terms
   of the GNU General Public License version 2 (the "GPL") as distributed
   in the kernel source COPYING file, in which case the provisions of
   the GPL are applicable instead of the above.  If you wish to allow
   the use of your version of this file only under the terms of the
   GPL and not to allow others to use your version of this file under
   the OSL, indicate your decision by deleting the provisions above and
   replace them with the notice and other provisions required by the GPL.
   If you do not delete the provisions above, a recipient may use your
   version of this file under either the OSL or the GPL.

 */

#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/spinlock.h>
#include <scsi/scsi.h>
#include "scsi.h"
#include <scsi/scsi_host.h>
#include <linux/libata.h>
#include <linux/hdreg.h>
#include <asm/uaccess.h>

#include "libata.h"

#define SECTOR_SIZE     512

typedef unsigned int (*ata_xlat_func_t)(struct ata_queued_cmd *qc, u8 *scsicmd);
static struct ata_device *
ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev);


/**
 *      ata_std_bios_param - generic bios head/sector/cylinder calculator used by sd.
 *      @sdev: SCSI device for which BIOS geometry is to be determined
 *      @bdev: block device associated with @sdev
 *      @capacity: capacity of SCSI device
 *      @geom: location to which geometry will be output
 *
 *      Generic bios head/sector/cylinder calculator
 *      used by sd. Most BIOSes nowadays expect a XXX/255/16  (CHS)
 *      mapping. Some situations may arise where the disk is not
 *      bootable if this is not used.
 *
 *      LOCKING:
 *      Defined by the SCSI layer.  We don't really care.
 *
 *      RETURNS:
 *      Zero.
 */
int ata_std_bios_param(struct scsi_device *sdev, struct block_device *bdev,
                       sector_t capacity, int geom[])
{
        geom[0] = 255;
        geom[1] = 63;
        sector_div(capacity, 255*63);
        geom[2] = capacity;

        return 0;
}

/**
 *      ata_cmd_ioctl - Handler for HDIO_DRIVE_CMD ioctl
 *      @dev: Device to whom we are issuing command
 *      @arg: User provided data for issuing command
 *
 *      LOCKING:
 *      Defined by the SCSI layer.  We don't really care.
 *
 *      RETURNS:
 *      Zero on success, negative errno on error.
 */

int ata_cmd_ioctl(struct scsi_device *scsidev, void __user *arg)
{
        int rc = 0;
        u8 scsi_cmd[MAX_COMMAND_SIZE];
        u8 args[4], *argbuf = NULL;
        int argsize = 0;
        struct scsi_request *sreq;

        if (NULL == (void *)arg)
                return -EINVAL;

        if (copy_from_user(args, arg, sizeof(args)))
                return -EFAULT;

        sreq = scsi_allocate_request(scsidev, GFP_KERNEL);
        if (!sreq)
                return -EINTR;

        memset(scsi_cmd, 0, sizeof(scsi_cmd));

        if (args[3]) {
                argsize = SECTOR_SIZE * args[3];
                argbuf = kmalloc(argsize, GFP_KERNEL);
                if (argbuf == NULL)
                        return -ENOMEM;

                scsi_cmd[1]  = (4 << 1); /* PIO Data-in */
                scsi_cmd[2]  = 0x0e;     /* no off.line or cc, read from dev,
                                            block count in sector count field */
                sreq->sr_data_direction = DMA_FROM_DEVICE;
        } else {
                scsi_cmd[1]  = (3 << 1); /* Non-data */
                /* scsi_cmd[2] is already 0 -- no off.line, cc, or data xfer */
                sreq->sr_data_direction = DMA_NONE;
        }

        scsi_cmd[0] = ATA_16;

        scsi_cmd[4] = args[2];
        if (args[0] == WIN_SMART) { /* hack -- ide driver does this too... */
                scsi_cmd[6]  = args[3];
                scsi_cmd[8]  = args[1];
                scsi_cmd[10] = 0x4f;
                scsi_cmd[12] = 0xc2;
        } else {
                scsi_cmd[6]  = args[1];
        }
        scsi_cmd[14] = args[0];

        /* Good values for timeout and retries?  Values below
           from scsi_ioctl_send_command() for default case... */
        scsi_wait_req(sreq, scsi_cmd, argbuf, argsize, (10*HZ), 5);

        if (sreq->sr_result) {
                rc = -EIO;
                goto error;
        }

        /* Need code to retrieve data from check condition? */

        if ((argbuf)
         && copy_to_user((void *)(arg + sizeof(args)), argbuf, argsize))
                rc = -EFAULT;
error:
        scsi_release_request(sreq);

        if (argbuf)
                kfree(argbuf);

        return rc;
}

/**
 *      ata_task_ioctl - Handler for HDIO_DRIVE_TASK ioctl
 *      @dev: Device to whom we are issuing command
 *      @arg: User provided data for issuing command
 *
 *      LOCKING:
 *      Defined by the SCSI layer.  We don't really care.
 *
 *      RETURNS:
 *      Zero on success, negative errno on error.
 */
int ata_task_ioctl(struct scsi_device *scsidev, void __user *arg)
{
        int rc = 0;
        u8 scsi_cmd[MAX_COMMAND_SIZE];
        u8 args[7];
        struct scsi_request *sreq;

        if (NULL == (void *)arg)
                return -EINVAL;

        if (copy_from_user(args, arg, sizeof(args)))
                return -EFAULT;

        memset(scsi_cmd, 0, sizeof(scsi_cmd));
        scsi_cmd[0]  = ATA_16;
        scsi_cmd[1]  = (3 << 1); /* Non-data */
        /* scsi_cmd[2] is already 0 -- no off.line, cc, or data xfer */
        scsi_cmd[4]  = args[1];
        scsi_cmd[6]  = args[2];
        scsi_cmd[8]  = args[3];
        scsi_cmd[10] = args[4];
        scsi_cmd[12] = args[5];
        scsi_cmd[14] = args[0];

        sreq = scsi_allocate_request(scsidev, GFP_KERNEL);
        if (!sreq) {
                rc = -EINTR;
                goto error;
        }

        sreq->sr_data_direction = DMA_NONE;
        /* Good values for timeout and retries?  Values below
           from scsi_ioctl_send_command() for default case... */
        scsi_wait_req(sreq, scsi_cmd, NULL, 0, (10*HZ), 5);

        if (sreq->sr_result) {
                rc = -EIO;
                goto error;
        }

        /* Need code to retrieve data from check condition? */

error:
        scsi_release_request(sreq);
        return rc;
}

int ata_scsi_ioctl(struct scsi_device *scsidev, int cmd, void __user *arg)
{
        struct ata_port *ap;
        struct ata_device *dev;
        int val = -EINVAL, rc = -EINVAL;

        ap = (struct ata_port *) &scsidev->host->hostdata[0];
        if (!ap)
                goto out;

        dev = ata_scsi_find_dev(ap, scsidev);
        if (!dev) {
                rc = -ENODEV;
                goto out;
        }

        switch (cmd) {
        case ATA_IOC_GET_IO32:
                val = 0;
                if (copy_to_user(arg, &val, 1))
                        return -EFAULT;
                return 0;

        case ATA_IOC_SET_IO32:
                val = (unsigned long) arg;
                if (val != 0)
                        return -EINVAL;
                return 0;

        case HDIO_DRIVE_CMD:
                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                        return -EACCES;
                return ata_cmd_ioctl(scsidev, arg);

        case HDIO_DRIVE_TASK:
                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                        return -EACCES;
                return ata_task_ioctl(scsidev, arg);

        default:
                rc = -ENOTTY;
                break;
        }

out:
        return rc;
}

/**
 *      ata_scsi_qc_new - acquire new ata_queued_cmd reference
 *      @ap: ATA port to which the new command is attached
 *      @dev: ATA device to which the new command is attached
 *      @cmd: SCSI command that originated this ATA command
 *      @done: SCSI command completion function
 *
 *      Obtain a reference to an unused ata_queued_cmd structure,
 *      which is the basic libata structure representing a single
 *      ATA command sent to the hardware.
 *
 *      If a command was available, fill in the SCSI-specific
 *      portions of the structure with information on the
 *      current command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Command allocated, or %NULL if none available.
 */
struct ata_queued_cmd *ata_scsi_qc_new(struct ata_port *ap,
                                       struct ata_device *dev,
                                       struct scsi_cmnd *cmd,
                                       void (*done)(struct scsi_cmnd *))
{
        struct ata_queued_cmd *qc;

        qc = ata_qc_new_init(ap, dev);
        if (qc) {
                qc->scsicmd = cmd;
                qc->scsidone = done;

                if (cmd->use_sg) {
                        qc->sg = (struct scatterlist *) cmd->request_buffer;
                        qc->n_elem = cmd->use_sg;
                } else {
                        qc->sg = &qc->sgent;
                        qc->n_elem = 1;
                }
        } else {
                cmd->result = (DID_OK << 16) | (QUEUE_FULL << 1);
                done(cmd);
        }

        return qc;
}

/**
 *      ata_dump_status - user friendly display of error info
 *      @id: id of the port in question
 *      @tf: ptr to filled out taskfile
 *
 *      Decode and dump the ATA error/status registers for the user so
 *      that they have some idea what really happened at the non
 *      make-believe layer.
 *
 *      LOCKING:
 *      inherited from caller
 */
void ata_dump_status(unsigned id, struct ata_taskfile *tf)
{
        u8 stat = tf->command, err = tf->feature;

        printk(KERN_WARNING "ata%u: status=0x%02x { ", id, stat);
        if (stat & ATA_BUSY) {
                printk("Busy }\n");     /* Data is not valid in this case */
        } else {
                if (stat & 0x40)        printk("DriveReady ");
                if (stat & 0x20)        printk("DeviceFault ");
                if (stat & 0x10)        printk("SeekComplete ");
                if (stat & 0x08)        printk("DataRequest ");
                if (stat & 0x04)        printk("CorrectedError ");
                if (stat & 0x02)        printk("Index ");
                if (stat & 0x01)        printk("Error ");
                printk("}\n");

                if (err) {
                        printk(KERN_WARNING "ata%u: error=0x%02x { ", id, err);
                        if (err & 0x04)         printk("DriveStatusError ");
                        if (err & 0x80) {
                                if (err & 0x04) printk("BadCRC ");
                                else            printk("Sector ");
                        }
                        if (err & 0x40)         printk("UncorrectableError ");
                        if (err & 0x10)         printk("SectorIdNotFound ");
                        if (err & 0x02)         printk("TrackZeroNotFound ");
                        if (err & 0x01)         printk("AddrMarkNotFound ");
                        printk("}\n");
                }
        }
}

/**
 *      ata_to_sense_error - convert ATA error to SCSI error
 *      @drv_stat: value contained in ATA status register
 *      @drv_err: value contained in ATA error register
 *      @sk: the sense key we'll fill out
 *      @asc: the additional sense code we'll fill out
 *      @ascq: the additional sense code qualifier we'll fill out
 *
 *      Converts an ATA error into a SCSI error.  Fill out pointers to
 *      SK, ASC, and ASCQ bytes for later use in fixed or descriptor
 *      format sense blocks.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */
void ata_to_sense_error(unsigned id, u8 drv_stat, u8 drv_err, u8 *sk, u8 *asc, 
                        u8 *ascq)
{
        int i;
        /* Based on the 3ware driver translation table */
        static unsigned char sense_table[][4] = {
                /* BBD|ECC|ID|MAR */
                {0xd1,          ABORTED_COMMAND, 0x00, 0x00},   // Device busy                  Aborted command
                /* BBD|ECC|ID */
                {0xd0,          ABORTED_COMMAND, 0x00, 0x00},   // Device busy                  Aborted command
                /* ECC|MC|MARK */
                {0x61,          HARDWARE_ERROR, 0x00, 0x00},    // Device fault                 Hardware error
                /* ICRC|ABRT */         /* NB: ICRC & !ABRT is BBD */
                {0x84,          ABORTED_COMMAND, 0x47, 0x00},   // Data CRC error               SCSI parity error
                /* MC|ID|ABRT|TRK0|MARK */
                {0x37,          NOT_READY, 0x04, 0x00},         // Unit offline                 Not ready
                /* MCR|MARK */
                {0x09,          NOT_READY, 0x04, 0x00},         // Unrecovered disk error       Not ready
                /*  Bad address mark */
                {0x01,          MEDIUM_ERROR, 0x13, 0x00},      // Address mark not found       Address mark not found for data field
                /* TRK0 */
                {0x02,          HARDWARE_ERROR, 0x00, 0x00},    // Track 0 not found              Hardware error
                /* Abort & !ICRC */
                {0x04,          ABORTED_COMMAND, 0x00, 0x00},   // Aborted command              Aborted command
                /* Media change request */
                {0x08,          NOT_READY, 0x04, 0x00},         // Media change request   FIXME: faking offline
                /* SRV */
                {0x10,          ABORTED_COMMAND, 0x14, 0x00},   // ID not found                 Recorded entity not found
                /* Media change */
                {0x08,          NOT_READY, 0x04, 0x00},         // Media change           FIXME: faking offline
                /* ECC */
                {0x40,          MEDIUM_ERROR, 0x11, 0x04},      // Uncorrectable ECC error      Unrecovered read error
                /* BBD - block marked bad */
                {0x80,          MEDIUM_ERROR, 0x11, 0x04},      // Block marked bad               Medium error, unrecovered read error
                {0xFF, 0xFF, 0xFF, 0xFF}, // END mark
        };
        static unsigned char stat_table[][4] = {
                /* Must be first because BUSY means no other bits valid */
                {0x80,          ABORTED_COMMAND, 0x47, 0x00},   // Busy, fake parity for now
                {0x20,          HARDWARE_ERROR,  0x00, 0x00},   // Device fault
                {0x08,          ABORTED_COMMAND, 0x47, 0x00},   // Timed out in xfer, fake parity for now
                {0x04,          RECOVERED_ERROR, 0x11, 0x00},   // Recovered ECC error    Medium error, recovered
                {0xFF, 0xFF, 0xFF, 0xFF}, // END mark
        };

        /*
         *      Is this an error we can process/parse
         */
        if (drv_stat & ATA_BUSY) {
                drv_err = 0;    /* Ignore the err bits, they're invalid */
        }

        if (drv_err) {
                /* Look for drv_err */
                for (i = 0; sense_table[i][0] != 0xFF; i++) {
                        /* Look for best matches first */
                        if ((sense_table[i][0] & drv_err) == 
                            sense_table[i][0]) {
                                *sk = sense_table[i][1];
                                *asc = sense_table[i][2];
                                *ascq = sense_table[i][3];
                                goto translate_done;
                        }
                }
                /* No immediate match */
                printk(KERN_WARNING "ata%u: no sense translation for "
                       "error 0x%02x\n", id, drv_err);
        }

        /* Fall back to interpreting status bits */
        for (i = 0; stat_table[i][0] != 0xFF; i++) {
                if (stat_table[i][0] & drv_stat) {
                        *sk = stat_table[i][1];
                        *asc = stat_table[i][2];
                        *ascq = stat_table[i][3];
                        goto translate_done;
                }
        }
        /* No error?  Undecoded? */
        printk(KERN_WARNING "ata%u: no sense translation for status: 0x%02x\n", 
               id, drv_stat);

        /* For our last chance pick, use medium read error because
         * it's much more common than an ATA drive telling you a write
         * has failed.
         */
        *sk = MEDIUM_ERROR;
        *asc = 0x11; /* "unrecovered read error" */
        *ascq = 0x04; /*  "auto-reallocation failed" */

 translate_done:
        printk(KERN_ERR "ata%u: translated ATA stat/err 0x%02x/%02x to "
               "SCSI SK/ASC/ASCQ 0x%x/%02x/%02x\n", id, drv_stat, drv_err,
               *sk, *asc, *ascq);
        return;
}

/*
 *      ata_gen_ata_desc_sense - Generate check condition sense block.
 *      @qc: Command that completed.
 *
 *      This function is specific to the ATA descriptor format sense
 *      block specified for the ATA pass through commands.  Regardless
 *      of whether the command errored or not, return a sense
 *      block. Copy all controller registers into the sense
 *      block. Clear sense key, ASC & ASCQ if there is no error.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */
void ata_gen_ata_desc_sense(struct ata_queued_cmd *qc)
{
        struct scsi_cmnd *cmd = qc->scsicmd;
        struct ata_taskfile *tf = &qc->tf;
        unsigned char *sb = cmd->sense_buffer;
        unsigned char *desc = sb + 8;

        memset(sb, 0, SCSI_SENSE_BUFFERSIZE);

        cmd->result = SAM_STAT_CHECK_CONDITION;

        /*
         * Read the controller registers.
         */
        assert(NULL != qc->ap->ops->tf_read);
        qc->ap->ops->tf_read(qc->ap, tf);

        /*
         * Use ata_to_sense_error() to map status register bits
         * onto sense key, asc & ascq.
         */
        if (unlikely(tf->command & (ATA_BUSY | ATA_DF | ATA_ERR | ATA_DRQ))) {
                ata_to_sense_error(qc->ap->id, tf->command, tf->feature,
                                   &sb[1], &sb[2], &sb[3]);
                sb[1] &= 0x0f;
        }

        /*
         * Sense data is current and format is descriptor.
         */
        sb[0] = 0x72;

        desc[0] = 0x09;

        /*
         * Set length of additional sense data.
         * Since we only populate descriptor 0, the total
         * length is the same (fixed) length as descriptor 0.
         */
        desc[1] = sb[7] = 14;

        /*
         * Copy registers into sense buffer.
         */
        desc[2] = 0x00;
        desc[3] = tf->feature;  /* == error reg */
        desc[5] = tf->nsect;
        desc[7] = tf->lbal;
        desc[9] = tf->lbam;
        desc[11] = tf->lbah;
        desc[12] = tf->device;
        desc[13] = tf->command; /* == status reg */

        /*
         * Fill in Extend bit, and the high order bytes
         * if applicable.
         */
        if (tf->flags & ATA_TFLAG_LBA48) {
                desc[2] |= 0x01;
                desc[4] = tf->hob_nsect;
                desc[6] = tf->hob_lbal;
                desc[8] = tf->hob_lbam;
                desc[10] = tf->hob_lbah;
        }
}

/**
 *      ata_gen_fixed_sense - generate a SCSI fixed sense block
 *      @qc: Command that we are erroring out
 *
 *      Leverage ata_to_sense_error() to give us the codes.  Fit our
 *      LBA in here if there's room.
 *
 *      LOCKING:
 *      inherited from caller
 */
void ata_gen_fixed_sense(struct ata_queued_cmd *qc)
{
        struct scsi_cmnd *cmd = qc->scsicmd;
        struct ata_taskfile *tf = &qc->tf;
        unsigned char *sb = cmd->sense_buffer;

        memset(sb, 0, SCSI_SENSE_BUFFERSIZE);

        cmd->result = SAM_STAT_CHECK_CONDITION;

        /*
         * Read the controller registers.
         */
        assert(NULL != qc->ap->ops->tf_read);
        qc->ap->ops->tf_read(qc->ap, tf);

        /*
         * Use ata_to_sense_error() to map status register bits
         * onto sense key, asc & ascq.
         */
        if (unlikely(tf->command & (ATA_BUSY | ATA_DF | ATA_ERR | ATA_DRQ))) {
                ata_to_sense_error(qc->ap->id, tf->command, tf->feature,
                                   &sb[2], &sb[12], &sb[13]);
                sb[2] &= 0x0f;
        }

        sb[0] = 0x70;
        sb[7] = 0x0a;
        if (tf->flags & ATA_TFLAG_LBA && !(tf->flags & ATA_TFLAG_LBA48)) {
                /* A small (28b) LBA will fit in the 32b info field */
                sb[0] |= 0x80;          /* set valid bit */
                sb[3] = tf->device & 0x0f;
                sb[4] = tf->lbah;
                sb[5] = tf->lbam;
                sb[6] = tf->lbal;
        }
}

/**
 *      ata_scsi_slave_config - Set SCSI device attributes
 *      @sdev: SCSI device to examine
 *
 *      This is called before we actually start reading
 *      and writing to the device, to configure certain
 *      SCSI mid-layer behaviors.
 *
 *      LOCKING:
 *      Defined by SCSI layer.  We don't really care.
 */

int ata_scsi_slave_config(struct scsi_device *sdev)
{
        sdev->use_10_for_rw = 1;
        sdev->use_10_for_ms = 1;

        blk_queue_max_phys_segments(sdev->request_queue, LIBATA_MAX_PRD);

        if (sdev->id < ATA_MAX_DEVICES) {
                struct ata_port *ap;
                struct ata_device *dev;

                ap = (struct ata_port *) &sdev->host->hostdata[0];
                dev = &ap->device[sdev->id];

                /* TODO: 1024 is an arbitrary number, not the
                 * hardware maximum.  This should be increased to
                 * 65534 when Jens Axboe's patch for dynamically
                 * determining max_sectors is merged.
                 */
                if ((dev->flags & ATA_DFLAG_LBA48) &&
                    ((dev->flags & ATA_DFLAG_LOCK_SECTORS) == 0)) {
                        sdev->host->max_sectors = 2048;
                        blk_queue_max_sectors(sdev->request_queue, 2048);
                }
        }

        return 0;       /* scsi layer doesn't check return value, sigh */
}

/**
 *      ata_scsi_error - SCSI layer error handler callback
 *      @host: SCSI host on which error occurred
 *
 *      Handles SCSI-layer-thrown error events.
 *
 *      LOCKING:
 *      Inherited from SCSI layer (none, can sleep)
 *
 *      RETURNS:
 *      Zero.
 */

int ata_scsi_error(struct Scsi_Host *host)
{
        struct ata_port *ap;

        DPRINTK("ENTER\n");

        ap = (struct ata_port *) &host->hostdata[0];
        ap->ops->eng_timeout(ap);

        /* TODO: this is per-command; when queueing is supported
         * this code will either change or move to a more
         * appropriate place
         */
        host->host_failed--;

        DPRINTK("EXIT\n");
        return 0;
}

/**
 *      ata_scsi_flush_xlat - Translate SCSI SYNCHRONIZE CACHE command
 *      @qc: Storage for translated ATA taskfile
 *      @scsicmd: SCSI command to translate (ignored)
 *
 *      Sets up an ATA taskfile to issue FLUSH CACHE or
 *      FLUSH CACHE EXT.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, non-zero on error.
 */

static unsigned int ata_scsi_flush_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
{
        struct ata_taskfile *tf = &qc->tf;

        tf->flags |= ATA_TFLAG_DEVICE;
        tf->protocol = ATA_PROT_NODATA;

        if ((tf->flags & ATA_TFLAG_LBA48) &&
            (ata_id_has_flush_ext(qc->dev->id)))
                tf->command = ATA_CMD_FLUSH_EXT;
        else
                tf->command = ATA_CMD_FLUSH;

        return 0;
}

/**
 *      ata_scsi_verify_xlat - Translate SCSI VERIFY command into an ATA one
 *      @qc: Storage for translated ATA taskfile
 *      @scsicmd: SCSI command to translate
 *
 *      Converts SCSI VERIFY command to an ATA READ VERIFY command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, non-zero on error.
 */

static unsigned int ata_scsi_verify_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
{
        struct ata_taskfile *tf = &qc->tf;
        unsigned int lba48 = tf->flags & ATA_TFLAG_LBA48;
        u64 dev_sectors = qc->dev->n_sectors;
        u64 sect = 0;
        u32 n_sect = 0;

        tf->flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        tf->protocol = ATA_PROT_NODATA;
        tf->device |= ATA_LBA;

        if (scsicmd[0] == VERIFY) {
                sect |= ((u64)scsicmd[2]) << 24;
                sect |= ((u64)scsicmd[3]) << 16;
                sect |= ((u64)scsicmd[4]) << 8;
                sect |= ((u64)scsicmd[5]);

                n_sect |= ((u32)scsicmd[7]) << 8;
                n_sect |= ((u32)scsicmd[8]);
        }

        else if (scsicmd[0] == VERIFY_16) {
                sect |= ((u64)scsicmd[2]) << 56;
                sect |= ((u64)scsicmd[3]) << 48;
                sect |= ((u64)scsicmd[4]) << 40;
                sect |= ((u64)scsicmd[5]) << 32;
                sect |= ((u64)scsicmd[6]) << 24;
                sect |= ((u64)scsicmd[7]) << 16;
                sect |= ((u64)scsicmd[8]) << 8;
                sect |= ((u64)scsicmd[9]);

                n_sect |= ((u32)scsicmd[10]) << 24;
                n_sect |= ((u32)scsicmd[11]) << 16;
                n_sect |= ((u32)scsicmd[12]) << 8;
                n_sect |= ((u32)scsicmd[13]);
        }

        else
                return 1;

        if (!n_sect)
                return 1;
        if (sect >= dev_sectors)
                return 1;
        if ((sect + n_sect) > dev_sectors)
                return 1;
        if (lba48) {
                if (n_sect > (64 * 1024))
                        return 1;
        } else {
                if (n_sect > 256)
                        return 1;
        }

        if (lba48) {
                tf->command = ATA_CMD_VERIFY_EXT;

                tf->hob_nsect = (n_sect >> 8) & 0xff;

                tf->hob_lbah = (sect >> 40) & 0xff;
                tf->hob_lbam = (sect >> 32) & 0xff;
                tf->hob_lbal = (sect >> 24) & 0xff;
        } else {
                tf->command = ATA_CMD_VERIFY;

                tf->device |= (sect >> 24) & 0xf;
        }

        tf->nsect = n_sect & 0xff;

        tf->lbah = (sect >> 16) & 0xff;
        tf->lbam = (sect >> 8) & 0xff;
        tf->lbal = sect & 0xff;

        return 0;
}

/**
 *      ata_scsi_rw_xlat - Translate SCSI r/w command into an ATA one
 *      @qc: Storage for translated ATA taskfile
 *      @scsicmd: SCSI command to translate
 *
 *      Converts any of six SCSI read/write commands into the
 *      ATA counterpart, including starting sector (LBA),
 *      sector count, and taking into account the device's LBA48
 *      support.
 *
 *      Commands %READ_6, %READ_10, %READ_16, %WRITE_6, %WRITE_10, and
 *      %WRITE_16 are currently supported.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, non-zero on error.
 */

static unsigned int ata_scsi_rw_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
{
        struct ata_taskfile *tf = &qc->tf;
        unsigned int lba48 = tf->flags & ATA_TFLAG_LBA48;

        tf->flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        tf->protocol = qc->dev->xfer_protocol;
        tf->device |= ATA_LBA;

        if (scsicmd[0] == READ_10 || scsicmd[0] == READ_6 ||
            scsicmd[0] == READ_16) {
                tf->command = qc->dev->read_cmd;
        } else {
                tf->command = qc->dev->write_cmd;
                tf->flags |= ATA_TFLAG_WRITE;
        }

        if (scsicmd[0] == READ_10 || scsicmd[0] == WRITE_10) {
                if (lba48) {
                        tf->hob_nsect = scsicmd[7];
                        tf->hob_lbal = scsicmd[2];

                        qc->nsect = ((unsigned int)scsicmd[7] << 8) |
                                        scsicmd[8];
                } else {
                        /* if we don't support LBA48 addressing, the request
                         * -may- be too large. */
                        if ((scsicmd[2] & 0xf0) || scsicmd[7])
                                return 1;

                        /* stores LBA27:24 in lower 4 bits of device reg */
                        tf->device |= scsicmd[2];

                        qc->nsect = scsicmd[8];
                }

                tf->nsect = scsicmd[8];
                tf->lbal = scsicmd[5];
                tf->lbam = scsicmd[4];
                tf->lbah = scsicmd[3];

                VPRINTK("ten-byte command\n");
                return 0;
        }

        if (scsicmd[0] == READ_6 || scsicmd[0] == WRITE_6) {
                qc->nsect = tf->nsect = scsicmd[4];
                tf->lbal = scsicmd[3];
                tf->lbam = scsicmd[2];
                tf->lbah = scsicmd[1] & 0x1f; /* mask out reserved bits */

                VPRINTK("six-byte command\n");
                return 0;
        }

        if (scsicmd[0] == READ_16 || scsicmd[0] == WRITE_16) {
                /* rule out impossible LBAs and sector counts */
                if (scsicmd[2] || scsicmd[3] || scsicmd[10] || scsicmd[11])
                        return 1;

                if (lba48) {
                        tf->hob_nsect = scsicmd[12];
                        tf->hob_lbal = scsicmd[6];
                        tf->hob_lbam = scsicmd[5];
                        tf->hob_lbah = scsicmd[4];

                        qc->nsect = ((unsigned int)scsicmd[12] << 8) |
                                        scsicmd[13];
                } else {
                        /* once again, filter out impossible non-zero values */
                        if (scsicmd[4] || scsicmd[5] || scsicmd[12] ||
                            (scsicmd[6] & 0xf0))
                                return 1;

                        /* stores LBA27:24 in lower 4 bits of device reg */
                        tf->device |= scsicmd[6];

                        qc->nsect = scsicmd[13];
                }

                tf->nsect = scsicmd[13];
                tf->lbal = scsicmd[9];
                tf->lbam = scsicmd[8];
                tf->lbah = scsicmd[7];

                VPRINTK("sixteen-byte command\n");
                return 0;
        }

        DPRINTK("no-byte command\n");
        return 1;
}

static int ata_scsi_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
{
        struct scsi_cmnd *cmd = qc->scsicmd;
        int need_sense = drv_stat & (ATA_ERR | ATA_BUSY | ATA_DRQ);

        /* For ATA pass thru (SAT) commands, generate a sense block if
         * user mandated it or if there's an error.  Note that if we
         * generate because the user forced us to, a check condition
         * is generated and the ATA register values are returned
         * whether the command completed successfully or not. If there
         * was no error, SK, ASC and ASCQ will all be zero.
         */
        if (((cmd->cmnd[0] == ATA_16) || (cmd->cmnd[0] == ATA_12)) &&
            ((cmd->cmnd[2] & 0x20) || need_sense)) {
                ata_gen_ata_desc_sense(qc);
        } else {
                if (!need_sense) {
                        cmd->result = SAM_STAT_GOOD;
                } else {
                        /* TODO: decide which descriptor format to use
                         * for 48b LBA devices and call that here
                         * instead of the fixed desc, which is only
                         * good for smaller LBA (and maybe CHS?)
                         * devices.
                         */
                        ata_gen_fixed_sense(qc);
                }
        }

        if (need_sense) {
                /* The ata_gen_..._sense routines fill in tf */
                ata_dump_status(qc->ap->id, &qc->tf);
        }

        qc->scsidone(cmd);

        return 0;
}

/**
 *      ata_scsi_translate - Translate then issue SCSI command to ATA device
 *      @ap: ATA port to which the command is addressed
 *      @dev: ATA device to which the command is addressed
 *      @cmd: SCSI command to execute
 *      @done: SCSI command completion function
 *      @xlat_func: Actor which translates @cmd to an ATA taskfile
 *
 *      Our ->queuecommand() function has decided that the SCSI
 *      command issued can be directly translated into an ATA
 *      command, rather than handled internally.
 *
 *      This function sets up an ata_queued_cmd structure for the
 *      SCSI command, and sends that ata_queued_cmd to the hardware.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static void ata_scsi_translate(struct ata_port *ap, struct ata_device *dev,
                              struct scsi_cmnd *cmd,
                              void (*done)(struct scsi_cmnd *),
                              ata_xlat_func_t xlat_func)
{
        struct ata_queued_cmd *qc;
        u8 *scsicmd = cmd->cmnd;

        VPRINTK("ENTER\n");

        qc = ata_scsi_qc_new(ap, dev, cmd, done);
        if (!qc)
                return;

        /* data is present; dma-map it */
        if (cmd->sc_data_direction == SCSI_DATA_READ ||
            cmd->sc_data_direction == SCSI_DATA_WRITE) {
                if (unlikely(cmd->request_bufflen < 1)) {
                        printk(KERN_WARNING "ata%u(%u): WARNING: zero len r/w req\n",
                               ap->id, dev->devno);
                        goto err_out;
                }

                if (cmd->use_sg)
                        ata_sg_init(qc, cmd->request_buffer, cmd->use_sg);
                else
                        ata_sg_init_one(qc, cmd->request_buffer,
                                        cmd->request_bufflen);

                qc->dma_dir = cmd->sc_data_direction;
        }

        qc->complete_fn = ata_scsi_qc_complete;

        if (xlat_func(qc, scsicmd))
                goto err_out;
        /* select device, send command to hardware */
        if (ata_qc_issue(qc))
                goto err_out;

        VPRINTK("EXIT\n");
        return;

err_out:
        ata_qc_free(qc);
        ata_bad_cdb(cmd, done);
        DPRINTK("EXIT - badcmd\n");
}

/**
 *      ata_scsi_rbuf_get - Map response buffer.
 *      @cmd: SCSI command containing buffer to be mapped.
 *      @buf_out: Pointer to mapped area.
 *
 *      Maps buffer contained within SCSI command @cmd.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Length of response buffer.
 */

static unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
{
        u8 *buf;
        unsigned int buflen;

        if (cmd->use_sg) {
                struct scatterlist *sg;

                sg = (struct scatterlist *) cmd->request_buffer;
                buf = kmap_atomic(sg->page, KM_USER0) + sg->offset;
                buflen = sg->length;
        } else {
                buf = cmd->request_buffer;
                buflen = cmd->request_bufflen;
        }

        *buf_out = buf;
        return buflen;
}

/**
 *      ata_scsi_rbuf_put - Unmap response buffer.
 *      @cmd: SCSI command containing buffer to be unmapped.
 *      @buf: buffer to unmap
 *
 *      Unmaps response buffer contained within @cmd.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

static inline void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, u8 *buf)
{
        if (cmd->use_sg) {
                struct scatterlist *sg;

                sg = (struct scatterlist *) cmd->request_buffer;
                kunmap_atomic(buf - sg->offset, KM_USER0);
        }
}

/**
 *      ata_scsi_rbuf_fill - wrapper for SCSI command simulators
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @actor: Callback hook for desired SCSI command simulator
 *
 *      Takes care of the hard work of simulating a SCSI command...
 *      Mapping the response buffer, calling the command's handler,
 *      and handling the handler's return value.  This return value
 *      indicates whether the handler wishes the SCSI command to be
 *      completed successfully, or not.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_scsi_rbuf_fill(struct ata_scsi_args *args,
                        unsigned int (*actor) (struct ata_scsi_args *args,
                                           u8 *rbuf, unsigned int buflen))
{
        u8 *rbuf;
        unsigned int buflen, rc;
        struct scsi_cmnd *cmd = args->cmd;

        buflen = ata_scsi_rbuf_get(cmd, &rbuf);
        memset(rbuf, 0, buflen);
        rc = actor(args, rbuf, buflen);
        ata_scsi_rbuf_put(cmd, rbuf);

        if (rc)
                ata_bad_cdb(cmd, args->done);
        else {
                cmd->result = SAM_STAT_GOOD;
                args->done(cmd);
        }
}

/**
 *      ata_scsiop_inq_std - Simulate INQUIRY command
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Returns standard device identification data associated
 *      with non-EVPD INQUIRY command output.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_inq_std(struct ata_scsi_args *args, u8 *rbuf,
                               unsigned int buflen)
{
        u8 hdr[] = {
                TYPE_DISK,
                0,
                0x5,    /* claim SPC-3 version compatibility */
                2,
                95 - 4
        };

        /* set scsi removeable (RMB) bit per ata bit */
        if (ata_id_removeable(args->id))
                hdr[1] |= (1 << 7);

        VPRINTK("ENTER\n");

        memcpy(rbuf, hdr, sizeof(hdr));

        if (buflen > 35) {
                memcpy(&rbuf[8], "ATA     ", 8);
                ata_dev_id_string(args->id, &rbuf[16], ATA_ID_PROD_OFS, 16);
                ata_dev_id_string(args->id, &rbuf[32], ATA_ID_FW_REV_OFS, 4);
                if (rbuf[32] == 0 || rbuf[32] == ' ')
                        memcpy(&rbuf[32], "n/a ", 4);
        }

        if (buflen > 63) {
                const u8 versions[] = {
                        0x60,   /* SAM-3 (no version claimed) */

                        0x03,
                        0x20,   /* SBC-2 (no version claimed) */

                        0x02,
                        0x60    /* SPC-3 (no version claimed) */
                };

                memcpy(rbuf + 59, versions, sizeof(versions));
        }

        return 0;
}

/**
 *      ata_scsiop_inq_00 - Simulate INQUIRY EVPD page 0, list of pages
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Returns list of inquiry EVPD pages available.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_inq_00(struct ata_scsi_args *args, u8 *rbuf,
                              unsigned int buflen)
{
        const u8 pages[] = {
                0x00,   /* page 0x00, this page */
                0x80,   /* page 0x80, unit serial no page */
                0x83    /* page 0x83, device ident page */
        };
        rbuf[3] = sizeof(pages);        /* number of supported EVPD pages */

        if (buflen > 6)
                memcpy(rbuf + 4, pages, sizeof(pages));

        return 0;
}

/**
 *      ata_scsiop_inq_80 - Simulate INQUIRY EVPD page 80, device serial number
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Returns ATA device serial number.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_inq_80(struct ata_scsi_args *args, u8 *rbuf,
                              unsigned int buflen)
{
        const u8 hdr[] = {
                0,
                0x80,                   /* this page code */
                0,
                ATA_SERNO_LEN,          /* page len */
        };
        memcpy(rbuf, hdr, sizeof(hdr));

        if (buflen > (ATA_SERNO_LEN + 4 - 1))
                ata_dev_id_string(args->id, (unsigned char *) &rbuf[4],
                                  ATA_ID_SERNO_OFS, ATA_SERNO_LEN);

        return 0;
}

static const char *inq_83_str = "Linux ATA-SCSI simulator";

/**
 *      ata_scsiop_inq_83 - Simulate INQUIRY EVPD page 83, device identity
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Returns device identification.  Currently hardcoded to
 *      return "Linux ATA-SCSI simulator".
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_inq_83(struct ata_scsi_args *args, u8 *rbuf,
                              unsigned int buflen)
{
        rbuf[1] = 0x83;                 /* this page code */
        rbuf[3] = 4 + strlen(inq_83_str);       /* page len */

        /* our one and only identification descriptor (vendor-specific) */
        if (buflen > (strlen(inq_83_str) + 4 + 4 - 1)) {
                rbuf[4 + 0] = 2;        /* code set: ASCII */
                rbuf[4 + 3] = strlen(inq_83_str);
                memcpy(rbuf + 4 + 4, inq_83_str, strlen(inq_83_str));
        }

        return 0;
}

/**
 *      ata_scsiop_noop -
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      No operation.  Simply returns success to caller, to indicate
 *      that the caller should successfully complete this SCSI command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_noop(struct ata_scsi_args *args, u8 *rbuf,
                            unsigned int buflen)
{
        VPRINTK("ENTER\n");
        return 0;
}

/**
 *      ata_msense_push - Push data onto MODE SENSE data output buffer
 *      @ptr_io: (input/output) Location to store more output data
 *      @last: End of output data buffer
 *      @buf: Pointer to BLOB being added to output buffer
 *      @buflen: Length of BLOB
 *
 *      Store MODE SENSE data on an output buffer.
 *
 *      LOCKING:
 *      None.
 */

static void ata_msense_push(u8 **ptr_io, const u8 *last,
                            const u8 *buf, unsigned int buflen)
{
        u8 *ptr = *ptr_io;

        if ((ptr + buflen - 1) > last)
                return;

        memcpy(ptr, buf, buflen);

        ptr += buflen;

        *ptr_io = ptr;
}

/**
 *      ata_msense_caching - Simulate MODE SENSE caching info page
 *      @id: device IDENTIFY data
 *      @ptr_io: (input/output) Location to store more output data
 *      @last: End of output data buffer
 *
 *      Generate a caching info page, which conditionally indicates
 *      write caching to the SCSI layer, depending on device
 *      capabilities.
 *
 *      LOCKING:
 *      None.
 */

static unsigned int ata_msense_caching(u16 *id, u8 **ptr_io,
                                       const u8 *last)
{
        u8 page[] = {
                0x8,                            /* page code */
                0x12,                           /* page length */
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0,   /* 10 zeroes */
                0, 0, 0, 0, 0, 0, 0, 0          /* 8 zeroes */
        };

        if (ata_id_wcache_enabled(id))
                page[2] |= (1 << 2);    /* write cache enable */
        if (!ata_id_rahead_enabled(id))
                page[12] |= (1 << 5);   /* disable read ahead */

        ata_msense_push(ptr_io, last, page, sizeof(page));
        return sizeof(page);
}

/**
 *      ata_msense_ctl_mode - Simulate MODE SENSE control mode page
 *      @dev: Device associated with this MODE SENSE command
 *      @ptr_io: (input/output) Location to store more output data
 *      @last: End of output data buffer
 *
 *      Generate a generic MODE SENSE control mode page.
 *
 *      LOCKING:
 *      None.
 */

static unsigned int ata_msense_ctl_mode(u8 **ptr_io, const u8 *last)
{
        const u8 page[] = {0xa, 0xa, 6, 0, 0, 0, 0, 0, 0xff, 0xff, 0, 30};

        /* byte 2: set the descriptor format sense data bit (bit 2)
         * since we need to support returning this format for SAT
         * commands and any SCSI commands against a 48b LBA device.
         */

        ata_msense_push(ptr_io, last, page, sizeof(page));
        return sizeof(page);
}

/**
 *      ata_msense_rw_recovery - Simulate MODE SENSE r/w error recovery page
 *      @dev: Device associated with this MODE SENSE command
 *      @ptr_io: (input/output) Location to store more output data
 *      @last: End of output data buffer
 *
 *      Generate a generic MODE SENSE r/w error recovery page.
 *
 *      LOCKING:
 *      None.
 */

static unsigned int ata_msense_rw_recovery(u8 **ptr_io, const u8 *last)
{
        const u8 page[] = {
                0x1,                      /* page code */
                0xa,                      /* page length */
                (1 << 7) | (1 << 6),      /* note auto r/w reallocation */
                0, 0, 0, 0, 0, 0, 0, 0, 0 /* 9 zeroes */
        };

        ata_msense_push(ptr_io, last, page, sizeof(page));
        return sizeof(page);
}

/**
 *      ata_scsiop_mode_sense - Simulate MODE SENSE 6, 10 commands
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Simulate MODE SENSE commands.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_mode_sense(struct ata_scsi_args *args, u8 *rbuf,
                                  unsigned int buflen)
{
        u8 *scsicmd = args->cmd->cmnd, *p, *last;
        unsigned int page_control, six_byte, output_len;

        VPRINTK("ENTER\n");

        six_byte = (scsicmd[0] == MODE_SENSE);

        /* we only support saved and current values (which we treat
         * in the same manner)
         */
        page_control = scsicmd[2] >> 6;
        if ((page_control != 0) && (page_control != 3))
                return 1;

        if (six_byte)
                output_len = 4;
        else
                output_len = 8;

        p = rbuf + output_len;
        last = rbuf + buflen - 1;

        switch(scsicmd[2] & 0x3f) {
        case 0x01:              /* r/w error recovery */
                output_len += ata_msense_rw_recovery(&p, last);
                break;

        case 0x08:              /* caching */
                output_len += ata_msense_caching(args->id, &p, last);
                break;

        case 0x0a: {            /* control mode */
                output_len += ata_msense_ctl_mode(&p, last);
                break;
                }

        case 0x3f:              /* all pages */
                output_len += ata_msense_rw_recovery(&p, last);
                output_len += ata_msense_caching(args->id, &p, last);
                output_len += ata_msense_ctl_mode(&p, last);
                break;

        default:                /* invalid page code */
                return 1;
        }

        if (six_byte) {
                output_len--;
                rbuf[0] = output_len;
        } else {
                output_len -= 2;
                rbuf[0] = output_len >> 8;
                rbuf[1] = output_len;
        }

        return 0;
}

/**
 *      ata_scsiop_read_cap - Simulate READ CAPACITY[ 16] commands
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Simulate READ CAPACITY commands.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_read_cap(struct ata_scsi_args *args, u8 *rbuf,
                                unsigned int buflen)
{
        u64 n_sectors;
        u32 tmp;

        VPRINTK("ENTER\n");

        if (ata_id_has_lba48(args->id))
                n_sectors = ata_id_u64(args->id, 100);
        else
                n_sectors = ata_id_u32(args->id, 60);
        n_sectors--;            /* ATA TotalUserSectors - 1 */

        tmp = n_sectors;        /* note: truncates, if lba48 */
        if (args->cmd->cmnd[0] == READ_CAPACITY) {
                /* sector count, 32-bit */
                rbuf[0] = tmp >> (8 * 3);
                rbuf[1] = tmp >> (8 * 2);
                rbuf[2] = tmp >> (8 * 1);
                rbuf[3] = tmp;

                /* sector size */
                tmp = ATA_SECT_SIZE;
                rbuf[6] = tmp >> 8;
                rbuf[7] = tmp;

        } else {
                /* sector count, 64-bit */
                rbuf[2] = n_sectors >> (8 * 7);
                rbuf[3] = n_sectors >> (8 * 6);
                rbuf[4] = n_sectors >> (8 * 5);
                rbuf[5] = n_sectors >> (8 * 4);
                rbuf[6] = tmp >> (8 * 3);
                rbuf[7] = tmp >> (8 * 2);
                rbuf[8] = tmp >> (8 * 1);
                rbuf[9] = tmp;

                /* sector size */
                tmp = ATA_SECT_SIZE;
                rbuf[12] = tmp >> 8;
                rbuf[13] = tmp;
        }

        return 0;
}

/**
 *      ata_scsiop_report_luns - Simulate REPORT LUNS command
 *      @args: device IDENTIFY data / SCSI command of interest.
 *      @rbuf: Response buffer, to which simulated SCSI cmd output is sent.
 *      @buflen: Response buffer length.
 *
 *      Simulate REPORT LUNS command.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

unsigned int ata_scsiop_report_luns(struct ata_scsi_args *args, u8 *rbuf,
                                   unsigned int buflen)
{
        VPRINTK("ENTER\n");
        rbuf[3] = 8;    /* just one lun, LUN 0, size 8 bytes */

        return 0;
}

/**
 *      ata_scsi_badcmd - End a SCSI request with an error
 *      @cmd: SCSI request to be handled
 *      @done: SCSI command completion function
 *      @asc: SCSI-defined additional sense code
 *      @ascq: SCSI-defined additional sense code qualifier
 *
 *      Helper function that completes a SCSI command with
 *      %SAM_STAT_CHECK_CONDITION, with a sense key %ILLEGAL_REQUEST
 *      and the specified additional sense codes.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_scsi_badcmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *), u8 asc, u8 ascq)
{
        DPRINTK("ENTER\n");
        cmd->result = SAM_STAT_CHECK_CONDITION;

        cmd->sense_buffer[0] = 0x70;
        cmd->sense_buffer[2] = ILLEGAL_REQUEST;
        cmd->sense_buffer[7] = 14 - 8;  /* addnl. sense len. FIXME: correct? */
        cmd->sense_buffer[12] = asc;
        cmd->sense_buffer[13] = ascq;

        done(cmd);
}

static int atapi_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
{
        struct scsi_cmnd *cmd = qc->scsicmd;

        if (unlikely(drv_stat & (ATA_ERR | ATA_BUSY | ATA_DRQ))) {
                DPRINTK("request check condition\n");

                cmd->result = SAM_STAT_CHECK_CONDITION;

                qc->scsidone(cmd);

                return 1;
        } else {
                u8 *scsicmd = cmd->cmnd;

                if (scsicmd[0] == INQUIRY) {
                        u8 *buf = NULL;
                        unsigned int buflen;

                        buflen = ata_scsi_rbuf_get(cmd, &buf);
                        buf[2] = 0x5;
                        buf[3] = (buf[3] & 0xf0) | 2;
                        ata_scsi_rbuf_put(cmd, buf);
                }
                cmd->result = SAM_STAT_GOOD;
        }

        qc->scsidone(cmd);

        return 0;
}
/**
 *      atapi_xlat - Initialize PACKET taskfile
 *      @qc: command structure to be initialized
 *      @scsicmd: SCSI CDB associated with this PACKET command
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Zero on success, non-zero on failure.
 */

static unsigned int atapi_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
{
        struct scsi_cmnd *cmd = qc->scsicmd;
        struct ata_device *dev = qc->dev;
        int using_pio = (dev->flags & ATA_DFLAG_PIO);
        int nodata = (cmd->sc_data_direction == SCSI_DATA_NONE);

        if (!using_pio)
                /* Check whether ATAPI DMA is safe */
                if (ata_check_atapi_dma(qc))
                        using_pio = 1;

        memcpy(&qc->cdb, scsicmd, qc->ap->cdb_len);

        qc->complete_fn = atapi_qc_complete;

        qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
        if (cmd->sc_data_direction == SCSI_DATA_WRITE) {
                qc->tf.flags |= ATA_TFLAG_WRITE;
                DPRINTK("direction: write\n");
        }

        qc->tf.command = ATA_CMD_PACKET;

        /* no data, or PIO data xfer */
        if (using_pio || nodata) {
                if (nodata)
                        qc->tf.protocol = ATA_PROT_ATAPI_NODATA;
                else
                        qc->tf.protocol = ATA_PROT_ATAPI;
                qc->tf.lbam = (8 * 1024) & 0xff;
                qc->tf.lbah = (8 * 1024) >> 8;
        }

        /* DMA data xfer */
        else {
                qc->tf.protocol = ATA_PROT_ATAPI_DMA;
                qc->tf.feature |= ATAPI_PKT_DMA;

#ifdef ATAPI_ENABLE_DMADIR
                /* some SATA bridges need us to indicate data xfer direction */
                if (cmd->sc_data_direction != SCSI_DATA_WRITE)
                        qc->tf.feature |= ATAPI_DMADIR;
#endif
        }

        qc->nbytes = cmd->bufflen;

        return 0;
}

/**
 *      ata_scsi_find_dev - lookup ata_device from scsi_cmnd
 *      @ap: ATA port to which the device is attached
 *      @scsidev: SCSI device from which we derive the ATA device
 *
 *      Given various information provided in struct scsi_cmnd,
 *      map that onto an ATA bus, and using that mapping
 *      determine which ata_device is associated with the
 *      SCSI command to be sent.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 *
 *      RETURNS:
 *      Associated ATA device, or %NULL if not found.
 */

static struct ata_device *
ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev)
{
        struct ata_device *dev;

        /* skip commands not addressed to targets we simulate */
        if (likely(scsidev->id < ATA_MAX_DEVICES))
                dev = &ap->device[scsidev->id];
        else
                return NULL;

        if (unlikely((scsidev->channel != 0) ||
                     (scsidev->lun != 0)))
                return NULL;

        if (unlikely(!ata_dev_present(dev)))
                return NULL;

#ifndef ATA_ENABLE_ATAPI
        if (unlikely(dev->class == ATA_DEV_ATAPI))
                return NULL;
#endif

        return dev;
}

/*
 *      ata_scsi_map_proto - Map pass-thru protocol value to taskfile value.
 *      @byte1: Byte 1 from pass-thru CDB.
 *
 *      RETURNS:
 *      ATA_PROT_UNKNOWN if mapping failed/unimplemented, protocol otherwise.
 */
static u8
ata_scsi_map_proto(u8 byte1)
{
        switch((byte1 & 0x1e) >> 1) {
                case 3:         /* Non-data */
                        return ATA_PROT_NODATA;

                case 6:         /* DMA */
                        return ATA_PROT_DMA;

                case 4:         /* PIO Data-in */
                case 5:         /* PIO Data-out */
                        if (byte1 & 0xe0) {
                                return ATA_PROT_PIO_MULT;
                        }
                        return ATA_PROT_PIO;

                case 10:        /* Device Reset */
                case 0:         /* Hard Reset */
                case 1:         /* SRST */
                case 2:         /* Bus Idle */
                case 7:         /* Packet */
                case 8:         /* DMA Queued */
                case 9:         /* Device Diagnostic */
                case 11:        /* UDMA Data-in */
                case 12:        /* UDMA Data-Out */
                case 13:        /* FPDMA */
                default:        /* Reserved */
                        break;
        }

        return ATA_PROT_UNKNOWN;
}

/**
 *      ata_scsi_pass_thru - convert ATA pass-thru CDB to taskfile
 *      @qc: command structure to be initialized
 *      @cmd: SCSI command to convert
 *
 *      Handles either 12 or 16-byte versions of the CDB.
 *
 *      RETURNS:
 *      Zero on success, non-zero on failure.
 */
static unsigned int
ata_scsi_pass_thru(struct ata_queued_cmd *qc, u8 *scsicmd)
{
        struct ata_taskfile *tf = &(qc->tf);
        struct scsi_cmnd *cmd = qc->scsicmd;

        if ((tf->protocol = ata_scsi_map_proto(scsicmd[1])) == ATA_PROT_UNKNOWN)
                return 1;

        /*
         * 12 and 16 byte CDBs use different offsets to
         * provide the various register values.
         */
        if (scsicmd[0] == ATA_16) {
                /*
                 * 16-byte CDB - may contain extended commands.
                 *
                 * If that is the case, copy the upper byte register values.
                 */
                if (scsicmd[1] & 0x01) {
                        tf->hob_feature = scsicmd[3];
                        tf->hob_nsect = scsicmd[5];
                        tf->hob_lbal = scsicmd[7];
                        tf->hob_lbam = scsicmd[9];
                        tf->hob_lbah = scsicmd[11];
                        tf->flags |= ATA_TFLAG_LBA48;
                } else
                        tf->flags &= ~ATA_TFLAG_LBA48;

                /*
                 * Always copy low byte, device and command registers.
                 */
                tf->feature = scsicmd[4];
                tf->nsect = scsicmd[6];
                tf->lbal = scsicmd[8];
                tf->lbam = scsicmd[10];
                tf->lbah = scsicmd[12];
                tf->device = scsicmd[13];
                tf->command = scsicmd[14];
        } else {
                /*
                 * 12-byte CDB - incapable of extended commands.
                 */
                tf->flags &= ~ATA_TFLAG_LBA48;

                tf->feature = scsicmd[3];
                tf->nsect = scsicmd[4];
                tf->lbal = scsicmd[5];
                tf->lbam = scsicmd[6];
                tf->lbah = scsicmd[7];
                tf->device = scsicmd[8];
                tf->command = scsicmd[9];
        }

        /*
         * Filter SET_FEATURES - XFER MODE command -- otherwise,
         * SET_FEATURES - XFER MODE must be preceded/succeeded
         * by an update to hardware-specific registers for each
         * controller (i.e. the reason for ->set_piomode(),
         * ->set_dmamode(), and ->post_set_mode() hooks).
         */
        if ((tf->command == ATA_CMD_SET_FEATURES)
         && (tf->feature == SETFEATURES_XFER))
                return 1;

        /*
         * Set flags so that all registers will be written,
         * and pass on write indication (used for PIO/DMA
         * setup.)
         */
        tf->flags |= (ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE);

        if (cmd->sc_data_direction == SCSI_DATA_WRITE)
                tf->flags |= ATA_TFLAG_WRITE;

        /*
         * Set transfer length.
         *
         * TODO: find out if we need to do more here to
         *       cover scatter/gather case.
         */
        qc->nsect = cmd->bufflen / ATA_SECT_SIZE;

        return 0;
}

/**
 *      ata_get_xlat_func - check if SCSI to ATA translation is possible
 *      @dev: ATA device
 *      @cmd: SCSI command opcode to consider
 *
 *      Look up the SCSI command given, and determine whether the
 *      SCSI command is to be translated or simulated.
 *
 *      RETURNS:
 *      Pointer to translation function if possible, %NULL if not.
 */

static inline ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)
{
        switch (cmd) {
        case READ_6:
        case READ_10:
        case READ_16:

        case WRITE_6:
        case WRITE_10:
        case WRITE_16:
                return ata_scsi_rw_xlat;

        case SYNCHRONIZE_CACHE:
                if (ata_try_flush_cache(dev))
                        return ata_scsi_flush_xlat;
                break;

        case VERIFY:
        case VERIFY_16:
                return ata_scsi_verify_xlat;

        case ATA_12:
        case ATA_16:
                return ata_scsi_pass_thru;
        }

        return NULL;
}

/**
 *      ata_scsi_dump_cdb - dump SCSI command contents to dmesg
 *      @ap: ATA port to which the command was being sent
 *      @cmd: SCSI command to dump
 *
 *      Prints the contents of a SCSI command via printk().
 */

static inline void ata_scsi_dump_cdb(struct ata_port *ap,
                                     struct scsi_cmnd *cmd)
{
#ifdef ATA_DEBUG
        struct scsi_device *scsidev = cmd->device;
        u8 *scsicmd = cmd->cmnd;

        DPRINTK("CDB (%u:%d,%d,%d) %02x %02x %02x %02x %02x %02x %02x %02x %02x\n",
                ap->id,
                scsidev->channel, scsidev->id, scsidev->lun,
                scsicmd[0], scsicmd[1], scsicmd[2], scsicmd[3],
                scsicmd[4], scsicmd[5], scsicmd[6], scsicmd[7],
                scsicmd[8]);
#endif
}

/**
 *      ata_scsi_queuecmd - Issue SCSI cdb to libata-managed device
 *      @cmd: SCSI command to be sent
 *      @done: Completion function, called when command is complete
 *
 *      In some cases, this function translates SCSI commands into
 *      ATA taskfiles, and queues the taskfiles to be sent to
 *      hardware.  In other cases, this function simulates a
 *      SCSI device by evaluating and responding to certain
 *      SCSI commands.  This creates the overall effect of
 *      ATA and ATAPI devices appearing as SCSI devices.
 *
 *      LOCKING:
 *      Releases scsi-layer-held lock, and obtains host_set lock.
 *
 *      RETURNS:
 *      Zero.
 */

int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
{
        struct ata_port *ap;
        struct ata_device *dev;
        struct scsi_device *scsidev = cmd->device;

        ap = (struct ata_port *) &scsidev->host->hostdata[0];

        ata_scsi_dump_cdb(ap, cmd);

        dev = ata_scsi_find_dev(ap, scsidev);
        if (unlikely(!dev)) {
                cmd->result = (DID_BAD_TARGET << 16);
                done(cmd);
                goto out_unlock;
        }

        if (dev->class == ATA_DEV_ATA) {
                ata_xlat_func_t xlat_func = ata_get_xlat_func(dev,
                                                              cmd->cmnd[0]);

                if (xlat_func)
                        ata_scsi_translate(ap, dev, cmd, done, xlat_func);
                else
                        ata_scsi_simulate(dev->id, cmd, done);
        } else
                ata_scsi_translate(ap, dev, cmd, done, atapi_xlat);

out_unlock:
        return 0;
}

/**
 *      ata_scsi_simulate - simulate SCSI command on ATA device
 *      @id: current IDENTIFY data for target device.
 *      @cmd: SCSI command being sent to device.
 *      @done: SCSI command completion function.
 *
 *      Interprets and directly executes a select list of SCSI commands
 *      that can be handled internally.
 *
 *      LOCKING:
 *      spin_lock_irqsave(host_set lock)
 */

void ata_scsi_simulate(u16 *id,
                      struct scsi_cmnd *cmd,
                      void (*done)(struct scsi_cmnd *))
{
        struct ata_scsi_args args;
        u8 *scsicmd = cmd->cmnd;

        args.id = id;
        args.cmd = cmd;
        args.done = done;

        switch(scsicmd[0]) {
                /* no-op's, complete with success */
                case SYNCHRONIZE_CACHE:
                case REZERO_UNIT:
                case SEEK_6:
                case SEEK_10:
                case TEST_UNIT_READY:
                case FORMAT_UNIT:               /* FIXME: correct? */
                case SEND_DIAGNOSTIC:           /* FIXME: correct? */
                        ata_scsi_rbuf_fill(&args, ata_scsiop_noop);
                        break;

                case INQUIRY:
                        if (scsicmd[1] & 2)                /* is CmdDt set?  */
                                ata_bad_cdb(cmd, done);
                        else if ((scsicmd[1] & 1) == 0)    /* is EVPD clear? */
                                ata_scsi_rbuf_fill(&args, ata_scsiop_inq_std);
                        else if (scsicmd[2] == 0x00)
                                ata_scsi_rbuf_fill(&args, ata_scsiop_inq_00);
                        else if (scsicmd[2] == 0x80)
                                ata_scsi_rbuf_fill(&args, ata_scsiop_inq_80);
                        else if (scsicmd[2] == 0x83)
                                ata_scsi_rbuf_fill(&args, ata_scsiop_inq_83);
                        else
                                ata_bad_cdb(cmd, done);
                        break;

                case MODE_SENSE:
                case MODE_SENSE_10:
                        ata_scsi_rbuf_fill(&args, ata_scsiop_mode_sense);
                        break;

                case MODE_SELECT:       /* unconditionally return */
                case MODE_SELECT_10:    /* bad-field-in-cdb */
                        ata_bad_cdb(cmd, done);
                        break;

                case READ_CAPACITY:
                        ata_scsi_rbuf_fill(&args, ata_scsiop_read_cap);
                        break;

                case SERVICE_ACTION_IN:
                        if ((scsicmd[1] & 0x1f) == SAI_READ_CAPACITY_16)
                                ata_scsi_rbuf_fill(&args, ata_scsiop_read_cap);
                        else
                                ata_bad_cdb(cmd, done);
                        break;

                case REPORT_LUNS:
                        ata_scsi_rbuf_fill(&args, ata_scsiop_report_luns);
                        break;

                /* mandatory commands we haven't implemented yet */
                case REQUEST_SENSE:

                /* all other commands */
                default:
                        ata_bad_scsiop(cmd, done);
                        break;
        }
}