ide-tape.c

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/*
 * IDE ATAPI streaming tape driver.
 *
 * Copyright (C) 1995-1999  Gadi Oxman <[email protected]>
 * Copyright (C) 2003-2005  Bartlomiej Zolnierkiewicz
 *
 * This driver was constructed as a student project in the software laboratory
 * of the faculty of electrical engineering in the Technion - Israel's
 * Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David.
 *
 * It is hereby placed under the terms of the GNU general public license.
 * (See linux/COPYING).
 *
 * For a historical changelog see
 * Documentation/ide/ChangeLog.ide-tape.1995-2002
 */

#define DRV_NAME "ide-tape"

#define IDETAPE_VERSION "1.20"

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/ide.h>
#include <linux/completion.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <scsi/scsi.h>

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

/* define to see debug info */
#undef IDETAPE_DEBUG_LOG

#ifdef IDETAPE_DEBUG_LOG
#define ide_debug_log(lvl, fmt, args...) __ide_debug_log(lvl, fmt, ## args)
#else
#define ide_debug_log(lvl, fmt, args...) do {} while (0)
#endif

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

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

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

/* DSC timings. */
#define IDETAPE_DSC_RW_MIN      5*HZ/100    /* 50 msec */
#define IDETAPE_DSC_RW_MAX      40*HZ/100   /* 400 msec */
#define IDETAPE_DSC_RW_TIMEOUT      2*60*HZ     /* 2 minutes */
#define IDETAPE_DSC_MA_FAST     2*HZ        /* 2 seconds */
#define IDETAPE_DSC_MA_THRESHOLD    5*60*HZ     /* 5 minutes */
#define IDETAPE_DSC_MA_SLOW     30*HZ       /* 30 seconds */
#define IDETAPE_DSC_MA_TIMEOUT      2*60*60*HZ  /* 2 hours */

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

/* tape directions */
enum {
    IDETAPE_DIR_NONE  = (1 << 0),
    IDETAPE_DIR_READ  = (1 << 1),
    IDETAPE_DIR_WRITE = (1 << 2),
};

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

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

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

/* Structures related to the SELECT SENSE / MODE SENSE packet commands. */
#define IDETAPE_BLOCK_DESCRIPTOR    0
#define IDETAPE_CAPABILITIES_PAGE   0x2a

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

    /* used by REQ_IDETAPE_{READ,WRITE} requests */
    struct ide_atapi_pc queued_pc;

    /*
     * DSC polling variables.
     *
     * While polling for DSC we use postponed_rq to postpone the current
     * request so that ide.c will be able to service pending requests on the
     * other device. Note that at most we will have only one DSC (usually
     * data transfer) request in the device request queue.
     */
    bool postponed_rq;

    /* The time in which we started polling for DSC */
    unsigned long dsc_polling_start;
    /* Timer used to poll for dsc */
    struct timer_list dsc_timer;
    /* Read/Write dsc polling frequency */
    unsigned long best_dsc_rw_freq;
    unsigned long dsc_poll_freq;
    unsigned long dsc_timeout;

    /* Read position information */
    u8 partition;
    /* Current block */
    unsigned int first_frame;

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

    /* Character device operation */
    unsigned int minor;
    /* device name */
    char name[4];
    /* Current character device data transfer direction */
    u8 chrdev_dir;

    /* tape block size, usually 512 or 1024 bytes */
    unsigned short blk_size;
    int user_bs_factor;

    /* Copy of the tape's Capabilities and Mechanical Page */
    u8 caps[20];

    /*
     * Active data transfer request parameters.
     *
     * At most, there is only one ide-tape originated data transfer request
     * in the device request queue. This allows ide.c to easily service
     * requests from the other device when we postpone our active request.
     */

    /* Data buffer size chosen based on the tape's recommendation */
    int buffer_size;
    /* Staging buffer of buffer_size bytes */
    void *buf;
    /* The read/write cursor */
    void *cur;
    /* The number of valid bytes in buf */
    size_t valid;

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

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

static DEFINE_MUTEX(ide_tape_mutex);
static DEFINE_MUTEX(idetape_ref_mutex);

static DEFINE_MUTEX(idetape_chrdev_mutex);

static struct class *idetape_sysfs_class;

static void ide_tape_release(struct device *);

static struct ide_tape_obj *idetape_devs[MAX_HWIFS * MAX_DRIVES];

static struct ide_tape_obj *ide_tape_get(struct gendisk *disk, bool cdev,
                     unsigned int i)
{
    struct ide_tape_obj *tape = NULL;

    mutex_lock(&idetape_ref_mutex);

    if (cdev)
        tape = idetape_devs[i];
    else
        tape = ide_drv_g(disk, ide_tape_obj);

    if (tape) {
        if (ide_device_get(tape->drive))
            tape = NULL;
        else
            get_device(&tape->dev);
    }

    mutex_unlock(&idetape_ref_mutex);
    return tape;
}

static void ide_tape_put(struct ide_tape_obj *tape)
{
    ide_drive_t *drive = tape->drive;

    mutex_lock(&idetape_ref_mutex);
    put_device(&tape->dev);
    ide_device_put(drive);
    mutex_unlock(&idetape_ref_mutex);
}

/*
 * called on each failed packet command retry to analyze the request sense. We
 * currently do not utilize this information.
 */
static void idetape_analyze_error(ide_drive_t *drive)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc *pc = drive->failed_pc;
    struct request *rq = drive->hwif->rq;
    u8 *sense = bio_data(rq->bio);

    tape->sense_key = sense[2] & 0xF;
    tape->asc       = sense[12];
    tape->ascq      = sense[13];

    ide_debug_log(IDE_DBG_FUNC,
              "cmd: 0x%x, sense key = %x, asc = %x, ascq = %x",
              rq->cmd[0], tape->sense_key, tape->asc, tape->ascq);

    /* correct remaining bytes to transfer */
    if (pc->flags & PC_FLAG_DMA_ERROR)
        rq->resid_len = tape->blk_size * get_unaligned_be32(&sense[3]);

    /*
     * If error was the result of a zero-length read or write command,
     * with sense key=5, asc=0x22, ascq=0, let it slide.  Some drives
     * (i.e. Seagate STT3401A Travan) don't support 0-length read/writes.
     */
    if ((pc->c[0] == READ_6 || pc->c[0] == WRITE_6)
        /* length == 0 */
        && pc->c[4] == 0 && pc->c[3] == 0 && pc->c[2] == 0) {
        if (tape->sense_key == 5) {
            /* don't report an error, everything's ok */
            pc->error = 0;
            /* don't retry read/write */
            pc->flags |= PC_FLAG_ABORT;
        }
    }
    if (pc->c[0] == READ_6 && (sense[2] & 0x80)) {
        pc->error = IDE_DRV_ERROR_FILEMARK;
        pc->flags |= PC_FLAG_ABORT;
    }
    if (pc->c[0] == WRITE_6) {
        if ((sense[2] & 0x40) || (tape->sense_key == 0xd
             && tape->asc == 0x0 && tape->ascq == 0x2)) {
            pc->error = IDE_DRV_ERROR_EOD;
            pc->flags |= PC_FLAG_ABORT;
        }
    }
    if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
        if (tape->sense_key == 8) {
            pc->error = IDE_DRV_ERROR_EOD;
            pc->flags |= PC_FLAG_ABORT;
        }
        if (!(pc->flags & PC_FLAG_ABORT) &&
            (blk_rq_bytes(rq) - rq->resid_len))
            pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
    }
}

static void ide_tape_handle_dsc(ide_drive_t *);

static int ide_tape_callback(ide_drive_t *drive, int dsc)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc *pc = drive->pc;
    struct request *rq = drive->hwif->rq;
    int uptodate = pc->error ? 0 : 1;
    int err = uptodate ? 0 : IDE_DRV_ERROR_GENERAL;

    ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, dsc: %d, err: %d", rq->cmd[0],
              dsc, err);

    if (dsc)
        ide_tape_handle_dsc(drive);

    if (drive->failed_pc == pc)
        drive->failed_pc = NULL;

    if (pc->c[0] == REQUEST_SENSE) {
        if (uptodate)
            idetape_analyze_error(drive);
        else
            printk(KERN_ERR "ide-tape: Error in REQUEST SENSE "
                    "itself - Aborting request!\n");
    } else if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
        unsigned int blocks =
            (blk_rq_bytes(rq) - rq->resid_len) / tape->blk_size;

        tape->avg_size += blocks * tape->blk_size;

        if (time_after_eq(jiffies, tape->avg_time + HZ)) {
            tape->avg_speed = tape->avg_size * HZ /
                (jiffies - tape->avg_time) / 1024;
            tape->avg_size = 0;
            tape->avg_time = jiffies;
        }

        tape->first_frame += blocks;

        if (pc->error) {
            uptodate = 0;
            err = pc->error;
        }
    }
    rq->errors = err;

    return uptodate;
}

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

    ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, dsc_poll_freq: %lu",
              drive->hwif->rq->cmd[0], tape->dsc_poll_freq);

    tape->postponed_rq = true;

    ide_stall_queue(drive, tape->dsc_poll_freq);
}

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

    /* Media access command */
    tape->dsc_polling_start = jiffies;
    tape->dsc_poll_freq = IDETAPE_DSC_MA_FAST;
    tape->dsc_timeout = jiffies + IDETAPE_DSC_MA_TIMEOUT;
    /* Allow ide.c to handle other requests */
    ide_tape_stall_queue(drive);
}

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

static ide_startstop_t ide_tape_issue_pc(ide_drive_t *drive,
                     struct ide_cmd *cmd,
                     struct ide_atapi_pc *pc)
{
    idetape_tape_t *tape = drive->driver_data;
    struct request *rq = drive->hwif->rq;

    if (drive->failed_pc == NULL && pc->c[0] != REQUEST_SENSE)
        drive->failed_pc = pc;

    /* Set the current packet command */
    drive->pc = pc;

    if (pc->retries > IDETAPE_MAX_PC_RETRIES ||
        (pc->flags & PC_FLAG_ABORT)) {

        /*
         * We will "abort" retrying a packet command in case legitimate
         * error code was received (crossing a filemark, or end of the
         * media, for example).
         */
        if (!(pc->flags & PC_FLAG_ABORT)) {
            if (!(pc->c[0] == TEST_UNIT_READY &&
                  tape->sense_key == 2 && tape->asc == 4 &&
                 (tape->ascq == 1 || tape->ascq == 8))) {
                printk(KERN_ERR "ide-tape: %s: I/O error, "
                        "pc = %2x, key = %2x, "
                        "asc = %2x, ascq = %2x\n",
                        tape->name, pc->c[0],
                        tape->sense_key, tape->asc,
                        tape->ascq);
            }
            /* Giving up */
            pc->error = IDE_DRV_ERROR_GENERAL;
        }

        drive->failed_pc = NULL;
        drive->pc_callback(drive, 0);
        ide_complete_rq(drive, -EIO, blk_rq_bytes(rq));
        return ide_stopped;
    }
    ide_debug_log(IDE_DBG_SENSE, "retry #%d, cmd: 0x%02x", pc->retries,
              pc->c[0]);

    pc->retries++;

    return ide_issue_pc(drive, cmd);
}

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

static ide_startstop_t idetape_media_access_finished(ide_drive_t *drive)
{
    ide_hwif_t *hwif = drive->hwif;
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc *pc = drive->pc;
    u8 stat;

    stat = hwif->tp_ops->read_status(hwif);

    if (stat & ATA_DSC) {
        if (stat & ATA_ERR) {
            /* Error detected */
            if (pc->c[0] != TEST_UNIT_READY)
                printk(KERN_ERR "ide-tape: %s: I/O error, ",
                        tape->name);
            /* Retry operation */
            ide_retry_pc(drive);
            return ide_stopped;
        }
        pc->error = 0;
    } else {
        pc->error = IDE_DRV_ERROR_GENERAL;
        drive->failed_pc = NULL;
    }
    drive->pc_callback(drive, 0);
    return ide_stopped;
}

static void ide_tape_create_rw_cmd(idetape_tape_t *tape,
                   struct ide_atapi_pc *pc, struct request *rq,
                   u8 opcode)
{
    unsigned int length = blk_rq_sectors(rq) / (tape->blk_size >> 9);

    ide_init_pc(pc);
    put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);
    pc->c[1] = 1;

    if (blk_rq_bytes(rq) == tape->buffer_size)
        pc->flags |= PC_FLAG_DMA_OK;

    if (opcode == READ_6)
        pc->c[0] = READ_6;
    else if (opcode == WRITE_6) {
        pc->c[0] = WRITE_6;
        pc->flags |= PC_FLAG_WRITING;
    }

    memcpy(rq->cmd, pc->c, 12);
}

static ide_startstop_t idetape_do_request(ide_drive_t *drive,
                      struct request *rq, sector_t block)
{
    ide_hwif_t *hwif = drive->hwif;
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc *pc = NULL;
    struct ide_cmd cmd;
    u8 stat;

    ide_debug_log(IDE_DBG_RQ, "cmd: 0x%x, sector: %llu, nr_sectors: %u",
              rq->cmd[0], (unsigned long long)blk_rq_pos(rq),
              blk_rq_sectors(rq));

    BUG_ON(!(rq->cmd_type == REQ_TYPE_SPECIAL ||
         rq->cmd_type == REQ_TYPE_SENSE));

    /* Retry a failed packet command */
    if (drive->failed_pc && drive->pc->c[0] == REQUEST_SENSE) {
        pc = drive->failed_pc;
        goto out;
    }

    /*
     * If the tape is still busy, postpone our request and service
     * the other device meanwhile.
     */
    stat = hwif->tp_ops->read_status(hwif);

    if ((drive->dev_flags & IDE_DFLAG_DSC_OVERLAP) == 0 &&
        (rq->cmd[13] & REQ_IDETAPE_PC2) == 0)
        drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;

    if (drive->dev_flags & IDE_DFLAG_POST_RESET) {
        drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;
        drive->dev_flags &= ~IDE_DFLAG_POST_RESET;
    }

    if (!(drive->atapi_flags & IDE_AFLAG_IGNORE_DSC) &&
        !(stat & ATA_DSC)) {
        if (!tape->postponed_rq) {
            tape->dsc_polling_start = jiffies;
            tape->dsc_poll_freq = tape->best_dsc_rw_freq;
            tape->dsc_timeout = jiffies + IDETAPE_DSC_RW_TIMEOUT;
        } else if (time_after(jiffies, tape->dsc_timeout)) {
            printk(KERN_ERR "ide-tape: %s: DSC timeout\n",
                tape->name);
            if (rq->cmd[13] & REQ_IDETAPE_PC2) {
                idetape_media_access_finished(drive);
                return ide_stopped;
            } else {
                return ide_do_reset(drive);
            }
        } else if (time_after(jiffies,
                    tape->dsc_polling_start +
                    IDETAPE_DSC_MA_THRESHOLD))
            tape->dsc_poll_freq = IDETAPE_DSC_MA_SLOW;
        ide_tape_stall_queue(drive);
        return ide_stopped;
    } else {
        drive->atapi_flags &= ~IDE_AFLAG_IGNORE_DSC;
        tape->postponed_rq = false;
    }

    if (rq->cmd[13] & REQ_IDETAPE_READ) {
        pc = &tape->queued_pc;
        ide_tape_create_rw_cmd(tape, pc, rq, READ_6);
        goto out;
    }
    if (rq->cmd[13] & REQ_IDETAPE_WRITE) {
        pc = &tape->queued_pc;
        ide_tape_create_rw_cmd(tape, pc, rq, WRITE_6);
        goto out;
    }
    if (rq->cmd[13] & REQ_IDETAPE_PC1) {
        pc = (struct ide_atapi_pc *)rq->special;
        rq->cmd[13] &= ~(REQ_IDETAPE_PC1);
        rq->cmd[13] |= REQ_IDETAPE_PC2;
        goto out;
    }
    if (rq->cmd[13] & REQ_IDETAPE_PC2) {
        idetape_media_access_finished(drive);
        return ide_stopped;
    }
    BUG();

out:
    /* prepare sense request for this command */
    ide_prep_sense(drive, rq);

    memset(&cmd, 0, sizeof(cmd));

    if (rq_data_dir(rq))
        cmd.tf_flags |= IDE_TFLAG_WRITE;

    cmd.rq = rq;

    ide_init_sg_cmd(&cmd, blk_rq_bytes(rq));
    ide_map_sg(drive, &cmd);

    return ide_tape_issue_pc(drive, &cmd, pc);
}

/*
 * Write a filemark if write_filemark=1. Flush the device buffers without
 * writing a filemark otherwise.
 */
static void idetape_create_write_filemark_cmd(ide_drive_t *drive,
        struct ide_atapi_pc *pc, int write_filemark)
{
    ide_init_pc(pc);
    pc->c[0] = WRITE_FILEMARKS;
    pc->c[4] = write_filemark;
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
}

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

    /* Wait for the tape to become ready */
    set_bit(ilog2(IDE_AFLAG_MEDIUM_PRESENT), &drive->atapi_flags);
    timeout += jiffies;
    while (time_before(jiffies, timeout)) {
        if (ide_do_test_unit_ready(drive, disk) == 0)
            return 0;
        if ((tape->sense_key == 2 && tape->asc == 4 && tape->ascq == 2)
            || (tape->asc == 0x3A)) {
            /* no media */
            if (load_attempted)
                return -ENOMEDIUM;
            ide_do_start_stop(drive, disk, IDETAPE_LU_LOAD_MASK);
            load_attempted = 1;
        /* not about to be ready */
        } else if (!(tape->sense_key == 2 && tape->asc == 4 &&
                 (tape->ascq == 1 || tape->ascq == 8)))
            return -EIO;
        msleep(100);
    }
    return -EIO;
}

static int idetape_flush_tape_buffers(ide_drive_t *drive)
{
    struct ide_tape_obj *tape = drive->driver_data;
    struct ide_atapi_pc pc;
    int rc;

    idetape_create_write_filemark_cmd(drive, &pc, 0);
    rc = ide_queue_pc_tail(drive, tape->disk, &pc, NULL, 0);
    if (rc)
        return rc;
    idetape_wait_ready(drive, 60 * 5 * HZ);
    return 0;
}

static int ide_tape_read_position(ide_drive_t *drive)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc pc;
    u8 buf[20];

    ide_debug_log(IDE_DBG_FUNC, "enter");

    /* prep cmd */
    ide_init_pc(&pc);
    pc.c[0] = READ_POSITION;
    pc.req_xfer = 20;

    if (ide_queue_pc_tail(drive, tape->disk, &pc, buf, pc.req_xfer))
        return -1;

    if (!pc.error) {
        ide_debug_log(IDE_DBG_FUNC, "BOP - %s",
                (buf[0] & 0x80) ? "Yes" : "No");
        ide_debug_log(IDE_DBG_FUNC, "EOP - %s",
                (buf[0] & 0x40) ? "Yes" : "No");

        if (buf[0] & 0x4) {
            printk(KERN_INFO "ide-tape: Block location is unknown"
                     "to the tape\n");
            clear_bit(ilog2(IDE_AFLAG_ADDRESS_VALID),
                  &drive->atapi_flags);
            return -1;
        } else {
            ide_debug_log(IDE_DBG_FUNC, "Block Location: %u",
                      be32_to_cpup((__be32 *)&buf[4]));

            tape->partition = buf[1];
            tape->first_frame = be32_to_cpup((__be32 *)&buf[4]);
            set_bit(ilog2(IDE_AFLAG_ADDRESS_VALID),
                &drive->atapi_flags);
        }
    }

    return tape->first_frame;
}

static void idetape_create_locate_cmd(ide_drive_t *drive,
        struct ide_atapi_pc *pc,
        unsigned int block, u8 partition, int skip)
{
    ide_init_pc(pc);
    pc->c[0] = POSITION_TO_ELEMENT;
    pc->c[1] = 2;
    put_unaligned(cpu_to_be32(block), (unsigned int *) &pc->c[3]);
    pc->c[8] = partition;
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
}

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

    if (tape->chrdev_dir != IDETAPE_DIR_READ)
        return;

    clear_bit(ilog2(IDE_AFLAG_FILEMARK), &drive->atapi_flags);
    tape->valid = 0;
    if (tape->buf != NULL) {
        kfree(tape->buf);
        tape->buf = NULL;
    }

    tape->chrdev_dir = IDETAPE_DIR_NONE;
}

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

    if (tape->chrdev_dir == IDETAPE_DIR_READ)
        __ide_tape_discard_merge_buffer(drive);
    idetape_wait_ready(drive, 60 * 5 * HZ);
    idetape_create_locate_cmd(drive, &pc, block, partition, skip);
    ret = ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
    if (ret)
        return ret;

    ret = ide_tape_read_position(drive);
    if (ret < 0)
        return ret;
    return 0;
}

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

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

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

    ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, size: %d", cmd, size);

    BUG_ON(cmd != REQ_IDETAPE_READ && cmd != REQ_IDETAPE_WRITE);
    BUG_ON(size < 0 || size % tape->blk_size);

    rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
    rq->cmd_type = REQ_TYPE_SPECIAL;
    rq->cmd[13] = cmd;
    rq->rq_disk = tape->disk;
    rq->__sector = tape->first_frame;

    if (size) {
        ret = blk_rq_map_kern(drive->queue, rq, tape->buf, size,
                      __GFP_WAIT);
        if (ret)
            goto out_put;
    }

    blk_execute_rq(drive->queue, tape->disk, rq, 0);

    /* calculate the number of transferred bytes and update buffer state */
    size -= rq->resid_len;
    tape->cur = tape->buf;
    if (cmd == REQ_IDETAPE_READ)
        tape->valid = size;
    else
        tape->valid = 0;

    ret = size;
    if (rq->errors == IDE_DRV_ERROR_GENERAL)
        ret = -EIO;
out_put:
    blk_put_request(rq);
    return ret;
}

static void idetape_create_inquiry_cmd(struct ide_atapi_pc *pc)
{
    ide_init_pc(pc);
    pc->c[0] = INQUIRY;
    pc->c[4] = 254;
    pc->req_xfer = 254;
}

static void idetape_create_rewind_cmd(ide_drive_t *drive,
        struct ide_atapi_pc *pc)
{
    ide_init_pc(pc);
    pc->c[0] = REZERO_UNIT;
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
}

static void idetape_create_erase_cmd(struct ide_atapi_pc *pc)
{
    ide_init_pc(pc);
    pc->c[0] = ERASE;
    pc->c[1] = 1;
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
}

static void idetape_create_space_cmd(struct ide_atapi_pc *pc, int count, u8 cmd)
{
    ide_init_pc(pc);
    pc->c[0] = SPACE;
    put_unaligned(cpu_to_be32(count), (unsigned int *) &pc->c[1]);
    pc->c[1] = cmd;
    pc->flags |= PC_FLAG_WAIT_FOR_DSC;
}

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

    if (tape->chrdev_dir != IDETAPE_DIR_WRITE) {
        printk(KERN_ERR "ide-tape: bug: Trying to empty merge buffer"
                " but we are not writing.\n");
        return;
    }
    if (tape->buf) {
        size_t aligned = roundup(tape->valid, tape->blk_size);

        memset(tape->cur, 0, aligned - tape->valid);
        idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, aligned);
        kfree(tape->buf);
        tape->buf = NULL;
    }
    tape->chrdev_dir = IDETAPE_DIR_NONE;
}

static int idetape_init_rw(ide_drive_t *drive, int dir)
{
    idetape_tape_t *tape = drive->driver_data;
    int rc;

    BUG_ON(dir != IDETAPE_DIR_READ && dir != IDETAPE_DIR_WRITE);

    if (tape->chrdev_dir == dir)
        return 0;

    if (tape->chrdev_dir == IDETAPE_DIR_READ)
        ide_tape_discard_merge_buffer(drive, 1);
    else if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
        ide_tape_flush_merge_buffer(drive);
        idetape_flush_tape_buffers(drive);
    }

    if (tape->buf || tape->valid) {
        printk(KERN_ERR "ide-tape: valid should be 0 now\n");
        tape->valid = 0;
    }

    tape->buf = kmalloc(tape->buffer_size, GFP_KERNEL);
    if (!tape->buf)
        return -ENOMEM;
    tape->chrdev_dir = dir;
    tape->cur = tape->buf;

    /*
     * Issue a 0 rw command to ensure that DSC handshake is
     * switched from completion mode to buffer available mode.  No
     * point in issuing this if DSC overlap isn't supported, some
     * drives (Seagate STT3401A) will return an error.
     */
    if (drive->dev_flags & IDE_DFLAG_DSC_OVERLAP) {
        int cmd = dir == IDETAPE_DIR_READ ? REQ_IDETAPE_READ
                          : REQ_IDETAPE_WRITE;

        rc = idetape_queue_rw_tail(drive, cmd, 0);
        if (rc < 0) {
            kfree(tape->buf);
            tape->buf = NULL;
            tape->chrdev_dir = IDETAPE_DIR_NONE;
            return rc;
        }
    }

    return 0;
}

static void idetape_pad_zeros(ide_drive_t *drive, int bcount)
{
    idetape_tape_t *tape = drive->driver_data;

    memset(tape->buf, 0, tape->buffer_size);

    while (bcount) {
        unsigned int count = min(tape->buffer_size, bcount);

        idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, count);
        bcount -= count;
    }
}

/*
 * Rewinds the tape to the Beginning Of the current Partition (BOP). We
 * currently support only one partition.
 */
static int idetape_rewind_tape(ide_drive_t *drive)
{
    struct ide_tape_obj *tape = drive->driver_data;
    struct gendisk *disk = tape->disk;
    struct ide_atapi_pc pc;
    int ret;

    ide_debug_log(IDE_DBG_FUNC, "enter");

    idetape_create_rewind_cmd(drive, &pc);
    ret = ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
    if (ret)
        return ret;

    ret = ide_tape_read_position(drive);
    if (ret < 0)
        return ret;
    return 0;
}

/* mtio.h compatible commands should be issued to the chrdev interface. */
static int idetape_blkdev_ioctl(ide_drive_t *drive, unsigned int cmd,
                unsigned long arg)
{
    idetape_tape_t *tape = drive->driver_data;
    void __user *argp = (void __user *)arg;

    struct idetape_config {
        int dsc_rw_frequency;
        int dsc_media_access_frequency;
        int nr_stages;
    } config;

    ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%04x", cmd);

    switch (cmd) {
    case 0x0340:
        if (copy_from_user(&config, argp, sizeof(config)))
            return -EFAULT;
        tape->best_dsc_rw_freq = config.dsc_rw_frequency;
        break;
    case 0x0350:
        memset(&config, 0, sizeof(config));
        config.dsc_rw_frequency = (int) tape->best_dsc_rw_freq;
        config.nr_stages = 1;
        if (copy_to_user(argp, &config, sizeof(config)))
            return -EFAULT;
        break;
    default:
        return -EIO;
    }
    return 0;
}

static int idetape_space_over_filemarks(ide_drive_t *drive, short mt_op,
                    int mt_count)
{
    idetape_tape_t *tape = drive->driver_data;
    struct gendisk *disk = tape->disk;
    struct ide_atapi_pc pc;
    int retval, count = 0;
    int sprev = !!(tape->caps[4] & 0x20);


    ide_debug_log(IDE_DBG_FUNC, "mt_op: %d, mt_count: %d", mt_op, mt_count);

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

    if (tape->chrdev_dir == IDETAPE_DIR_READ) {
        tape->valid = 0;
        if (test_and_clear_bit(ilog2(IDE_AFLAG_FILEMARK),
                       &drive->atapi_flags))
            ++count;
        ide_tape_discard_merge_buffer(drive, 0);
    }

    switch (mt_op) {
    case MTFSF:
    case MTBSF:
        idetape_create_space_cmd(&pc, mt_count - count,
                     IDETAPE_SPACE_OVER_FILEMARK);
        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
    case MTFSFM:
    case MTBSFM:
        if (!sprev)
            return -EIO;
        retval = idetape_space_over_filemarks(drive, MTFSF,
                              mt_count - count);
        if (retval)
            return retval;
        count = (MTBSFM == mt_op ? 1 : -1);
        return idetape_space_over_filemarks(drive, MTFSF, count);
    default:
        printk(KERN_ERR "ide-tape: MTIO operation %d not supported\n",
                mt_op);
        return -EIO;
    }
}

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

    ide_debug_log(IDE_DBG_FUNC, "count %Zd", count);

    if (tape->chrdev_dir != IDETAPE_DIR_READ) {
        if (test_bit(ilog2(IDE_AFLAG_DETECT_BS), &drive->atapi_flags))
            if (count > tape->blk_size &&
                (count % tape->blk_size) == 0)
                tape->user_bs_factor = count / tape->blk_size;
    }

    rc = idetape_init_rw(drive, IDETAPE_DIR_READ);
    if (rc < 0)
        return rc;

    while (done < count) {
        size_t todo;

        /* refill if staging buffer is empty */
        if (!tape->valid) {
            /* If we are at a filemark, nothing more to read */
            if (test_bit(ilog2(IDE_AFLAG_FILEMARK),
                     &drive->atapi_flags))
                break;
            /* read */
            if (idetape_queue_rw_tail(drive, REQ_IDETAPE_READ,
                          tape->buffer_size) <= 0)
                break;
        }

        /* copy out */
        todo = min_t(size_t, count - done, tape->valid);
        if (copy_to_user(buf + done, tape->cur, todo))
            ret = -EFAULT;

        tape->cur += todo;
        tape->valid -= todo;
        done += todo;
    }

    if (!done && test_bit(ilog2(IDE_AFLAG_FILEMARK), &drive->atapi_flags)) {
        idetape_space_over_filemarks(drive, MTFSF, 1);
        return 0;
    }

    return ret ? ret : done;
}

static ssize_t idetape_chrdev_write(struct file *file, const char __user *buf,
                     size_t count, loff_t *ppos)
{
    struct ide_tape_obj *tape = file->private_data;
    ide_drive_t *drive = tape->drive;
    size_t done = 0;
    ssize_t ret = 0;
    int rc;

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

    ide_debug_log(IDE_DBG_FUNC, "count %Zd", count);

    /* Initialize write operation */
    rc = idetape_init_rw(drive, IDETAPE_DIR_WRITE);
    if (rc < 0)
        return rc;

    while (done < count) {
        size_t todo;

        /* flush if staging buffer is full */
        if (tape->valid == tape->buffer_size &&
            idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE,
                      tape->buffer_size) <= 0)
            return rc;

        /* copy in */
        todo = min_t(size_t, count - done,
                 tape->buffer_size - tape->valid);
        if (copy_from_user(tape->cur, buf + done, todo))
            ret = -EFAULT;

        tape->cur += todo;
        tape->valid += todo;
        done += todo;
    }

    return ret ? ret : done;
}

static int idetape_write_filemark(ide_drive_t *drive)
{
    struct ide_tape_obj *tape = drive->driver_data;
    struct ide_atapi_pc pc;

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

/*
 * Called from idetape_chrdev_ioctl when the general mtio MTIOCTOP ioctl is
 * requested.
 *
 * Note: MTBSF and MTBSFM are not supported when the tape doesn't support
 * spacing over filemarks in the reverse direction. In this case, MTFSFM is also
 * usually not supported.
 *
 * The following commands are currently not supported:
 *
 * MTFSS, MTBSS, MTWSM, MTSETDENSITY, MTSETDRVBUFFER, MT_ST_BOOLEANS,
 * MT_ST_WRITE_THRESHOLD.
 */
static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
{
    idetape_tape_t *tape = drive->driver_data;
    struct gendisk *disk = tape->disk;
    struct ide_atapi_pc pc;
    int i, retval;

    ide_debug_log(IDE_DBG_FUNC, "MTIOCTOP ioctl: mt_op: %d, mt_count: %d",
              mt_op, mt_count);

    switch (mt_op) {
    case MTFSF:
    case MTFSFM:
    case MTBSF:
    case MTBSFM:
        if (!mt_count)
            return 0;
        return idetape_space_over_filemarks(drive, mt_op, mt_count);
    default:
        break;
    }

    switch (mt_op) {
    case MTWEOF:
        if (tape->write_prot)
            return -EACCES;
        ide_tape_discard_merge_buffer(drive, 1);
        for (i = 0; i < mt_count; i++) {
            retval = idetape_write_filemark(drive);
            if (retval)
                return retval;
        }
        return 0;
    case MTREW:
        ide_tape_discard_merge_buffer(drive, 0);
        if (idetape_rewind_tape(drive))
            return -EIO;
        return 0;
    case MTLOAD:
        ide_tape_discard_merge_buffer(drive, 0);
        return ide_do_start_stop(drive, disk, IDETAPE_LU_LOAD_MASK);
    case MTUNLOAD:
    case MTOFFL:
        /*
         * If door is locked, attempt to unlock before
         * attempting to eject.
         */
        if (tape->door_locked) {
            if (!ide_set_media_lock(drive, disk, 0))
                tape->door_locked = DOOR_UNLOCKED;
        }
        ide_tape_discard_merge_buffer(drive, 0);
        retval = ide_do_start_stop(drive, disk, !IDETAPE_LU_LOAD_MASK);
        if (!retval)
            clear_bit(ilog2(IDE_AFLAG_MEDIUM_PRESENT),
                  &drive->atapi_flags);
        return retval;
    case MTNOP:
        ide_tape_discard_merge_buffer(drive, 0);
        return idetape_flush_tape_buffers(drive);
    case MTRETEN:
        ide_tape_discard_merge_buffer(drive, 0);
        return ide_do_start_stop(drive, disk,
            IDETAPE_LU_RETENSION_MASK | IDETAPE_LU_LOAD_MASK);
    case MTEOM:
        idetape_create_space_cmd(&pc, 0, IDETAPE_SPACE_TO_EOD);
        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
    case MTERASE:
        (void)idetape_rewind_tape(drive);
        idetape_create_erase_cmd(&pc);
        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
    case MTSETBLK:
        if (mt_count) {
            if (mt_count < tape->blk_size ||
                mt_count % tape->blk_size)
                return -EIO;
            tape->user_bs_factor = mt_count / tape->blk_size;
            clear_bit(ilog2(IDE_AFLAG_DETECT_BS),
                  &drive->atapi_flags);
        } else
            set_bit(ilog2(IDE_AFLAG_DETECT_BS),
                &drive->atapi_flags);
        return 0;
    case MTSEEK:
        ide_tape_discard_merge_buffer(drive, 0);
        return idetape_position_tape(drive,
            mt_count * tape->user_bs_factor, tape->partition, 0);
    case MTSETPART:
        ide_tape_discard_merge_buffer(drive, 0);
        return idetape_position_tape(drive, 0, mt_count, 0);
    case MTFSR:
    case MTBSR:
    case MTLOCK:
        retval = ide_set_media_lock(drive, disk, 1);
        if (retval)
            return retval;
        tape->door_locked = DOOR_EXPLICITLY_LOCKED;
        return 0;
    case MTUNLOCK:
        retval = ide_set_media_lock(drive, disk, 0);
        if (retval)
            return retval;
        tape->door_locked = DOOR_UNLOCKED;
        return 0;
    default:
        printk(KERN_ERR "ide-tape: MTIO operation %d not supported\n",
                mt_op);
        return -EIO;
    }
}

/*
 * Our character device ioctls. General mtio.h magnetic io commands are
 * supported here, and not in the corresponding block interface. Our own
 * ide-tape ioctls are supported on both interfaces.
 */
static long do_idetape_chrdev_ioctl(struct file *file,
                unsigned int cmd, unsigned long arg)
{
    struct ide_tape_obj *tape = file->private_data;
    ide_drive_t *drive = tape->drive;
    struct mtop mtop;
    struct mtget mtget;
    struct mtpos mtpos;
    int block_offset = 0, position = tape->first_frame;
    void __user *argp = (void __user *)arg;

    ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x", cmd);

    if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
        ide_tape_flush_merge_buffer(drive);
        idetape_flush_tape_buffers(drive);
    }
    if (cmd == MTIOCGET || cmd == MTIOCPOS) {
        block_offset = tape->valid /
            (tape->blk_size * tape->user_bs_factor);
        position = ide_tape_read_position(drive);
        if (position < 0)
            return -EIO;
    }
    switch (cmd) {
    case MTIOCTOP:
        if (copy_from_user(&mtop, argp, sizeof(struct mtop)))
            return -EFAULT;
        return idetape_mtioctop(drive, mtop.mt_op, mtop.mt_count);
    case MTIOCGET:
        memset(&mtget, 0, sizeof(struct mtget));
        mtget.mt_type = MT_ISSCSI2;
        mtget.mt_blkno = position / tape->user_bs_factor - block_offset;
        mtget.mt_dsreg =
            ((tape->blk_size * tape->user_bs_factor)
             << MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK;

        if (tape->drv_write_prot)
            mtget.mt_gstat |= GMT_WR_PROT(0xffffffff);

        if (copy_to_user(argp, &mtget, sizeof(struct mtget)))
            return -EFAULT;
        return 0;
    case MTIOCPOS:
        mtpos.mt_blkno = position / tape->user_bs_factor - block_offset;
        if (copy_to_user(argp, &mtpos, sizeof(struct mtpos)))
            return -EFAULT;
        return 0;
    default:
        if (tape->chrdev_dir == IDETAPE_DIR_READ)
            ide_tape_discard_merge_buffer(drive, 1);
        return idetape_blkdev_ioctl(drive, cmd, arg);
    }
}

static long idetape_chrdev_ioctl(struct file *file,
                unsigned int cmd, unsigned long arg)
{
    long ret;
    mutex_lock(&ide_tape_mutex);
    ret = do_idetape_chrdev_ioctl(file, cmd, arg);
    mutex_unlock(&ide_tape_mutex);
    return ret;
}

/*
 * Do a mode sense page 0 with block descriptor and if it succeeds set the tape
 * block size with the reported value.
 */
static void ide_tape_get_bsize_from_bdesc(ide_drive_t *drive)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc pc;
    u8 buf[12];

    idetape_create_mode_sense_cmd(&pc, IDETAPE_BLOCK_DESCRIPTOR);
    if (ide_queue_pc_tail(drive, tape->disk, &pc, buf, pc.req_xfer)) {
        printk(KERN_ERR "ide-tape: Can't get block descriptor\n");
        if (tape->blk_size == 0) {
            printk(KERN_WARNING "ide-tape: Cannot deal with zero "
                        "block size, assuming 32k\n");
            tape->blk_size = 32768;
        }
        return;
    }
    tape->blk_size = (buf[4 + 5] << 16) +
                (buf[4 + 6] << 8)  +
                 buf[4 + 7];
    tape->drv_write_prot = (buf[2] & 0x80) >> 7;

    ide_debug_log(IDE_DBG_FUNC, "blk_size: %d, write_prot: %d",
              tape->blk_size, tape->drv_write_prot);
}

static int idetape_chrdev_open(struct inode *inode, struct file *filp)
{
    unsigned int minor = iminor(inode), i = minor & ~0xc0;
    ide_drive_t *drive;
    idetape_tape_t *tape;
    int retval;

    if (i >= MAX_HWIFS * MAX_DRIVES)
        return -ENXIO;

    mutex_lock(&idetape_chrdev_mutex);

    tape = ide_tape_get(NULL, true, i);
    if (!tape) {
        mutex_unlock(&idetape_chrdev_mutex);
        return -ENXIO;
    }

    drive = tape->drive;
    filp->private_data = tape;

    ide_debug_log(IDE_DBG_FUNC, "enter");

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


    if (test_and_set_bit(ilog2(IDE_AFLAG_BUSY), &drive->atapi_flags)) {
        retval = -EBUSY;
        goto out_put_tape;
    }

    retval = idetape_wait_ready(drive, 60 * HZ);
    if (retval) {
        clear_bit(ilog2(IDE_AFLAG_BUSY), &drive->atapi_flags);
        printk(KERN_ERR "ide-tape: %s: drive not ready\n", tape->name);
        goto out_put_tape;
    }

    ide_tape_read_position(drive);
    if (!test_bit(ilog2(IDE_AFLAG_ADDRESS_VALID), &drive->atapi_flags))
        (void)idetape_rewind_tape(drive);

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

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

    /* Make sure drive isn't write protected if user wants to write. */
    if (tape->write_prot) {
        if ((filp->f_flags & O_ACCMODE) == O_WRONLY ||
            (filp->f_flags & O_ACCMODE) == O_RDWR) {
            clear_bit(ilog2(IDE_AFLAG_BUSY), &drive->atapi_flags);
            retval = -EROFS;
            goto out_put_tape;
        }
    }

    /* Lock the tape drive door so user can't eject. */
    if (tape->chrdev_dir == IDETAPE_DIR_NONE) {
        if (!ide_set_media_lock(drive, tape->disk, 1)) {
            if (tape->door_locked != DOOR_EXPLICITLY_LOCKED)
                tape->door_locked = DOOR_LOCKED;
        }
    }
    mutex_unlock(&idetape_chrdev_mutex);

    return 0;

out_put_tape:
    ide_tape_put(tape);

    mutex_unlock(&idetape_chrdev_mutex);

    return retval;
}

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

    ide_tape_flush_merge_buffer(drive);
    tape->buf = kmalloc(tape->buffer_size, GFP_KERNEL);
    if (tape->buf != NULL) {
        idetape_pad_zeros(drive, tape->blk_size *
                (tape->user_bs_factor - 1));
        kfree(tape->buf);
        tape->buf = NULL;
    }
    idetape_write_filemark(drive);
    idetape_flush_tape_buffers(drive);
    idetape_flush_tape_buffers(drive);
}

static int idetape_chrdev_release(struct inode *inode, struct file *filp)
{
    struct ide_tape_obj *tape = filp->private_data;
    ide_drive_t *drive = tape->drive;
    unsigned int minor = iminor(inode);

    mutex_lock(&idetape_chrdev_mutex);

    tape = drive->driver_data;

    ide_debug_log(IDE_DBG_FUNC, "enter");

    if (tape->chrdev_dir == IDETAPE_DIR_WRITE)
        idetape_write_release(drive, minor);
    if (tape->chrdev_dir == IDETAPE_DIR_READ) {
        if (minor < 128)
            ide_tape_discard_merge_buffer(drive, 1);
    }

    if (minor < 128 && test_bit(ilog2(IDE_AFLAG_MEDIUM_PRESENT),
                    &drive->atapi_flags))
        (void) idetape_rewind_tape(drive);

    if (tape->chrdev_dir == IDETAPE_DIR_NONE) {
        if (tape->door_locked == DOOR_LOCKED) {
            if (!ide_set_media_lock(drive, tape->disk, 0))
                tape->door_locked = DOOR_UNLOCKED;
        }
    }
    clear_bit(ilog2(IDE_AFLAG_BUSY), &drive->atapi_flags);
    ide_tape_put(tape);

    mutex_unlock(&idetape_chrdev_mutex);

    return 0;
}

static void idetape_get_inquiry_results(ide_drive_t *drive)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc pc;
    u8 pc_buf[256];
    char fw_rev[4], vendor_id[8], product_id[16];

    idetape_create_inquiry_cmd(&pc);
    if (ide_queue_pc_tail(drive, tape->disk, &pc, pc_buf, pc.req_xfer)) {
        printk(KERN_ERR "ide-tape: %s: can't get INQUIRY results\n",
                tape->name);
        return;
    }
    memcpy(vendor_id, &pc_buf[8], 8);
    memcpy(product_id, &pc_buf[16], 16);
    memcpy(fw_rev, &pc_buf[32], 4);

    ide_fixstring(vendor_id, 8, 0);
    ide_fixstring(product_id, 16, 0);
    ide_fixstring(fw_rev, 4, 0);

    printk(KERN_INFO "ide-tape: %s <-> %s: %.8s %.16s rev %.4s\n",
            drive->name, tape->name, vendor_id, product_id, fw_rev);
}

/*
 * Ask the tape about its various parameters. In particular, we will adjust our
 * data transfer buffer size to the recommended value as returned by the tape.
 */
static void idetape_get_mode_sense_results(ide_drive_t *drive)
{
    idetape_tape_t *tape = drive->driver_data;
    struct ide_atapi_pc pc;
    u8 buf[24], *caps;
    u8 speed, max_speed;

    idetape_create_mode_sense_cmd(&pc, IDETAPE_CAPABILITIES_PAGE);
    if (ide_queue_pc_tail(drive, tape->disk, &pc, buf, pc.req_xfer)) {
        printk(KERN_ERR "ide-tape: Can't get tape parameters - assuming"
                " some default values\n");
        tape->blk_size = 512;
        put_unaligned(52,   (u16 *)&tape->caps[12]);
        put_unaligned(540,  (u16 *)&tape->caps[14]);
        put_unaligned(6*52, (u16 *)&tape->caps[16]);
        return;
    }
    caps = buf + 4 + buf[3];

    /* convert to host order and save for later use */
    speed = be16_to_cpup((__be16 *)&caps[14]);
    max_speed = be16_to_cpup((__be16 *)&caps[8]);

    *(u16 *)&caps[8] = max_speed;
    *(u16 *)&caps[12] = be16_to_cpup((__be16 *)&caps[12]);
    *(u16 *)&caps[14] = speed;
    *(u16 *)&caps[16] = be16_to_cpup((__be16 *)&caps[16]);

    if (!speed) {
        printk(KERN_INFO "ide-tape: %s: invalid tape speed "
                "(assuming 650KB/sec)\n", drive->name);
        *(u16 *)&caps[14] = 650;
    }
    if (!max_speed) {
        printk(KERN_INFO "ide-tape: %s: invalid max_speed "
                "(assuming 650KB/sec)\n", drive->name);
        *(u16 *)&caps[8] = 650;
    }

    memcpy(&tape->caps, caps, 20);

    /* device lacks locking support according to capabilities page */
    if ((caps[6] & 1) == 0)
        drive->dev_flags &= ~IDE_DFLAG_DOORLOCKING;

    if (caps[7] & 0x02)
        tape->blk_size = 512;
    else if (caps[7] & 0x04)
        tape->blk_size = 1024;
}

#ifdef CONFIG_IDE_PROC_FS
#define ide_tape_devset_get(name, field) \
static int get_##name(ide_drive_t *drive) \
{ \
    idetape_tape_t *tape = drive->driver_data; \
    return tape->field; \
}

#define ide_tape_devset_set(name, field) \
static int set_##name(ide_drive_t *drive, int arg) \
{ \
    idetape_tape_t *tape = drive->driver_data; \
    tape->field = arg; \
    return 0; \
}

#define ide_tape_devset_rw_field(_name, _field) \
ide_tape_devset_get(_name, _field) \
ide_tape_devset_set(_name, _field) \
IDE_DEVSET(_name, DS_SYNC, get_##_name, set_##_name)

#define ide_tape_devset_r_field(_name, _field) \
ide_tape_devset_get(_name, _field) \
IDE_DEVSET(_name, 0, get_##_name, NULL)

static int mulf_tdsc(ide_drive_t *drive)    { return 1000; }
static int divf_tdsc(ide_drive_t *drive)    { return   HZ; }
static int divf_buffer(ide_drive_t *drive)  { return    2; }
static int divf_buffer_size(ide_drive_t *drive) { return 1024; }

ide_devset_rw_flag(dsc_overlap, IDE_DFLAG_DSC_OVERLAP);

ide_tape_devset_rw_field(tdsc, best_dsc_rw_freq);

ide_tape_devset_r_field(avg_speed, avg_speed);
ide_tape_devset_r_field(speed, caps[14]);
ide_tape_devset_r_field(buffer, caps[16]);
ide_tape_devset_r_field(buffer_size, buffer_size);

static const struct ide_proc_devset idetape_settings[] = {
    __IDE_PROC_DEVSET(avg_speed,    0, 0xffff, NULL, NULL),
    __IDE_PROC_DEVSET(buffer,   0, 0xffff, NULL, divf_buffer),
    __IDE_PROC_DEVSET(buffer_size,  0, 0xffff, NULL, divf_buffer_size),
    __IDE_PROC_DEVSET(dsc_overlap,  0,      1, NULL, NULL),
    __IDE_PROC_DEVSET(speed,    0, 0xffff, NULL, NULL),
    __IDE_PROC_DEVSET(tdsc,     IDETAPE_DSC_RW_MIN, IDETAPE_DSC_RW_MAX,
                    mulf_tdsc, divf_tdsc),
    { NULL },
};
#endif

/*
 * The function below is called to:
 *
 * 1. Initialize our various state variables.
 * 2. Ask the tape for its capabilities.
 * 3. Allocate a buffer which will be used for data transfer. The buffer size
 * is chosen based on the recommendation which we received in step 2.
 *
 * Note that at this point ide.c already assigned us an irq, so that we can
 * queue requests here and wait for their completion.
 */
static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
{
    unsigned long t;
    int speed;
    int buffer_size;
    u16 *ctl = (u16 *)&tape->caps[12];

    ide_debug_log(IDE_DBG_FUNC, "minor: %d", minor);

    drive->pc_callback = ide_tape_callback;

    drive->dev_flags |= IDE_DFLAG_DSC_OVERLAP;

    if (drive->hwif->host_flags & IDE_HFLAG_NO_DSC) {
        printk(KERN_INFO "ide-tape: %s: disabling DSC overlap\n",
                 tape->name);
        drive->dev_flags &= ~IDE_DFLAG_DSC_OVERLAP;
    }

    /* Seagate Travan drives do not support DSC overlap. */
    if (strstr((char *)&drive->id[ATA_ID_PROD], "Seagate STT3401"))
        drive->dev_flags &= ~IDE_DFLAG_DSC_OVERLAP;

    tape->minor = minor;
    tape->name[0] = 'h';
    tape->name[1] = 't';
    tape->name[2] = '0' + minor;
    tape->chrdev_dir = IDETAPE_DIR_NONE;

    idetape_get_inquiry_results(drive);
    idetape_get_mode_sense_results(drive);
    ide_tape_get_bsize_from_bdesc(drive);
    tape->user_bs_factor = 1;
    tape->buffer_size = *ctl * tape->blk_size;
    while (tape->buffer_size > 0xffff) {
        printk(KERN_NOTICE "ide-tape: decreasing stage size\n");
        *ctl /= 2;
        tape->buffer_size = *ctl * tape->blk_size;
    }
    buffer_size = tape->buffer_size;

    /* select the "best" DSC read/write polling freq */
    speed = max(*(u16 *)&tape->caps[14], *(u16 *)&tape->caps[8]);

    t = (IDETAPE_FIFO_THRESHOLD * tape->buffer_size * HZ) / (speed * 1000);

    /*
     * Ensure that the number we got makes sense; limit it within
     * IDETAPE_DSC_RW_MIN and IDETAPE_DSC_RW_MAX.
     */
    tape->best_dsc_rw_freq = clamp_t(unsigned long, t, IDETAPE_DSC_RW_MIN,
                     IDETAPE_DSC_RW_MAX);
    printk(KERN_INFO "ide-tape: %s <-> %s: %dKBps, %d*%dkB buffer, "
        "%lums tDSC%s\n",
        drive->name, tape->name, *(u16 *)&tape->caps[14],
        (*(u16 *)&tape->caps[16] * 512) / tape->buffer_size,
        tape->buffer_size / 1024,
        tape->best_dsc_rw_freq * 1000 / HZ,
        (drive->dev_flags & IDE_DFLAG_USING_DMA) ? ", DMA" : "");

    ide_proc_register_driver(drive, tape->driver);
}

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

    ide_proc_unregister_driver(drive, tape->driver);
    device_del(&tape->dev);
    ide_unregister_region(tape->disk);

    mutex_lock(&idetape_ref_mutex);
    put_device(&tape->dev);
    mutex_unlock(&idetape_ref_mutex);
}

static void ide_tape_release(struct device *dev)
{
    struct ide_tape_obj *tape = to_ide_drv(dev, ide_tape_obj);
    ide_drive_t *drive = tape->drive;
    struct gendisk *g = tape->disk;

    BUG_ON(tape->valid);

    drive->dev_flags &= ~IDE_DFLAG_DSC_OVERLAP;
    drive->driver_data = NULL;
    device_destroy(idetape_sysfs_class, MKDEV(IDETAPE_MAJOR, tape->minor));
    device_destroy(idetape_sysfs_class,
            MKDEV(IDETAPE_MAJOR, tape->minor + 128));
    idetape_devs[tape->minor] = NULL;
    g->private_data = NULL;
    put_disk(g);
    kfree(tape);
}

#ifdef CONFIG_IDE_PROC_FS
static int idetape_name_proc_show(struct seq_file *m, void *v)
{
    ide_drive_t *drive = (ide_drive_t *) m->private;
    idetape_tape_t  *tape = drive->driver_data;

    seq_printf(m, "%s\n", tape->name);
    return 0;
}

static int idetape_name_proc_open(struct inode *inode, struct file *file)
{
    return single_open(file, idetape_name_proc_show, PDE(inode)->data);
}

static const struct file_operations idetape_name_proc_fops = {
    .owner      = THIS_MODULE,
    .open       = idetape_name_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static ide_proc_entry_t idetape_proc[] = {
    { "capacity",   S_IFREG|S_IRUGO,    &ide_capacity_proc_fops },
    { "name",   S_IFREG|S_IRUGO,    &idetape_name_proc_fops },
    {}
};

static ide_proc_entry_t *ide_tape_proc_entries(ide_drive_t *drive)
{
    return idetape_proc;
}

static const struct ide_proc_devset *ide_tape_proc_devsets(ide_drive_t *drive)
{
    return idetape_settings;
}
#endif

static int ide_tape_probe(ide_drive_t *);

static struct ide_driver idetape_driver = {
    .gen_driver = {
        .owner      = THIS_MODULE,
        .name       = "ide-tape",
        .bus        = &ide_bus_type,
    },
    .probe          = ide_tape_probe,
    .remove         = ide_tape_remove,
    .version        = IDETAPE_VERSION,
    .do_request     = idetape_do_request,
#ifdef CONFIG_IDE_PROC_FS
    .proc_entries       = ide_tape_proc_entries,
    .proc_devsets       = ide_tape_proc_devsets,
#endif
};

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

static int idetape_open(struct block_device *bdev, fmode_t mode)
{
    struct ide_tape_obj *tape;

    mutex_lock(&ide_tape_mutex);
    tape = ide_tape_get(bdev->bd_disk, false, 0);
    mutex_unlock(&ide_tape_mutex);

    if (!tape)
        return -ENXIO;

    return 0;
}

static int idetape_release(struct gendisk *disk, fmode_t mode)
{
    struct ide_tape_obj *tape = ide_drv_g(disk, ide_tape_obj);

    mutex_lock(&ide_tape_mutex);
    ide_tape_put(tape);
    mutex_unlock(&ide_tape_mutex);

    return 0;
}

static int idetape_ioctl(struct block_device *bdev, fmode_t mode,
            unsigned int cmd, unsigned long arg)
{
    struct ide_tape_obj *tape = ide_drv_g(bdev->bd_disk, ide_tape_obj);
    ide_drive_t *drive = tape->drive;
    int err;

    mutex_lock(&ide_tape_mutex);
    err = generic_ide_ioctl(drive, bdev, cmd, arg);
    if (err == -EINVAL)
        err = idetape_blkdev_ioctl(drive, cmd, arg);
    mutex_unlock(&ide_tape_mutex);

    return err;
}

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

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

    ide_debug_log(IDE_DBG_FUNC, "enter");

    if (!strstr(DRV_NAME, drive->driver_req))
        goto failed;

    if (drive->media != ide_tape)
        goto failed;

    if ((drive->dev_flags & IDE_DFLAG_ID_READ) &&
        ide_check_atapi_device(drive, DRV_NAME) == 0) {
        printk(KERN_ERR "ide-tape: %s: not supported by this version of"
                " the driver\n", drive->name);
        goto failed;
    }
    tape = kzalloc(sizeof(idetape_tape_t), GFP_KERNEL);
    if (tape == NULL) {
        printk(KERN_ERR "ide-tape: %s: Can't allocate a tape struct\n",
                drive->name);
        goto failed;
    }

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

    ide_init_disk(g, drive);

    tape->dev.parent = &drive->gendev;
    tape->dev.release = ide_tape_release;
    dev_set_name(&tape->dev, dev_name(&drive->gendev));

    if (device_register(&tape->dev))
        goto out_free_disk;

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

    g->private_data = &tape->driver;

    drive->driver_data = tape;

    mutex_lock(&idetape_ref_mutex);
    for (minor = 0; idetape_devs[minor]; minor++)
        ;
    idetape_devs[minor] = tape;
    mutex_unlock(&idetape_ref_mutex);

    idetape_setup(drive, tape, minor);

    device_create(idetape_sysfs_class, &drive->gendev,
              MKDEV(IDETAPE_MAJOR, minor), NULL, "%s", tape->name);
    device_create(idetape_sysfs_class, &drive->gendev,
              MKDEV(IDETAPE_MAJOR, minor + 128), NULL,
              "n%s", tape->name);

    g->fops = &idetape_block_ops;
    ide_register_region(g);

    return 0;

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

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

static int __init idetape_init(void)
{
    int error = 1;
    idetape_sysfs_class = class_create(THIS_MODULE, "ide_tape");
    if (IS_ERR(idetape_sysfs_class)) {
        idetape_sysfs_class = NULL;
        printk(KERN_ERR "Unable to create sysfs class for ide tapes\n");
        error = -EBUSY;
        goto out;
    }

    if (register_chrdev(IDETAPE_MAJOR, "ht", &idetape_fops)) {
        printk(KERN_ERR "ide-tape: Failed to register chrdev"
                " interface\n");
        error = -EBUSY;
        goto out_free_class;
    }

    error = driver_register(&idetape_driver.gen_driver);
    if (error)
        goto out_free_driver;

    return 0;

out_free_driver:
    driver_unregister(&idetape_driver.gen_driver);
out_free_class:
    class_destroy(idetape_sysfs_class);
out:
    return error;
}

MODULE_ALIAS("ide:*m-tape*");
module_init(idetape_init);
module_exit(idetape_exit);
MODULE_ALIAS_CHARDEV_MAJOR(IDETAPE_MAJOR);
MODULE_DESCRIPTION("ATAPI Streaming TAPE Driver");
MODULE_LICENSE("GPL");