// SPDX-License-Identifier: GPL-2.0-only
/*
 * ATAPI support.
 */

#include <linux/kernel.h>
#include <linux/cdrom.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/ide.h>
#include <linux/scatterlist.h>
#include <linux/gfp.h>

#include <scsi/scsi.h>

#define DRV_NAME "ide-atapi"
#define PFX DRV_NAME ": "

#ifdef DEBUG
#define debug_log(fmt, args...) \
        printk(KERN_INFO "ide: " fmt, ## args)
#else
#define debug_log(fmt, args...) do {} while (0)
#endif

#define ATAPI_MIN_CDB_BYTES     12

static inline int dev_is_idecd(ide_drive_t *drive)
{
        return drive->media == ide_cdrom || drive->media == ide_optical;
}

/*
 * Check whether we can support a device,
 * based on the ATAPI IDENTIFY command results.
 */
int ide_check_atapi_device(ide_drive_t *drive, const char *s)
{
        u16 *id = drive->id;
        u8 gcw[2], protocol, device_type, removable, drq_type, packet_size;

        *((u16 *)&gcw) = id[ATA_ID_CONFIG];

        protocol    = (gcw[1] & 0xC0) >> 6;
        device_type =  gcw[1] & 0x1F;
        removable   = (gcw[0] & 0x80) >> 7;
        drq_type    = (gcw[0] & 0x60) >> 5;
        packet_size =  gcw[0] & 0x03;

#ifdef CONFIG_PPC
        /* kludge for Apple PowerBook internal zip */
        if (drive->media == ide_floppy && device_type == 5 &&
            !strstr((char *)&id[ATA_ID_PROD], "CD-ROM") &&
            strstr((char *)&id[ATA_ID_PROD], "ZIP"))
                device_type = 0;
#endif

        if (protocol != 2)
                printk(KERN_ERR "%s: %s: protocol (0x%02x) is not ATAPI\n",
                        s, drive->name, protocol);
        else if ((drive->media == ide_floppy && device_type != 0) ||
                 (drive->media == ide_tape && device_type != 1))
                printk(KERN_ERR "%s: %s: invalid device type (0x%02x)\n",
                        s, drive->name, device_type);
        else if (removable == 0)
                printk(KERN_ERR "%s: %s: the removable flag is not set\n",
                        s, drive->name);
        else if (drive->media == ide_floppy && drq_type == 3)
                printk(KERN_ERR "%s: %s: sorry, DRQ type (0x%02x) not "
                        "supported\n", s, drive->name, drq_type);
        else if (packet_size != 0)
                printk(KERN_ERR "%s: %s: packet size (0x%02x) is not 12 "
                        "bytes\n", s, drive->name, packet_size);
        else
                return 1;
        return 0;
}
EXPORT_SYMBOL_GPL(ide_check_atapi_device);

void ide_init_pc(struct ide_atapi_pc *pc)
{
        memset(pc, 0, sizeof(*pc));
}
EXPORT_SYMBOL_GPL(ide_init_pc);

/*
 * Add a special packet command request to the tail of the request queue,
 * and wait for it to be serviced.
 */
int ide_queue_pc_tail(ide_drive_t *drive, struct gendisk *disk,
                      struct ide_atapi_pc *pc, void *buf, unsigned int bufflen)
{
        struct request *rq;
        int error;

        rq = blk_get_request(drive->queue, REQ_OP_DRV_IN, 0);
        ide_req(rq)->type = ATA_PRIV_MISC;
        ide_req(rq)->special = pc;

        if (buf && bufflen) {
                error = blk_rq_map_kern(drive->queue, rq, buf, bufflen,
                                        GFP_NOIO);
                if (error)
                        goto put_req;
        }

        memcpy(scsi_req(rq)->cmd, pc->c, 12);
        if (drive->media == ide_tape)
                scsi_req(rq)->cmd[13] = REQ_IDETAPE_PC1;
        blk_execute_rq(drive->queue, disk, rq, 0);
        error = scsi_req(rq)->result ? -EIO : 0;
put_req:
        blk_put_request(rq);
        return error;
}
EXPORT_SYMBOL_GPL(ide_queue_pc_tail);

int ide_do_test_unit_ready(ide_drive_t *drive, struct gendisk *disk)
{
        struct ide_atapi_pc pc;

        ide_init_pc(&pc);
        pc.c[0] = TEST_UNIT_READY;

        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
}
EXPORT_SYMBOL_GPL(ide_do_test_unit_ready);

int ide_do_start_stop(ide_drive_t *drive, struct gendisk *disk, int start)
{
        struct ide_atapi_pc pc;

        ide_init_pc(&pc);
        pc.c[0] = START_STOP;
        pc.c[4] = start;

        if (drive->media == ide_tape)
                pc.flags |= PC_FLAG_WAIT_FOR_DSC;

        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
}
EXPORT_SYMBOL_GPL(ide_do_start_stop);

int ide_set_media_lock(ide_drive_t *drive, struct gendisk *disk, int on)
{
        struct ide_atapi_pc pc;

        if ((drive->dev_flags & IDE_DFLAG_DOORLOCKING) == 0)
                return 0;

        ide_init_pc(&pc);
        pc.c[0] = ALLOW_MEDIUM_REMOVAL;
        pc.c[4] = on;

        return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
}
EXPORT_SYMBOL_GPL(ide_set_media_lock);

void ide_create_request_sense_cmd(ide_drive_t *drive, struct ide_atapi_pc *pc)
{
        ide_init_pc(pc);
        pc->c[0] = REQUEST_SENSE;
        if (drive->media == ide_floppy) {
                pc->c[4] = 255;
                pc->req_xfer = 18;
        } else {
                pc->c[4] = 20;
                pc->req_xfer = 20;
        }
}
EXPORT_SYMBOL_GPL(ide_create_request_sense_cmd);

void ide_prep_sense(ide_drive_t *drive, struct request *rq)
{
        struct request_sense *sense = &drive->sense_data;
        struct request *sense_rq;
        struct scsi_request *req;
        unsigned int cmd_len, sense_len;
        int err;

        switch (drive->media) {
        case ide_floppy:
                cmd_len = 255;
                sense_len = 18;
                break;
        case ide_tape:
                cmd_len = 20;
                sense_len = 20;
                break;
        default:
                cmd_len = 18;
                sense_len = 18;
        }

        BUG_ON(sense_len > sizeof(*sense));

        if (ata_sense_request(rq) || drive->sense_rq_armed)
                return;

        sense_rq = drive->sense_rq;
        if (!sense_rq) {
                sense_rq = blk_mq_alloc_request(drive->queue, REQ_OP_DRV_IN,
                                        BLK_MQ_REQ_RESERVED | BLK_MQ_REQ_NOWAIT);
                drive->sense_rq = sense_rq;
        }
        req = scsi_req(sense_rq);

        memset(sense, 0, sizeof(*sense));

        scsi_req_init(req);

        err = blk_rq_map_kern(drive->queue, sense_rq, sense, sense_len,
                              GFP_NOIO);
        if (unlikely(err)) {
                if (printk_ratelimit())
                        printk(KERN_WARNING PFX "%s: failed to map sense "
                                            "buffer\n", drive->name);
                blk_mq_free_request(sense_rq);
                drive->sense_rq = NULL;
                return;
        }

        sense_rq->rq_disk = rq->rq_disk;
        sense_rq->cmd_flags = REQ_OP_DRV_IN;
        ide_req(sense_rq)->type = ATA_PRIV_SENSE;

        req->cmd[0] = GPCMD_REQUEST_SENSE;
        req->cmd[4] = cmd_len;
        if (drive->media == ide_tape)
                req->cmd[13] = REQ_IDETAPE_PC1;

        drive->sense_rq_armed = true;
}
EXPORT_SYMBOL_GPL(ide_prep_sense);

int ide_queue_sense_rq(ide_drive_t *drive, void *special)
{
        ide_hwif_t *hwif = drive->hwif;
        struct request *sense_rq;
        unsigned long flags;

        spin_lock_irqsave(&hwif->lock, flags);

        /* deferred failure from ide_prep_sense() */
        if (!drive->sense_rq_armed) {
                printk(KERN_WARNING PFX "%s: error queuing a sense request\n",
                       drive->name);
                spin_unlock_irqrestore(&hwif->lock, flags);
                return -ENOMEM;
        }

        sense_rq = drive->sense_rq;
        ide_req(sense_rq)->special = special;
        drive->sense_rq_armed = false;

        drive->hwif->rq = NULL;

        ide_insert_request_head(drive, sense_rq);
        spin_unlock_irqrestore(&hwif->lock, flags);
        return 0;
}
EXPORT_SYMBOL_GPL(ide_queue_sense_rq);

/*
 * Called when an error was detected during the last packet command.
 * We queue a request sense packet command at the head of the request
 * queue.
 */
void ide_retry_pc(ide_drive_t *drive)
{
        struct request *failed_rq = drive->hwif->rq;
        struct request *sense_rq = drive->sense_rq;
        struct ide_atapi_pc *pc = &drive->request_sense_pc;

        (void)ide_read_error(drive);

        /* init pc from sense_rq */
        ide_init_pc(pc);
        memcpy(pc->c, scsi_req(sense_rq)->cmd, 12);

        if (drive->media == ide_tape)
                drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;

        /*
         * Push back the failed request and put request sense on top
         * of it.  The failed command will be retried after sense data
         * is acquired.
         */
        drive->hwif->rq = NULL;
        ide_requeue_and_plug(drive, failed_rq);
        if (ide_queue_sense_rq(drive, pc))
                ide_complete_rq(drive, BLK_STS_IOERR, blk_rq_bytes(failed_rq));
}
EXPORT_SYMBOL_GPL(ide_retry_pc);

int ide_cd_expiry(ide_drive_t *drive)
{
        struct request *rq = drive->hwif->rq;
        unsigned long wait = 0;

        debug_log("%s: scsi_req(rq)->cmd[0]: 0x%x\n", __func__, scsi_req(rq)->cmd[0]);

        /*
         * Some commands are *slow* and normally take a long time to complete.
         * Usually we can use the ATAPI "disconnect" to bypass this, but not all
         * commands/drives support that. Let ide_timer_expiry keep polling us
         * for these.
         */
        switch (scsi_req(rq)->cmd[0]) {
        case GPCMD_BLANK:
        case GPCMD_FORMAT_UNIT:
        case GPCMD_RESERVE_RZONE_TRACK:
        case GPCMD_CLOSE_TRACK:
        case GPCMD_FLUSH_CACHE:
                wait = ATAPI_WAIT_PC;
                break;
        default:
                if (!(rq->rq_flags & RQF_QUIET))
                        printk(KERN_INFO PFX "cmd 0x%x timed out\n",
                                         scsi_req(rq)->cmd[0]);
                wait = 0;
                break;
        }
        return wait;
}
EXPORT_SYMBOL_GPL(ide_cd_expiry);

int ide_cd_get_xferlen(struct request *rq)
{
        switch (req_op(rq)) {
        default:
                return 32768;
        case REQ_OP_SCSI_IN:
        case REQ_OP_SCSI_OUT:
                return blk_rq_bytes(rq);
        case REQ_OP_DRV_IN:
        case REQ_OP_DRV_OUT:
                switch (ide_req(rq)->type) {
                case ATA_PRIV_PC:
                case ATA_PRIV_SENSE:
                        return blk_rq_bytes(rq);
                default:
                        return 0;
                }
        }
}
EXPORT_SYMBOL_GPL(ide_cd_get_xferlen);

void ide_read_bcount_and_ireason(ide_drive_t *drive, u16 *bcount, u8 *ireason)
{
        struct ide_taskfile tf;

        drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT |
                                     IDE_VALID_LBAM | IDE_VALID_LBAH);

        *bcount = (tf.lbah << 8) | tf.lbam;
        *ireason = tf.nsect & 3;
}
EXPORT_SYMBOL_GPL(ide_read_bcount_and_ireason);

/*
 * Check the contents of the interrupt reason register and attempt to recover if
 * there are problems.
 *
 * Returns:
 * - 0 if everything's ok
 * - 1 if the request has to be terminated.
 */
int ide_check_ireason(ide_drive_t *drive, struct request *rq, int len,
                      int ireason, int rw)
{
        ide_hwif_t *hwif = drive->hwif;

        debug_log("ireason: 0x%x, rw: 0x%x\n", ireason, rw);

        if (ireason == (!rw << 1))
                return 0;
        else if (ireason == (rw << 1)) {
                printk(KERN_ERR PFX "%s: %s: wrong transfer direction!\n",
                                drive->name, __func__);

                if (dev_is_idecd(drive))
                        ide_pad_transfer(drive, rw, len);
        } else if (!rw && ireason == ATAPI_COD) {
                if (dev_is_idecd(drive)) {
                        /*
                         * Some drives (ASUS) seem to tell us that status info
                         * is available.  Just get it and ignore.
                         */
                        (void)hwif->tp_ops->read_status(hwif);
                        return 0;
                }
        } else {
                if (ireason & ATAPI_COD)
                        printk(KERN_ERR PFX "%s: CoD != 0 in %s\n", drive->name,
                                        __func__);

                /* drive wants a command packet, or invalid ireason... */
                printk(KERN_ERR PFX "%s: %s: bad interrupt reason 0x%02x\n",
                                drive->name, __func__, ireason);
        }

        if (dev_is_idecd(drive) && ata_pc_request(rq))
                rq->rq_flags |= RQF_FAILED;

        return 1;
}
EXPORT_SYMBOL_GPL(ide_check_ireason);

/*
 * This is the usual interrupt handler which will be called during a packet
 * command.  We will transfer some of the data (as requested by the drive)
 * and will re-point interrupt handler to us.
 */
static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
{
        struct ide_atapi_pc *pc = drive->pc;
        ide_hwif_t *hwif = drive->hwif;
        struct ide_cmd *cmd = &hwif->cmd;
        struct request *rq = hwif->rq;
        const struct ide_tp_ops *tp_ops = hwif->tp_ops;
        unsigned int timeout, done;
        u16 bcount;
        u8 stat, ireason, dsc = 0;
        u8 write = !!(pc->flags & PC_FLAG_WRITING);

        debug_log("Enter %s - interrupt handler\n", __func__);

        timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
                                               : WAIT_TAPE_CMD;

        /* Clear the interrupt */
        stat = tp_ops->read_status(hwif);

        if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
                int rc;

                drive->waiting_for_dma = 0;
                rc = hwif->dma_ops->dma_end(drive);
                ide_dma_unmap_sg(drive, cmd);

                if (rc || (drive->media == ide_tape && (stat & ATA_ERR))) {
                        if (drive->media == ide_floppy)
                                printk(KERN_ERR PFX "%s: DMA %s error\n",
                                        drive->name, rq_data_dir(pc->rq)
                                                     ? "write" : "read");
                        pc->flags |= PC_FLAG_DMA_ERROR;
                } else
                        scsi_req(rq)->resid_len = 0;
                debug_log("%s: DMA finished\n", drive->name);
        }

        /* No more interrupts */
        if ((stat & ATA_DRQ) == 0) {
                int uptodate;
                blk_status_t error;

                debug_log("Packet command completed, %d bytes transferred\n",
                          blk_rq_bytes(rq));

                pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;

                local_irq_enable_in_hardirq();

                if (drive->media == ide_tape &&
                    (stat & ATA_ERR) && scsi_req(rq)->cmd[0] == REQUEST_SENSE)
                        stat &= ~ATA_ERR;

                if ((stat & ATA_ERR) || (pc->flags & PC_FLAG_DMA_ERROR)) {
                        /* Error detected */
                        debug_log("%s: I/O error\n", drive->name);

                        if (drive->media != ide_tape)
                                scsi_req(pc->rq)->result++;

                        if (scsi_req(rq)->cmd[0] == REQUEST_SENSE) {
                                printk(KERN_ERR PFX "%s: I/O error in request "
                                                "sense command\n", drive->name);
                                return ide_do_reset(drive);
                        }

                        debug_log("[cmd %x]: check condition\n", scsi_req(rq)->cmd[0]);

                        /* Retry operation */
                        ide_retry_pc(drive);

                        /* queued, but not started */
                        return ide_stopped;
                }
                pc->error = 0;

                if ((pc->flags & PC_FLAG_WAIT_FOR_DSC) && (stat & ATA_DSC) == 0)
                        dsc = 1;

                /*
                 * ->pc_callback() might change rq->data_len for
                 * residual count, cache total length.
                 */
                done = blk_rq_bytes(rq);

                /* Command finished - Call the callback function */
                uptodate = drive->pc_callback(drive, dsc);

                if (uptodate == 0)
                        drive->failed_pc = NULL;

                if (ata_misc_request(rq)) {
                        scsi_req(rq)->result = 0;
                        error = BLK_STS_OK;
                } else {

                        if (blk_rq_is_passthrough(rq) && uptodate <= 0) {
                                if (scsi_req(rq)->result == 0)
                                        scsi_req(rq)->result = -EIO;
                        }

                        error = uptodate ? BLK_STS_OK : BLK_STS_IOERR;
                }

                ide_complete_rq(drive, error, blk_rq_bytes(rq));
                return ide_stopped;
        }

        if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
                pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;
                printk(KERN_ERR PFX "%s: The device wants to issue more "
                                "interrupts in DMA mode\n", drive->name);
                ide_dma_off(drive);
                return ide_do_reset(drive);
        }

        /* Get the number of bytes to transfer on this interrupt. */
        ide_read_bcount_and_ireason(drive, &bcount, &ireason);

        if (ide_check_ireason(drive, rq, bcount, ireason, write))
                return ide_do_reset(drive);

        done = min_t(unsigned int, bcount, cmd->nleft);
        ide_pio_bytes(drive, cmd, write, done);

        /* Update transferred byte count */
        scsi_req(rq)->resid_len -= done;

        bcount -= done;

        if (bcount)
                ide_pad_transfer(drive, write, bcount);

        debug_log("[cmd %x] transferred %d bytes, padded %d bytes, resid: %u\n",
                  scsi_req(rq)->cmd[0], done, bcount, scsi_req(rq)->resid_len);

        /* And set the interrupt handler again */
        ide_set_handler(drive, ide_pc_intr, timeout);
        return ide_started;
}

static void ide_init_packet_cmd(struct ide_cmd *cmd, u8 valid_tf,
                                u16 bcount, u8 dma)
{
        cmd->protocol = dma ? ATAPI_PROT_DMA : ATAPI_PROT_PIO;
        cmd->valid.out.tf = IDE_VALID_LBAH | IDE_VALID_LBAM |
                            IDE_VALID_FEATURE | valid_tf;
        cmd->tf.command = ATA_CMD_PACKET;
        cmd->tf.feature = dma;          /* Use PIO/DMA */
        cmd->tf.lbam    = bcount & 0xff;
        cmd->tf.lbah    = (bcount >> 8) & 0xff;
}

static u8 ide_read_ireason(ide_drive_t *drive)
{
        struct ide_taskfile tf;

        drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT);

        return tf.nsect & 3;
}

static u8 ide_wait_ireason(ide_drive_t *drive, u8 ireason)
{
        int retries = 100;

        while (retries-- && ((ireason & ATAPI_COD) == 0 ||
                (ireason & ATAPI_IO))) {
                printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing "
                                "a packet command, retrying\n", drive->name);
                udelay(100);
                ireason = ide_read_ireason(drive);
                if (retries == 0) {
                        printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing"
                                        " a packet command, ignoring\n",
                                        drive->name);
                        ireason |= ATAPI_COD;
                        ireason &= ~ATAPI_IO;
                }
        }

        return ireason;
}

static int ide_delayed_transfer_pc(ide_drive_t *drive)
{
        /* Send the actual packet */
        drive->hwif->tp_ops->output_data(drive, NULL, drive->pc->c, 12);

        /* Timeout for the packet command */
        return WAIT_FLOPPY_CMD;
}

static ide_startstop_t ide_transfer_pc(ide_drive_t *drive)
{
        struct ide_atapi_pc *pc;
        ide_hwif_t *hwif = drive->hwif;
        struct request *rq = hwif->rq;
        ide_expiry_t *expiry;
        unsigned int timeout;
        int cmd_len;
        ide_startstop_t startstop;
        u8 ireason;

        if (ide_wait_stat(&startstop, drive, ATA_DRQ, ATA_BUSY, WAIT_READY)) {
                printk(KERN_ERR PFX "%s: Strange, packet command initiated yet "
                                "DRQ isn't asserted\n", drive->name);
                return startstop;
        }

        if (drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT) {
                if (drive->dma)
                        drive->waiting_for_dma = 1;
        }

        if (dev_is_idecd(drive)) {
                /* ATAPI commands get padded out to 12 bytes minimum */
                cmd_len = COMMAND_SIZE(scsi_req(rq)->cmd[0]);
                if (cmd_len < ATAPI_MIN_CDB_BYTES)
                        cmd_len = ATAPI_MIN_CDB_BYTES;

                timeout = rq->timeout;
                expiry  = ide_cd_expiry;
        } else {
                pc = drive->pc;

                cmd_len = ATAPI_MIN_CDB_BYTES;

                /*
                 * If necessary schedule the packet transfer to occur 'timeout'
                 * milliseconds later in ide_delayed_transfer_pc() after the
                 * device says it's ready for a packet.
                 */
                if (drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) {
                        timeout = drive->pc_delay;
                        expiry = &ide_delayed_transfer_pc;
                } else {
                        timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
                                                               : WAIT_TAPE_CMD;
                        expiry = NULL;
                }

                ireason = ide_read_ireason(drive);
                if (drive->media == ide_tape)
                        ireason = ide_wait_ireason(drive, ireason);

                if ((ireason & ATAPI_COD) == 0 || (ireason & ATAPI_IO)) {
                        printk(KERN_ERR PFX "%s: (IO,CoD) != (0,1) while "
                                "issuing a packet command\n", drive->name);

                        return ide_do_reset(drive);
                }
        }

        hwif->expiry = expiry;

        /* Set the interrupt routine */
        ide_set_handler(drive,
                        (dev_is_idecd(drive) ? drive->irq_handler
                                             : ide_pc_intr),
                        timeout);

        /* Send the actual packet */
        if ((drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) == 0)
                hwif->tp_ops->output_data(drive, NULL, scsi_req(rq)->cmd, cmd_len);

        /* Begin DMA, if necessary */
        if (dev_is_idecd(drive)) {
                if (drive->dma)
                        hwif->dma_ops->dma_start(drive);
        } else {
                if (pc->flags & PC_FLAG_DMA_OK) {
                        pc->flags |= PC_FLAG_DMA_IN_PROGRESS;
                        hwif->dma_ops->dma_start(drive);
                }
        }

        return ide_started;
}

ide_startstop_t ide_issue_pc(ide_drive_t *drive, struct ide_cmd *cmd)
{
        struct ide_atapi_pc *pc;
        ide_hwif_t *hwif = drive->hwif;
        ide_expiry_t *expiry = NULL;
        struct request *rq = hwif->rq;
        unsigned int timeout, bytes;
        u16 bcount;
        u8 valid_tf;
        u8 drq_int = !!(drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT);

        if (dev_is_idecd(drive)) {
                valid_tf = IDE_VALID_NSECT | IDE_VALID_LBAL;
                bcount = ide_cd_get_xferlen(rq);
                expiry = ide_cd_expiry;
                timeout = ATAPI_WAIT_PC;

                if (drive->dma)
                        drive->dma = !ide_dma_prepare(drive, cmd);
        } else {
                pc = drive->pc;

                valid_tf = IDE_VALID_DEVICE;
                bytes = blk_rq_bytes(rq);
                bcount = ((drive->media == ide_tape) ? bytes
                                                     : min_t(unsigned int,
                                                             bytes, 63 * 1024));

                /* We haven't transferred any data yet */
                scsi_req(rq)->resid_len = bcount;

                if (pc->flags & PC_FLAG_DMA_ERROR) {
                        pc->flags &= ~PC_FLAG_DMA_ERROR;
                        ide_dma_off(drive);
                }

                if (pc->flags & PC_FLAG_DMA_OK)
                        drive->dma = !ide_dma_prepare(drive, cmd);

                if (!drive->dma)
                        pc->flags &= ~PC_FLAG_DMA_OK;

                timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
                                                       : WAIT_TAPE_CMD;
        }

        ide_init_packet_cmd(cmd, valid_tf, bcount, drive->dma);

        (void)do_rw_taskfile(drive, cmd);

        if (drq_int) {
                if (drive->dma)
                        drive->waiting_for_dma = 0;
                hwif->expiry = expiry;
        }

        ide_execute_command(drive, cmd, ide_transfer_pc, timeout);

        return drq_int ? ide_started : ide_transfer_pc(drive);
}
EXPORT_SYMBOL_GPL(ide_issue_pc);