ide-io.c

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/*
 *  IDE I/O functions
 *
 *  Basic PIO and command management functionality.
 *
 * This code was split off from ide.c. See ide.c for history and original
 * copyrights.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * For the avoidance of doubt the "preferred form" of this code is one which
 * is in an open non patent encumbered format. Where cryptographic key signing
 * forms part of the process of creating an executable the information
 * including keys needed to generate an equivalently functional executable
 * are deemed to be part of the source code.
 */
 
 
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/blkpg.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/completion.h>
#include <linux/reboot.h>
#include <linux/cdrom.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/kmod.h>
#include <linux/scatterlist.h>
#include <linux/bitops.h>

#include <asm/byteorder.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>

int ide_end_rq(ide_drive_t *drive, struct request *rq, int error,
           unsigned int nr_bytes)
{
    /*
     * decide whether to reenable DMA -- 3 is a random magic for now,
     * if we DMA timeout more than 3 times, just stay in PIO
     */
    if ((drive->dev_flags & IDE_DFLAG_DMA_PIO_RETRY) &&
        drive->retry_pio <= 3) {
        drive->dev_flags &= ~IDE_DFLAG_DMA_PIO_RETRY;
        ide_dma_on(drive);
    }

    return blk_end_request(rq, error, nr_bytes);
}
EXPORT_SYMBOL_GPL(ide_end_rq);

void ide_complete_cmd(ide_drive_t *drive, struct ide_cmd *cmd, u8 stat, u8 err)
{
    const struct ide_tp_ops *tp_ops = drive->hwif->tp_ops;
    struct ide_taskfile *tf = &cmd->tf;
    struct request *rq = cmd->rq;
    u8 tf_cmd = tf->command;

    tf->error = err;
    tf->status = stat;

    if (cmd->ftf_flags & IDE_FTFLAG_IN_DATA) {
        u8 data[2];

        tp_ops->input_data(drive, cmd, data, 2);

        cmd->tf.data  = data[0];
        cmd->hob.data = data[1];
    }

    ide_tf_readback(drive, cmd);

    if ((cmd->tf_flags & IDE_TFLAG_CUSTOM_HANDLER) &&
        tf_cmd == ATA_CMD_IDLEIMMEDIATE) {
        if (tf->lbal != 0xc4) {
            printk(KERN_ERR "%s: head unload failed!\n",
                   drive->name);
            ide_tf_dump(drive->name, cmd);
        } else
            drive->dev_flags |= IDE_DFLAG_PARKED;
    }

    if (rq && rq->cmd_type == REQ_TYPE_ATA_TASKFILE) {
        struct ide_cmd *orig_cmd = rq->special;

        if (cmd->tf_flags & IDE_TFLAG_DYN)
            kfree(orig_cmd);
        else
            memcpy(orig_cmd, cmd, sizeof(*cmd));
    }
}

int ide_complete_rq(ide_drive_t *drive, int error, unsigned int nr_bytes)
{
    ide_hwif_t *hwif = drive->hwif;
    struct request *rq = hwif->rq;
    int rc;

    /*
     * if failfast is set on a request, override number of sectors
     * and complete the whole request right now
     */
    if (blk_noretry_request(rq) && error <= 0)
        nr_bytes = blk_rq_sectors(rq) << 9;

    rc = ide_end_rq(drive, rq, error, nr_bytes);
    if (rc == 0)
        hwif->rq = NULL;

    return rc;
}
EXPORT_SYMBOL(ide_complete_rq);

void ide_kill_rq(ide_drive_t *drive, struct request *rq)
{
    u8 drv_req = (rq->cmd_type == REQ_TYPE_SPECIAL) && rq->rq_disk;
    u8 media = drive->media;

    drive->failed_pc = NULL;

    if ((media == ide_floppy || media == ide_tape) && drv_req) {
        rq->errors = 0;
    } else {
        if (media == ide_tape)
            rq->errors = IDE_DRV_ERROR_GENERAL;
        else if (rq->cmd_type != REQ_TYPE_FS && rq->errors == 0)
            rq->errors = -EIO;
    }

    ide_complete_rq(drive, -EIO, blk_rq_bytes(rq));
}

static void ide_tf_set_specify_cmd(ide_drive_t *drive, struct ide_taskfile *tf)
{
    tf->nsect   = drive->sect;
    tf->lbal    = drive->sect;
    tf->lbam    = drive->cyl;
    tf->lbah    = drive->cyl >> 8;
    tf->device  = (drive->head - 1) | drive->select;
    tf->command = ATA_CMD_INIT_DEV_PARAMS;
}

static void ide_tf_set_restore_cmd(ide_drive_t *drive, struct ide_taskfile *tf)
{
    tf->nsect   = drive->sect;
    tf->command = ATA_CMD_RESTORE;
}

static void ide_tf_set_setmult_cmd(ide_drive_t *drive, struct ide_taskfile *tf)
{
    tf->nsect   = drive->mult_req;
    tf->command = ATA_CMD_SET_MULTI;
}

static ide_startstop_t do_special(ide_drive_t *drive)
{
    struct ide_cmd cmd;

#ifdef DEBUG
    printk(KERN_DEBUG "%s: %s: 0x%02x\n", drive->name, __func__,
        drive->special_flags);
#endif
    if (drive->media != ide_disk) {
        drive->special_flags = 0;
        drive->mult_req = 0;
        return ide_stopped;
    }

    memset(&cmd, 0, sizeof(cmd));
    cmd.protocol = ATA_PROT_NODATA;

    if (drive->special_flags & IDE_SFLAG_SET_GEOMETRY) {
        drive->special_flags &= ~IDE_SFLAG_SET_GEOMETRY;
        ide_tf_set_specify_cmd(drive, &cmd.tf);
    } else if (drive->special_flags & IDE_SFLAG_RECALIBRATE) {
        drive->special_flags &= ~IDE_SFLAG_RECALIBRATE;
        ide_tf_set_restore_cmd(drive, &cmd.tf);
    } else if (drive->special_flags & IDE_SFLAG_SET_MULTMODE) {
        drive->special_flags &= ~IDE_SFLAG_SET_MULTMODE;
        ide_tf_set_setmult_cmd(drive, &cmd.tf);
    } else
        BUG();

    cmd.valid.out.tf = IDE_VALID_OUT_TF | IDE_VALID_DEVICE;
    cmd.valid.in.tf  = IDE_VALID_IN_TF  | IDE_VALID_DEVICE;
    cmd.tf_flags = IDE_TFLAG_CUSTOM_HANDLER;

    do_rw_taskfile(drive, &cmd);

    return ide_started;
}

void ide_map_sg(ide_drive_t *drive, struct ide_cmd *cmd)
{
    ide_hwif_t *hwif = drive->hwif;
    struct scatterlist *sg = hwif->sg_table;
    struct request *rq = cmd->rq;

    cmd->sg_nents = blk_rq_map_sg(drive->queue, rq, sg);
}
EXPORT_SYMBOL_GPL(ide_map_sg);

void ide_init_sg_cmd(struct ide_cmd *cmd, unsigned int nr_bytes)
{
    cmd->nbytes = cmd->nleft = nr_bytes;
    cmd->cursg_ofs = 0;
    cmd->cursg = NULL;
}
EXPORT_SYMBOL_GPL(ide_init_sg_cmd);

static ide_startstop_t execute_drive_cmd (ide_drive_t *drive,
        struct request *rq)
{
    struct ide_cmd *cmd = rq->special;

    if (cmd) {
        if (cmd->protocol == ATA_PROT_PIO) {
            ide_init_sg_cmd(cmd, blk_rq_sectors(rq) << 9);
            ide_map_sg(drive, cmd);
        }

        return do_rw_taskfile(drive, cmd);
    }

    /*
     * NULL is actually a valid way of waiting for
     * all current requests to be flushed from the queue.
     */
#ifdef DEBUG
    printk("%s: DRIVE_CMD (null)\n", drive->name);
#endif
    rq->errors = 0;
    ide_complete_rq(drive, 0, blk_rq_bytes(rq));

    return ide_stopped;
}

static ide_startstop_t ide_special_rq(ide_drive_t *drive, struct request *rq)
{
    u8 cmd = rq->cmd[0];

    switch (cmd) {
    case REQ_PARK_HEADS:
    case REQ_UNPARK_HEADS:
        return ide_do_park_unpark(drive, rq);
    case REQ_DEVSET_EXEC:
        return ide_do_devset(drive, rq);
    case REQ_DRIVE_RESET:
        return ide_do_reset(drive);
    default:
        BUG();
    }
}

static ide_startstop_t start_request (ide_drive_t *drive, struct request *rq)
{
    ide_startstop_t startstop;

    BUG_ON(!(rq->cmd_flags & REQ_STARTED));

#ifdef DEBUG
    printk("%s: start_request: current=0x%08lx\n",
        drive->hwif->name, (unsigned long) rq);
#endif

    /* bail early if we've exceeded max_failures */
    if (drive->max_failures && (drive->failures > drive->max_failures)) {
        rq->cmd_flags |= REQ_FAILED;
        goto kill_rq;
    }

    if (blk_pm_request(rq))
        ide_check_pm_state(drive, rq);

    drive->hwif->tp_ops->dev_select(drive);
    if (ide_wait_stat(&startstop, drive, drive->ready_stat,
              ATA_BUSY | ATA_DRQ, WAIT_READY)) {
        printk(KERN_ERR "%s: drive not ready for command\n", drive->name);
        return startstop;
    }

    if (drive->special_flags == 0) {
        struct ide_driver *drv;

        /*
         * We reset the drive so we need to issue a SETFEATURES.
         * Do it _after_ do_special() restored device parameters.
         */
        if (drive->current_speed == 0xff)
            ide_config_drive_speed(drive, drive->desired_speed);

        if (rq->cmd_type == REQ_TYPE_ATA_TASKFILE)
            return execute_drive_cmd(drive, rq);
        else if (blk_pm_request(rq)) {
            struct request_pm_state *pm = rq->special;
#ifdef DEBUG_PM
            printk("%s: start_power_step(step: %d)\n",
                drive->name, pm->pm_step);
#endif
            startstop = ide_start_power_step(drive, rq);
            if (startstop == ide_stopped &&
                pm->pm_step == IDE_PM_COMPLETED)
                ide_complete_pm_rq(drive, rq);
            return startstop;
        } else if (!rq->rq_disk && rq->cmd_type == REQ_TYPE_SPECIAL)
            /*
             * TODO: Once all ULDs have been modified to
             * check for specific op codes rather than
             * blindly accepting any special request, the
             * check for ->rq_disk above may be replaced
             * by a more suitable mechanism or even
             * dropped entirely.
             */
            return ide_special_rq(drive, rq);

        drv = *(struct ide_driver **)rq->rq_disk->private_data;

        return drv->do_request(drive, rq, blk_rq_pos(rq));
    }
    return do_special(drive);
kill_rq:
    ide_kill_rq(drive, rq);
    return ide_stopped;
}

void ide_stall_queue (ide_drive_t *drive, unsigned long timeout)
{
    if (timeout > WAIT_WORSTCASE)
        timeout = WAIT_WORSTCASE;
    drive->sleep = timeout + jiffies;
    drive->dev_flags |= IDE_DFLAG_SLEEPING;
}
EXPORT_SYMBOL(ide_stall_queue);

static inline int ide_lock_port(ide_hwif_t *hwif)
{
    if (hwif->busy)
        return 1;

    hwif->busy = 1;

    return 0;
}

static inline void ide_unlock_port(ide_hwif_t *hwif)
{
    hwif->busy = 0;
}

static inline int ide_lock_host(struct ide_host *host, ide_hwif_t *hwif)
{
    int rc = 0;

    if (host->host_flags & IDE_HFLAG_SERIALIZE) {
        rc = test_and_set_bit_lock(IDE_HOST_BUSY, &host->host_busy);
        if (rc == 0) {
            if (host->get_lock)
                host->get_lock(ide_intr, hwif);
        }
    }
    return rc;
}

static inline void ide_unlock_host(struct ide_host *host)
{
    if (host->host_flags & IDE_HFLAG_SERIALIZE) {
        if (host->release_lock)
            host->release_lock();
        clear_bit_unlock(IDE_HOST_BUSY, &host->host_busy);
    }
}

static void __ide_requeue_and_plug(struct request_queue *q, struct request *rq)
{
    if (rq)
        blk_requeue_request(q, rq);
    if (rq || blk_peek_request(q)) {
        /* Use 3ms as that was the old plug delay */
        blk_delay_queue(q, 3);
    }
}

void ide_requeue_and_plug(ide_drive_t *drive, struct request *rq)
{
    struct request_queue *q = drive->queue;
    unsigned long flags;

    spin_lock_irqsave(q->queue_lock, flags);
    __ide_requeue_and_plug(q, rq);
    spin_unlock_irqrestore(q->queue_lock, flags);
}

/*
 * Issue a new request to a device.
 */
void do_ide_request(struct request_queue *q)
{
    ide_drive_t *drive = q->queuedata;
    ide_hwif_t  *hwif = drive->hwif;
    struct ide_host *host = hwif->host;
    struct request  *rq = NULL;
    ide_startstop_t startstop;
    unsigned long queue_run_ms = 3; /* old plug delay */

    spin_unlock_irq(q->queue_lock);

    /* HLD do_request() callback might sleep, make sure it's okay */
    might_sleep();

    if (ide_lock_host(host, hwif))
        goto plug_device_2;

    spin_lock_irq(&hwif->lock);

    if (!ide_lock_port(hwif)) {
        ide_hwif_t *prev_port;

        WARN_ON_ONCE(hwif->rq);
repeat:
        prev_port = hwif->host->cur_port;
        if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
            time_after(drive->sleep, jiffies)) {
            unsigned long left = jiffies - drive->sleep;

            queue_run_ms = jiffies_to_msecs(left + 1);
            ide_unlock_port(hwif);
            goto plug_device;
        }

        if ((hwif->host->host_flags & IDE_HFLAG_SERIALIZE) &&
            hwif != prev_port) {
            ide_drive_t *cur_dev =
                prev_port ? prev_port->cur_dev : NULL;

            /*
             * set nIEN for previous port, drives in the
             * quirk list may not like intr setups/cleanups
             */
            if (cur_dev &&
                (cur_dev->dev_flags & IDE_DFLAG_NIEN_QUIRK) == 0)
                prev_port->tp_ops->write_devctl(prev_port,
                                ATA_NIEN |
                                ATA_DEVCTL_OBS);

            hwif->host->cur_port = hwif;
        }
        hwif->cur_dev = drive;
        drive->dev_flags &= ~(IDE_DFLAG_SLEEPING | IDE_DFLAG_PARKED);

        spin_unlock_irq(&hwif->lock);
        spin_lock_irq(q->queue_lock);
        /*
         * we know that the queue isn't empty, but this can happen
         * if the q->prep_rq_fn() decides to kill a request
         */
        if (!rq)
            rq = blk_fetch_request(drive->queue);

        spin_unlock_irq(q->queue_lock);
        spin_lock_irq(&hwif->lock);

        if (!rq) {
            ide_unlock_port(hwif);
            goto out;
        }

        /*
         * Sanity: don't accept a request that isn't a PM request
         * if we are currently power managed. This is very important as
         * blk_stop_queue() doesn't prevent the blk_fetch_request()
         * above to return us whatever is in the queue. Since we call
         * ide_do_request() ourselves, we end up taking requests while
         * the queue is blocked...
         * 
         * We let requests forced at head of queue with ide-preempt
         * though. I hope that doesn't happen too much, hopefully not
         * unless the subdriver triggers such a thing in its own PM
         * state machine.
         */
        if ((drive->dev_flags & IDE_DFLAG_BLOCKED) &&
            blk_pm_request(rq) == 0 &&
            (rq->cmd_flags & REQ_PREEMPT) == 0) {
            /* there should be no pending command at this point */
            ide_unlock_port(hwif);
            goto plug_device;
        }

        hwif->rq = rq;

        spin_unlock_irq(&hwif->lock);
        startstop = start_request(drive, rq);
        spin_lock_irq(&hwif->lock);

        if (startstop == ide_stopped) {
            rq = hwif->rq;
            hwif->rq = NULL;
            goto repeat;
        }
    } else
        goto plug_device;
out:
    spin_unlock_irq(&hwif->lock);
    if (rq == NULL)
        ide_unlock_host(host);
    spin_lock_irq(q->queue_lock);
    return;

plug_device:
    spin_unlock_irq(&hwif->lock);
    ide_unlock_host(host);
plug_device_2:
    spin_lock_irq(q->queue_lock);
    __ide_requeue_and_plug(q, rq);
}

static int drive_is_ready(ide_drive_t *drive)
{
    ide_hwif_t *hwif = drive->hwif;
    u8 stat = 0;

    if (drive->waiting_for_dma)
        return hwif->dma_ops->dma_test_irq(drive);

    if (hwif->io_ports.ctl_addr &&
        (hwif->host_flags & IDE_HFLAG_BROKEN_ALTSTATUS) == 0)
        stat = hwif->tp_ops->read_altstatus(hwif);
    else
        /* Note: this may clear a pending IRQ!! */
        stat = hwif->tp_ops->read_status(hwif);

    if (stat & ATA_BUSY)
        /* drive busy: definitely not interrupting */
        return 0;

    /* drive ready: *might* be interrupting */
    return 1;
}

void ide_timer_expiry (unsigned long data)
{
    ide_hwif_t  *hwif = (ide_hwif_t *)data;
    ide_drive_t *uninitialized_var(drive);
    ide_handler_t   *handler;
    unsigned long   flags;
    int     wait = -1;
    int     plug_device = 0;
    struct request  *uninitialized_var(rq_in_flight);

    spin_lock_irqsave(&hwif->lock, flags);

    handler = hwif->handler;

    if (handler == NULL || hwif->req_gen != hwif->req_gen_timer) {
        /*
         * Either a marginal timeout occurred
         * (got the interrupt just as timer expired),
         * or we were "sleeping" to give other devices a chance.
         * Either way, we don't really want to complain about anything.
         */
    } else {
        ide_expiry_t *expiry = hwif->expiry;
        ide_startstop_t startstop = ide_stopped;

        drive = hwif->cur_dev;

        if (expiry) {
            wait = expiry(drive);
            if (wait > 0) { /* continue */
                /* reset timer */
                hwif->timer.expires = jiffies + wait;
                hwif->req_gen_timer = hwif->req_gen;
                add_timer(&hwif->timer);
                spin_unlock_irqrestore(&hwif->lock, flags);
                return;
            }
        }
        hwif->handler = NULL;
        hwif->expiry = NULL;
        /*
         * We need to simulate a real interrupt when invoking
         * the handler() function, which means we need to
         * globally mask the specific IRQ:
         */
        spin_unlock(&hwif->lock);
        /* disable_irq_nosync ?? */
        disable_irq(hwif->irq);
        /* local CPU only, as if we were handling an interrupt */
        local_irq_disable();
        if (hwif->polling) {
            startstop = handler(drive);
        } else if (drive_is_ready(drive)) {
            if (drive->waiting_for_dma)
                hwif->dma_ops->dma_lost_irq(drive);
            if (hwif->port_ops && hwif->port_ops->clear_irq)
                hwif->port_ops->clear_irq(drive);

            printk(KERN_WARNING "%s: lost interrupt\n",
                drive->name);
            startstop = handler(drive);
        } else {
            if (drive->waiting_for_dma)
                startstop = ide_dma_timeout_retry(drive, wait);
            else
                startstop = ide_error(drive, "irq timeout",
                    hwif->tp_ops->read_status(hwif));
        }
        spin_lock_irq(&hwif->lock);
        enable_irq(hwif->irq);
        if (startstop == ide_stopped && hwif->polling == 0) {
            rq_in_flight = hwif->rq;
            hwif->rq = NULL;
            ide_unlock_port(hwif);
            plug_device = 1;
        }
    }
    spin_unlock_irqrestore(&hwif->lock, flags);

    if (plug_device) {
        ide_unlock_host(hwif->host);
        ide_requeue_and_plug(drive, rq_in_flight);
    }
}

static void unexpected_intr(int irq, ide_hwif_t *hwif)
{
    u8 stat = hwif->tp_ops->read_status(hwif);

    if (!OK_STAT(stat, ATA_DRDY, BAD_STAT)) {
        /* Try to not flood the console with msgs */
        static unsigned long last_msgtime, count;
        ++count;

        if (time_after(jiffies, last_msgtime + HZ)) {
            last_msgtime = jiffies;
            printk(KERN_ERR "%s: unexpected interrupt, "
                "status=0x%02x, count=%ld\n",
                hwif->name, stat, count);
        }
    }
}

irqreturn_t ide_intr (int irq, void *dev_id)
{
    ide_hwif_t *hwif = (ide_hwif_t *)dev_id;
    struct ide_host *host = hwif->host;
    ide_drive_t *uninitialized_var(drive);
    ide_handler_t *handler;
    unsigned long flags;
    ide_startstop_t startstop;
    irqreturn_t irq_ret = IRQ_NONE;
    int plug_device = 0;
    struct request *uninitialized_var(rq_in_flight);

    if (host->host_flags & IDE_HFLAG_SERIALIZE) {
        if (hwif != host->cur_port)
            goto out_early;
    }

    spin_lock_irqsave(&hwif->lock, flags);

    if (hwif->port_ops && hwif->port_ops->test_irq &&
        hwif->port_ops->test_irq(hwif) == 0)
        goto out;

    handler = hwif->handler;

    if (handler == NULL || hwif->polling) {
        /*
         * Not expecting an interrupt from this drive.
         * That means this could be:
         *  (1) an interrupt from another PCI device
         *  sharing the same PCI INT# as us.
         * or   (2) a drive just entered sleep or standby mode,
         *  and is interrupting to let us know.
         * or   (3) a spurious interrupt of unknown origin.
         *
         * For PCI, we cannot tell the difference,
         * so in that case we just ignore it and hope it goes away.
         */
        if ((host->irq_flags & IRQF_SHARED) == 0) {
            /*
             * Probably not a shared PCI interrupt,
             * so we can safely try to do something about it:
             */
            unexpected_intr(irq, hwif);
        } else {
            /*
             * Whack the status register, just in case
             * we have a leftover pending IRQ.
             */
            (void)hwif->tp_ops->read_status(hwif);
        }
        goto out;
    }

    drive = hwif->cur_dev;

    if (!drive_is_ready(drive))
        /*
         * This happens regularly when we share a PCI IRQ with
         * another device.  Unfortunately, it can also happen
         * with some buggy drives that trigger the IRQ before
         * their status register is up to date.  Hopefully we have
         * enough advance overhead that the latter isn't a problem.
         */
        goto out;

    hwif->handler = NULL;
    hwif->expiry = NULL;
    hwif->req_gen++;
    del_timer(&hwif->timer);
    spin_unlock(&hwif->lock);

    if (hwif->port_ops && hwif->port_ops->clear_irq)
        hwif->port_ops->clear_irq(drive);

    if (drive->dev_flags & IDE_DFLAG_UNMASK)
        local_irq_enable_in_hardirq();

    /* service this interrupt, may set handler for next interrupt */
    startstop = handler(drive);

    spin_lock_irq(&hwif->lock);
    /*
     * Note that handler() may have set things up for another
     * interrupt to occur soon, but it cannot happen until
     * we exit from this routine, because it will be the
     * same irq as is currently being serviced here, and Linux
     * won't allow another of the same (on any CPU) until we return.
     */
    if (startstop == ide_stopped && hwif->polling == 0) {
        BUG_ON(hwif->handler);
        rq_in_flight = hwif->rq;
        hwif->rq = NULL;
        ide_unlock_port(hwif);
        plug_device = 1;
    }
    irq_ret = IRQ_HANDLED;
out:
    spin_unlock_irqrestore(&hwif->lock, flags);
out_early:
    if (plug_device) {
        ide_unlock_host(hwif->host);
        ide_requeue_and_plug(drive, rq_in_flight);
    }

    return irq_ret;
}
EXPORT_SYMBOL_GPL(ide_intr);

void ide_pad_transfer(ide_drive_t *drive, int write, int len)
{
    ide_hwif_t *hwif = drive->hwif;
    u8 buf[4] = { 0 };

    while (len > 0) {
        if (write)
            hwif->tp_ops->output_data(drive, NULL, buf, min(4, len));
        else
            hwif->tp_ops->input_data(drive, NULL, buf, min(4, len));
        len -= 4;
    }
}
EXPORT_SYMBOL_GPL(ide_pad_transfer);