r6040: bump release number to 0.19

[linux-2.6] / drivers / ide / ide-io.c

/*
 *      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/hdreg.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>

static int __ide_end_request(ide_drive_t *drive, struct request *rq,
                             int uptodate, unsigned int nr_bytes, int dequeue)
{
        int ret = 1;
        int error = 0;

        if (uptodate <= 0)
                error = uptodate ? uptodate : -EIO;

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

        if (!blk_fs_request(rq) && error && !rq->errors)
                rq->errors = -EIO;

        /*
         * 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);
        }

        if (!__blk_end_request(rq, error, nr_bytes)) {
                if (dequeue)
                        HWGROUP(drive)->rq = NULL;
                ret = 0;
        }

        return ret;
}

/**
 *      ide_end_request         -       complete an IDE I/O
 *      @drive: IDE device for the I/O
 *      @uptodate:
 *      @nr_sectors: number of sectors completed
 *
 *      This is our end_request wrapper function. We complete the I/O
 *      update random number input and dequeue the request, which if
 *      it was tagged may be out of order.
 */

int ide_end_request (ide_drive_t *drive, int uptodate, int nr_sectors)
{
        unsigned int nr_bytes = nr_sectors << 9;
        struct request *rq;
        unsigned long flags;
        int ret = 1;

        /*
         * room for locking improvements here, the calls below don't
         * need the queue lock held at all
         */
        spin_lock_irqsave(&ide_lock, flags);
        rq = HWGROUP(drive)->rq;

        if (!nr_bytes) {
                if (blk_pc_request(rq))
                        nr_bytes = rq->data_len;
                else
                        nr_bytes = rq->hard_cur_sectors << 9;
        }

        ret = __ide_end_request(drive, rq, uptodate, nr_bytes, 1);

        spin_unlock_irqrestore(&ide_lock, flags);
        return ret;
}
EXPORT_SYMBOL(ide_end_request);

static void ide_complete_power_step(ide_drive_t *drive, struct request *rq)
{
        struct request_pm_state *pm = rq->data;

#ifdef DEBUG_PM
        printk(KERN_INFO "%s: complete_power_step(step: %d)\n",
                drive->name, pm->pm_step);
#endif
        if (drive->media != ide_disk)
                return;

        switch (pm->pm_step) {
        case IDE_PM_FLUSH_CACHE:        /* Suspend step 1 (flush cache) */
                if (pm->pm_state == PM_EVENT_FREEZE)
                        pm->pm_step = IDE_PM_COMPLETED;
                else
                        pm->pm_step = IDE_PM_STANDBY;
                break;
        case IDE_PM_STANDBY:            /* Suspend step 2 (standby) */
                pm->pm_step = IDE_PM_COMPLETED;
                break;
        case IDE_PM_RESTORE_PIO:        /* Resume step 1 (restore PIO) */
                pm->pm_step = IDE_PM_IDLE;
                break;
        case IDE_PM_IDLE:               /* Resume step 2 (idle)*/
                pm->pm_step = IDE_PM_RESTORE_DMA;
                break;
        }
}

static ide_startstop_t ide_start_power_step(ide_drive_t *drive, struct request *rq)
{
        struct request_pm_state *pm = rq->data;
        ide_task_t *args = rq->special;

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

        switch (pm->pm_step) {
        case IDE_PM_FLUSH_CACHE:        /* Suspend step 1 (flush cache) */
                if (drive->media != ide_disk)
                        break;
                /* Not supported? Switch to next step now. */
                if (ata_id_flush_enabled(drive->id) == 0 ||
                    (drive->dev_flags & IDE_DFLAG_WCACHE) == 0) {
                        ide_complete_power_step(drive, rq);
                        return ide_stopped;
                }
                if (ata_id_flush_ext_enabled(drive->id))
                        args->tf.command = ATA_CMD_FLUSH_EXT;
                else
                        args->tf.command = ATA_CMD_FLUSH;
                goto out_do_tf;
        case IDE_PM_STANDBY:            /* Suspend step 2 (standby) */
                args->tf.command = ATA_CMD_STANDBYNOW1;
                goto out_do_tf;
        case IDE_PM_RESTORE_PIO:        /* Resume step 1 (restore PIO) */
                ide_set_max_pio(drive);
                /*
                 * skip IDE_PM_IDLE for ATAPI devices
                 */
                if (drive->media != ide_disk)
                        pm->pm_step = IDE_PM_RESTORE_DMA;
                else
                        ide_complete_power_step(drive, rq);
                return ide_stopped;
        case IDE_PM_IDLE:               /* Resume step 2 (idle) */
                args->tf.command = ATA_CMD_IDLEIMMEDIATE;
                goto out_do_tf;
        case IDE_PM_RESTORE_DMA:        /* Resume step 3 (restore DMA) */
                /*
                 * Right now, all we do is call ide_set_dma(drive),
                 * we could be smarter and check for current xfer_speed
                 * in struct drive etc...
                 */
                if (drive->hwif->dma_ops == NULL)
                        break;
                /*
                 * TODO: respect IDE_DFLAG_USING_DMA
                 */
                ide_set_dma(drive);
                break;
        }

        pm->pm_step = IDE_PM_COMPLETED;
        return ide_stopped;

out_do_tf:
        args->tf_flags   = IDE_TFLAG_TF | IDE_TFLAG_DEVICE;
        args->data_phase = TASKFILE_NO_DATA;
        return do_rw_taskfile(drive, args);
}

/**
 *      ide_end_dequeued_request        -       complete an IDE I/O
 *      @drive: IDE device for the I/O
 *      @uptodate:
 *      @nr_sectors: number of sectors completed
 *
 *      Complete an I/O that is no longer on the request queue. This
 *      typically occurs when we pull the request and issue a REQUEST_SENSE.
 *      We must still finish the old request but we must not tamper with the
 *      queue in the meantime.
 *
 *      NOTE: This path does not handle barrier, but barrier is not supported
 *      on ide-cd anyway.
 */

int ide_end_dequeued_request(ide_drive_t *drive, struct request *rq,
                             int uptodate, int nr_sectors)
{
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&ide_lock, flags);
        BUG_ON(!blk_rq_started(rq));
        ret = __ide_end_request(drive, rq, uptodate, nr_sectors << 9, 0);
        spin_unlock_irqrestore(&ide_lock, flags);

        return ret;
}
EXPORT_SYMBOL_GPL(ide_end_dequeued_request);


/**
 *      ide_complete_pm_request - end the current Power Management request
 *      @drive: target drive
 *      @rq: request
 *
 *      This function cleans up the current PM request and stops the queue
 *      if necessary.
 */
static void ide_complete_pm_request (ide_drive_t *drive, struct request *rq)
{
        unsigned long flags;

#ifdef DEBUG_PM
        printk("%s: completing PM request, %s\n", drive->name,
               blk_pm_suspend_request(rq) ? "suspend" : "resume");
#endif
        spin_lock_irqsave(&ide_lock, flags);
        if (blk_pm_suspend_request(rq)) {
                blk_stop_queue(drive->queue);
        } else {
                drive->dev_flags &= ~IDE_DFLAG_BLOCKED;
                blk_start_queue(drive->queue);
        }
        HWGROUP(drive)->rq = NULL;
        if (__blk_end_request(rq, 0, 0))
                BUG();
        spin_unlock_irqrestore(&ide_lock, flags);
}

/**
 *      ide_end_drive_cmd       -       end an explicit drive command
 *      @drive: command 
 *      @stat: status bits
 *      @err: error bits
 *
 *      Clean up after success/failure of an explicit drive command.
 *      These get thrown onto the queue so they are synchronized with
 *      real I/O operations on the drive.
 *
 *      In LBA48 mode we have to read the register set twice to get
 *      all the extra information out.
 */
 
void ide_end_drive_cmd (ide_drive_t *drive, u8 stat, u8 err)
{
        unsigned long flags;
        struct request *rq;

        spin_lock_irqsave(&ide_lock, flags);
        rq = HWGROUP(drive)->rq;
        spin_unlock_irqrestore(&ide_lock, flags);

        if (rq->cmd_type == REQ_TYPE_ATA_TASKFILE) {
                ide_task_t *task = (ide_task_t *)rq->special;

                if (rq->errors == 0)
                        rq->errors = !OK_STAT(stat, ATA_DRDY, BAD_STAT);

                if (task) {
                        struct ide_taskfile *tf = &task->tf;

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

                        drive->hwif->tp_ops->tf_read(drive, task);

                        if (task->tf_flags & IDE_TFLAG_DYN)
                                kfree(task);
                }
        } else if (blk_pm_request(rq)) {
                struct request_pm_state *pm = rq->data;

                ide_complete_power_step(drive, rq);
                if (pm->pm_step == IDE_PM_COMPLETED)
                        ide_complete_pm_request(drive, rq);
                return;
        }

        spin_lock_irqsave(&ide_lock, flags);
        HWGROUP(drive)->rq = NULL;
        rq->errors = err;
        if (unlikely(__blk_end_request(rq, (rq->errors ? -EIO : 0),
                                       blk_rq_bytes(rq))))
                BUG();
        spin_unlock_irqrestore(&ide_lock, flags);
}

EXPORT_SYMBOL(ide_end_drive_cmd);

static void ide_kill_rq(ide_drive_t *drive, struct request *rq)
{
        if (rq->rq_disk) {
                ide_driver_t *drv;

                drv = *(ide_driver_t **)rq->rq_disk->private_data;
                drv->end_request(drive, 0, 0);
        } else
                ide_end_request(drive, 0, 0);
}

static ide_startstop_t ide_ata_error(ide_drive_t *drive, struct request *rq, u8 stat, u8 err)
{
        ide_hwif_t *hwif = drive->hwif;

        if ((stat & ATA_BUSY) ||
            ((stat & ATA_DF) && (drive->dev_flags & IDE_DFLAG_NOWERR) == 0)) {
                /* other bits are useless when BUSY */
                rq->errors |= ERROR_RESET;
        } else if (stat & ATA_ERR) {
                /* err has different meaning on cdrom and tape */
                if (err == ATA_ABORTED) {
                        if ((drive->dev_flags & IDE_DFLAG_LBA) &&
                            /* some newer drives don't support ATA_CMD_INIT_DEV_PARAMS */
                            hwif->tp_ops->read_status(hwif) == ATA_CMD_INIT_DEV_PARAMS)
                                return ide_stopped;
                } else if ((err & BAD_CRC) == BAD_CRC) {
                        /* UDMA crc error, just retry the operation */
                        drive->crc_count++;
                } else if (err & (ATA_BBK | ATA_UNC)) {
                        /* retries won't help these */
                        rq->errors = ERROR_MAX;
                } else if (err & ATA_TRK0NF) {
                        /* help it find track zero */
                        rq->errors |= ERROR_RECAL;
                }
        }

        if ((stat & ATA_DRQ) && rq_data_dir(rq) == READ &&
            (hwif->host_flags & IDE_HFLAG_ERROR_STOPS_FIFO) == 0) {
                int nsect = drive->mult_count ? drive->mult_count : 1;

                ide_pad_transfer(drive, READ, nsect * SECTOR_SIZE);
        }

        if (rq->errors >= ERROR_MAX || blk_noretry_request(rq)) {
                ide_kill_rq(drive, rq);
                return ide_stopped;
        }

        if (hwif->tp_ops->read_status(hwif) & (ATA_BUSY | ATA_DRQ))
                rq->errors |= ERROR_RESET;

        if ((rq->errors & ERROR_RESET) == ERROR_RESET) {
                ++rq->errors;
                return ide_do_reset(drive);
        }

        if ((rq->errors & ERROR_RECAL) == ERROR_RECAL)
                drive->special.b.recalibrate = 1;

        ++rq->errors;

        return ide_stopped;
}

static ide_startstop_t ide_atapi_error(ide_drive_t *drive, struct request *rq, u8 stat, u8 err)
{
        ide_hwif_t *hwif = drive->hwif;

        if ((stat & ATA_BUSY) ||
            ((stat & ATA_DF) && (drive->dev_flags & IDE_DFLAG_NOWERR) == 0)) {
                /* other bits are useless when BUSY */
                rq->errors |= ERROR_RESET;
        } else {
                /* add decoding error stuff */
        }

        if (hwif->tp_ops->read_status(hwif) & (ATA_BUSY | ATA_DRQ))
                /* force an abort */
                hwif->tp_ops->exec_command(hwif, ATA_CMD_IDLEIMMEDIATE);

        if (rq->errors >= ERROR_MAX) {
                ide_kill_rq(drive, rq);
        } else {
                if ((rq->errors & ERROR_RESET) == ERROR_RESET) {
                        ++rq->errors;
                        return ide_do_reset(drive);
                }
                ++rq->errors;
        }

        return ide_stopped;
}

ide_startstop_t
__ide_error(ide_drive_t *drive, struct request *rq, u8 stat, u8 err)
{
        if (drive->media == ide_disk)
                return ide_ata_error(drive, rq, stat, err);
        return ide_atapi_error(drive, rq, stat, err);
}

EXPORT_SYMBOL_GPL(__ide_error);

/**
 *      ide_error       -       handle an error on the IDE
 *      @drive: drive the error occurred on
 *      @msg: message to report
 *      @stat: status bits
 *
 *      ide_error() takes action based on the error returned by the drive.
 *      For normal I/O that may well include retries. We deal with
 *      both new-style (taskfile) and old style command handling here.
 *      In the case of taskfile command handling there is work left to
 *      do
 */
 
ide_startstop_t ide_error (ide_drive_t *drive, const char *msg, u8 stat)
{
        struct request *rq;
        u8 err;

        err = ide_dump_status(drive, msg, stat);

        if ((rq = HWGROUP(drive)->rq) == NULL)
                return ide_stopped;

        /* retry only "normal" I/O: */
        if (!blk_fs_request(rq)) {
                rq->errors = 1;
                ide_end_drive_cmd(drive, stat, err);
                return ide_stopped;
        }

        if (rq->rq_disk) {
                ide_driver_t *drv;

                drv = *(ide_driver_t **)rq->rq_disk->private_data;
                return drv->error(drive, rq, stat, err);
        } else
                return __ide_error(drive, rq, stat, err);
}

EXPORT_SYMBOL_GPL(ide_error);

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 ide_disk_special(ide_drive_t *drive)
{
        special_t *s = &drive->special;
        ide_task_t args;

        memset(&args, 0, sizeof(ide_task_t));
        args.data_phase = TASKFILE_NO_DATA;

        if (s->b.set_geometry) {
                s->b.set_geometry = 0;
                ide_tf_set_specify_cmd(drive, &args.tf);
        } else if (s->b.recalibrate) {
                s->b.recalibrate = 0;
                ide_tf_set_restore_cmd(drive, &args.tf);
        } else if (s->b.set_multmode) {
                s->b.set_multmode = 0;
                ide_tf_set_setmult_cmd(drive, &args.tf);
        } else if (s->all) {
                int special = s->all;
                s->all = 0;
                printk(KERN_ERR "%s: bad special flag: 0x%02x\n", drive->name, special);
                return ide_stopped;
        }

        args.tf_flags = IDE_TFLAG_TF | IDE_TFLAG_DEVICE |
                        IDE_TFLAG_CUSTOM_HANDLER;

        do_rw_taskfile(drive, &args);

        return ide_started;
}

/**
 *      do_special              -       issue some special commands
 *      @drive: drive the command is for
 *
 *      do_special() is used to issue ATA_CMD_INIT_DEV_PARAMS,
 *      ATA_CMD_RESTORE and ATA_CMD_SET_MULTI commands to a drive.
 *
 *      It used to do much more, but has been scaled back.
 */

static ide_startstop_t do_special (ide_drive_t *drive)
{
        special_t *s = &drive->special;

#ifdef DEBUG
        printk("%s: do_special: 0x%02x\n", drive->name, s->all);
#endif
        if (drive->media == ide_disk)
                return ide_disk_special(drive);

        s->all = 0;
        drive->mult_req = 0;
        return ide_stopped;
}

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

        if (hwif->sg_mapped)    /* needed by ide-scsi */
                return;

        if (rq->cmd_type != REQ_TYPE_ATA_TASKFILE) {
                hwif->sg_nents = blk_rq_map_sg(drive->queue, rq, sg);
        } else {
                sg_init_one(sg, rq->buffer, rq->nr_sectors * SECTOR_SIZE);
                hwif->sg_nents = 1;
        }
}

EXPORT_SYMBOL_GPL(ide_map_sg);

void ide_init_sg_cmd(ide_drive_t *drive, struct request *rq)
{
        ide_hwif_t *hwif = drive->hwif;

        hwif->nsect = hwif->nleft = rq->nr_sectors;
        hwif->cursg_ofs = 0;
        hwif->cursg = NULL;
}

EXPORT_SYMBOL_GPL(ide_init_sg_cmd);

/**
 *      execute_drive_command   -       issue special drive command
 *      @drive: the drive to issue the command on
 *      @rq: the request structure holding the command
 *
 *      execute_drive_cmd() issues a special drive command,  usually 
 *      initiated by ioctl() from the external hdparm program. The
 *      command can be a drive command, drive task or taskfile 
 *      operation. Weirdly you can call it with NULL to wait for
 *      all commands to finish. Don't do this as that is due to change
 */

static ide_startstop_t execute_drive_cmd (ide_drive_t *drive,
                struct request *rq)
{
        ide_hwif_t *hwif = HWIF(drive);
        ide_task_t *task = rq->special;

        if (task) {
                hwif->data_phase = task->data_phase;

                switch (hwif->data_phase) {
                case TASKFILE_MULTI_OUT:
                case TASKFILE_OUT:
                case TASKFILE_MULTI_IN:
                case TASKFILE_IN:
                        ide_init_sg_cmd(drive, rq);
                        ide_map_sg(drive, rq);
                default:
                        break;
                }

                return do_rw_taskfile(drive, task);
        }

        /*
         * 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
        ide_end_drive_cmd(drive, hwif->tp_ops->read_status(hwif),
                          ide_read_error(drive));

        return ide_stopped;
}

int ide_devset_execute(ide_drive_t *drive, const struct ide_devset *setting,
                       int arg)
{
        struct request_queue *q = drive->queue;
        struct request *rq;
        int ret = 0;

        if (!(setting->flags & DS_SYNC))
                return setting->set(drive, arg);

        rq = blk_get_request(q, READ, __GFP_WAIT);
        rq->cmd_type = REQ_TYPE_SPECIAL;
        rq->cmd_len = 5;
        rq->cmd[0] = REQ_DEVSET_EXEC;
        *(int *)&rq->cmd[1] = arg;
        rq->special = setting->set;

        if (blk_execute_rq(q, NULL, rq, 0))
                ret = rq->errors;
        blk_put_request(rq);

        return ret;
}
EXPORT_SYMBOL_GPL(ide_devset_execute);

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

        if (cmd == REQ_PARK_HEADS || cmd == REQ_UNPARK_HEADS) {
                ide_task_t task;
                struct ide_taskfile *tf = &task.tf;

                memset(&task, 0, sizeof(task));
                if (cmd == REQ_PARK_HEADS) {
                        drive->sleep = *(unsigned long *)rq->special;
                        drive->dev_flags |= IDE_DFLAG_SLEEPING;
                        tf->command = ATA_CMD_IDLEIMMEDIATE;
                        tf->feature = 0x44;
                        tf->lbal = 0x4c;
                        tf->lbam = 0x4e;
                        tf->lbah = 0x55;
                        task.tf_flags |= IDE_TFLAG_CUSTOM_HANDLER;
                } else          /* cmd == REQ_UNPARK_HEADS */
                        tf->command = ATA_CMD_CHK_POWER;

                task.tf_flags |= IDE_TFLAG_TF | IDE_TFLAG_DEVICE;
                task.rq = rq;
                drive->hwif->data_phase = task.data_phase = TASKFILE_NO_DATA;
                return do_rw_taskfile(drive, &task);
        }

        switch (cmd) {
        case REQ_DEVSET_EXEC:
        {
                int err, (*setfunc)(ide_drive_t *, int) = rq->special;

                err = setfunc(drive, *(int *)&rq->cmd[1]);
                if (err)
                        rq->errors = err;
                else
                        err = 1;
                ide_end_request(drive, err, 0);
                return ide_stopped;
        }
        case REQ_DRIVE_RESET:
                return ide_do_reset(drive);
        default:
                blk_dump_rq_flags(rq, "ide_special_rq - bad request");
                ide_end_request(drive, 0, 0);
                return ide_stopped;
        }
}

static void ide_check_pm_state(ide_drive_t *drive, struct request *rq)
{
        struct request_pm_state *pm = rq->data;

        if (blk_pm_suspend_request(rq) &&
            pm->pm_step == IDE_PM_START_SUSPEND)
                /* Mark drive blocked when starting the suspend sequence. */
                drive->dev_flags |= IDE_DFLAG_BLOCKED;
        else if (blk_pm_resume_request(rq) &&
                 pm->pm_step == IDE_PM_START_RESUME) {
                /* 
                 * The first thing we do on wakeup is to wait for BSY bit to
                 * go away (with a looong timeout) as a drive on this hwif may
                 * just be POSTing itself.
                 * We do that before even selecting as the "other" device on
                 * the bus may be broken enough to walk on our toes at this
                 * point.
                 */
                ide_hwif_t *hwif = drive->hwif;
                int rc;
#ifdef DEBUG_PM
                printk("%s: Wakeup request inited, waiting for !BSY...\n", drive->name);
#endif
                rc = ide_wait_not_busy(hwif, 35000);
                if (rc)
                        printk(KERN_WARNING "%s: bus not ready on wakeup\n", drive->name);
                SELECT_DRIVE(drive);
                hwif->tp_ops->set_irq(hwif, 1);
                rc = ide_wait_not_busy(hwif, 100000);
                if (rc)
                        printk(KERN_WARNING "%s: drive not ready on wakeup\n", drive->name);
        }
}

/**
 *      start_request   -       start of I/O and command issuing for IDE
 *
 *      start_request() initiates handling of a new I/O request. It
 *      accepts commands and I/O (read/write) requests.
 *
 *      FIXME: this function needs a rename
 */
 
static ide_startstop_t start_request (ide_drive_t *drive, struct request *rq)
{
        ide_startstop_t startstop;

        BUG_ON(!blk_rq_started(rq));

#ifdef DEBUG
        printk("%s: start_request: current=0x%08lx\n",
                HWIF(drive)->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);

        SELECT_DRIVE(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.all) {
                ide_driver_t *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->data;
#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_request(drive, rq);
                        return startstop;
                } else if (!rq->rq_disk && blk_special_request(rq))
                        /*
                         * 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 = *(ide_driver_t **)rq->rq_disk->private_data;

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

/**
 *      ide_stall_queue         -       pause an IDE device
 *      @drive: drive to stall
 *      @timeout: time to stall for (jiffies)
 *
 *      ide_stall_queue() can be used by a drive to give excess bandwidth back
 *      to the hwgroup by sleeping for timeout jiffies.
 */
 
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);

#define WAKEUP(drive)   ((drive)->service_start + 2 * (drive)->service_time)

/**
 *      choose_drive            -       select a drive to service
 *      @hwgroup: hardware group to select on
 *
 *      choose_drive() selects the next drive which will be serviced.
 *      This is necessary because the IDE layer can't issue commands
 *      to both drives on the same cable, unlike SCSI.
 */
 
static inline ide_drive_t *choose_drive (ide_hwgroup_t *hwgroup)
{
        ide_drive_t *drive, *best;

repeat: 
        best = NULL;
        drive = hwgroup->drive;

        /*
         * drive is doing pre-flush, ordered write, post-flush sequence. even
         * though that is 3 requests, it must be seen as a single transaction.
         * we must not preempt this drive until that is complete
         */
        if (blk_queue_flushing(drive->queue)) {
                /*
                 * small race where queue could get replugged during
                 * the 3-request flush cycle, just yank the plug since
                 * we want it to finish asap
                 */
                blk_remove_plug(drive->queue);
                return drive;
        }

        do {
                u8 dev_s = !!(drive->dev_flags & IDE_DFLAG_SLEEPING);
                u8 best_s = (best && !!(best->dev_flags & IDE_DFLAG_SLEEPING));

                if ((dev_s == 0 || time_after_eq(jiffies, drive->sleep)) &&
                    !elv_queue_empty(drive->queue)) {
                        if (best == NULL ||
                            (dev_s && (best_s == 0 || time_before(drive->sleep, best->sleep))) ||
                            (best_s == 0 && time_before(WAKEUP(drive), WAKEUP(best)))) {
                                if (!blk_queue_plugged(drive->queue))
                                        best = drive;
                        }
                }
        } while ((drive = drive->next) != hwgroup->drive);

        if (best && (best->dev_flags & IDE_DFLAG_NICE1) &&
            (best->dev_flags & IDE_DFLAG_SLEEPING) == 0 &&
            best != hwgroup->drive && best->service_time > WAIT_MIN_SLEEP) {
                long t = (signed long)(WAKEUP(best) - jiffies);
                if (t >= WAIT_MIN_SLEEP) {
                /*
                 * We *may* have some time to spare, but first let's see if
                 * someone can potentially benefit from our nice mood today..
                 */
                        drive = best->next;
                        do {
                                if ((drive->dev_flags & IDE_DFLAG_SLEEPING) == 0
                                 && time_before(jiffies - best->service_time, WAKEUP(drive))
                                 && time_before(WAKEUP(drive), jiffies + t))
                                {
                                        ide_stall_queue(best, min_t(long, t, 10 * WAIT_MIN_SLEEP));
                                        goto repeat;
                                }
                        } while ((drive = drive->next) != best);
                }
        }
        return best;
}

/*
 * Issue a new request to a drive from hwgroup
 * Caller must have already done spin_lock_irqsave(&ide_lock, ..);
 *
 * A hwgroup is a serialized group of IDE interfaces.  Usually there is
 * exactly one hwif (interface) per hwgroup, but buggy controllers (eg. CMD640)
 * may have both interfaces in a single hwgroup to "serialize" access.
 * Or possibly multiple ISA interfaces can share a common IRQ by being grouped
 * together into one hwgroup for serialized access.
 *
 * Note also that several hwgroups can end up sharing a single IRQ,
 * possibly along with many other devices.  This is especially common in
 * PCI-based systems with off-board IDE controller cards.
 *
 * The IDE driver uses the single global ide_lock spinlock to protect
 * access to the request queues, and to protect the hwgroup->busy flag.
 *
 * The first thread into the driver for a particular hwgroup sets the
 * hwgroup->busy flag to indicate that this hwgroup is now active,
 * and then initiates processing of the top request from the request queue.
 *
 * Other threads attempting entry notice the busy setting, and will simply
 * queue their new requests and exit immediately.  Note that hwgroup->busy
 * remains set even when the driver is merely awaiting the next interrupt.
 * Thus, the meaning is "this hwgroup is busy processing a request".
 *
 * When processing of a request completes, the completing thread or IRQ-handler
 * will start the next request from the queue.  If no more work remains,
 * the driver will clear the hwgroup->busy flag and exit.
 *
 * The ide_lock (spinlock) is used to protect all access to the
 * hwgroup->busy flag, but is otherwise not needed for most processing in
 * the driver.  This makes the driver much more friendlier to shared IRQs
 * than previous designs, while remaining 100% (?) SMP safe and capable.
 */
static void ide_do_request (ide_hwgroup_t *hwgroup, int masked_irq)
{
        ide_drive_t     *drive;
        ide_hwif_t      *hwif;
        struct request  *rq;
        ide_startstop_t startstop;
        int             loops = 0;

        /* caller must own ide_lock */
        BUG_ON(!irqs_disabled());

        while (!hwgroup->busy) {
                hwgroup->busy = 1;
                /* for atari only */
                ide_get_lock(ide_intr, hwgroup);
                drive = choose_drive(hwgroup);
                if (drive == NULL) {
                        int sleeping = 0;
                        unsigned long sleep = 0; /* shut up, gcc */
                        hwgroup->rq = NULL;
                        drive = hwgroup->drive;
                        do {
                                if ((drive->dev_flags & IDE_DFLAG_SLEEPING) &&
                                    (sleeping == 0 ||
                                     time_before(drive->sleep, sleep))) {
                                        sleeping = 1;
                                        sleep = drive->sleep;
                                }
                        } while ((drive = drive->next) != hwgroup->drive);
                        if (sleeping) {
                /*
                 * Take a short snooze, and then wake up this hwgroup again.
                 * This gives other hwgroups on the same a chance to
                 * play fairly with us, just in case there are big differences
                 * in relative throughputs.. don't want to hog the cpu too much.
                 */
                                if (time_before(sleep, jiffies + WAIT_MIN_SLEEP))
                                        sleep = jiffies + WAIT_MIN_SLEEP;
#if 1
                                if (timer_pending(&hwgroup->timer))
                                        printk(KERN_CRIT "ide_set_handler: timer already active\n");
#endif
                                /* so that ide_timer_expiry knows what to do */
                                hwgroup->sleeping = 1;
                                hwgroup->req_gen_timer = hwgroup->req_gen;
                                mod_timer(&hwgroup->timer, sleep);
                                /* we purposely leave hwgroup->busy==1
                                 * while sleeping */
                        } else {
                                /* Ugly, but how can we sleep for the lock
                                 * otherwise? perhaps from tq_disk?
                                 */

                                /* for atari only */
                                ide_release_lock();
                                hwgroup->busy = 0;
                        }

                        /* no more work for this hwgroup (for now) */
                        return;
                }
        again:
                hwif = HWIF(drive);
                if (hwgroup->hwif->sharing_irq && hwif != hwgroup->hwif) {
                        /*
                         * set nIEN for previous hwif, drives in the
                         * quirk_list may not like intr setups/cleanups
                         */
                        if (drive->quirk_list != 1)
                                hwif->tp_ops->set_irq(hwif, 0);
                }
                hwgroup->hwif = hwif;
                hwgroup->drive = drive;
                drive->dev_flags &= ~(IDE_DFLAG_SLEEPING | IDE_DFLAG_PARKED);
                drive->service_start = jiffies;

                if (blk_queue_plugged(drive->queue)) {
                        printk(KERN_ERR "ide: huh? queue was plugged!\n");
                        break;
                }

                /*
                 * we know that the queue isn't empty, but this can happen
                 * if the q->prep_rq_fn() decides to kill a request
                 */
                rq = elv_next_request(drive->queue);
                if (!rq) {
                        hwgroup->busy = 0;
                        break;
                }

                /*
                 * 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 elv_next_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.
                 *
                 * We count how many times we loop here to make sure we service
                 * all drives in the hwgroup without looping for ever
                 */
                if ((drive->dev_flags & IDE_DFLAG_BLOCKED) &&
                    blk_pm_request(rq) == 0 &&
                    (rq->cmd_flags & REQ_PREEMPT) == 0) {
                        drive = drive->next ? drive->next : hwgroup->drive;
                        if (loops++ < 4 && !blk_queue_plugged(drive->queue))
                                goto again;
                        /* We clear busy, there should be no pending ATA command at this point. */
                        hwgroup->busy = 0;
                        break;
                }

                hwgroup->rq = rq;

                /*
                 * Some systems have trouble with IDE IRQs arriving while
                 * the driver is still setting things up.  So, here we disable
                 * the IRQ used by this interface while the request is being started.
                 * This may look bad at first, but pretty much the same thing
                 * happens anyway when any interrupt comes in, IDE or otherwise
                 *  -- the kernel masks the IRQ while it is being handled.
                 */
                if (masked_irq != IDE_NO_IRQ && hwif->irq != masked_irq)
                        disable_irq_nosync(hwif->irq);
                spin_unlock(&ide_lock);
                local_irq_enable_in_hardirq();
                        /* allow other IRQs while we start this request */
                startstop = start_request(drive, rq);
                spin_lock_irq(&ide_lock);
                if (masked_irq != IDE_NO_IRQ && hwif->irq != masked_irq)
                        enable_irq(hwif->irq);
                if (startstop == ide_stopped)
                        hwgroup->busy = 0;
        }
}

/*
 * Passes the stuff to ide_do_request
 */
void do_ide_request(struct request_queue *q)
{
        ide_drive_t *drive = q->queuedata;

        ide_do_request(HWGROUP(drive), IDE_NO_IRQ);
}

/*
 * un-busy the hwgroup etc, and clear any pending DMA status. we want to
 * retry the current request in pio mode instead of risking tossing it
 * all away
 */
static ide_startstop_t ide_dma_timeout_retry(ide_drive_t *drive, int error)
{
        ide_hwif_t *hwif = HWIF(drive);
        struct request *rq;
        ide_startstop_t ret = ide_stopped;

        /*
         * end current dma transaction
         */

        if (error < 0) {
                printk(KERN_WARNING "%s: DMA timeout error\n", drive->name);
                (void)hwif->dma_ops->dma_end(drive);
                ret = ide_error(drive, "dma timeout error",
                                hwif->tp_ops->read_status(hwif));
        } else {
                printk(KERN_WARNING "%s: DMA timeout retry\n", drive->name);
                hwif->dma_ops->dma_timeout(drive);
        }

        /*
         * disable dma for now, but remember that we did so because of
         * a timeout -- we'll reenable after we finish this next request
         * (or rather the first chunk of it) in pio.
         */
        drive->dev_flags |= IDE_DFLAG_DMA_PIO_RETRY;
        drive->retry_pio++;
        ide_dma_off_quietly(drive);

        /*
         * un-busy drive etc (hwgroup->busy is cleared on return) and
         * make sure request is sane
         */
        rq = HWGROUP(drive)->rq;

        if (!rq)
                goto out;

        HWGROUP(drive)->rq = NULL;

        rq->errors = 0;

        if (!rq->bio)
                goto out;

        rq->sector = rq->bio->bi_sector;
        rq->current_nr_sectors = bio_iovec(rq->bio)->bv_len >> 9;
        rq->hard_cur_sectors = rq->current_nr_sectors;
        rq->buffer = bio_data(rq->bio);
out:
        return ret;
}

/**
 *      ide_timer_expiry        -       handle lack of an IDE interrupt
 *      @data: timer callback magic (hwgroup)
 *
 *      An IDE command has timed out before the expected drive return
 *      occurred. At this point we attempt to clean up the current
 *      mess. If the current handler includes an expiry handler then
 *      we invoke the expiry handler, and providing it is happy the
 *      work is done. If that fails we apply generic recovery rules
 *      invoking the handler and checking the drive DMA status. We
 *      have an excessively incestuous relationship with the DMA
 *      logic that wants cleaning up.
 */
 
void ide_timer_expiry (unsigned long data)
{
        ide_hwgroup_t   *hwgroup = (ide_hwgroup_t *) data;
        ide_handler_t   *handler;
        ide_expiry_t    *expiry;
        unsigned long   flags;
        unsigned long   wait = -1;

        spin_lock_irqsave(&ide_lock, flags);

        if (((handler = hwgroup->handler) == NULL) ||
            (hwgroup->req_gen != hwgroup->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.
                 */
                if (hwgroup->sleeping) {
                        hwgroup->sleeping = 0;
                        hwgroup->busy = 0;
                }
        } else {
                ide_drive_t *drive = hwgroup->drive;
                if (!drive) {
                        printk(KERN_ERR "ide_timer_expiry: hwgroup->drive was NULL\n");
                        hwgroup->handler = NULL;
                } else {
                        ide_hwif_t *hwif;
                        ide_startstop_t startstop = ide_stopped;
                        if (!hwgroup->busy) {
                                hwgroup->busy = 1;      /* paranoia */
                                printk(KERN_ERR "%s: ide_timer_expiry: hwgroup->busy was 0 ??\n", drive->name);
                        }
                        if ((expiry = hwgroup->expiry) != NULL) {
                                /* continue */
                                if ((wait = expiry(drive)) > 0) {
                                        /* reset timer */
                                        hwgroup->timer.expires  = jiffies + wait;
                                        hwgroup->req_gen_timer = hwgroup->req_gen;
                                        add_timer(&hwgroup->timer);
                                        spin_unlock_irqrestore(&ide_lock, flags);
                                        return;
                                }
                        }
                        hwgroup->handler = 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(&ide_lock);
                        hwif  = HWIF(drive);
                        /* disable_irq_nosync ?? */
                        disable_irq(hwif->irq);
                        /* local CPU only,
                         * as if we were handling an interrupt */
                        local_irq_disable();
                        if (hwgroup->polling) {
                                startstop = handler(drive);
                        } else if (drive_is_ready(drive)) {
                                if (drive->waiting_for_dma)
                                        hwif->dma_ops->dma_lost_irq(drive);
                                (void)ide_ack_intr(hwif);
                                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));
                        }
                        drive->service_time = jiffies - drive->service_start;
                        spin_lock_irq(&ide_lock);
                        enable_irq(hwif->irq);
                        if (startstop == ide_stopped)
                                hwgroup->busy = 0;
                }
        }
        ide_do_request(hwgroup, IDE_NO_IRQ);
        spin_unlock_irqrestore(&ide_lock, flags);
}

/**
 *      unexpected_intr         -       handle an unexpected IDE interrupt
 *      @irq: interrupt line
 *      @hwgroup: hwgroup being processed
 *
 *      There's nothing really useful we can do with an unexpected interrupt,
 *      other than reading the status register (to clear it), and logging it.
 *      There should be no way that an irq can happen before we're ready for it,
 *      so we needn't worry much about losing an "important" interrupt here.
 *
 *      On laptops (and "green" PCs), an unexpected interrupt occurs whenever
 *      the drive enters "idle", "standby", or "sleep" mode, so if the status
 *      looks "good", we just ignore the interrupt completely.
 *
 *      This routine assumes __cli() is in effect when called.
 *
 *      If an unexpected interrupt happens on irq15 while we are handling irq14
 *      and if the two interfaces are "serialized" (CMD640), then it looks like
 *      we could screw up by interfering with a new request being set up for 
 *      irq15.
 *
 *      In reality, this is a non-issue.  The new command is not sent unless 
 *      the drive is ready to accept one, in which case we know the drive is
 *      not trying to interrupt us.  And ide_set_handler() is always invoked
 *      before completing the issuance of any new drive command, so we will not
 *      be accidentally invoked as a result of any valid command completion
 *      interrupt.
 *
 *      Note that we must walk the entire hwgroup here. We know which hwif
 *      is doing the current command, but we don't know which hwif burped
 *      mysteriously.
 */
 
static void unexpected_intr (int irq, ide_hwgroup_t *hwgroup)
{
        u8 stat;
        ide_hwif_t *hwif = hwgroup->hwif;

        /*
         * handle the unexpected interrupt
         */
        do {
                if (hwif->irq == irq) {
                        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%s: unexpected interrupt, "
                                                "status=0x%02x, count=%ld\n",
                                                hwif->name,
                                                (hwif->next==hwgroup->hwif) ? "" : "(?)", stat, count);
                                }
                        }
                }
        } while ((hwif = hwif->next) != hwgroup->hwif);
}

/**
 *      ide_intr        -       default IDE interrupt handler
 *      @irq: interrupt number
 *      @dev_id: hwif group
 *      @regs: unused weirdness from the kernel irq layer
 *
 *      This is the default IRQ handler for the IDE layer. You should
 *      not need to override it. If you do be aware it is subtle in
 *      places
 *
 *      hwgroup->hwif is the interface in the group currently performing
 *      a command. hwgroup->drive is the drive and hwgroup->handler is
 *      the IRQ handler to call. As we issue a command the handlers
 *      step through multiple states, reassigning the handler to the
 *      next step in the process. Unlike a smart SCSI controller IDE
 *      expects the main processor to sequence the various transfer
 *      stages. We also manage a poll timer to catch up with most
 *      timeout situations. There are still a few where the handlers
 *      don't ever decide to give up.
 *
 *      The handler eventually returns ide_stopped to indicate the
 *      request completed. At this point we issue the next request
 *      on the hwgroup and the process begins again.
 */
 
irqreturn_t ide_intr (int irq, void *dev_id)
{
        unsigned long flags;
        ide_hwgroup_t *hwgroup = (ide_hwgroup_t *)dev_id;
        ide_hwif_t *hwif;
        ide_drive_t *drive;
        ide_handler_t *handler;
        ide_startstop_t startstop;

        spin_lock_irqsave(&ide_lock, flags);
        hwif = hwgroup->hwif;

        if (!ide_ack_intr(hwif)) {
                spin_unlock_irqrestore(&ide_lock, flags);
                return IRQ_NONE;
        }

        if ((handler = hwgroup->handler) == NULL || hwgroup->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.
                 *
                 * FIXME: unexpected_intr should be hwif-> then we can
                 * remove all the ifdef PCI crap
                 */
#ifdef CONFIG_BLK_DEV_IDEPCI
                if (hwif->chipset != ide_pci)
#endif  /* CONFIG_BLK_DEV_IDEPCI */
                {
                        /*
                         * Probably not a shared PCI interrupt,
                         * so we can safely try to do something about it:
                         */
                        unexpected_intr(irq, hwgroup);
#ifdef CONFIG_BLK_DEV_IDEPCI
                } else {
                        /*
                         * Whack the status register, just in case
                         * we have a leftover pending IRQ.
                         */
                        (void)hwif->tp_ops->read_status(hwif);
#endif /* CONFIG_BLK_DEV_IDEPCI */
                }
                spin_unlock_irqrestore(&ide_lock, flags);
                return IRQ_NONE;
        }
        drive = hwgroup->drive;
        if (!drive) {
                /*
                 * This should NEVER happen, and there isn't much
                 * we could do about it here.
                 *
                 * [Note - this can occur if the drive is hot unplugged]
                 */
                spin_unlock_irqrestore(&ide_lock, flags);
                return IRQ_HANDLED;
        }
        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.
                 */
                spin_unlock_irqrestore(&ide_lock, flags);
                return IRQ_NONE;
        }
        if (!hwgroup->busy) {
                hwgroup->busy = 1;      /* paranoia */
                printk(KERN_ERR "%s: ide_intr: hwgroup->busy was 0 ??\n", drive->name);
        }
        hwgroup->handler = NULL;
        hwgroup->req_gen++;
        del_timer(&hwgroup->timer);
        spin_unlock(&ide_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(&ide_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.
         */
        drive->service_time = jiffies - drive->service_start;
        if (startstop == ide_stopped) {
                if (hwgroup->handler == NULL) { /* paranoia */
                        hwgroup->busy = 0;
                        ide_do_request(hwgroup, hwif->irq);
                } else {
                        printk(KERN_ERR "%s: ide_intr: huh? expected NULL handler "
                                "on exit\n", drive->name);
                }
        }
        spin_unlock_irqrestore(&ide_lock, flags);
        return IRQ_HANDLED;
}

/**
 *      ide_do_drive_cmd        -       issue IDE special command
 *      @drive: device to issue command
 *      @rq: request to issue
 *
 *      This function issues a special IDE device request
 *      onto the request queue.
 *
 *      the rq is queued at the head of the request queue, displacing
 *      the currently-being-processed request and this function
 *      returns immediately without waiting for the new rq to be
 *      completed.  This is VERY DANGEROUS, and is intended for
 *      careful use by the ATAPI tape/cdrom driver code.
 */

void ide_do_drive_cmd(ide_drive_t *drive, struct request *rq)
{
        unsigned long flags;
        ide_hwgroup_t *hwgroup = HWGROUP(drive);

        spin_lock_irqsave(&ide_lock, flags);
        hwgroup->rq = NULL;
        __elv_add_request(drive->queue, rq, ELEVATOR_INSERT_FRONT, 0);
        blk_start_queueing(drive->queue);
        spin_unlock_irqrestore(&ide_lock, flags);
}

EXPORT_SYMBOL(ide_do_drive_cmd);

void ide_pktcmd_tf_load(ide_drive_t *drive, u32 tf_flags, u16 bcount, u8 dma)
{
        ide_hwif_t *hwif = drive->hwif;
        ide_task_t task;

        memset(&task, 0, sizeof(task));
        task.tf_flags = IDE_TFLAG_OUT_LBAH | IDE_TFLAG_OUT_LBAM |
                        IDE_TFLAG_OUT_FEATURE | tf_flags;
        task.tf.feature = dma;          /* Use PIO/DMA */
        task.tf.lbam    = bcount & 0xff;
        task.tf.lbah    = (bcount >> 8) & 0xff;

        ide_tf_dump(drive->name, &task.tf);
        hwif->tp_ops->set_irq(hwif, 1);
        SELECT_MASK(drive, 0);
        hwif->tp_ops->tf_load(drive, &task);
}

EXPORT_SYMBOL_GPL(ide_pktcmd_tf_load);

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);