Merge branch 'for-linus' into for-next

[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/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));
        }
}

/* obsolete, blk_rq_bytes() should be used instead */
unsigned int ide_rq_bytes(struct request *rq)
{
        if (blk_pc_request(rq))
                return rq->data_len;
        else
                return rq->hard_cur_sectors << 9;
}
EXPORT_SYMBOL_GPL(ide_rq_bytes);

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 = rq->hard_nr_sectors << 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 = blk_special_request(rq) && rq->rq_disk;
        u8 media = drive->media;

        drive->failed_pc = NULL;

        if ((media == ide_floppy || media == ide_tape) && drv_req) {
                rq->errors = 0;
                ide_complete_rq(drive, 0, blk_rq_bytes(rq));
        } else {
                if (media == ide_tape)
                        rq->errors = IDE_DRV_ERROR_GENERAL;
                else if (blk_fs_request(rq) == 0 && rq->errors == 0)
                        rq->errors = -EIO;
                ide_complete_rq(drive, -EIO, ide_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;
}

/**
 *      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.
 */

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);

/**
 *      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)
{
        struct ide_cmd *cmd = rq->special;

        if (cmd) {
                if (cmd->protocol == ATA_PROT_PIO) {
                        ide_init_sg_cmd(cmd, rq->nr_sectors << 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();
        }
}

/**
 *      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",
                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 && 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 = *(struct ide_driver **)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 port 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);

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);
        }
}

/*
 * 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;

        /*
         * 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(q))
                /*
                 * 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(q);

        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;
repeat:
                prev_port = hwif->host->cur_port;
                hwif->rq = NULL;

                if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
                    time_after(drive->sleep, jiffies)) {
                        ide_unlock_port(hwif);
                        goto plug_device;
                }

                if ((hwif->host->host_flags & IDE_HFLAG_SERIALIZE) &&
                    hwif != prev_port) {
                        /*
                         * set nIEN for previous port, drives in the
                         * quirk_list may not like intr setups/cleanups
                         */
                        if (prev_port && prev_port->cur_dev->quirk_list == 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
                 */
                rq = elv_next_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 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.
                 */
                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)
                        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);

        if (!elv_queue_empty(q))
                blk_plug_device(q);
}

static void ide_plug_device(ide_drive_t *drive)
{
        struct request_queue *q = drive->queue;
        unsigned long flags;

        spin_lock_irqsave(q->queue_lock, flags);
        if (!elv_queue_empty(q))
                blk_plug_device(q);
        spin_unlock_irqrestore(q->queue_lock, flags);
}

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;
}

/**
 *      ide_timer_expiry        -       handle lack of an IDE interrupt
 *      @data: timer callback magic (hwif)
 *
 *      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_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;

        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->ack_intr)
                                hwif->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));
                }
                spin_lock_irq(&hwif->lock);
                enable_irq(hwif->irq);
                if (startstop == ide_stopped && hwif->polling == 0) {
                        ide_unlock_port(hwif);
                        plug_device = 1;
                }
        }
        spin_unlock_irqrestore(&hwif->lock, flags);

        if (plug_device) {
                ide_unlock_host(hwif->host);
                ide_plug_device(drive);
        }
}

/**
 *      unexpected_intr         -       handle an unexpected IDE interrupt
 *      @irq: interrupt line
 *      @hwif: port 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.
 */

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);
                }
        }
}

/**
 *      ide_intr        -       default IDE interrupt handler
 *      @irq: interrupt number
 *      @dev_id: hwif
 *      @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
 *
 *      hwif is the interface in the group currently performing
 *      a command. hwif->cur_dev is the drive and hwif->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 port and the process begins again.
 */

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;

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

        spin_lock_irqsave(&hwif->lock, flags);

        if (hwif->ack_intr && hwif->ack_intr(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);
                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_plug_device(drive);
        }

        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);