/* * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include 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; } /** * 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, 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(); } } /** * 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(!(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; } /** * 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); } } 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; } /** * 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; 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); } } /** * 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; 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);