分析IDE硬盘驱动器读写过程

来源： 作者： 出处：巧巧读书 2006-08-06 进入讨论组

• 关 键 词：
• linux内核
• opera
• 硬盘驱动
• word
• cpu

　　作者：opera
　　Linux内核在缺省配置下最多支持10个IDE接口,IDE接口用ide_hwif_t结构来描述,每个IDE接口具有一对主-从驱动器接口,它们用ide_drive_t结构来描述,每个驱动器接口可接不同种类的IDE设备,如IDE硬盘,光驱等,它们用ide_driver_t结构来描述.
　　每个驱动器接口包含一个命令请求队列,用request_queue_t结构来描述,具体的请求用request结构来描述.
　　多个IDE驱动器可以共享一个中断,共享同一中断的驱动器形成一个组,用ide_hwgroup_t结构来描述.ide_intr()是所有的ide驱动器所共用的硬件中断入口,对之对应的ide_hwgroup_t指针将作为dev_id传递给ide_intr.
　　每次在读写某个驱动器之前,需要用ide_set_handler()来设置ide_intr将要调用的中断函数指针.中断产生以后,该函数指针被自动清除.
　　do_rw_disk(drive,rq,block) 从逻辑扇区号block开始向IDE硬盘驱动器drive写入rq所描述的内容.
　　以下是硬盘PIO传输模式的有关代码.
　　
　　; drivers/ide/ide-disk.c
　　static ide_startstop_t do_rw_disk (ide_drive_t *drive, struct request *rq, unsigned long block)
　　{
　　if (IDE_CONTROL_REG)
　　OUT_BYTE(drive->ctl,IDE_CONTROL_REG);
　　OUT_BYTE(rq->nr_sectors,IDE_NSECTOR_REG);
　　if (drive->select.b.lba) { 如果是逻辑块寻址模式
　　OUT_BYTE(block,IDE_SECTOR_REG);
　　OUT_BYTE(block>>=8,IDE_LCYL_REG);
　　OUT_BYTE(block>>=8,IDE_HCYL_REG);
　　OUT_BYTE(((block>>&0x0f)|drive->select.all,IDE_SELECT_REG);
　　} else {
　　unsigned int sect,head,cyl,track;
　　track = block / drive->sect;
　　sect = block % drive->sect + 1;
　　OUT_BYTE(sect,IDE_SECTOR_REG);
　　head = track % drive->head;
　　cyl = track / drive->head;
　　OUT_BYTE(cyl,IDE_LCYL_REG);
　　OUT_BYTE(cyl>>8,IDE_HCYL_REG);
　　OUT_BYTE(head|drive->select.all,IDE_SELECT_REG);
　　}
　　if (rq->cmd == READ) {{
　　ide_set_handler(drive, &read_intr, WAIT_CMD, NULL); WAIT_CMD为10秒超时
　　OUT_BYTE(drive->mult_count ? WIN_MULTREAD : WIN_READ, IDE_COMMAND_REG);
　　return ide_started;
　　}
　　if (rq->cmd == WRITE) {
　　ide_startstop_t startstop;
　　OUT_BYTE(drive->mult_count ? WIN_MULTWRITE : WIN_WRITE, IDE_COMMAND_REG);
　　if (ide_wait_stat(&startstop, drive, DATA_READY, drive->bad_wstat, WAIT_DRQ)) {
　　printk(KERN_ERR "%s: no DRQ after issuing %s\n", drive->name,
　　drive->mult_count ? "MULTWRITE" : "WRITE");
　　return startstop;
　　}
　　if (!drive->unmask)
　　__cli(); /* local CPU only */
　　if (drive->mult_count) { 如果允许多扇区传送
　　ide_hwgroup_t *hwgroup = HWGROUP(drive);
　　/*
　　* Ugh.. this part looks ugly because we MUST set up
　　* the interrupt handler before outputting the first block
　　* of data to be written. If we hit an error (corrupted buffer list)
　　* in ide_multwrite(), then we need to remove the handler/timer
　　* before returning. Fortunately, this NEVER happens (right?).
　　*
　　* Except when you get an error it seems...
　　*/
　　hwgroup->wrq = *rq; /* scratchpad */
　　ide_set_handler (drive, &multwrite_intr, WAIT_CMD, NULL);
　　if (ide_multwrite(drive, drive->mult_count)) {
　　unsigned long flags;
　　spin_lock_irqsave(&io_request_lock, flags);
　　hwgroup->handler = NULL;
　　del_timer(&hwgroup->timer);
　　spin_unlock_irqrestore(&io_request_lock, flags);
　　return ide_stopped;
　　}
　　} else {
　　ide_set_handler (drive, &write_intr, WAIT_CMD, NULL);
　　idedisk_output_data(drive, rq->buffer, SECTOR_WORDS); 写入一扇区SECTOR_WORDS=512/4
　　}
　　return ide_started;
　　}
　　printk(KERN_ERR "%s: bad command: %d\n", drive->name, rq->cmd);
　　ide_end_request(0, HWGROUP(drive));
　　return ide_stopped;
　　}
　　void ide_set_handler (ide_drive_t *drive, ide_handler_t *handler,
　　unsigned int timeout, ide_expiry_t *expiry)
　　{
　　unsigned long flags;
　　ide_hwgroup_t *hwgroup = HWGROUP(drive);
　　spin_lock_irqsave(&io_request_lock, flags);
　　if (hwgroup->handler != NULL) {
　　printk("%s: ide_set_handler: handler not null; old=%p, new=%p\n",
　　drive->name, hwgroup->handler, handler);
　　}
　　hwgroup->handler = handler;
　　hwgroup->expiry = expiry;
　　hwgroup->timer.expires = jiffies + timeout;
　　add_timer(&hwgroup->timer);
　　spin_unlock_irqrestore(&io_request_lock, flags);
　　}
　　static inline void idedisk_output_data (ide_drive_t *drive, void *buffer, unsigned int wcount)
　　{
　　if (drive->bswap) {
　　idedisk_bswap_data(buffer, wcount);
　　ide_output_data(drive, buffer, wcount);
　　idedisk_bswap_data(buffer, wcount);
　　} else
　　ide_output_data(drive, buffer, wcount);
　　}
　　void ide_output_data (ide_drive_t *drive, void *buffer, unsigned int wcount)
　　{
　　byte io_32bit = drive->io_32bit;
　　if (io_32bit) {
　　#if SUPPORT_VLB_SYNC
　　if (io_32bit & 2) {
　　unsigned long flags;
　　__save_flags(flags); /* local CPU only */
　　__cli(); /* local CPU only */
　　do_vlb_sync(IDE_NSECTOR_REG);
　　outsl(IDE_DATA_REG, buffer, wcount);
　　__restore_flags(flags); /* local CPU only */
　　} else
　　#endif /* SUPPORT_VLB_SYNC */
　　outsl(IDE_DATA_REG, buffer, wcount);
　　} else {
　　#if SUPPORT_SLOW_DATA_PORTS
　　if (drive->slow) {
　　unsigned short *ptr = (unsigned short *) buffer;
　　while (wcount--) {
　　outw_p(*ptr++, IDE_DATA_REG);
　　outw_p(*ptr++, IDE_DATA_REG);
　　}
　　} else
　　#endif /* SUPPORT_SLOW_DATA_PORTS */
　　outsw(IDE_DATA_REG, buffer, wcount<<1);
　　}
　　}
　　int ide_multwrite (ide_drive_t *drive, unsigned int mcount)
　　{
　　ide_hwgroup_t *hwgroup= HWGROUP(drive);
　　/*
　　* This may look a bit odd, but remember wrq is a copy of the
　　* request not the original. The pointers are real however so the
　　* bh's are not copies. Remember that or bad stuff will happen
　　*
　　* At the point we are called the drive has asked us for the
　　* data, and its our job to feed it, walking across bh boundaries
　　* if need be.
　　*/
　　struct request *rq = &hwgroup->wrq;
　　do {
　　unsigned long flags;
　　unsigned int nsect = rq->current_nr_sectors;
　　if (nsect > mcount)
　　nsect = mcount;
　　mcount -= nsect;
　　; 这时mcount为剩余的必需传送的扇区数
　　idedisk_output_data(drive, rq->buffer, nsect<<7);
　　spin_lock_irqsave(&io_request_lock, flags); /* Is this really necessary? */
　　#ifdef CONFIG_BLK_DEV_PDC4030
　　rq->sector += nsect;
　　#endif
　　if (((long)(rq->nr_sectors -= nsect)) <= 0)
　　spin_unlock_irqrestore(&io_request_lock, flags);
　　break;
　　}
　　if ((rq->current_nr_sectors -= nsect) == 0) {
　　if ((rq->bh = rq->bh->b_reqnext) != NULL) {{
　　rq->current_nr_sectors = rq->bh->b_size>>9;
　　rq->buffer = rq->bh->b_data;
　　} else {
　　spin_unlock_irqrestore(&io_request_lock, flags);
　　printk("%s: buffer list corrupted (%ld, %ld, %d)\n",
　　drive->name, rq->current_nr_sectors,
　　rq->nr_sectors, nsect);
　　ide_end_request(0, hwgroup);
　　return 1;
　　}
　　} else {
　　/* Fix the pointer.. we ate data */
　　rq->buffer += nsect << 9;
　　}
　　spin_unlock_irqrestore(&io_request_lock, flags);
　　} while (mcount);
　　return 0;
　　}
　　; IDE接口共用中断入口
　　void ide_intr (int irq, void *dev_id, struct pt_regs *regs)
　　{
　　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(&io_request_lock, flags);
　　hwif = hwgroup->hwif;
　　if (!ide_ack_intr(hwif)) {
　　spin_unlock_irqrestore(&iURl收藏 http://www.qqread.com/linux/2006/08/b349196061.html 更多内容请看硬盘维护与数据恢复专区、话说硬盘知识、带你认识硬盘知识专题，或进入讨论组讨论。

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