ide-cd.c

讲述linux的初始化过程

	struct cdrom_info *info = drive->driver_data;
	struct request *rq = HWGROUP(drive)->rq;
	int minor = MINOR (rq->rq_dev);

	/* If the request is relative to a partition, fix it up to refer to the
	   absolute address.  */
	if ((minor & PARTN_MASK) != 0) {
		rq->sector = block;
		minor &= ~PARTN_MASK;
		rq->rq_dev = MKDEV (MAJOR(rq->rq_dev), minor);
	}

	/* We may be retrying this request after an error.  Fix up
	   any weirdness which might be present in the request packet. */
	restore_request (rq);

	/* Satisfy whatever we can of this request from our cached sector. */
	if (cdrom_read_from_buffer(drive))
		return ide_stopped;

	/* Clear the local sector buffer. */
	info->nsectors_buffered = 0;

	/* use dma, if possible. */
	if (drive->using_dma && (rq->sector % SECTORS_PER_FRAME == 0) &&
				(rq->nr_sectors % SECTORS_PER_FRAME == 0))
		info->dma = 1;
	else
		info->dma = 0;

	info->cmd = READ;
	/* Start sending the read request to the drive. */
	return cdrom_start_packet_command(drive, 32768, cdrom_start_read_continuation);
}

/****************************************************************************
 * Execute all other packet commands.
 */

/* Forward declarations. */
static int cdrom_lockdoor(ide_drive_t *drive, int lockflag,
			  struct request_sense *sense);

/* Interrupt routine for packet command completion. */
static ide_startstop_t cdrom_pc_intr (ide_drive_t *drive)
{
	int ireason, len, stat, thislen;
	struct request *rq = HWGROUP(drive)->rq;
	struct packet_command *pc = (struct packet_command *)rq->buffer;
	ide_startstop_t startstop;

	/* Check for errors. */
	if (cdrom_decode_status (&startstop, drive, 0, &stat))
		return startstop;

	/* Read the interrupt reason and the transfer length. */
	ireason = IN_BYTE (IDE_NSECTOR_REG);
	len = IN_BYTE (IDE_LCYL_REG) + 256 * IN_BYTE (IDE_HCYL_REG);

	/* If DRQ is clear, the command has completed.
	   Complain if we still have data left to transfer. */
	if ((stat & DRQ_STAT) == 0) {
		/* Some of the trailing request sense fields are optional, and
		   some drives don't send them.  Sigh. */
		if (pc->c[0] == GPCMD_REQUEST_SENSE &&
		    pc->buflen > 0 &&
		    pc->buflen <= 5) {
			while (pc->buflen > 0) {
				*pc->buffer++ = 0;
				--pc->buflen;
			}
		}

		if (pc->buflen == 0)
			cdrom_end_request (1, drive);
		else {
			/* Comment this out, because this always happens 
			   right after a reset occurs, and it is annoying to 
			   always print expected stuff.  */
			/*
			printk ("%s: cdrom_pc_intr: data underrun %d\n",
				drive->name, pc->buflen);
			*/
			pc->stat = 1;
			cdrom_end_request (1, drive);
		}
		return ide_stopped;
	}

	/* Figure out how much data to transfer. */
	thislen = pc->buflen;
	if (thislen > len) thislen = len;

	/* The drive wants to be written to. */
	if ((ireason & 3) == 0) {
		/* Transfer the data. */
		atapi_output_bytes (drive, pc->buffer, thislen);

		/* If we haven't moved enough data to satisfy the drive,
		   add some padding. */
		while (len > thislen) {
			int dum = 0;
			atapi_output_bytes (drive, &dum, sizeof (dum));
			len -= sizeof (dum);
		}

		/* Keep count of how much data we've moved. */
		pc->buffer += thislen;
		pc->buflen -= thislen;
	}

	/* Same drill for reading. */
	else if ((ireason & 3) == 2) {

		/* Transfer the data. */
		atapi_input_bytes (drive, pc->buffer, thislen);

		/* If we haven't moved enough data to satisfy the drive,
		   add some padding. */
		while (len > thislen) {
			int dum = 0;
			atapi_input_bytes (drive, &dum, sizeof (dum));
			len -= sizeof (dum);
		}

		/* Keep count of how much data we've moved. */
		pc->buffer += thislen;
		pc->buflen -= thislen;
	} else {
		printk ("%s: cdrom_pc_intr: The drive "
			"appears confused (ireason = 0x%2x)\n",
			drive->name, ireason);
		pc->stat = 1;
	}

	/* Now we wait for another interrupt. */
	ide_set_handler (drive, &cdrom_pc_intr, WAIT_CMD, cdrom_timer_expiry);
	return ide_started;
}


static ide_startstop_t cdrom_do_pc_continuation (ide_drive_t *drive)
{
	struct request *rq = HWGROUP(drive)->rq;
	struct packet_command *pc = (struct packet_command *)rq->buffer;

	if (!pc->timeout)
		pc->timeout = WAIT_CMD;

	/* Send the command to the drive and return. */
	return cdrom_transfer_packet_command(drive, pc, &cdrom_pc_intr);
}


static ide_startstop_t cdrom_do_packet_command (ide_drive_t *drive)
{
	int len;
	struct request *rq = HWGROUP(drive)->rq;
	struct packet_command *pc = (struct packet_command *)rq->buffer;
	struct cdrom_info *info = drive->driver_data;

	info->dma = 0;
	info->cmd = 0;
	pc->stat = 0;
	len = pc->buflen;

	/* Start sending the command to the drive. */
	return cdrom_start_packet_command (drive, len, cdrom_do_pc_continuation);
}


/* Sleep for TIME jiffies.
   Not to be called from an interrupt handler. */
static
void cdrom_sleep (int time)
{
	int sleep = time;

	do {
		set_current_state(TASK_INTERRUPTIBLE);
		sleep = schedule_timeout(sleep);
	} while (sleep);
}

static
int cdrom_queue_packet_command(ide_drive_t *drive, struct packet_command *pc)
{
	struct request_sense sense;
	struct request req;
	int retries = 10;

	if (pc->sense == NULL)
		pc->sense = &sense;

	/* Start of retry loop. */
	do {
		ide_init_drive_cmd (&req);
		req.cmd = PACKET_COMMAND;
		req.buffer = (char *)pc;
		if (ide_do_drive_cmd (drive, &req, ide_wait)) {
			printk("%s: do_drive_cmd returned stat=%02x,err=%02x\n",
				drive->name, req.buffer[0], req.buffer[1]);
			/* FIXME: we should probably abort/retry or something */
		}
		if (pc->stat != 0) {
			/* The request failed.  Retry if it was due to a unit
			   attention status
			   (usually means media was changed). */
			struct request_sense *reqbuf = pc->sense;

			if (reqbuf->sense_key == UNIT_ATTENTION)
				cdrom_saw_media_change (drive);
			else if (reqbuf->sense_key == NOT_READY &&
				 reqbuf->asc == 4 && reqbuf->ascq != 4) {
				/* The drive is in the process of loading
				   a disk.  Retry, but wait a little to give
				   the drive time to complete the load. */
				cdrom_sleep(2 * HZ);
			} else {
				/* Otherwise, don't retry. */
				retries = 0;
			}
			--retries;
		}

		/* End of retry loop. */
	} while (pc->stat != 0 && retries >= 0);

	/* Return an error if the command failed. */
	return pc->stat ? -EIO : 0;
}

/*
 * Write handling
 */
static inline int cdrom_write_check_ireason(ide_drive_t *drive, int len, int ireason)
{
	/* Two notes about IDE interrupt reason here - 0 means that
	 * the drive wants to receive data from us, 2 means that
	 * the drive is expecting data from us.
	 */
	ireason &= 3;

	if (ireason == 2) {
		/* Whoops... The drive wants to send data. */
		printk("%s: cdrom_write_intr: wrong transfer direction!\n",
			drive->name);

		/* Throw some data at the drive so it doesn't hang
		   and quit this request. */
		while (len > 0) {
			int dum = 0;
			atapi_output_bytes(drive, &dum, sizeof(dum));
			len -= sizeof(dum);
		}
	} else {
		/* Drive wants a command packet, or invalid ireason... */
		printk("%s: cdrom_write_intr: bad interrupt reason %d\n",
			drive->name, ireason);
	}

	cdrom_end_request(0, drive);
	return 1;
}

static ide_startstop_t cdrom_write_intr(ide_drive_t *drive)
{
	int stat, ireason, len, sectors_to_transfer;
	struct cdrom_info *info = drive->driver_data;
	int i, dma_error = 0, dma = info->dma;
	ide_startstop_t startstop;

	struct request *rq = HWGROUP(drive)->rq;

	/* Check for errors. */
	if (dma) {
		info->dma = 0;
		if ((dma_error = HWIF(drive)->dmaproc(ide_dma_end, drive))) {
			printk("ide-cd: write dma error\n");
			HWIF(drive)->dmaproc(ide_dma_off, drive);
		}
	}

	if (cdrom_decode_status(&startstop, drive, 0, &stat)) {
		printk("ide-cd: write_intr decode_status bad\n");
		return startstop;
	}
 
	if (dma) {
		if (dma_error)
			return ide_error(drive, "dma error", stat);

		rq = HWGROUP(drive)->rq;
		for (i = rq->nr_sectors; i > 0;) {
			i -= rq->current_nr_sectors;
			ide_end_request(1, HWGROUP(drive));
		}
		return ide_stopped;
	}

	/* Read the interrupt reason and the transfer length. */
	ireason = IN_BYTE(IDE_NSECTOR_REG);
	len = IN_BYTE(IDE_LCYL_REG) + 256 * IN_BYTE(IDE_HCYL_REG);

	/* If DRQ is clear, the command has completed. */
	if ((stat & DRQ_STAT) == 0) {
		/* If we're not done writing, complain.
		 * Otherwise, complete the command normally.
		 */
		if (rq->current_nr_sectors > 0) {
			printk("%s: write_intr: data underrun (%ld blocks)\n",
				drive->name, rq->current_nr_sectors);
			cdrom_end_request(0, drive);
		} else
			cdrom_end_request(1, drive);
		return ide_stopped;
	}

	/* Check that the drive is expecting to do the same thing we are. */
	if (ireason & 3)
		if (cdrom_write_check_ireason(drive, len, ireason))
			return ide_stopped;

	/* The number of sectors we need to read from the drive. */
	sectors_to_transfer = len / SECTOR_SIZE;

	/* Now loop while we still have data to read from the drive. DMA
	 * transfers will already have been complete
	 */
	while (sectors_to_transfer > 0) {
		/* If we've filled the present buffer but there's another
		   chained buffer after it, move on. */
		if (rq->current_nr_sectors == 0 && rq->nr_sectors > 0)
			cdrom_end_request(1, drive);

		atapi_output_bytes(drive, rq->buffer, rq->current_nr_sectors);
		rq->nr_sectors -= rq->current_nr_sectors;
		rq->current_nr_sectors = 0;
		rq->sector += rq->current_nr_sectors;
		sectors_to_transfer -= rq->current_nr_sectors;
	}

	/* arm handler */
	ide_set_handler(drive, &cdrom_write_intr, 5 * WAIT_CMD, NULL);
	return ide_started;
}

static ide_startstop_t cdrom_start_write_cont(ide_drive_t *drive)
{
	struct packet_command pc;	/* packet_command_t pc; */
	struct request *rq = HWGROUP(drive)->rq;
	unsigned nframes, frame;

	nframes = rq->nr_sectors >> 2;
	frame = rq->sector >> 2;

	memset(&pc.c, 0, sizeof(pc.c));
	/*
	 * we might as well use WRITE_12, but none of the device I have
	 * support the streaming feature anyway, so who cares.
	 */
	pc.c[0] = GPCMD_WRITE_10;
#if 0	/* the immediate bit */
	pc.c[1] = 1 << 3;
#endif
	pc.c[7] = (nframes >> 8) & 0xff;
	pc.c[8] = nframes & 0xff;
	put_unaligned(cpu_to_be32(frame), (unsigned int *)&pc.c[2]);
	pc.timeout = 2 * WAIT_CMD;

	return cdrom_transfer_packet_command(drive, &pc, cdrom_write_intr);
}

static ide_startstop_t cdrom_start_write(ide_drive_t *drive)
{
	struct cdrom_info *info = drive->driver_data;

	info->nsectors_buffered = 0;

        /* use dma, if possible. we don't need to check more, since we
	 * know that the transfer is always (at least!) 2KB aligned */
	info->dma = drive->using_dma ? 1 : 0;
	info->cmd = WRITE;

	/* Start sending the read request to the drive. */
	return cdrom_start_packet_command(drive, 32768, cdrom_start_write_cont);
}

/****************************************************************************
 * cdrom driver request routine.
 */
static ide_startstop_t
ide_do_rw_cdrom (ide_drive_t *drive, struct request *rq, unsigned long block)
{
	ide_startstop_t action;
	struct cdrom_info *info = drive->driver_data;

	switch (rq->cmd) {
		case WRITE:
		case READ: {
			if (CDROM_CONFIG_FLAGS(drive)->seeking) {
				unsigned long elpased = jiffies - info->start_seek;
				int stat = GET_STAT();

				if ((stat & SEEK_STAT) != SEEK_STAT) {
					if (elpased < IDECD_SEEK_TIMEOUT) {
						ide_stall_queue(drive, IDECD_SEEK_TIMER);
						return ide_stopped;