ide-cd.c

讲述linux的初始化过程

 * the buffer is cleared.)
 */
static void cdrom_buffer_sectors (ide_drive_t *drive, unsigned long sector,
                                  int sectors_to_transfer)
{
	struct cdrom_info *info = drive->driver_data;

	/* Number of sectors to read into the buffer. */
	int sectors_to_buffer = MIN (sectors_to_transfer,
				     (SECTOR_BUFFER_SIZE >> SECTOR_BITS) -
				       info->nsectors_buffered);

	char *dest;

	/* If we couldn't get a buffer, don't try to buffer anything... */
	if (info->buffer == NULL)
		sectors_to_buffer = 0;

	/* If this is the first sector in the buffer, remember its number. */
	if (info->nsectors_buffered == 0)
		info->sector_buffered = sector;

	/* Read the data into the buffer. */
	dest = info->buffer + info->nsectors_buffered * SECTOR_SIZE;
	while (sectors_to_buffer > 0) {
		atapi_input_bytes (drive, dest, SECTOR_SIZE);
		--sectors_to_buffer;
		--sectors_to_transfer;
		++info->nsectors_buffered;
		dest += SECTOR_SIZE;
	}

	/* Throw away any remaining data. */
	while (sectors_to_transfer > 0) {
		char dum[SECTOR_SIZE];
		atapi_input_bytes (drive, dum, sizeof (dum));
		--sectors_to_transfer;
	}
}

/*
 * Check the contents of the interrupt reason register from the cdrom
 * and attempt to recover if there are problems.  Returns  0 if everything's
 * ok; nonzero if the request has been terminated.
 */
static inline
int cdrom_read_check_ireason (ide_drive_t *drive, int len, int ireason)
{
	ireason &= 3;
	if (ireason == 2) return 0;

	if (ireason == 0) {
		/* Whoops... The drive is expecting to receive data from us! */
		printk ("%s: cdrom_read_intr: "
			"Drive wants to transfer data the wrong way!\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  if (ireason == 1) {
		/* Some drives (ASUS) seem to tell us that status
		 * info is available. just get it and ignore.
		 */
		GET_STAT();
		return 0;
	} else {
		/* Drive wants a command packet, or invalid ireason... */
		printk ("%s: cdrom_read_intr: bad interrupt reason %d\n",
			drive->name, ireason);
	}

	cdrom_end_request (0, drive);
	return -1;
}

/*
 * Interrupt routine.  Called when a read request has completed.
 */
static ide_startstop_t cdrom_read_intr (ide_drive_t *drive)
{
	int stat;
	int ireason, len, sectors_to_transfer, nskip;
	struct cdrom_info *info = drive->driver_data;
	int i, dma = info->dma, dma_error = 0;
	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)))
			HWIF(drive)->dmaproc(ide_dma_off, drive);
	}

	if (cdrom_decode_status (&startstop, drive, 0, &stat))
		return startstop;
 
	if (dma) {
		if (!dma_error) {
			for (i = rq->nr_sectors; i > 0;) {
				i -= rq->current_nr_sectors;
				ide_end_request(1, HWGROUP(drive));
			}
			return ide_stopped;
		} else
			return ide_error (drive, "dma error", stat);
	}

	/* 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 filling the current buffer, complain.
		   Otherwise, complete the command normally. */
		if (rq->current_nr_sectors > 0) {
			printk ("%s: cdrom_read_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 (cdrom_read_check_ireason (drive, len, ireason))
		return ide_stopped;

	/* Assume that the drive will always provide data in multiples
	   of at least SECTOR_SIZE, as it gets hairy to keep track
	   of the transfers otherwise. */
	if ((len % SECTOR_SIZE) != 0) {
		printk ("%s: cdrom_read_intr: Bad transfer size %d\n",
			drive->name, len);
		if (CDROM_CONFIG_FLAGS (drive)->limit_nframes)
			printk ("  This drive is not supported by this version of the driver\n");
		else {
			printk ("  Trying to limit transfer sizes\n");
			CDROM_CONFIG_FLAGS (drive)->limit_nframes = 1;
		}
		cdrom_end_request (0, drive);
		return ide_stopped;
	}

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

	/* First, figure out if we need to bit-bucket
	   any of the leading sectors. */
	nskip = MIN ((int)(rq->current_nr_sectors - (rq->bh->b_size >> SECTOR_BITS)),
		     sectors_to_transfer);

	while (nskip > 0) {
		/* We need to throw away a sector. */
		char dum[SECTOR_SIZE];
		atapi_input_bytes (drive, dum, sizeof (dum));

		--rq->current_nr_sectors;
		--nskip;
		--sectors_to_transfer;
	}

	/* Now loop while we still have data to read from the drive. */
	while (sectors_to_transfer > 0) {
		int this_transfer;

		/* 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);

		/* If the buffers are full, cache the rest of the data in our
		   internal buffer. */
		if (rq->current_nr_sectors == 0) {
			cdrom_buffer_sectors(drive, rq->sector, sectors_to_transfer);
			sectors_to_transfer = 0;
		} else {
			/* Transfer data to the buffers.
			   Figure out how many sectors we can transfer
			   to the current buffer. */
			this_transfer = MIN (sectors_to_transfer,
					     rq->current_nr_sectors);

			/* Read this_transfer sectors
			   into the current buffer. */
			while (this_transfer > 0) {
				atapi_input_bytes(drive, rq->buffer, SECTOR_SIZE);
				rq->buffer += SECTOR_SIZE;
				--rq->nr_sectors;
				--rq->current_nr_sectors;
				++rq->sector;
				--this_transfer;
				--sectors_to_transfer;
			}
		}
	}

	/* Done moving data!
	   Wait for another interrupt. */
	ide_set_handler(drive, &cdrom_read_intr, WAIT_CMD, NULL);
	return ide_started;
}

/*
 * Try to satisfy some of the current read request from our cached data.
 * Returns nonzero if the request has been completed, zero otherwise.
 */
static int cdrom_read_from_buffer (ide_drive_t *drive)
{
	struct cdrom_info *info = drive->driver_data;
	struct request *rq = HWGROUP(drive)->rq;

	/* Can't do anything if there's no buffer. */
	if (info->buffer == NULL) return 0;

	/* Loop while this request needs data and the next block is present
	   in our cache. */
	while (rq->nr_sectors > 0 &&
	       rq->sector >= info->sector_buffered &&
	       rq->sector < info->sector_buffered + info->nsectors_buffered) {
		if (rq->current_nr_sectors == 0)
			cdrom_end_request (1, drive);

		memcpy (rq->buffer,
			info->buffer +
			(rq->sector - info->sector_buffered) * SECTOR_SIZE,
			SECTOR_SIZE);
		rq->buffer += SECTOR_SIZE;
		--rq->current_nr_sectors;
		--rq->nr_sectors;
		++rq->sector;
	}

	/* If we've satisfied the current request,
	   terminate it successfully. */
	if (rq->nr_sectors == 0) {
		cdrom_end_request (1, drive);
		return -1;
	}

	/* Move on to the next buffer if needed. */
	if (rq->current_nr_sectors == 0)
		cdrom_end_request (1, drive);

	/* If this condition does not hold, then the kluge i use to
	   represent the number of sectors to skip at the start of a transfer
	   will fail.  I think that this will never happen, but let's be
	   paranoid and check. */
	if (rq->current_nr_sectors < (rq->bh->b_size >> SECTOR_BITS) &&
	    (rq->sector % SECTORS_PER_FRAME) != 0) {
		printk ("%s: cdrom_read_from_buffer: buffer botch (%ld)\n",
			drive->name, rq->sector);
		cdrom_end_request (0, drive);
		return -1;
	}

	return 0;
}

/*
 * Routine to send a read packet command to the drive.
 * This is usually called directly from cdrom_start_read.
 * However, for drq_interrupt devices, it is called from an interrupt
 * when the drive is ready to accept the command.
 */
static ide_startstop_t cdrom_start_read_continuation (ide_drive_t *drive)
{
	struct packet_command pc;
	struct request *rq = HWGROUP(drive)->rq;
	int nsect, sector, nframes, frame, nskip;

	/* Number of sectors to transfer. */
	nsect = rq->nr_sectors;

	/* Starting sector. */
	sector = rq->sector;

	/* If the requested sector doesn't start on a cdrom block boundary,
	   we must adjust the start of the transfer so that it does,
	   and remember to skip the first few sectors.
	   If the CURRENT_NR_SECTORS field is larger than the size
	   of the buffer, it will mean that we're to skip a number
	   of sectors equal to the amount by which CURRENT_NR_SECTORS
	   is larger than the buffer size. */
	nskip = (sector % SECTORS_PER_FRAME);
	if (nskip > 0) {
		/* Sanity check... */
		if (rq->current_nr_sectors != (rq->bh->b_size >> SECTOR_BITS) &&
			(rq->sector % CD_FRAMESIZE != 0)) {
			printk ("%s: cdrom_start_read_continuation: buffer botch (%lu)\n",
				drive->name, rq->current_nr_sectors);
			cdrom_end_request (0, drive);
			return ide_stopped;
		}
		sector -= nskip;
		nsect += nskip;
		rq->current_nr_sectors += nskip;
	}

	/* Convert from sectors to cdrom blocks, rounding up the transfer
	   length if needed. */
	nframes = (nsect + SECTORS_PER_FRAME-1) / SECTORS_PER_FRAME;
	frame = sector / SECTORS_PER_FRAME;

	/* Largest number of frames was can transfer at once is 64k-1. For
	   some drives we need to limit this even more. */
	nframes = MIN (nframes, (CDROM_CONFIG_FLAGS (drive)->limit_nframes) ?
		(65534 / CD_FRAMESIZE) : 65535);

	/* Set up the command */
	memset (&pc.c, 0, sizeof (pc.c));
	pc.c[0] = GPCMD_READ_10;
	pc.c[7] = (nframes >> 8);
	pc.c[8] = (nframes & 0xff);
	put_unaligned(cpu_to_be32(frame), (unsigned int *) &pc.c[2]);
	pc.timeout = WAIT_CMD;

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


#define IDECD_SEEK_THRESHOLD	(1000)			/* 1000 blocks */
#define IDECD_SEEK_TIMER	(5 * WAIT_MIN_SLEEP)	/* 100 ms */
#define IDECD_SEEK_TIMEOUT     WAIT_CMD			/* 10 sec */

static ide_startstop_t cdrom_seek_intr (ide_drive_t *drive)
{
	struct cdrom_info *info = drive->driver_data;
	int stat;
	static int retry = 10;
	ide_startstop_t startstop;

	if (cdrom_decode_status (&startstop, drive, 0, &stat))
		return startstop;
	CDROM_CONFIG_FLAGS(drive)->seeking = 1;

	if (retry && jiffies - info->start_seek > IDECD_SEEK_TIMER) {
		if (--retry == 0) {
			/*
			 * this condition is far too common, to bother
			 * users about it
			 */
#if 0
			printk("%s: disabled DSC seek overlap\n", drive->name);
#endif
			drive->dsc_overlap = 0;
		}
	}
	return ide_stopped;
}

static ide_startstop_t cdrom_start_seek_continuation (ide_drive_t *drive)
{
	struct packet_command pc;
	struct request *rq = HWGROUP(drive)->rq;
	int sector, frame, nskip;

	sector = rq->sector;
	nskip = (sector % SECTORS_PER_FRAME);
	if (nskip > 0)
		sector -= nskip;
	frame = sector / SECTORS_PER_FRAME;

	memset (&pc.c, 0, sizeof (pc.c));
	pc.c[0] = GPCMD_SEEK;
	put_unaligned(cpu_to_be32(frame), (unsigned int *) &pc.c[2]);

	pc.timeout = WAIT_CMD;
	return cdrom_transfer_packet_command(drive, &pc, &cdrom_seek_intr);
}

static ide_startstop_t cdrom_start_seek (ide_drive_t *drive, unsigned int block)
{
	struct cdrom_info *info = drive->driver_data;

	info->dma = 0;
	info->cmd = 0;
	info->start_seek = jiffies;
	return cdrom_start_packet_command (drive, 0, cdrom_start_seek_continuation);
}

/* Fix up a possibly partially-processed request so that we can
   start it over entirely, or even put it back on the request queue. */
static void restore_request (struct request *rq)
{
	if (rq->buffer != rq->bh->b_data) {
		int n = (rq->buffer - rq->bh->b_data) / SECTOR_SIZE;
		rq->buffer = rq->bh->b_data;
		rq->nr_sectors += n;
		rq->sector -= n;
	}
	rq->current_nr_sectors = rq->bh->b_size >> SECTOR_BITS;
}

/*
 * Start a read request from the CD-ROM.
 */
static ide_startstop_t cdrom_start_read (ide_drive_t *drive, unsigned int block)
{