sr.c

讲述linux的初始化过程

/*
 *  sr.c Copyright (C) 1992 David Giller
 *           Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
 *
 *  adapted from:
 *      sd.c Copyright (C) 1992 Drew Eckhardt
 *      Linux scsi disk driver by
 *              Drew Eckhardt <[e-mail]>
 *
 *      Modified by Eric Youngdale [e-mail] to
 *      add scatter-gather, multiple outstanding request, and other
 *      enhancements.
 *
 *          Modified by Eric Youngdale [e-mail] to support loadable
 *          low-level scsi drivers.
 *
 *       Modified by Thomas Quinot [e-mail] to
 *       provide auto-eject.
 *
 *          Modified by Gerd Knorr <[e-mail]> to support the
 *          generic cdrom interface
 *
 *       Modified by Jens Axboe <[e-mail]> - Uniform sr_packet()
 *       interface, capabilities probe additions, ioctl cleanups, etc.
 *
 *       Modified by Richard Gooch <[e-mail]> to support devfs
 *
 *       Modified by Jens Axboe <[e-mail]> - support DVD-RAM
 *	 transparently and loose the GHOST hack
 *
 *	 Modified by Arnaldo Carvalho de Melo <[e-mail]>
 *	 check resource allocation in sr_init and some cleanups
 *
 */

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/cdrom.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/uaccess.h>

#define MAJOR_NR SCSI_CDROM_MAJOR
#include <linux/blk.h>
#include "scsi.h"
#include "hosts.h"
#include "sr.h"
#include <scsi/scsi_ioctl.h>	/* For the door lock/unlock commands */
#include "constants.h"

MODULE_PARM(xa_test, "i");	/* see sr_ioctl.c */

#define MAX_RETRIES	3
#define SR_TIMEOUT	(30 * HZ)

static int sr_init(void);
static void sr_finish(void);
static int sr_attach(Scsi_Device *);
static int sr_detect(Scsi_Device *);
static void sr_detach(Scsi_Device *);

static int sr_init_command(Scsi_Cmnd *);

static struct Scsi_Device_Template sr_template =
{
	name:"cdrom",
	tag:"sr",
	scsi_type:TYPE_ROM,
	major:SCSI_CDROM_MAJOR,
	blk:1,
	detect:sr_detect,
	init:sr_init,
	finish:sr_finish,
	attach:sr_attach,
	detach:sr_detach,
	init_command:sr_init_command
};

Scsi_CD *scsi_CDs;
static int *sr_sizes;

static int *sr_blocksizes;
static int *sr_hardsizes;

static int sr_open(struct cdrom_device_info *, int);
void get_sectorsize(int);
void get_capabilities(int);

static int sr_media_change(struct cdrom_device_info *, int);
static int sr_packet(struct cdrom_device_info *, struct cdrom_generic_command *);

static void sr_release(struct cdrom_device_info *cdi)
{
	if (scsi_CDs[MINOR(cdi->dev)].device->sector_size > 2048)
		sr_set_blocklength(MINOR(cdi->dev), 2048);
	sync_dev(cdi->dev);
	scsi_CDs[MINOR(cdi->dev)].device->access_count--;
	if (scsi_CDs[MINOR(cdi->dev)].device->host->hostt->module)
		__MOD_DEC_USE_COUNT(scsi_CDs[MINOR(cdi->dev)].device->host->hostt->module);
	if (sr_template.module)
		__MOD_DEC_USE_COUNT(sr_template.module);
}

static struct cdrom_device_ops sr_dops =
{
	open:			sr_open,
	release:		sr_release,
	drive_status:		sr_drive_status,
	media_changed:		sr_media_change,
	tray_move:		sr_tray_move,
	lock_door:		sr_lock_door,
	select_speed:		sr_select_speed,
	get_last_session:	sr_get_last_session,
	get_mcn:		sr_get_mcn,
	reset:			sr_reset,
	audio_ioctl:		sr_audio_ioctl,
	dev_ioctl:		sr_dev_ioctl,
	capability:		CDC_CLOSE_TRAY | CDC_OPEN_TRAY | CDC_LOCK |
				CDC_SELECT_SPEED | CDC_SELECT_DISC |
				CDC_MULTI_SESSION | CDC_MCN |
				CDC_MEDIA_CHANGED | CDC_PLAY_AUDIO |
				CDC_RESET | CDC_IOCTLS | CDC_DRIVE_STATUS |
				CDC_CD_R | CDC_CD_RW | CDC_DVD | CDC_DVD_R |
				CDC_DVD_RAM | CDC_GENERIC_PACKET,
	generic_packet:		sr_packet,
};

/*
 * This function checks to see if the media has been changed in the
 * CDROM drive.  It is possible that we have already sensed a change,
 * or the drive may have sensed one and not yet reported it.  We must
 * be ready for either case. This function always reports the current
 * value of the changed bit.  If flag is 0, then the changed bit is reset.
 * This function could be done as an ioctl, but we would need to have
 * an inode for that to work, and we do not always have one.
 */

int sr_media_change(struct cdrom_device_info *cdi, int slot)
{
	int retval;

	if (CDSL_CURRENT != slot) {
		/* no changer support */
		return -EINVAL;
	}
	retval = scsi_ioctl(scsi_CDs[MINOR(cdi->dev)].device,
			    SCSI_IOCTL_TEST_UNIT_READY, 0);

	if (retval) {
		/* Unable to test, unit probably not ready.  This usually
		 * means there is no disc in the drive.  Mark as changed,
		 * and we will figure it out later once the drive is
		 * available again.  */

		scsi_CDs[MINOR(cdi->dev)].device->changed = 1;
		return 1;	/* This will force a flush, if called from
				 * check_disk_change */
	};

	retval = scsi_CDs[MINOR(cdi->dev)].device->changed;
	scsi_CDs[MINOR(cdi->dev)].device->changed = 0;
	/* If the disk changed, the capacity will now be different,
	 * so we force a re-read of this information */
	if (retval) {
		/* check multisession offset etc */
		sr_cd_check(cdi);

		/* 
		 * If the disk changed, the capacity will now be different,
		 * so we force a re-read of this information 
		 * Force 2048 for the sector size so that filesystems won't
		 * be trying to use something that is too small if the disc
		 * has changed.
		 */
		scsi_CDs[MINOR(cdi->dev)].needs_sector_size = 1;

		scsi_CDs[MINOR(cdi->dev)].device->sector_size = 2048;
	}
	return retval;
}

/*
 * rw_intr is the interrupt routine for the device driver.  It will be notified on the
 * end of a SCSI read / write, and will take on of several actions based on success or failure.
 */

static void rw_intr(Scsi_Cmnd * SCpnt)
{
	int result = SCpnt->result;
	int this_count = SCpnt->bufflen >> 9;
	int good_sectors = (result == 0 ? this_count : 0);
	int block_sectors = 0;
	int device_nr = DEVICE_NR(SCpnt->request.rq_dev);

#ifdef DEBUG
	printk("sr.c done: %x %p\n", result, SCpnt->request.bh->b_data);
#endif
	/*
	   Handle MEDIUM ERRORs or VOLUME OVERFLOWs that indicate partial success.
	   Since this is a relatively rare error condition, no care is taken to
	   avoid unnecessary additional work such as memcpy's that could be avoided.
	 */


	if (driver_byte(result) != 0 &&		/* An error occurred */
	    SCpnt->sense_buffer[0] == 0xF0 &&	/* Sense data is valid */
	    (SCpnt->sense_buffer[2] == MEDIUM_ERROR ||
	     SCpnt->sense_buffer[2] == VOLUME_OVERFLOW ||
	     SCpnt->sense_buffer[2] == ILLEGAL_REQUEST)) {
		long error_sector = (SCpnt->sense_buffer[3] << 24) |
		(SCpnt->sense_buffer[4] << 16) |
		(SCpnt->sense_buffer[5] << 8) |
		SCpnt->sense_buffer[6];
		if (SCpnt->request.bh != NULL)
			block_sectors = SCpnt->request.bh->b_size >> 9;
		if (block_sectors < 4)
			block_sectors = 4;
		if (scsi_CDs[device_nr].device->sector_size == 2048)
			error_sector <<= 2;
		error_sector &= ~(block_sectors - 1);
		good_sectors = error_sector - SCpnt->request.sector;
		if (good_sectors < 0 || good_sectors >= this_count)
			good_sectors = 0;
		/*
		 * The SCSI specification allows for the value returned by READ
		 * CAPACITY to be up to 75 2K sectors past the last readable
		 * block.  Therefore, if we hit a medium error within the last
		 * 75 2K sectors, we decrease the saved size value.
		 */
		if ((error_sector >> 1) < sr_sizes[device_nr] &&
		    scsi_CDs[device_nr].capacity - error_sector < 4 * 75)
			sr_sizes[device_nr] = error_sector >> 1;
	}

	/*
	 * This calls the generic completion function, now that we know
	 * how many actual sectors finished, and how many sectors we need
	 * to say have failed.
	 */
	scsi_io_completion(SCpnt, good_sectors, block_sectors);
}


static request_queue_t *sr_find_queue(kdev_t dev)
{
	/*
	 * No such device
	 */
	if (MINOR(dev) >= sr_template.dev_max || !scsi_CDs[MINOR(dev)].device)
		return NULL;

	return &scsi_CDs[MINOR(dev)].device->request_queue;
}

static int sr_scatter_pad(Scsi_Cmnd *SCpnt, int s_size)
{
	struct scatterlist *sg, *old_sg = NULL;
	int i, fsize, bsize, sg_ent;
	char *front, *back;

	back = front = NULL;
	sg_ent = SCpnt->use_sg;
	bsize = 0; /* gcc... */

	/*
	 * need front pad
	 */
	if ((fsize = SCpnt->request.sector % (s_size >> 9))) {
		fsize <<= 9;
		sg_ent++;
		if ((front = scsi_malloc(fsize)) == NULL)
			goto no_mem;
	}
	/*
	 * need a back pad too
	 */
	if ((bsize = s_size - ((SCpnt->request_bufflen + fsize) % s_size))) {
		sg_ent++;
		if ((back = scsi_malloc(bsize)) == NULL)
			goto no_mem;
	}

	/*
	 * extend or allocate new scatter-gather table
	 */
	if (SCpnt->use_sg)
		old_sg = (struct scatterlist *) SCpnt->request_buffer;
	else {
		SCpnt->use_sg = 1;
		sg_ent++;
	}

	SCpnt->sglist_len = ((sg_ent * sizeof(struct scatterlist)) + 511) & ~511;
	if ((sg = scsi_malloc(SCpnt->sglist_len)) == NULL)
		goto no_mem;

	memset(sg, 0, SCpnt->sglist_len);

	i = 0;
	if (fsize) {
		sg[0].address = sg[0].alt_address = front;
		sg[0].length = fsize;
		i++;
	}
	if (old_sg) {
		memcpy(sg + i, old_sg, SCpnt->use_sg * sizeof(struct scatterlist));
		scsi_free(old_sg, ((SCpnt->use_sg * sizeof(struct scatterlist)) + 511) & ~511);
	} else {
		sg[i].address = SCpnt->request_buffer;
		sg[i].length = SCpnt->request_bufflen;
	}

	SCpnt->request_bufflen += (fsize + bsize);
	SCpnt->request_buffer = sg;
	SCpnt->use_sg += i;

	if (bsize) {
		sg[SCpnt->use_sg].address = back;
		sg[SCpnt->use_sg].alt_address = back;
		sg[SCpnt->use_sg].length = bsize;
		SCpnt->use_sg++;
	}

	return 0;

no_mem:
	printk("sr: ran out of mem for scatter pad\n");
	if (front)
		scsi_free(front, fsize);
	if (back)
		scsi_free(back, bsize);

	return 1;
}


static int sr_init_command(Scsi_Cmnd * SCpnt)
{
	int dev, devm, block, this_count, s_size;

	devm = MINOR(SCpnt->request.rq_dev);
	dev = DEVICE_NR(SCpnt->request.rq_dev);

	SCSI_LOG_HLQUEUE(1, printk("Doing sr request, dev = %d, block = %d\n", devm, block));

	if (dev >= sr_template.nr_dev ||
	    !scsi_CDs[dev].device ||
	    !scsi_CDs[dev].device->online) {
		SCSI_LOG_HLQUEUE(2, printk("Finishing %ld sectors\n", SCpnt->request.nr_sectors));
		SCSI_LOG_HLQUEUE(2, printk("Retry with 0x%p\n", SCpnt));
		return 0;
	}
	if (scsi_CDs[dev].device->changed) {
		/*
		 * quietly refuse to do anything to a changed disc until the
		 * changed bit has been reset
		 */
		return 0;
	}

	if ((SCpnt->request.cmd == WRITE) && !scsi_CDs[dev].device->writeable)
		return 0;

	/*
	 * we do lazy blocksize switching (when reading XA sectors,
	 * see CDROMREADMODE2 ioctl) 
	 */
	s_size = scsi_CDs[dev].device->sector_size;
	if (s_size > 2048) {
		if (!in_interrupt())
			sr_set_blocklength(DEVICE_NR(CURRENT->rq_dev), 2048);
		else
			printk("sr: can't switch blocksize: in interrupt\n");
	}

	if (s_size != 512 && s_size != 1024 && s_size != 2048) {
		printk("sr: bad sector size %d\n", s_size);
		return 0;
	}

	block = SCpnt->request.sector / (s_size >> 9);

	/*
	 * request doesn't start on hw block boundary, add scatter pads
	 */
	if ((SCpnt->request.sector % (s_size >> 9)) || (SCpnt->request_bufflen % s_size))
		if (sr_scatter_pad(SCpnt, s_size))
			return 0;

	this_count = (SCpnt->request_bufflen >> 9) / (s_size >> 9);

	switch (SCpnt->request.cmd) {
	case WRITE:
		SCpnt->cmnd[0] = WRITE_10;
		SCpnt->sc_data_direction = SCSI_DATA_WRITE;
		break;
	case READ:
		SCpnt->cmnd[0] = READ_10;
		SCpnt->sc_data_direction = SCSI_DATA_READ;
		break;
	default:
		printk("Unknown sr command %d\n", SCpnt->request.cmd);
		return 0;
	}

	SCSI_LOG_HLQUEUE(2, printk("sr%d : %s %d/%ld 512 byte blocks.\n",
                                   devm,
		   (SCpnt->request.cmd == WRITE) ? "writing" : "reading",
				 this_count, SCpnt->request.nr_sectors));

	SCpnt->cmnd[1] = (SCpnt->lun << 5) & 0xe0;

	if (this_count > 0xffff)
		this_count = 0xffff;

	SCpnt->cmnd[2] = (unsigned char) (block >> 24) & 0xff;
	SCpnt->cmnd[3] = (unsigned char) (block >> 16) & 0xff;
	SCpnt->cmnd[4] = (unsigned char) (block >> 8) & 0xff;
	SCpnt->cmnd[5] = (unsigned char) block & 0xff;
	SCpnt->cmnd[6] = SCpnt->cmnd[9] = 0;
	SCpnt->cmnd[7] = (unsigned char) (this_count >> 8) & 0xff;
	SCpnt->cmnd[8] = (unsigned char) this_count & 0xff;

	/*
	 * We shouldn't disconnect in the middle of a sector, so with a dumb
	 * host adapter, it's safe to assume that we can at least transfer
	 * this many bytes between each connect / disconnect.
	 */
	SCpnt->transfersize = scsi_CDs[dev].device->sector_size;
	SCpnt->underflow = this_count << 9;

	SCpnt->allowed = MAX_RETRIES;
	SCpnt->timeout_per_command = SR_TIMEOUT;

	/*
	 * This is the completion routine we use.  This is matched in terms
	 * of capability to this function.
	 */
	SCpnt->done = rw_intr;

	{
		struct scatterlist *sg = SCpnt->request_buffer;
		int i, size = 0;
		for (i = 0; i < SCpnt->use_sg; i++)
			size += sg[i].length;

		if (size != SCpnt->request_bufflen && SCpnt->use_sg) {
			printk("sr: mismatch count %d, bytes %d\n", size, SCpnt->request_bufflen);
			SCpnt->request_bufflen = size;
		}
	}

	/*
	 * This indicates that the command is ready from our end to be
	 * queued.
	 */
	return 1;
}

static int sr_open(struct cdrom_device_info *cdi, int purpose)