/*
 *  sr.c Copyright (C) 1992 David Giller
 *           Copyright (C) 1993, 1994, 1995 Eric Youngdale
 *
 *  adapted from:
 *      sd.c Copyright (C) 1992 Drew Eckhardt
 *      Linux scsi disk driver by
 *              Drew Eckhardt <drew@colorado.edu>
 *
 *      Modified by Eric Youngdale ericy@cais.com to
 *      add scatter-gather, multiple outstanding request, and other
 *      enhancements.
 *
 *          Modified by Eric Youngdale eric@aib.com to support loadable
 *          low-level scsi drivers.
 *
 *       Modified by Thomas Quinot thomas@melchior.cuivre.fdn.fr to
 *       provide auto-eject.
 *
 *          Modified by Gerd Knorr <kraxel@cs.tu-berlin.de> to support the
 *          generic cdrom interface
 *
 *       Modified by Jens Axboe <axboe@image.dk> - Uniform sr_packet()
 *       interface, capabilities probe additions, ioctl cleanups, etc.
 *
 */

#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 <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 *);

struct Scsi_Device_Template sr_template = {
	NULL, "cdrom", "sr", NULL, TYPE_ROM,
	SCSI_CDROM_MAJOR, 0, 0, 0, 1,
	sr_detect, sr_init,
	sr_finish, sr_attach, sr_detach
};

Scsi_CD *scsi_CDs = NULL;
static int *sr_sizes = NULL;

static int *sr_blocksizes = NULL;

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

void requeue_sr_request(Scsi_Cmnd * SCpnt);
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)].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 =
{
	sr_open,		/* open */
	sr_release,		/* release */
	sr_drive_status,	/* drive status */
	sr_media_change,	/* media changed */
	sr_tray_move,		/* tray move */
	sr_lock_door,		/* lock door */
	sr_select_speed,	/* select speed */
	NULL,			/* select disc */
	sr_get_last_session,	/* get last session */
	sr_get_mcn,		/* get universal product code */
	sr_reset,		/* hard reset */
	sr_audio_ioctl,		/* audio ioctl */
	sr_dev_ioctl,		/* device-specific ioctl */
	CDC_CLOSE_TRAY | CDC_OPEN_TRAY | CDC_LOCK | CDC_SELECT_SPEED |
	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,
	0,
	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)].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->this_count;
	int good_sectors = (result == 0 ? this_count : 0);
	int block_sectors = 0;

#ifdef DEBUG
	printk("sr.c done: %x %x\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];
		int device_nr = DEVICE_NR(SCpnt->request.rq_dev);
		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].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;
	}
	if (good_sectors > 0) {	/* Some sectors were read successfully. */
		if (SCpnt->use_sg == 0) {
			if (SCpnt->buffer != SCpnt->request.buffer) {
				int offset;
				offset = (SCpnt->request.sector % 4) << 9;
				memcpy((char *) SCpnt->request.buffer,
				       (char *) SCpnt->buffer + offset,
				       good_sectors << 9);
				/* Even though we are not using scatter-gather, we look
				 * ahead and see if there is a linked request for the
				 * other half of this buffer.  If there is, then satisfy
				 * it. */
				if ((offset == 0) && good_sectors == 2 &&
				    SCpnt->request.nr_sectors > good_sectors &&
				    SCpnt->request.bh &&
				    SCpnt->request.bh->b_reqnext &&
				    SCpnt->request.bh->b_reqnext->b_size == 1024) {
					memcpy((char *) SCpnt->request.bh->b_reqnext->b_data,
					   (char *) SCpnt->buffer + 1024,
					       1024);
					good_sectors += 2;
				};

				scsi_free(SCpnt->buffer, 2048);
			}
		} else {
			struct scatterlist *sgpnt;
			int i;
			sgpnt = (struct scatterlist *) SCpnt->buffer;
			for (i = 0; i < SCpnt->use_sg; i++) {
				if (sgpnt[i].alt_address) {
					if (sgpnt[i].alt_address != sgpnt[i].address) {
						memcpy(sgpnt[i].alt_address, sgpnt[i].address, sgpnt[i].length);
					};
					scsi_free(sgpnt[i].address, sgpnt[i].length);
				};
			};
			scsi_free(SCpnt->buffer, SCpnt->sglist_len);	/* Free list of scatter-gather pointers */
			if (SCpnt->request.sector % 4)
				good_sectors -= 2;
			/* See   if there is a padding record at the end that needs to be removed */
			if (good_sectors > SCpnt->request.nr_sectors)
				good_sectors -= 2;
		};

#ifdef DEBUG
		printk("(%x %x %x) ", SCpnt->request.bh, SCpnt->request.nr_sectors,
		       good_sectors);
#endif
		if (SCpnt->request.nr_sectors > this_count) {
			SCpnt->request.errors = 0;
			if (!SCpnt->request.bh)
				panic("sr.c: linked page request (%lx %x)",
				      SCpnt->request.sector, this_count);
		}
		SCpnt = end_scsi_request(SCpnt, 1, good_sectors);	/* All done */
		if (result == 0) {
			requeue_sr_request(SCpnt);
			return;
		}
	}
	if (good_sectors == 0) {
		/* We only come through here if no sectors were read successfully. */

		/* Free up any indirection buffers we allocated for DMA purposes. */
		if (SCpnt->use_sg) {
			struct scatterlist *sgpnt;
			int i;
			sgpnt = (struct scatterlist *) SCpnt->buffer;
			for (i = 0; i < SCpnt->use_sg; i++) {
				if (sgpnt[i].alt_address) {
					scsi_free(sgpnt[i].address, sgpnt[i].length);
				}
			}
			scsi_free(SCpnt->buffer, SCpnt->sglist_len);	/* Free list of scatter-gather pointers */
		} else {
			if (SCpnt->buffer != SCpnt->request.buffer)
				scsi_free(SCpnt->buffer, SCpnt->bufflen);
		}

	}
	if (driver_byte(result) != 0) {
		if ((SCpnt->sense_buffer[0] & 0x7f) == 0x70) {
			if ((SCpnt->sense_buffer[2] & 0xf) == UNIT_ATTENTION) {
				/* detected disc change.  set a bit and quietly refuse
				 * further access.    */

				scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].device->changed = 1;
				SCpnt = end_scsi_request(SCpnt, 0, this_count);
				requeue_sr_request(SCpnt);
				return;
			}
		}
		if (SCpnt->sense_buffer[2] == ILLEGAL_REQUEST) {
			printk("sr%d: CD-ROM error: ",
			       DEVICE_NR(SCpnt->request.rq_dev));
			print_sense("sr", SCpnt);
			printk("command was: ");
			print_command(SCpnt->cmnd);
			if (scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].ten) {
				scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].ten = 0;
				requeue_sr_request(SCpnt);
				result = 0;
				return;
			} else {
				SCpnt = end_scsi_request(SCpnt, 0, this_count);
				requeue_sr_request(SCpnt);	/* Do next request */
				return;
			}

		}
		if (SCpnt->sense_buffer[2] == NOT_READY) {
			printk(KERN_INFO "sr%d: CD-ROM not ready.  Make sure you have a disc in the drive.\n",
			       DEVICE_NR(SCpnt->request.rq_dev));
			SCpnt = end_scsi_request(SCpnt, 0, this_count);
			requeue_sr_request(SCpnt);	/* Do next request */
			return;
		}
		if (SCpnt->sense_buffer[2] == MEDIUM_ERROR) {
			printk("scsi%d: MEDIUM ERROR on "
			       "channel %d, id %d, lun %d, CDB: ",
			       SCpnt->host->host_no, (int) SCpnt->channel,
			       (int) SCpnt->target, (int) SCpnt->lun);
			print_command(SCpnt->cmnd);
			print_sense("sr", SCpnt);
			SCpnt = end_scsi_request(SCpnt, 0, block_sectors);
			requeue_sr_request(SCpnt);
			return;
		}
		if (SCpnt->sense_buffer[2] == VOLUME_OVERFLOW) {
			printk("scsi%d: VOLUME OVERFLOW on "
			       "channel %d, id %d, lun %d, CDB: ",
			       SCpnt->host->host_no, (int) SCpnt->channel,
			       (int) SCpnt->target, (int) SCpnt->lun);
			print_command(SCpnt->cmnd);
			print_sense("sr", SCpnt);
			SCpnt = end_scsi_request(SCpnt, 0, block_sectors);
			requeue_sr_request(SCpnt);
			return;
		}
	}
	/* We only get this far if we have an error we have not recognized */
	if (result) {
		printk("SCSI CD error : host %d id %d lun %d return code = %03x\n",
		       scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].device->host->host_no,
		   scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].device->id,
		  scsi_CDs[DEVICE_NR(SCpnt->request.rq_dev)].device->lun,
		       result);

		if (status_byte(result) == CHECK_CONDITION)
			print_sense("sr", SCpnt);

		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.current_nr_sectors);
		requeue_sr_request(SCpnt);
	}
}

static int sr_open(struct cdrom_device_info *cdi, int purpose)
{
	check_disk_change(cdi->dev);

	if (MINOR(cdi->dev) >= sr_template.dev_max
	    || !scsi_CDs[MINOR(cdi->dev)].device) {
		return -ENXIO;	/* No such device */
	}
	/*
	 * If the device is in error recovery, wait until it is done.
	 * If the device is offline, then disallow any access to it.
	 */
	if (!scsi_block_when_processing_errors(scsi_CDs[MINOR(cdi->dev)].device)) {
		return -ENXIO;
	}
	scsi_CDs[MINOR(cdi->dev)].device->access_count++;
	if (scsi_CDs[MINOR(cdi->dev)].device->host->hostt->module)
		__MOD_INC_USE_COUNT(scsi_CDs[MINOR(cdi->dev)].device->host->hostt->module);
	if (sr_template.module)
		__MOD_INC_USE_COUNT(sr_template.module);

	/* If this device did not have media in the drive at boot time, then
	 * we would have been unable to get the sector size.  Check to see if
	 * this is the case, and try again.
	 */

	if (scsi_CDs[MINOR(cdi->dev)].needs_sector_size)
		get_sectorsize(MINOR(cdi->dev));

	return 0;
}

/*
 * do_sr_request() is the request handler function for the sr driver.
 * Its function in life is to take block device requests, and
 * translate them to SCSI commands.
 */

static void do_sr_request(void)
{
	Scsi_Cmnd *SCpnt = NULL;
	struct request *req = NULL;
	Scsi_Device *SDev;
	int flag = 0;

	while (1 == 1) {
		if (CURRENT != NULL && CURRENT->rq_status == RQ_INACTIVE) {
			return;
		};

		INIT_SCSI_REQUEST;

		SDev = scsi_CDs[DEVICE_NR(CURRENT->rq_dev)].device;

		/*
		 * If the host for this device is in error recovery mode, don't
		 * do anything at all here.  When the host leaves error recovery
		 * mode, it will automatically restart things and start queueing
		 * commands again.
		 */
		if (SDev->host->in_recovery) {
			return;
		}
		/*
		 * I am not sure where the best place to do this is.  We need
		 * to hook in a place where we are likely to come if in user
		 * space.
		 */
		if (SDev->was_reset) {
			/*
			 * We need to relock the door, but we might
			 * be in an interrupt handler.  Only do this
			 * from user space, since we do not want to
			 * sleep from an interrupt.
			 */
			if (SDev->removable && !in_interrupt()) {
				spin_unlock_irq(&io_request_lock);	/* FIXME!!!! */
				scsi_ioctl(SDev, SCSI_IOCTL_DOORLOCK, 0);
				spin_lock_irq(&io_request_lock);	/* FIXME!!!! */
				/* scsi_ioctl may allow CURRENT to change, so start over. */
				SDev->was_reset = 0;
				continue;
			}
			SDev->was_reset = 0;
		}
		/* we do lazy blocksize switching (when reading XA sectors,
		 * see CDROMREADMODE2 ioctl) */
		if (scsi_CDs[DEVICE_NR(CURRENT->rq_dev)].sector_size > 2048) {
			if (!in_interrupt())
				sr_set_blocklength(DEVICE_NR(CURRENT->rq_dev), 2048);
#if 1
			else
				printk("sr: can't switch blocksize: in interrupt\n");
#endif
		}
		if (flag++ == 0)
			SCpnt = scsi_allocate_device(&CURRENT,
			 scsi_CDs[DEVICE_NR(CURRENT->rq_dev)].device, 0);
		else
			SCpnt = NULL;

		/* This is a performance enhancement.  We dig down into the request list and
		 * try to find a queueable request (i.e. device not busy, and host able to
		 * accept another command.  If we find one, then we queue it. This can
		 * make a big difference on systems with more than one disk drive.  We want
		 * to have the interrupts off when monkeying with the request list, because
		 * otherwise the kernel might try to slip in a request in between somewhere. */

		if (!SCpnt && sr_template.nr_dev > 1) {
			struct request *req1;
			req1 = NULL;
			req = CURRENT;
			while (req) {
				SCpnt = scsi_request_queueable(req,
				scsi_CDs[DEVICE_NR(req->rq_dev)].device);
				if (SCpnt)
					break;
				req1 = req;
				req = req->next;
			}
			if (SCpnt && req->rq_status == RQ_INACTIVE) {
				if (req == CURRENT)
					CURRENT = CURRENT->next;
				else
					req1->next = req->next;
			}
		}
		if (!SCpnt)
			return;	/* Could not find anything to do */

		wake_up(&wait_for_request);

		/* Queue command */
		requeue_sr_request(SCpnt);
	}			/* While */
}

void requeue_sr_request(Scsi_Cmnd * SCpnt)
{
	unsigned int dev, block, realcount;
	unsigned char cmd[10], *buffer, tries;
	int this_count, start, end_rec;

	tries = 2;

repeat:
	if (!SCpnt || SCpnt->request.rq_status == RQ_INACTIVE) {
		do_sr_request();
		return;
	}
	dev = MINOR(SCpnt->request.rq_dev);
	block = SCpnt->request.sector;
	buffer = NULL;
	this_count = 0;

	if (dev >= sr_template.nr_dev) {
		/* printk("CD-ROM request error: invalid device.\n");                   */
		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
		tries = 2;
		goto repeat;
	}
	if (!scsi_CDs[dev].use) {
		/* printk("CD-ROM request error: device marked not in use.\n");         */
		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
		tries = 2;
		goto repeat;
	}
	if (!scsi_CDs[dev].device->online) {
		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
		tries = 2;
		goto repeat;
	}
	if (scsi_CDs[dev].device->changed) {
		/*
		 * quietly refuse to do anything to a changed disc
		 * until the changed bit has been reset
		 */
		/* printk("CD-ROM has been changed.  Prohibiting further I/O.\n");      */
		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
		tries = 2;
		goto repeat;
	}
	switch (SCpnt->request.cmd) {
	case WRITE:
		SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
		goto repeat;
		break;
	case READ:
		cmd[0] = READ_6;
		break;
	default:
		panic("Unknown sr command %d\n", SCpnt->request.cmd);
	}

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

	/*
	 * Now do the grungy work of figuring out which sectors we need, and
	 * where in memory we are going to put them.
	 *
	 * The variables we need are:
	 *
	 * this_count= number of 512 byte sectors being read
	 * block     = starting cdrom sector to read.
	 * realcount = # of cdrom sectors to read
	 *
	 * The major difference between a scsi disk and a scsi cdrom
	 * is that we will always use scatter-gather if we can, because we can
	 * work around the fact that the buffer cache has a block size of 1024,
	 * and we have 2048 byte sectors.  This code should work for buffers that
	 * are any multiple of 512 bytes long.
	 */

	SCpnt->use_sg = 0;

	if (SCpnt->host->sg_tablesize > 0 &&
	    (!scsi_need_isa_buffer ||
	     scsi_dma_free_sectors >= 10)) {
		struct buffer_head *bh;
		struct scatterlist *sgpnt;
		int count, this_count_max;
		bh = SCpnt->request.bh;
		this_count = 0;
		count = 0;
		this_count_max = (scsi_CDs[dev].ten ? 0xffff : 0xff) << 4;
		/* Calculate how many links we can use.  First see if we need
		 * a padding record at the start */
		this_count = SCpnt->request.sector % 4;
		if (this_count)
			count++;
		while (bh && count < SCpnt->host->sg_tablesize) {
			if ((this_count + (bh->b_size >> 9)) > this_count_max)
				break;
			this_count += (bh->b_size >> 9);
			count++;
			bh = bh->b_reqnext;
		};
		/* Fix up in case of an odd record at the end */
		end_rec = 0;
		if (this_count % 4) {
			if (count < SCpnt->host->sg_tablesize) {
				count++;
				end_rec = (4 - (this_count % 4)) << 9;
				this_count += 4 - (this_count % 4);
			} else {
				count--;
				this_count -= (this_count % 4);
			};
		};
		SCpnt->use_sg = count;	/* Number of chains */
		/* scsi_malloc can only allocate in chunks of 512 bytes */
		count = (SCpnt->use_sg * sizeof(struct scatterlist) + 511) & ~511;

		SCpnt->sglist_len = count;
		sgpnt = (struct scatterlist *) scsi_malloc(count);
		if (!sgpnt) {
			printk("Warning - running *really* short on DMA buffers\n");
			SCpnt->use_sg = 0;	/* No memory left - bail out */
		} else {
			buffer = (unsigned char *) sgpnt;
			count = 0;
			bh = SCpnt->request.bh;
			if (SCpnt->request.sector % 4) {
				sgpnt[count].length = (SCpnt->request.sector % 4) << 9;
				sgpnt[count].address = (char *) scsi_malloc(sgpnt[count].length);
				if (!sgpnt[count].address)
					panic("SCSI DMA pool exhausted.");
				sgpnt[count].alt_address = sgpnt[count].address;	/* Flag to delete
											   if needed */
				count++;
			};
			for (bh = SCpnt->request.bh; count < SCpnt->use_sg;
			     count++, bh = bh->b_reqnext) {
				if (bh) {	/* Need a placeholder at the end of the record? */
					sgpnt[count].address = bh->b_data;
					sgpnt[count].length = bh->b_size;
					sgpnt[count].alt_address = NULL;
				} else {
					sgpnt[count].address = (char *) scsi_malloc(end_rec);
					if (!sgpnt[count].address)
						panic("SCSI DMA pool exhausted.");
					sgpnt[count].length = end_rec;
					sgpnt[count].alt_address = sgpnt[count].address;
					if (count + 1 != SCpnt->use_sg)
						panic("Bad sr request list");
					break;
				};
				if (virt_to_phys(sgpnt[count].address) + sgpnt[count].length - 1 >
				    ISA_DMA_THRESHOLD && SCpnt->host->unchecked_isa_dma) {
					sgpnt[count].alt_address = sgpnt[count].address;
					/* We try to avoid exhausting the DMA pool, since it is easier
					 * to control usage here.  In other places we might have a more
					 * pressing need, and we would be screwed if we ran out */
					if (scsi_dma_free_sectors < (sgpnt[count].length >> 9) + 5) {
						sgpnt[count].address = NULL;
					} else {
						sgpnt[count].address = (char *) scsi_malloc(sgpnt[count].length);
					};
					/* If we start running low on DMA buffers, we abort the scatter-gather
					 * operation, and free all of the memory we have allocated.  We want to
					 * ensure that all scsi operations are able to do at least a non-scatter/gather
					 * operation */
					if (sgpnt[count].address == NULL) {	/* Out of dma memory */
						printk("Warning: Running low on SCSI DMA buffers\n");
						/* Try switching back to a non scatter-gather operation. */
						while (--count >= 0) {
							if (sgpnt[count].alt_address)
								scsi_free(sgpnt[count].address, sgpnt[count].length);
						};
						SCpnt->use_sg = 0;
						scsi_free(buffer, SCpnt->sglist_len);
						break;
					};	/* if address == NULL */
				};	/* if need DMA fixup */
			};	/* for loop to fill list */
#ifdef DEBUG
			printk("SR: %d %d %d %d %d *** ", SCpnt->use_sg, SCpnt->request.sector,
			       this_count,
			       SCpnt->request.current_nr_sectors,
			       SCpnt->request.nr_sectors);
			for (count = 0; count < SCpnt->use_sg; count++)
				printk("SGlist: %d %x %x %x\n", count,
				       sgpnt[count].address,
				       sgpnt[count].alt_address,
				       sgpnt[count].length);
#endif
		};		/* Able to allocate scatter-gather list */
	};

	if (SCpnt->use_sg == 0) {
		/* We cannot use scatter-gather.  Do this the old fashion way */
		if (!SCpnt->request.bh)
			this_count = SCpnt->request.nr_sectors;
		else
			this_count = (SCpnt->request.bh->b_size >> 9);

		start = block % 4;
		if (start) {
			this_count = ((this_count > 4 - start) ?
				      (4 - start) : (this_count));
			buffer = (unsigned char *) scsi_malloc(2048);
		} else if (this_count < 4) {
			buffer = (unsigned char *) scsi_malloc(2048);
		} else {
			this_count -= this_count % 4;
			buffer = (unsigned char *) SCpnt->request.buffer;
			if (virt_to_phys(buffer) + (this_count << 9) > ISA_DMA_THRESHOLD &&
			    SCpnt->host->unchecked_isa_dma)
				buffer = (unsigned char *) scsi_malloc(this_count << 9);
		}
	};

	if (scsi_CDs[dev].sector_size == 2048)
		block = block >> 2;	/* These are the sectors that the cdrom uses */
	else
		block = block & 0xfffffffc;

	realcount = (this_count + 3) / 4;

	if (scsi_CDs[dev].sector_size == 512)
		realcount = realcount << 2;

	/*
	 * Note: The scsi standard says that READ_6 is *optional*, while
	 * READ_10 is mandatory.   Thus there is no point in using
	 * READ_6.
	 */
	if (scsi_CDs[dev].ten) {
		if (realcount > 0xffff) {
			realcount = 0xffff;
			this_count = realcount * (scsi_CDs[dev].sector_size >> 9);
		}
		cmd[0] += READ_10 - READ_6;
		cmd[2] = (unsigned char) (block >> 24) & 0xff;
		cmd[3] = (unsigned char) (block >> 16) & 0xff;
		cmd[4] = (unsigned char) (block >> 8) & 0xff;
		cmd[5] = (unsigned char) block & 0xff;
		cmd[6] = cmd[9] = 0;
		cmd[7] = (unsigned char) (realcount >> 8) & 0xff;
		cmd[8] = (unsigned char) realcount & 0xff;
	} else {
		if (realcount > 0xff) {
			realcount = 0xff;
			this_count = realcount * (scsi_CDs[dev].sector_size >> 9);
		}
		cmd[1] |= (unsigned char) ((block >> 16) & 0x1f);
		cmd[2] = (unsigned char) ((block >> 8) & 0xff);
		cmd[3] = (unsigned char) block & 0xff;
		cmd[4] = (unsigned char) realcount;
		cmd[5] = 0;
	}

#ifdef DEBUG
	{
		int i;
		printk("ReadCD: %d %d %d %d\n", block, realcount, buffer, this_count);
		printk("Use sg: %d\n", SCpnt->use_sg);
		printk("Dumping command: ");
		for (i = 0; i < 12; i++)
			printk("%2.2x ", cmd[i]);
		printk("\n");
	};
#endif

	/* Some dumb host adapters can speed transfers by knowing the
	 * minimum transfersize in advance.
	 *
	 * We shouldn't disconnect in the middle of a sector, but the cdrom
	 * sector size can be larger than the size of a buffer and the
	 * transfer may be split to the size of a buffer.  So it's safe to
	 * assume that we can at least transfer the minimum of the buffer
	 * size (1024) and the sector size between each connect / disconnect.
	 */

	SCpnt->transfersize = (scsi_CDs[dev].sector_size > 1024) ?
	    1024 : scsi_CDs[dev].sector_size;

	SCpnt->this_count = this_count;
	scsi_do_cmd(SCpnt, (void *) cmd, buffer,
		    realcount * scsi_CDs[dev].sector_size,
		    rw_intr, SR_TIMEOUT, MAX_RETRIES);
}

static int sr_detect(Scsi_Device * SDp)
{

	if (SDp->type != TYPE_ROM && SDp->type != TYPE_WORM)
		return 0;

	printk("Detected scsi CD-ROM sr%d at scsi%d, channel %d, id %d, lun %d\n",
	       sr_template.dev_noticed++,
	       SDp->host->host_no, SDp->channel, SDp->id, SDp->lun);

	return 1;
}

static int sr_attach(Scsi_Device * SDp)
{
	Scsi_CD *cpnt;
	int i;

	if (SDp->type != TYPE_ROM && SDp->type != TYPE_WORM)
		return 1;

	if (sr_template.nr_dev >= sr_template.dev_max) {
		SDp->attached--;
		return 1;
	}
	for (cpnt = scsi_CDs, i = 0; i < sr_template.dev_max; i++, cpnt++)
		if (!cpnt->device)
			break;

	if (i >= sr_template.dev_max)
		panic("scsi_devices corrupt (sr)");

	SDp->scsi_request_fn = do_sr_request;
	scsi_CDs[i].device = SDp;

	sr_template.nr_dev++;
	if (sr_template.nr_dev > sr_template.dev_max)
		panic("scsi_devices corrupt (sr)");
	return 0;
}


static void sr_init_done(Scsi_Cmnd * SCpnt)
{
	struct request *req;

	req = &SCpnt->request;
	req->rq_status = RQ_SCSI_DONE;	/* Busy, but indicate request done */

	if (req->sem != NULL) {
		up(req->sem);
	}
}

void get_sectorsize(int i)
{
	unsigned char cmd[10];
	unsigned char *buffer;
	int the_result, retries;
	Scsi_Cmnd *SCpnt;
	unsigned long flags;

	buffer = (unsigned char *) scsi_malloc(512);
	SCpnt = scsi_allocate_device(NULL, scsi_CDs[i].device, 1);

	retries = 3;
	do {
		cmd[0] = READ_CAPACITY;
		cmd[1] = (scsi_CDs[i].device->lun << 5) & 0xe0;
		memset((void *) &cmd[2], 0, 8);
		SCpnt->request.rq_status = RQ_SCSI_BUSY;	/* Mark as really busy */
		SCpnt->cmd_len = 0;

		memset(buffer, 0, 8);

		/* Do the command and wait.. */
		{
			DECLARE_MUTEX_LOCKED(sem);
			SCpnt->request.sem = &sem;
			spin_lock_irqsave(&io_request_lock, flags);
			scsi_do_cmd(SCpnt,
				    (void *) cmd, (void *) buffer,
				    512, sr_init_done, SR_TIMEOUT,
				    MAX_RETRIES);
			spin_unlock_irqrestore(&io_request_lock, flags);
			down(&sem);
		}

		the_result = SCpnt->result;
		retries--;

	} while (the_result && retries);


	wake_up(&SCpnt->device->device_wait);
	scsi_release_command(SCpnt);
	SCpnt = NULL;

	if (the_result) {
		scsi_CDs[i].capacity = 0x1fffff;
		scsi_CDs[i].sector_size = 2048;		/* A guess, just in case */
		scsi_CDs[i].needs_sector_size = 1;
	} else {
#if 0
		if (cdrom_get_last_written(MKDEV(MAJOR_NR, i),
					 (long *) &scsi_CDs[i].capacity))
#endif
			scsi_CDs[i].capacity = 1 + ((buffer[0] << 24) |
						    (buffer[1] << 16) |
						    (buffer[2] << 8) |
						    buffer[3]);
		scsi_CDs[i].sector_size = (buffer[4] << 24) |
		    (buffer[5] << 16) | (buffer[6] << 8) | buffer[7];
		switch (scsi_CDs[i].sector_size) {
			/*
			 * HP 4020i CD-Recorder reports 2340 byte sectors
			 * Philips CD-Writers report 2352 byte sectors
			 *
			 * Use 2k sectors for them..
			 */
		case 0:
		case 2340:
		case 2352:
			scsi_CDs[i].sector_size = 2048;
			/* fall through */
		case 2048:
			scsi_CDs[i].capacity *= 4;
			/* fall through */
		case 512:
			break;
		default:
			printk("sr%d: unsupported sector size %d.\n",
			       i, scsi_CDs[i].sector_size);
			scsi_CDs[i].capacity = 0;
			scsi_CDs[i].needs_sector_size = 1;
		}

		/*
		 * Add this so that we have the ability to correctly gauge
		 * what the device is capable of.
		 */
		scsi_CDs[i].needs_sector_size = 0;
		sr_sizes[i] = scsi_CDs[i].capacity >> (BLOCK_SIZE_BITS - 9);
	};
	scsi_free(buffer, 512);
}

void get_capabilities(int i)
{
	unsigned char cmd[6];
	unsigned char *buffer;
	int rc, n;

	static char *loadmech[] =
	{
		"caddy",
		"tray",
		"pop-up",
		"",
		"changer",
		"changer",
		"",
		""
	};

	buffer = (unsigned char *) scsi_malloc(512);
	cmd[0] = MODE_SENSE;
	cmd[1] = (scsi_CDs[i].device->lun << 5) & 0xe0;
	cmd[2] = 0x2a;
	cmd[4] = 128;
	cmd[3] = cmd[5] = 0;
	rc = sr_do_ioctl(i, cmd, buffer, 128, 1);

	if (-EINVAL == rc) {
		/* failed, drive has'nt this mode page */
		scsi_CDs[i].cdi.speed = 1;
		/* disable speed select, drive probably can't do this either */
		scsi_CDs[i].cdi.mask |= CDC_SELECT_SPEED;
		scsi_free(buffer, 512);
		return;
	}
	n = buffer[3] + 4;
	scsi_CDs[i].cdi.speed = ((buffer[n + 8] << 8) + buffer[n + 9]) / 176;
	scsi_CDs[i].readcd_known = 1;
	scsi_CDs[i].readcd_cdda = buffer[n + 5] & 0x01;
	/* print some capability bits */
	printk("sr%i: scsi3-mmc drive: %dx/%dx %s%s%s%s%s\n", i,
	       ((buffer[n + 14] << 8) + buffer[n + 15]) / 176,
	       scsi_CDs[i].cdi.speed,
	       buffer[n + 3] & 0x01 ? "writer " : "",	/* CD Writer */
	       buffer[n + 2] & 0x02 ? "cd/rw " : "",	/* can read rewriteable */
	       buffer[n + 4] & 0x20 ? "xa/form2 " : "",		/* can read xa/from2 */
	       buffer[n + 5] & 0x01 ? "cdda " : "",	/* can read audio data */
	       loadmech[buffer[n + 6] >> 5]);
	if ((buffer[n + 6] >> 5) == 0)
		/* caddy drives can't close tray... */
		scsi_CDs[i].cdi.mask |= CDC_CLOSE_TRAY;
	if ((buffer[n + 2] & 0x8) == 0)
		/* not a DVD drive */
		scsi_CDs[i].cdi.mask |= CDC_DVD;
	if ((buffer[n + 3] & 0x20) == 0)
		/* can't write DVD-RAM media */
		scsi_CDs[i].cdi.mask |= CDC_DVD_RAM;
	if ((buffer[n + 3] & 0x10) == 0)
		/* can't write DVD-R media */
		scsi_CDs[i].cdi.mask |= CDC_DVD_R;
	if ((buffer[n + 3] & 0x2) == 0)
		/* can't write CD-RW media */
		scsi_CDs[i].cdi.mask |= CDC_CD_RW;
	if ((buffer[n + 3] & 0x1) == 0)
		/* can't write CD-R media */
		scsi_CDs[i].cdi.mask |= CDC_CD_R;

	scsi_free(buffer, 512);
}

/*
 * sr_packet() is the entry point for the generic commands generated
 * by the Uniform CD-ROM layer. 
 */
static int sr_packet(struct cdrom_device_info *cdi, struct cdrom_generic_command *cgc)
{
	Scsi_Cmnd *SCpnt;
	Scsi_Device *device = scsi_CDs[MINOR(cdi->dev)].device;
	DECLARE_MUTEX_LOCKED(sem);
	unsigned long flags;
	int stat;

	/* get the device */
	SCpnt = scsi_allocate_device(NULL, device, 1);
	if (SCpnt == NULL)
		return -ENODEV;	/* this just doesn't seem right /axboe */

	/* set the LUN */
	cgc->cmd[1] |= device->lun << 5;

	/* do the locking and issue the command */
	SCpnt->request.rq_dev = cdi->dev;
	SCpnt->request.rq_status = RQ_SCSI_BUSY;
	/* scsi_do_cmd sets the command length */
	SCpnt->cmd_len = 0;
	SCpnt->request.sem = &sem;
	spin_lock_irqsave(&io_request_lock, flags);
	scsi_do_cmd(SCpnt, (void *) cgc->cmd, (void *) cgc->buffer, cgc->buflen,
		    sr_init_done, SR_TIMEOUT, MAX_RETRIES);
	spin_unlock_irqrestore(&io_request_lock, flags);
	down(&sem);

	stat = SCpnt->result;

	/* release */
	SCpnt->request.rq_dev = MKDEV(0, 0);
	scsi_release_command(SCpnt);
	SCpnt = NULL;

	return stat;
}

static int sr_registered = 0;

static int sr_init()
{
	int i;

	if (sr_template.dev_noticed == 0)
		return 0;

	if (!sr_registered) {
		if (register_blkdev(MAJOR_NR, "sr", &cdrom_fops)) {
			printk("Unable to get major %d for SCSI-CD\n", MAJOR_NR);
			return 1;
		}
		sr_registered++;
	}
	if (scsi_CDs)
		return 0;
	sr_template.dev_max =
	    sr_template.dev_noticed + SR_EXTRA_DEVS;
	scsi_CDs = (Scsi_CD *) scsi_init_malloc(sr_template.dev_max * sizeof(Scsi_CD), GFP_ATOMIC);
	memset(scsi_CDs, 0, sr_template.dev_max * sizeof(Scsi_CD));

	sr_sizes = (int *) scsi_init_malloc(sr_template.dev_max * sizeof(int), GFP_ATOMIC);
	memset(sr_sizes, 0, sr_template.dev_max * sizeof(int));

	sr_blocksizes = (int *) scsi_init_malloc(sr_template.dev_max *
						 sizeof(int), GFP_ATOMIC);

	/*
	 * These are good guesses for the time being.
	 */
	for (i = 0; i < sr_template.dev_max; i++)
		sr_blocksizes[i] = 2048;
	blksize_size[MAJOR_NR] = sr_blocksizes;
	return 0;
}

void sr_finish()
{
	int i;
	char name[6];

	blk_dev[MAJOR_NR].request_fn = DEVICE_REQUEST;
	blk_size[MAJOR_NR] = sr_sizes;

	for (i = 0; i < sr_template.nr_dev; ++i) {
		/* If we have already seen this, then skip it.  Comes up
		 * with loadable modules. */
		if (scsi_CDs[i].capacity)
			continue;
		scsi_CDs[i].capacity = 0x1fffff;
		scsi_CDs[i].sector_size = 2048;		/* A guess, just in case */
		scsi_CDs[i].needs_sector_size = 1;
		scsi_CDs[i].device->changed = 1;	/* force recheck CD type */
#if 0
		/* seems better to leave this for later */
		get_sectorsize(i);
		printk("Scd sectorsize = %d bytes.\n", scsi_CDs[i].sector_size);
#endif
		scsi_CDs[i].use = 1;
		scsi_CDs[i].ten = 1;
		scsi_CDs[i].remap = 1;
		scsi_CDs[i].readcd_known = 0;
		scsi_CDs[i].readcd_cdda = 0;
		sr_sizes[i] = scsi_CDs[i].capacity >> (BLOCK_SIZE_BITS - 9);

		scsi_CDs[i].cdi.ops = &sr_dops;
		scsi_CDs[i].cdi.handle = &scsi_CDs[i];
		scsi_CDs[i].cdi.dev = MKDEV(MAJOR_NR, i);
		scsi_CDs[i].cdi.mask = 0;
		scsi_CDs[i].cdi.capacity = 1;
		get_capabilities(i);
		sr_vendor_init(i);

		sprintf(name, "sr%d", i);
		strcpy(scsi_CDs[i].cdi.name, name);
		register_cdrom(&scsi_CDs[i].cdi);
	}


	/* If our host adapter is capable of scatter-gather, then we increase
	 * the read-ahead to 16 blocks (32 sectors).  If not, we use
	 * a two block (4 sector) read ahead. */
	if (scsi_CDs[0].device && scsi_CDs[0].device->host->sg_tablesize)
		read_ahead[MAJOR_NR] = 32;	/* 32 sector read-ahead.  Always removable. */
	else
		read_ahead[MAJOR_NR] = 4;	/* 4 sector read-ahead */

	return;
}

static void sr_detach(Scsi_Device * SDp)
{
	Scsi_CD *cpnt;
	int i;

	for (cpnt = scsi_CDs, i = 0; i < sr_template.dev_max; i++, cpnt++)
		if (cpnt->device == SDp) {
			kdev_t devi = MKDEV(MAJOR_NR, i);
			struct super_block *sb = get_super(devi);

			/*
			 * Since the cdrom is read-only, no need to sync the device.
			 * We should be kind to our buffer cache, however.
			 */
			if (sb)
				invalidate_inodes(sb);
			invalidate_buffers(devi);

			/*
			 * Reset things back to a sane state so that one can re-load a new
			 * driver (perhaps the same one).
			 */
			unregister_cdrom(&(cpnt->cdi));
			cpnt->device = NULL;
			cpnt->capacity = 0;
			SDp->attached--;
			sr_template.nr_dev--;
			sr_template.dev_noticed--;
			sr_sizes[i] = 0;
			return;
		}
	return;
}


#ifdef MODULE

int init_module(void)
{
	sr_template.module = &__this_module;
	return scsi_register_module(MODULE_SCSI_DEV, &sr_template);
}

void cleanup_module(void)
{
	scsi_unregister_module(MODULE_SCSI_DEV, &sr_template);
	unregister_blkdev(MAJOR_NR, "sr");
	sr_registered--;
	if (scsi_CDs != NULL) {
		scsi_init_free((char *) scsi_CDs,
			       (sr_template.dev_noticed + SR_EXTRA_DEVS)
			       * sizeof(Scsi_CD));

		scsi_init_free((char *) sr_sizes, sr_template.dev_max * sizeof(int));
		sr_sizes = NULL;

		scsi_init_free((char *) sr_blocksizes, sr_template.dev_max * sizeof(int));
		sr_blocksizes = NULL;
	}
	blksize_size[MAJOR_NR] = NULL;
	blk_dev[MAJOR_NR].request_fn = NULL;
	blk_size[MAJOR_NR] = NULL;
	read_ahead[MAJOR_NR] = 0;

	sr_template.dev_max = 0;
}

#endif				/* MODULE */

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-indent-level: 4
 * c-brace-imaginary-offset: 0
 * c-brace-offset: -4
 * c-argdecl-indent: 4
 * c-label-offset: -4
 * c-continued-statement-offset: 4
 * c-continued-brace-offset: 0
 * indent-tabs-mode: nil
 * tab-width: 8
 * End:
 */