Import 2.3.18pre1

[davej-history.git] / drivers / scsi / sr.c

/*
 *  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:
 */