Import 2.1.118

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

/*
 *      sd.c Copyright (C) 1992 Drew Eckhardt
 *           Copyright (C) 1993, 1994, 1995 Eric Youngdale
 *
 *      Linux scsi disk driver
 *              Initial versions: Drew Eckhardt
 *              Subsequent revisions: Eric Youngdale
 *
 *      <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.
 */

#include <linux/module.h>
#ifdef MODULE
/*
 * This is a variable in scsi.c that is set when we are processing something
 * after boot time.  By definition, this is true when we are a loadable module
 * ourselves.
 */
#define MODULE_FLAG 1
#else
#define MODULE_FLAG scsi_loadable_module_flag
#endif /* MODULE */

#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/interrupt.h>

#include <linux/smp.h>

#include <asm/system.h>
#include <asm/io.h>

#define MAJOR_NR SCSI_DISK_MAJOR
#include <linux/blk.h>
#include "scsi.h"
#include "hosts.h"
#include "sd.h"
#include <scsi/scsi_ioctl.h>
#include "constants.h"

#include <linux/genhd.h>

/*
 *  static const char RCSid[] = "$Header:";
 */

#define MAX_RETRIES 5

/*
 *  Time out in seconds for disks and Magneto-opticals (which are slower).
 */

#define SD_TIMEOUT (15 * HZ)
#define SD_MOD_TIMEOUT (75 * HZ)

#define CLUSTERABLE_DEVICE(SC) (SC->host->use_clustering && \
                                SC->device->type != TYPE_MOD)

struct hd_struct * sd;

Scsi_Disk * rscsi_disks = NULL;
static int * sd_sizes;
static int * sd_blocksizes;
static int * sd_hardsizes;              /* Hardware sector size */

extern int sd_ioctl(struct inode *, struct file *, unsigned int, unsigned long);

static int check_scsidisk_media_change(kdev_t);
static int fop_revalidate_scsidisk(kdev_t);

static int sd_init_onedisk(int);

static void requeue_sd_request (Scsi_Cmnd * SCpnt);

static int sd_init(void);
static void sd_finish(void);
static int sd_attach(Scsi_Device *);
static int sd_detect(Scsi_Device *);
static void sd_detach(Scsi_Device *);

static void sd_devname(unsigned int disknum, char * buffer)
{
    if( disknum <= 26 )
    {
        sprintf(buffer, "sd%c", 'a' + disknum);
    }
    else
    {
        unsigned int min1;
        unsigned int min2;
        /*
         * For larger numbers of disks, we need to go to a new
         * naming scheme.
         */
        min1 = disknum / 26;
        min2 = disknum % 26;
        sprintf(buffer, "sd%c%c", 'a' + min1, 'a' + min2);
    }
}

struct Scsi_Device_Template sd_template =
{ NULL, "disk", "sd", NULL, TYPE_DISK,
      SCSI_DISK_MAJOR, 0, 0, 0, 1,
      sd_detect, sd_init,
      sd_finish, sd_attach, sd_detach
};

static int sd_open(struct inode * inode, struct file * filp)
{
    int target;
    target =  DEVICE_NR(inode->i_rdev);

    SCSI_LOG_HLQUEUE(1,printk("target=%d, max=%d\n", target, sd_template.dev_max));

    if(target >= sd_template.dev_max || !rscsi_disks[target].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(rscsi_disks[target].device) )
      {
        return -ENXIO;
      }

    /*
     * Make sure that only one process can do a check_change_disk at one time.
     * This is also used to lock out further access when the partition table
     * is being re-read.
     */

    while (rscsi_disks[target].device->busy)
        barrier();
    if(rscsi_disks[target].device->removable) {
        check_disk_change(inode->i_rdev);

        /*
         * If the drive is empty, just let the open fail.
         */
        if ( !rscsi_disks[target].ready )
            return -ENXIO;

        /*
         * Similarly, if the device has the write protect tab set,
         * have the open fail if the user expects to be able to write
         * to the thing.
         */
        if ( (rscsi_disks[target].write_prot) && (filp->f_mode & 2) )
            return -EROFS;
    }

    /*
     * It is possible that the disk changing stuff resulted in the device being taken
     * offline.  If this is the case, report this to the user, and don't pretend that
     * the open actually succeeded.
     */
    if( !rscsi_disks[target].device->online )
    {
        return -ENXIO;
    }

    /*
     * See if we are requesting a non-existent partition.  Do this
     * after checking for disk change.
     */
    if(sd_sizes[MINOR(inode->i_rdev)] == 0)
        return -ENXIO;

    if(rscsi_disks[target].device->removable)
        if(!rscsi_disks[target].device->access_count)
            sd_ioctl(inode, NULL, SCSI_IOCTL_DOORLOCK, 0);

    rscsi_disks[target].device->access_count++;
    if (rscsi_disks[target].device->host->hostt->module)
        __MOD_INC_USE_COUNT(rscsi_disks[target].device->host->hostt->module);
    if(sd_template.module)
        __MOD_INC_USE_COUNT(sd_template.module);
    return 0;
}

static int sd_release(struct inode * inode, struct file * file)
{
    int target;
    fsync_dev(inode->i_rdev);

    target =  DEVICE_NR(inode->i_rdev);

    rscsi_disks[target].device->access_count--;

    if(rscsi_disks[target].device->removable) {
        if(!rscsi_disks[target].device->access_count)
            sd_ioctl(inode, NULL, SCSI_IOCTL_DOORUNLOCK, 0);
    }

    if(rscsi_disks[target].device->host->hostt->module)
        __MOD_DEC_USE_COUNT(rscsi_disks[target].device->host->hostt->module);
    if(sd_template.module)
        __MOD_DEC_USE_COUNT(sd_template.module);
    return 0;
}

static void sd_geninit(struct gendisk *);

static struct file_operations sd_fops = {
    NULL,                        /* lseek - default */
    block_read,                  /* read - general block-dev read */
    block_write,                 /* write - general block-dev write */
    NULL,                        /* readdir - bad */
    NULL,                        /* select */
    sd_ioctl,                    /* ioctl */
    NULL,                        /* mmap */
    sd_open,                     /* open code */
    NULL,                        /* flush */
    sd_release,                  /* release */
    block_fsync,                 /* fsync */
    NULL,                        /* fasync */
    check_scsidisk_media_change, /* Disk change */
    fop_revalidate_scsidisk      /* revalidate */
};

static struct gendisk sd_gendisk = {
    MAJOR_NR,                    /* Major number */
    "sd",                        /* Major name */
    4,                           /* Bits to shift to get real from partition */
    1 << 4,                      /* Number of partitions per real */
    0,                           /* maximum number of real */
    sd_geninit,                  /* init function */
    NULL,                        /* hd struct */
    NULL,                        /* block sizes */
    0,                           /* number */
    NULL,                        /* internal */
    NULL                         /* next */
};

static void sd_geninit (struct gendisk *ignored)
{
    int i;

    for (i = 0; i < sd_template.dev_max; ++i)
        if(rscsi_disks[i].device)
            sd[i << 4].nr_sects = rscsi_disks[i].capacity;
#if 0
    /* No longer needed - we keep track of this as we attach/detach */
    sd_gendisk.nr_real = sd_template.dev_max;
#endif
}

/*
 * 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 one of several actions based on success or failure.
 */

static void rw_intr (Scsi_Cmnd *SCpnt)
{
    int result = SCpnt->result;
    char nbuff[6];
    int this_count = SCpnt->bufflen >> 9;
    int good_sectors = (result == 0 ? this_count : 0);
    int block_sectors = 1;

    sd_devname(MINOR(SCpnt->request.rq_dev) >> 4, nbuff);

    SCSI_LOG_HLCOMPLETE(1,printk("%s : rw_intr(%d, %x [%x %x])\n", nbuff,
           SCpnt->host->host_no, 
                                 result, 
                                 SCpnt->sense_buffer[0],
                                 SCpnt->sense_buffer[2]));

    /*
      Handle MEDIUM ERRORs 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)
      {
        long error_sector = (SCpnt->sense_buffer[3] << 24) |
                            (SCpnt->sense_buffer[4] << 16) |
                            (SCpnt->sense_buffer[5] << 8) |
                            SCpnt->sense_buffer[6];
        int sector_size =
          rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].sector_size;
        if (SCpnt->request.bh != NULL)
          block_sectors = SCpnt->request.bh->b_size >> 9;
        if (sector_size == 1024)
          {
            error_sector <<= 1;
            if (block_sectors < 2) block_sectors = 2;
          }
        else if (sector_size == 2048)
          {
            error_sector <<= 2;
            if (block_sectors < 4) block_sectors = 4;
          }
        else if (sector_size == 256)
          error_sector >>= 1;
        error_sector -= sd[MINOR(SCpnt->request.rq_dev)].start_sect;
        error_sector &= ~ (block_sectors - 1);
        good_sectors = error_sector - SCpnt->request.sector;
        if (good_sectors < 0 || good_sectors >= this_count)
          good_sectors = 0;
      }

    /*
     * First case : we assume that the command succeeded.  One of two things
     * will happen here.  Either we will be finished, or there will be more
     * sectors that we were unable to read last time.
     */

    if (good_sectors > 0) {

        SCSI_LOG_HLCOMPLETE(1,printk("%s : %ld sectors remain.\n", nbuff,
               SCpnt->request.nr_sectors));
        SCSI_LOG_HLCOMPLETE(1,printk("use_sg is %d\n ",SCpnt->use_sg));

        if (SCpnt->use_sg) {
            struct scatterlist * sgpnt;
            int i;
            sgpnt = (struct scatterlist *) SCpnt->buffer;
            for(i=0; i<SCpnt->use_sg; i++) {

#if 0
                SCSI_LOG_HLCOMPLETE(3,printk(":%p %p %d\n",sgpnt[i].alt_address, sgpnt[i].address,
                       sgpnt[i].length));
#endif

                if (sgpnt[i].alt_address) {
                    if (SCpnt->request.cmd == READ)
                        memcpy(sgpnt[i].alt_address, sgpnt[i].address,
                               sgpnt[i].length);
                    scsi_free(sgpnt[i].address, sgpnt[i].length);
                }
            }

            /* Free list of scatter-gather pointers */
            scsi_free(SCpnt->buffer, SCpnt->sglist_len);
        } else {
            if (SCpnt->buffer != SCpnt->request.buffer) {
                SCSI_LOG_HLCOMPLETE(3,printk("nosg: %p %p %d\n",
                                             SCpnt->request.buffer, SCpnt->buffer,
                                             SCpnt->bufflen));

                if (SCpnt->request.cmd == READ)
                    memcpy(SCpnt->request.buffer, SCpnt->buffer,
                           SCpnt->bufflen);
                scsi_free(SCpnt->buffer, SCpnt->bufflen);
            }
        }
        /*
         * If multiple sectors are requested in one buffer, then
         * they will have been finished off by the first command.
         * If not, then we have a multi-buffer command.
         */
        if (SCpnt->request.nr_sectors > this_count)
        {
            SCpnt->request.errors = 0;

            if (!SCpnt->request.bh)
            {
                SCSI_LOG_HLCOMPLETE(2,printk("%s : handling page request, no buffer\n",
                       nbuff));

                /*
                 * The SCpnt->request.nr_sectors field is always done in
                 * 512 byte sectors, even if this really isn't the case.
                 */
                panic("sd.c: linked page request (%lx %x)",
                      SCpnt->request.sector, this_count);
            }
        }
        SCpnt = end_scsi_request(SCpnt, 1, good_sectors);
        if (result == 0)
          {
            requeue_sd_request(SCpnt);
            return;
          }
    }

    if (good_sectors == 0) {

    /* 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++) {
            SCSI_LOG_HLCOMPLETE(3,printk("err: %p %p %d\n",
                                         SCpnt->request.buffer, SCpnt->buffer,
                                         SCpnt->bufflen));
            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 {
        SCSI_LOG_HLCOMPLETE(2,printk("nosgerr: %p %p %d\n",
                                     SCpnt->request.buffer, SCpnt->buffer,
                                     SCpnt->bufflen));
        if (SCpnt->buffer != SCpnt->request.buffer)
            scsi_free(SCpnt->buffer, SCpnt->bufflen);
    }
    }

    /*
     * Now, if we were good little boys and girls, Santa left us a request
     * sense buffer.  We can extract information from this, so we
     * can choose a block to remap, etc.
     */

    if (driver_byte(result) != 0) {
        if (suggestion(result) == SUGGEST_REMAP) {
#ifdef REMAP
            /*
             * Not yet implemented.  A read will fail after being remapped,
             * a write will call the strategy routine again.
             */
            if rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].remap
            {
                result = 0;
            }
            else
#endif
        }

        if ((SCpnt->sense_buffer[0] & 0x7f) == 0x70) {
            if ((SCpnt->sense_buffer[2] & 0xf) == UNIT_ATTENTION) {
                if(rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->removable) {
                    /* detected disc change.  set a bit and quietly refuse
                     * further access.
                     */
                    rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->changed = 1;
                    SCpnt = end_scsi_request(SCpnt, 0, this_count);
                    requeue_sd_request(SCpnt);
                    return;
                }
                else
                {
                    /*
                     * Must have been a power glitch, or a bus reset.
                     * Could not have been a media change, so we just retry
                     * the request and see what happens.
                     */
                    requeue_sd_request(SCpnt);
                    return;
                }
            }
        }


        /* If we had an ILLEGAL REQUEST returned, then we may have
         * performed an unsupported command.  The only thing this should be
         * would be a ten byte read where only a six byte read was supported.
         * Also, on a system where READ CAPACITY failed, we have have read
         * past the end of the disk.
         */

        if (SCpnt->sense_buffer[2] == ILLEGAL_REQUEST) {
            if (rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].ten) {
                rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].ten = 0;
                requeue_sd_request(SCpnt);
                result = 0;
            } else {
                /* ???? */
            }
        }

        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("sd", SCpnt);
            SCpnt = end_scsi_request(SCpnt, 0, block_sectors);
            requeue_sd_request(SCpnt);
            return;
         }
    }  /* driver byte != 0 */
    if (result) {
        printk("SCSI disk error : host %d channel %d id %d lun %d return code = %x\n",
               rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->host->host_no,
               rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->channel,
           rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->id,
             rscsi_disks[DEVICE_NR(SCpnt->request.rq_dev)].device->lun, result);

        if (driver_byte(result) & DRIVER_SENSE)
            print_sense("sd", SCpnt);
        SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.current_nr_sectors);
        requeue_sd_request(SCpnt);
        return;
    }
}

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

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

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

        INIT_SCSI_REQUEST;
        SDev = rscsi_disks[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.  FIXME(eric) - do this
             * from the kernel error handling thred.
             */
            if( SDev->removable && !in_interrupt() )
            {
                spin_unlock_irq(&io_request_lock);      /* FIXME!!!! */
                scsi_ioctl(SDev, SCSI_IOCTL_DOORLOCK, 0);
                /* scsi_ioctl may allow CURRENT to change, so start over. */
                SDev->was_reset = 0;
                spin_lock_irq(&io_request_lock);        /* FIXME!!!! */
                continue;
            }
            SDev->was_reset = 0;
        }

        /* We have to be careful here. scsi_allocate_device will get a free pointer,
         * but there is no guarantee that it is queueable.  In normal usage,
         * we want to call this, because other types of devices may have the
         * host all tied up, and we want to make sure that we have at least
         * one request pending for this type of device. We can also come
         * through here while servicing an interrupt, because of the need to
         * start another command. If we call scsi_allocate_device more than once,
         * then the system can wedge if the command is not queueable. The
         * scsi_request_queueable function is safe because it checks to make sure
         * that the host is able to take another command before it returns
         * a pointer.
         */

        if (flag++ == 0)
            SCpnt = scsi_allocate_device(&CURRENT,
                           rscsi_disks[DEVICE_NR(CURRENT->rq_dev)].device, 0);
        else SCpnt = NULL;

        /*
         * The following restore_flags leads to latency problems.  FIXME.
         * Using a "sti()" gets rid of the latency problems but causes
         * race conditions and crashes.
         */

        /* 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.
         *
         * FIXME(eric) - this doesn't belong at this level.  The device code in
         * ll_rw_blk.c should know how to dig down into the device queue to
         * figure out what it can deal with, and what it can't.  Consider
         * possibility of pulling entire queue down into scsi layer.
         */
        if (!SCpnt && sd_template.nr_dev > 1){
            struct request *req1;
            req1 = NULL;
            req = CURRENT;
            while(req){
                SCpnt = scsi_request_queueable(req,
                                   rscsi_disks[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 */

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

static void requeue_sd_request (Scsi_Cmnd * SCpnt)
{
    int dev, devm, block, this_count;
    unsigned char cmd[10];
    char nbuff[6];
    int bounce_size, contiguous;
    int max_sg;
    struct buffer_head * bh, *bhp;
    char * buff, *bounce_buffer;

 repeat:

    if(!SCpnt || SCpnt->request.rq_status == RQ_INACTIVE) {
        do_sd_request();
        return;
    }

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

    block = SCpnt->request.sector;
    this_count = 0;

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

    if (devm >= (sd_template.dev_max << 4) ||
        !rscsi_disks[dev].device ||
        !rscsi_disks[dev].device->online ||
        block + SCpnt->request.nr_sectors > sd[devm].nr_sects)
    {
        SCSI_LOG_HLQUEUE(2,printk("Finishing %ld sectors\n", SCpnt->request.nr_sectors));
        SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
        SCSI_LOG_HLQUEUE(2,printk("Retry with 0x%p\n", SCpnt));
        goto repeat;
    }

    block += sd[devm].start_sect;

    if (rscsi_disks[dev].device->changed)
    {
        /*
         * quietly refuse to do anything to a changed disc until the changed
         * bit has been reset
         */
        /* printk("SCSI disk has been changed. Prohibiting further I/O.\n"); */
        SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
        goto repeat;
    }

    sd_devname(devm, nbuff);
    SCSI_LOG_HLQUEUE(2,printk("%s : real dev = /dev/%d, block = %d\n",
           nbuff, dev, block));

    /*
     * If we have a 1K hardware sectorsize, prevent access to single
     * 512 byte sectors.  In theory we could handle this - in fact
     * the scsi cdrom driver must be able to handle this because
     * we typically use 1K blocksizes, and cdroms typically have
     * 2K hardware sectorsizes.  Of course, things are simpler
     * with the cdrom, since it is read-only.  For performance
     * reasons, the filesystems should be able to handle this
     * and not force the scsi disk driver to use bounce buffers
     * for this.
     */
    if (rscsi_disks[dev].sector_size == 1024)
        if((block & 1) || (SCpnt->request.nr_sectors & 1)) {
            printk("sd.c:Bad block number requested");
            SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
            goto repeat;
        }

     if (rscsi_disks[dev].sector_size == 2048)
        if((block & 3) || (SCpnt->request.nr_sectors & 3)) {
            printk("sd.c:Bad block number requested");
            SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
            goto repeat;
        }
     
    switch (SCpnt->request.cmd)
    {
    case WRITE :
        if (!rscsi_disks[dev].device->writeable)
        {
            SCpnt = end_scsi_request(SCpnt, 0, SCpnt->request.nr_sectors);
            goto repeat;
        }
        cmd[0] = WRITE_6;
        break;
    case READ :
        cmd[0] = READ_6;
        break;
    default :
        panic ("Unknown sd command %d\n", SCpnt->request.cmd);
    }

    SCpnt->this_count = 0;

    /* If the host adapter can deal with very large scatter-gather
     * requests, it is a waste of time to cluster
     */
    contiguous = (!CLUSTERABLE_DEVICE(SCpnt) ? 0 :1);
    bounce_buffer = NULL;
    bounce_size = (SCpnt->request.nr_sectors << 9);

    /* First see if we need a bounce buffer for this request. If we do, make
     * sure that we can allocate a buffer. Do not waste space by allocating
     * a bounce buffer if we are straddling the 16Mb line
     */
    if (contiguous && SCpnt->request.bh &&
      virt_to_phys(SCpnt->request.bh->b_data)
        + (SCpnt->request.nr_sectors << 9) - 1 > ISA_DMA_THRESHOLD
        && SCpnt->host->unchecked_isa_dma) {
      if(virt_to_phys(SCpnt->request.bh->b_data) > ISA_DMA_THRESHOLD)
            bounce_buffer = (char *) scsi_malloc(bounce_size);
        if(!bounce_buffer) contiguous = 0;
    }

    if(contiguous && SCpnt->request.bh && SCpnt->request.bh->b_reqnext)
        for(bh = SCpnt->request.bh, bhp = bh->b_reqnext; bhp; bh = bhp,
            bhp = bhp->b_reqnext) {
            if(!CONTIGUOUS_BUFFERS(bh,bhp)) {
                if(bounce_buffer) scsi_free(bounce_buffer, bounce_size);
                contiguous = 0;
                break;
            }
        }
    if (!SCpnt->request.bh || contiguous) {

        /* case of page request (i.e. raw device), or unlinked buffer */
        this_count = SCpnt->request.nr_sectors;
        buff = SCpnt->request.buffer;
        SCpnt->use_sg = 0;

    } else if (SCpnt->host->sg_tablesize == 0 ||
               (scsi_need_isa_buffer && scsi_dma_free_sectors <= 10)) {

        /* Case of host adapter that cannot scatter-gather.  We also
         * come here if we are running low on DMA buffer memory.  We set
         * a threshold higher than that we would need for this request so
         * we leave room for other requests.  Even though we would not need
         * it all, we need to be conservative, because if we run low enough
         * we have no choice but to panic.
         */
        if (SCpnt->host->sg_tablesize != 0 &&
            scsi_need_isa_buffer &&
            scsi_dma_free_sectors <= 10)
            printk("Warning: SCSI DMA buffer space running low.  Using non scatter-gather I/O.\n");

        this_count = SCpnt->request.current_nr_sectors;
        buff = SCpnt->request.buffer;
        SCpnt->use_sg = 0;

    } else {

        /* Scatter-gather capable host adapter */
        struct scatterlist * sgpnt;
        int count, this_count_max;
        int counted;

        bh = SCpnt->request.bh;
        this_count = 0;
        this_count_max = (rscsi_disks[dev].ten ? 0xffff : 0xff);
        count = 0;
        bhp = NULL;
        while(bh) {
            if ((this_count + (bh->b_size >> 9)) > this_count_max) break;
            if(!bhp || !CONTIGUOUS_BUFFERS(bhp,bh) ||
               !CLUSTERABLE_DEVICE(SCpnt) ||
               (SCpnt->host->unchecked_isa_dma &&
                virt_to_phys(bh->b_data-1) == ISA_DMA_THRESHOLD)) {
                if (count < SCpnt->host->sg_tablesize) count++;
                else break;
            }
            this_count += (bh->b_size >> 9);
            bhp = bh;
            bh = bh->b_reqnext;
        }
#if 0
        if(SCpnt->host->unchecked_isa_dma &&
         virt_to_phys(SCpnt->request.bh->b_data-1) == ISA_DMA_THRESHOLD) count--;
#endif
        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;
        max_sg = count / sizeof(struct scatterlist);
        if(SCpnt->host->sg_tablesize < max_sg)
            max_sg = SCpnt->host->sg_tablesize;
        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 */
            this_count = SCpnt->request.current_nr_sectors;
            buff = SCpnt->request.buffer;
        } else {
            memset(sgpnt, 0, count);  /* Zero so it is easy to fill, but only
                                       * if memory is available
                                       */
            buff = (char *) sgpnt;
            counted = 0;
            for(count = 0, bh = SCpnt->request.bh, bhp = bh->b_reqnext;
                count < SCpnt->use_sg && bh;
                count++, bh = bhp) {

                bhp = bh->b_reqnext;

                if(!sgpnt[count].address) sgpnt[count].address = bh->b_data;
                sgpnt[count].length += bh->b_size;
                counted += bh->b_size >> 9;

                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].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) + 10) {
                        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 */
#if 0
                        printk("Warning: Running low on SCSI DMA buffers");
                        /* Try switching back to a non s-g operation. */
                        while(--count >= 0){
                            if(sgpnt[count].alt_address)
                                scsi_free(sgpnt[count].address,
                                          sgpnt[count].length);
                        }
                        this_count = SCpnt->request.current_nr_sectors;
                        buff = SCpnt->request.buffer;
                        SCpnt->use_sg = 0;
                        scsi_free(sgpnt, SCpnt->sglist_len);
#endif
                        SCpnt->use_sg = count;
                        this_count = counted -= bh->b_size >> 9;
                        break;
                    }
                }

                /* Only cluster buffers if we know that we can supply DMA
                 * buffers large enough to satisfy the request. Do not cluster
                 * a new request if this would mean that we suddenly need to
                 * start using DMA bounce buffers */
                if(bhp && CONTIGUOUS_BUFFERS(bh,bhp)
                   && CLUSTERABLE_DEVICE(SCpnt)) {
                    char * tmp;

                  if (virt_to_phys(sgpnt[count].address) + sgpnt[count].length +
                        bhp->b_size - 1 > ISA_DMA_THRESHOLD &&
                        (SCpnt->host->unchecked_isa_dma) &&
                        !sgpnt[count].alt_address) continue;

                    if(!sgpnt[count].alt_address) {count--; continue; }
                    if(scsi_dma_free_sectors > 10)
                        tmp = (char *) scsi_malloc(sgpnt[count].length
                                                   + bhp->b_size);
                    else {
                        tmp = NULL;
                        max_sg = SCpnt->use_sg;
                    }
                    if(tmp){
                        scsi_free(sgpnt[count].address, sgpnt[count].length);
                        sgpnt[count].address = tmp;
                        count--;
                        continue;
                    }

                    /* If we are allowed another sg chain, then increment
                     * counter so we can insert it.  Otherwise we will end
                     up truncating */

                    if (SCpnt->use_sg < max_sg) SCpnt->use_sg++;
                }  /* contiguous buffers */
            } /* for loop */

            /* This is actually how many we are going to transfer */
            this_count = counted;

            if(count < SCpnt->use_sg || SCpnt->use_sg
               > SCpnt->host->sg_tablesize){
                bh = SCpnt->request.bh;
                printk("Use sg, count %d %x %d\n",
                       SCpnt->use_sg, count, scsi_dma_free_sectors);
                printk("maxsg = %x, counted = %d this_count = %d\n",
                       max_sg, counted, this_count);
                while(bh){
                    printk("[%p %lx] ", bh->b_data, bh->b_size);
                    bh = bh->b_reqnext;
                }
                if(SCpnt->use_sg < 16)
                    for(count=0; count<SCpnt->use_sg; count++)
                        printk("{%d:%p %p %d}  ", count,
                               sgpnt[count].address,
                               sgpnt[count].alt_address,
                               sgpnt[count].length);
                panic("Ooops");
            }

            if (SCpnt->request.cmd == WRITE)
                for(count=0; count<SCpnt->use_sg; count++)
                    if(sgpnt[count].alt_address)
                        memcpy(sgpnt[count].address, sgpnt[count].alt_address,
                               sgpnt[count].length);
        }  /* Able to malloc sgpnt */
    }  /* Host adapter capable of scatter-gather */

    /* Now handle the possibility of DMA to addresses > 16Mb */

    if(SCpnt->use_sg == 0){
      if (virt_to_phys(buff) + (this_count << 9) - 1 > ISA_DMA_THRESHOLD &&
            (SCpnt->host->unchecked_isa_dma)) {
            if(bounce_buffer)
                buff = bounce_buffer;
            else
                buff = (char *) scsi_malloc(this_count << 9);
            if(buff == NULL) {  /* Try backing off a bit if we are low on mem*/
                this_count = SCpnt->request.current_nr_sectors;
                buff = (char *) scsi_malloc(this_count << 9);
                if(!buff) panic("Ran out of DMA buffers.");
            }
            if (SCpnt->request.cmd == WRITE)
                memcpy(buff, (char *)SCpnt->request.buffer, this_count << 9);
        }
    }
    SCSI_LOG_HLQUEUE(2,printk("%s : %s %d/%ld 512 byte blocks.\n",
                              nbuff,
                              (SCpnt->request.cmd == WRITE) ? "writing" : "reading",
                              this_count, SCpnt->request.nr_sectors));

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

     if (rscsi_disks[dev].sector_size == 2048){
        if(block & 3) panic("sd.c:Bad block number requested");
        if(this_count & 3) panic("sd.c:Bad block number requested");
        block = block >> 2;
        this_count = this_count >> 2;
     }
     
    if (rscsi_disks[dev].sector_size == 1024){
        if(block & 1) panic("sd.c:Bad block number requested");
        if(this_count & 1) panic("sd.c:Bad block number requested");
        block = block >> 1;
        this_count = this_count >> 1;
    }

    if (rscsi_disks[dev].sector_size == 256){
        block = block << 1;
        this_count = this_count << 1;
    }

    if (((this_count > 0xff) ||  (block > 0x1fffff)) && rscsi_disks[dev].ten)
    {
        if (this_count > 0xffff)
            this_count = 0xffff;

        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) (this_count >> 8) & 0xff;
        cmd[8] = (unsigned char) this_count & 0xff;
    }
    else
    {
        if (this_count > 0xff)
            this_count = 0xff;

        cmd[1] |= (unsigned char) ((block >> 16) & 0x1f);
        cmd[2] = (unsigned char) ((block >> 8) & 0xff);
        cmd[3] = (unsigned char) block & 0xff;
        cmd[4] = (unsigned char) this_count;
        cmd[5] = 0;
    }

    /*
     * 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 = rscsi_disks[dev].sector_size;
    SCpnt->underflow = this_count << 9;
    scsi_do_cmd (SCpnt, (void *) cmd, buff,
                 this_count * rscsi_disks[dev].sector_size,
                 rw_intr,
                 (SCpnt->device->type == TYPE_DISK ?
                  SD_TIMEOUT : SD_MOD_TIMEOUT),
                 MAX_RETRIES);
}

static int check_scsidisk_media_change(kdev_t full_dev){
    int retval;
    int target;
    struct inode inode;
    int flag = 0;

    target =  DEVICE_NR(full_dev);

    if (target >= sd_template.dev_max ||
        !rscsi_disks[target].device) {
        printk("SCSI disk request error: invalid device.\n");
        return 0;
    }

    if(!rscsi_disks[target].device->removable) return 0;

    /*
     * If the device is offline, don't send any commands - just pretend as if
     * the command failed.  If the device ever comes back online, we can deal with
     * it then.  It is only because of unrecoverable errors that we would ever
     * take a device offline in the first place.
     */
    if( rscsi_disks[target].device->online == FALSE )
    {
        rscsi_disks[target].ready = 0;
        rscsi_disks[target].device->changed = 1;
        return 1; /* This will force a flush, if called from
                   * check_disk_change */
    }

    inode.i_rdev = full_dev;  /* This is all we really need here */

    /* Using Start/Stop enables differentiation between drive with
     * no cartridge loaded - NOT READY, drive with changed cartridge -
     * UNIT ATTENTION, or with same cartridge - GOOD STATUS.
     * This also handles drives that auto spin down. eg iomega jaz 1GB
     * as this will spin up the drive.
     */
    retval = sd_ioctl(&inode, NULL, SCSI_IOCTL_START_UNIT, 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.  */

        rscsi_disks[target].ready = 0;
        rscsi_disks[target].device->changed = 1;
        return 1; /* This will force a flush, if called from
                   * check_disk_change */
    }

    /*
     * for removable scsi disk ( FLOPTICAL ) we have to recognise the
     * presence of disk in the drive. This is kept in the Scsi_Disk
     * struct and tested at open !  Daniel Roche ( dan@lectra.fr )
     */

    rscsi_disks[target].ready = 1;      /* FLOPTICAL */

    retval = rscsi_disks[target].device->changed;
    if(!flag) rscsi_disks[target].device->changed = 0;
    return retval;
}

static void sd_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);
    }
}

static int sd_init_onedisk(int i)
{
    unsigned char cmd[10];
    char          nbuff[6];
    unsigned char *buffer;
    unsigned long spintime;
    int the_result, retries;
    Scsi_Cmnd * SCpnt;

    /*
     * Get the name of the disk, in case we need to log it somewhere.
     */
    sd_devname(i, nbuff);

    /*
     * If the device is offline, don't try and read capacity or any of the other
     * nicities.
     */
    if( rscsi_disks[i].device->online == FALSE )
    {
        return i;
    }

    spin_lock_irq(&io_request_lock);

    /* We need to retry the READ_CAPACITY because a UNIT_ATTENTION is
     * considered a fatal error, and many devices report such an error
     * just after a scsi bus reset.
     */

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

    spintime = 0;

    /* Spin up drives, as required.  Only do this at boot time */
    /* Spinup needs to be done for module loads too. */
        do{
            retries = 0;
            while(retries < 3)
            {
                cmd[0] = TEST_UNIT_READY;
                cmd[1] = (rscsi_disks[i].device->lun << 5) & 0xe0;
                memset ((void *) &cmd[2], 0, 8);
                SCpnt->cmd_len = 0;
                SCpnt->sense_buffer[0] = 0;
                SCpnt->sense_buffer[2] = 0;

                {
                    struct semaphore sem = MUTEX_LOCKED;
                    /* Mark as really busy again */
                    SCpnt->request.rq_status = RQ_SCSI_BUSY;
                    SCpnt->request.sem = &sem;
                    scsi_do_cmd (SCpnt,
                                 (void *) cmd, (void *) buffer,
                                 512, sd_init_done,  SD_TIMEOUT,
                                 MAX_RETRIES);
                    spin_unlock_irq(&io_request_lock);
                    down(&sem);
                    spin_lock_irq(&io_request_lock);
                    SCpnt->request.sem = NULL;
                }

                the_result = SCpnt->result;
                retries++;
                if(   the_result == 0
                   || SCpnt->sense_buffer[2] != UNIT_ATTENTION)
                    break;
            }

            /* Look for non-removable devices that return NOT_READY.
             * Issue command to spin up drive for these cases. */
            if(the_result && !rscsi_disks[i].device->removable &&
               SCpnt->sense_buffer[2] == NOT_READY) {
                unsigned long time1;
                if(!spintime){
                    printk( "%s: Spinning up disk...", nbuff );
                    cmd[0] = START_STOP;
                    cmd[1] = (rscsi_disks[i].device->lun << 5) & 0xe0;
                    cmd[1] |= 1;  /* Return immediately */
                    memset ((void *) &cmd[2], 0, 8);
                    cmd[4] = 1; /* Start spin cycle */
                    SCpnt->cmd_len = 0;
                    SCpnt->sense_buffer[0] = 0;
                    SCpnt->sense_buffer[2] = 0;

                    {
                        struct semaphore sem = MUTEX_LOCKED;
                        /* Mark as really busy again */
                        SCpnt->request.rq_status = RQ_SCSI_BUSY;
                        SCpnt->request.sem = &sem;
                        scsi_do_cmd (SCpnt,
                                     (void *) cmd, (void *) buffer,
                                     512, sd_init_done,  SD_TIMEOUT,
                                     MAX_RETRIES);
                        spin_unlock_irq(&io_request_lock);
                        down(&sem);
                        spin_lock_irq(&io_request_lock);
                        SCpnt->request.sem = NULL;
                    }

                    spintime = jiffies;
                }

                time1 = jiffies + HZ;
                spin_unlock_irq(&io_request_lock);
                while(jiffies < time1); /* Wait 1 second for next try */
                printk( "." );
                spin_lock_irq(&io_request_lock);
            }
        } while(the_result && spintime && spintime+100*HZ > jiffies);
        if (spintime) {
            if (the_result)
                printk( "not responding...\n" );
            else
                printk( "ready\n" );
        }

    retries = 3;
    do {
        cmd[0] = READ_CAPACITY;
        cmd[1] = (rscsi_disks[i].device->lun << 5) & 0xe0;
        memset ((void *) &cmd[2], 0, 8);
        memset ((void *) buffer, 0, 8);
        SCpnt->cmd_len = 0;
        SCpnt->sense_buffer[0] = 0;
        SCpnt->sense_buffer[2] = 0;

        {
            struct semaphore sem = MUTEX_LOCKED;
            /* Mark as really busy again */
            SCpnt->request.rq_status = RQ_SCSI_BUSY;
            SCpnt->request.sem = &sem;
            scsi_do_cmd (SCpnt,
                         (void *) cmd, (void *) buffer,
                         8, sd_init_done,  SD_TIMEOUT,
                         MAX_RETRIES);
            spin_unlock_irq(&io_request_lock);
            down(&sem); /* sleep until it is ready */
            spin_lock_irq(&io_request_lock);
            SCpnt->request.sem = NULL;
        }

        the_result = SCpnt->result;
        retries--;

    } while(the_result && retries);

    /*
     * The SCSI standard says:
     * "READ CAPACITY is necessary for self configuring software"
     *  While not mandatory, support of READ CAPACITY is strongly encouraged.
     *  We used to die if we couldn't successfully do a READ CAPACITY.
     *  But, now we go on about our way.  The side effects of this are
     *
     *  1. We can't know block size with certainty. I have said "512 bytes
     *     is it" as this is most common.
     *
     *  2. Recovery from when some one attempts to read past the end of the
     *     raw device will be slower.
     */

    if (the_result)
    {
        printk ("%s : READ CAPACITY failed.\n"
                "%s : status = %x, message = %02x, host = %d, driver = %02x \n",
                nbuff, nbuff,
                status_byte(the_result),
                msg_byte(the_result),
                host_byte(the_result),
                driver_byte(the_result)
                );
        if (driver_byte(the_result)  & DRIVER_SENSE)
            printk("%s : extended sense code = %1x \n",
                   nbuff, SCpnt->sense_buffer[2] & 0xf);
        else
            printk("%s : sense not available. \n", nbuff);

        printk("%s : block size assumed to be 512 bytes, disk size 1GB.  \n",
               nbuff);
        rscsi_disks[i].capacity = 0x1fffff;
        rscsi_disks[i].sector_size = 512;

        /* Set dirty bit for removable devices if not ready - sometimes drives
         * will not report this properly. */
        if(rscsi_disks[i].device->removable &&
           SCpnt->sense_buffer[2] == NOT_READY)
            rscsi_disks[i].device->changed = 1;

    }
    else
    {
        /*
         * FLOPTICAL , if read_capa is ok , drive is assumed to be ready
         */
        rscsi_disks[i].ready = 1;

        rscsi_disks[i].capacity = 1 + ((buffer[0] << 24) |
                                       (buffer[1] << 16) |
                                       (buffer[2] << 8) |
                                       buffer[3]);

        rscsi_disks[i].sector_size = (buffer[4] << 24) |
            (buffer[5] << 16) | (buffer[6] << 8) | buffer[7];

        if (rscsi_disks[i].sector_size == 0) {
          rscsi_disks[i].sector_size = 512;
          printk("%s : sector size 0 reported, assuming 512.\n", nbuff);
        }


        if (rscsi_disks[i].sector_size != 512 &&
            rscsi_disks[i].sector_size != 1024 &&
            rscsi_disks[i].sector_size != 2048 &&
            rscsi_disks[i].sector_size != 256)
        {
            printk ("%s : unsupported sector size %d.\n",
                    nbuff, rscsi_disks[i].sector_size);
            if(rscsi_disks[i].device->removable){
                rscsi_disks[i].capacity = 0;
            } else {
                printk ("scsi : deleting disk entry.\n");
                rscsi_disks[i].device = NULL;
                sd_template.nr_dev--;
                sd_gendisk.nr_real--;

                /* Wake up a process waiting for device */
                wake_up(&SCpnt->device->device_wait);
                scsi_release_command(SCpnt);
                SCpnt = NULL;
                
                return i;
            }
        }

        if( rscsi_disks[i].sector_size == 2048 )
          {
            int m;

            /*
             * We must fix the sd_blocksizes and sd_hardsizes
             * to allow us to read the partition tables.
             * The disk reading code does not allow for reading
             * of partial sectors.
             */
            for (m=i<<4; m<((i+1)<<4); m++)
              {
                sd_blocksizes[m] = 2048;
              }
          }
    {
        /*
         * The msdos fs needs to know the hardware sector size
         * So I have created this table. See ll_rw_blk.c
         * Jacques Gelinas (Jacques@solucorp.qc.ca)
         */
        int m, mb;
        int sz_quot, sz_rem;
        int hard_sector = rscsi_disks[i].sector_size;
        /* There are 16 minors allocated for each major device */
        for (m=i<<4; m<((i+1)<<4); m++){
            sd_hardsizes[m] = hard_sector;
        }
        mb = rscsi_disks[i].capacity / 1024 * hard_sector / 1024;
        /* sz = div(m/100, 10);  this seems to not be in the libr */
        m = (mb + 50) / 100;
        sz_quot = m / 10;
        sz_rem = m - (10 * sz_quot);
        printk ("SCSI device %s: hdwr sector= %d bytes."
               " Sectors= %d [%d MB] [%d.%1d GB]\n",
                nbuff, hard_sector, rscsi_disks[i].capacity,
                mb, sz_quot, sz_rem);
    }
        if(rscsi_disks[i].sector_size == 2048)
            rscsi_disks[i].capacity <<= 2;  /* Change into 512 byte sectors */
        if(rscsi_disks[i].sector_size == 1024)
            rscsi_disks[i].capacity <<= 1;  /* Change into 512 byte sectors */
        if(rscsi_disks[i].sector_size == 256)
            rscsi_disks[i].capacity >>= 1;  /* Change into 512 byte sectors */
    }


    /*
     * Unless otherwise specified, this is not write protected.
     */
    rscsi_disks[i].write_prot = 0;
    if ( rscsi_disks[i].device->removable && rscsi_disks[i].ready ) {
        /* FLOPTICAL */

        /*
         *      for removable scsi disk ( FLOPTICAL ) we have to recognise
         * the Write Protect Flag. This flag is kept in the Scsi_Disk struct
         * and tested at open !
         * Daniel Roche ( dan@lectra.fr )
         */

        memset ((void *) &cmd[0], 0, 8);
        cmd[0] = MODE_SENSE;
        cmd[1] = (rscsi_disks[i].device->lun << 5) & 0xe0;
        cmd[2] = 1;      /* page code 1 ?? */
        cmd[4] = 12;
        SCpnt->cmd_len = 0;
        SCpnt->sense_buffer[0] = 0;
        SCpnt->sense_buffer[2] = 0;

        /* same code as READCAPA !! */
        {
            struct semaphore sem = MUTEX_LOCKED;
            SCpnt->request.rq_status = RQ_SCSI_BUSY;  /* Mark as really busy again */
            SCpnt->request.sem = &sem;
            scsi_do_cmd (SCpnt,
                         (void *) cmd, (void *) buffer,
                         512, sd_init_done,  SD_TIMEOUT,
                         MAX_RETRIES);
            spin_unlock_irq(&io_request_lock);
            down(&sem);
            spin_lock_irq(&io_request_lock);
            SCpnt->request.sem = NULL;
        }

        the_result = SCpnt->result;

        if ( the_result ) {
            printk ("%s: test WP failed, assume Write Protected\n",nbuff);
            rscsi_disks[i].write_prot = 1;
        } else {
            rscsi_disks[i].write_prot = ((buffer[2] & 0x80) != 0);
            printk ("%s: Write Protect is %s\n",nbuff,
                    rscsi_disks[i].write_prot ? "on" : "off");
        }

    }   /* check for write protect */

    /* Wake up a process waiting for device */
    wake_up(&SCpnt->device->device_wait);
    scsi_release_command(SCpnt);
    SCpnt = NULL;

    rscsi_disks[i].ten = 1;
    rscsi_disks[i].remap = 1;
    scsi_free(buffer, 512);
    spin_unlock_irq(&io_request_lock);
    return i;
}

/*
 * The sd_init() function looks at all SCSI drives present, determines
 * their size, and reads partition table entries for them.
 */

static int sd_registered = 0;

static int sd_init()
{
    int i;

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

    if(!sd_registered) {
          if (register_blkdev(MAJOR_NR,"sd",&sd_fops)) {
              printk("Unable to get major %d for SCSI disk\n",MAJOR_NR);
              return 1;
          }
          sd_registered++;
      }

    /* We do not support attaching loadable devices yet. */
    if(rscsi_disks) return 0;

    sd_template.dev_max = sd_template.dev_noticed + SD_EXTRA_DEVS;

    rscsi_disks = (Scsi_Disk *)
        scsi_init_malloc(sd_template.dev_max * sizeof(Scsi_Disk), GFP_ATOMIC);
    memset(rscsi_disks, 0, sd_template.dev_max * sizeof(Scsi_Disk));

    sd_sizes = (int *) scsi_init_malloc((sd_template.dev_max << 4) *
                                        sizeof(int), GFP_ATOMIC);
    memset(sd_sizes, 0, (sd_template.dev_max << 4) * sizeof(int));

    sd_blocksizes = (int *) scsi_init_malloc((sd_template.dev_max << 4) *
                                             sizeof(int), GFP_ATOMIC);

    sd_hardsizes = (int *) scsi_init_malloc((sd_template.dev_max << 4) *
                                            sizeof(int), GFP_ATOMIC);

     for(i=0;i<(sd_template.dev_max << 4);i++)
       {
         sd_blocksizes[i] = 1024;
         sd_hardsizes[i] = 512;
       }
 
    blksize_size[MAJOR_NR] = sd_blocksizes;
    hardsect_size[MAJOR_NR] = sd_hardsizes;
    sd = (struct hd_struct *) scsi_init_malloc((sd_template.dev_max << 4) *
                                               sizeof(struct hd_struct),
                                               GFP_ATOMIC);


    sd_gendisk.max_nr = sd_template.dev_max;
    sd_gendisk.part = sd;
    sd_gendisk.sizes = sd_sizes;
    sd_gendisk.real_devices = (void *) rscsi_disks;
    return 0;
}

static void sd_finish()
{
    struct gendisk *gendisk;
    int i;

    blk_dev[MAJOR_NR].request_fn = DEVICE_REQUEST;

    for (gendisk = gendisk_head; gendisk != NULL; gendisk = gendisk->next)
      if (gendisk == &sd_gendisk)
        break;
    if (gendisk == NULL)
      {
        sd_gendisk.next = gendisk_head;
        gendisk_head = &sd_gendisk;
      }

    for (i = 0; i < sd_template.dev_max; ++i)
        if (!rscsi_disks[i].capacity &&
            rscsi_disks[i].device)
        {
            if (MODULE_FLAG
                && !rscsi_disks[i].has_part_table) {
                sd_sizes[i << 4] = rscsi_disks[i].capacity;
                /* revalidate does sd_init_onedisk via MAYBE_REINIT*/
                revalidate_scsidisk(MKDEV(MAJOR_NR, i << 4), 0);
            }
            else
                i=sd_init_onedisk(i);
            rscsi_disks[i].has_part_table = 1;
        }

    /* 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(rscsi_disks[0].device && rscsi_disks[0].device->host->sg_tablesize)
        read_ahead[MAJOR_NR] = 120;  /* 120 sector read-ahead */
    else
        read_ahead[MAJOR_NR] = 4;  /* 4 sector read-ahead */

    return;
}

static int sd_detect(Scsi_Device * SDp){
    char nbuff[6];
    if(SDp->type != TYPE_DISK && SDp->type != TYPE_MOD) return 0;

    sd_devname(sd_template.dev_noticed++, nbuff);
    printk("Detected scsi %sdisk %s at scsi%d, channel %d, id %d, lun %d\n",
           SDp->removable ? "removable " : "",
           nbuff,
           SDp->host->host_no, SDp->channel, SDp->id, SDp->lun);

    return 1;
}

static int sd_attach(Scsi_Device * SDp){
    Scsi_Disk * dpnt;
    int i;

    if(SDp->type != TYPE_DISK && SDp->type != TYPE_MOD) return 0;

    if(sd_template.nr_dev >= sd_template.dev_max) {
        SDp->attached--;
        return 1;
    }

    for(dpnt = rscsi_disks, i=0; i<sd_template.dev_max; i++, dpnt++)
        if(!dpnt->device) break;

    if(i >= sd_template.dev_max) panic ("scsi_devices corrupt (sd)");

    SDp->scsi_request_fn = do_sd_request;
    rscsi_disks[i].device = SDp;
    rscsi_disks[i].has_part_table = 0;
    sd_template.nr_dev++;
    sd_gendisk.nr_real++;
    return 0;
}

#define DEVICE_BUSY rscsi_disks[target].device->busy
#define USAGE rscsi_disks[target].device->access_count
#define CAPACITY rscsi_disks[target].capacity
#define MAYBE_REINIT  sd_init_onedisk(target)
#define GENDISK_STRUCT sd_gendisk

/* This routine is called to flush all partitions and partition tables
 * for a changed scsi disk, and then re-read the new partition table.
 * If we are revalidating a disk because of a media change, then we
 * enter with usage == 0.  If we are using an ioctl, we automatically have
 * usage == 1 (we need an open channel to use an ioctl :-), so this
 * is our limit.
 */
int revalidate_scsidisk(kdev_t dev, int maxusage){
    int target;
    struct gendisk * gdev;
    int max_p;
    int start;
    int i;

    target =  DEVICE_NR(dev);
    gdev = &GENDISK_STRUCT;

    if (DEVICE_BUSY || USAGE > maxusage) {
        printk("Device busy for revalidation (usage=%d)\n", USAGE);
        return -EBUSY;
    }
    DEVICE_BUSY = 1;

    max_p = gdev->max_p;
    start = target << gdev->minor_shift;

    for (i=max_p - 1; i >=0 ; i--) {
        int minor = start+i;
        kdev_t devi = MKDEV(MAJOR_NR, minor);
        struct super_block *sb = get_super(devi);
        sync_dev(devi);
        if (sb) invalidate_inodes(sb);
        invalidate_buffers(devi);
        gdev->part[minor].start_sect = 0;
        gdev->part[minor].nr_sects = 0;
        /*
         * Reset the blocksize for everything so that we can read
         * the partition table.  Technically we will determine the
         * correct block size when we revalidate, but we do this just
         * to make sure that everything remains consistent.
         */
        blksize_size[MAJOR_NR][minor] = 1024;
        if( rscsi_disks[target].sector_size == 2048 )
          blksize_size[MAJOR_NR][minor] = 2048;
        else
          blksize_size[MAJOR_NR][minor] = 1024;
    }

#ifdef MAYBE_REINIT
    MAYBE_REINIT;
#endif

    gdev->part[start].nr_sects = CAPACITY;
    resetup_one_dev(gdev, target);

    DEVICE_BUSY = 0;
    return 0;
}

static int fop_revalidate_scsidisk(kdev_t dev){
    return revalidate_scsidisk(dev, 0);
}


static void sd_detach(Scsi_Device * SDp)
{
    Scsi_Disk * dpnt;
    int i;
    int max_p;
    int start;

    for(dpnt = rscsi_disks, i=0; i<sd_template.dev_max; i++, dpnt++)
        if(dpnt->device == SDp) {

            /* If we are disconnecting a disk driver, sync and invalidate
             * everything */
            max_p = sd_gendisk.max_p;
            start = i << sd_gendisk.minor_shift;

            for (i=max_p - 1; i >=0 ; i--) {
                int minor = start+i;
                kdev_t devi = MKDEV(MAJOR_NR, minor);
                struct super_block *sb = get_super(devi);
                sync_dev(devi);
                if (sb) invalidate_inodes(sb);
                invalidate_buffers(devi);
                sd_gendisk.part[minor].start_sect = 0;
                sd_gendisk.part[minor].nr_sects = 0;
                sd_sizes[minor] = 0;
            }

            dpnt->has_part_table = 0;
            dpnt->device = NULL;
            dpnt->capacity = 0;
            SDp->attached--;
            sd_template.dev_noticed--;
            sd_template.nr_dev--;
            sd_gendisk.nr_real--;
            return;
        }
    return;
}

#ifdef MODULE

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

void cleanup_module( void)
{
    struct gendisk * prev_sdgd;
    struct gendisk * sdgd;

    scsi_unregister_module(MODULE_SCSI_DEV, &sd_template);
    unregister_blkdev(SCSI_DISK_MAJOR, "sd");
    sd_registered--;
    if( rscsi_disks != NULL )
    {
        scsi_init_free((char *) rscsi_disks,
                       (sd_template.dev_noticed + SD_EXTRA_DEVS)
                       * sizeof(Scsi_Disk));

        scsi_init_free((char *) sd_sizes, sd_template.dev_max * sizeof(int));
        scsi_init_free((char *) sd_blocksizes, sd_template.dev_max * sizeof(int));
        scsi_init_free((char *) sd_hardsizes, sd_template.dev_max * sizeof(int));
        scsi_init_free((char *) sd,
                       (sd_template.dev_max << 4) * sizeof(struct hd_struct));
        /*
         * Now remove sd_gendisk from the linked list
         */
        sdgd = gendisk_head;
        prev_sdgd = NULL;
        while(sdgd != &sd_gendisk)
        {
            prev_sdgd = sdgd;
            sdgd = sdgd->next;
        }

        if(sdgd != &sd_gendisk)
            printk("sd_gendisk not in disk chain.\n");
        else {
            if(prev_sdgd != NULL)
                prev_sdgd->next = sdgd->next;
            else
                gendisk_head = sdgd->next;
        }
    }

    blksize_size[MAJOR_NR] = NULL;
    blk_dev[MAJOR_NR].request_fn = NULL;
    blk_size[MAJOR_NR] = NULL;
    hardsect_size[MAJOR_NR] = NULL;
    read_ahead[MAJOR_NR] = 0;
    sd_template.dev_max = 0;
}
#endif /* MODULE */

/*
 * Overrides for Emacs so that we almost 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:
 */