path: root/drivers/scsi/st.c

/*
   SCSI Tape Driver for Linux version 1.1 and newer. See the accompanying
   file README.st for more information.

   History:
   Rewritten from Dwayne Forsyth's SCSI tape driver by Kai Makisara.
   Contribution and ideas from several people including (in alphabetical
   order) Klaus Ehrenfried, Wolfgang Denk, Steve Hirsch, Andreas Koppenh"ofer,
   Michael Leodolter, Eyal Lebedinsky, J"org Weule, and Eric Youngdale.

   Copyright 1992 - 2000 Kai Makisara
   email Kai.Makisara@metla.fi

   Last modified: Tue Jan  4 21:43:17 2000 by makisara@kai.makisara.local
   Some small formal changes - aeb, 950809
 */

#include <linux/module.h>

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/mtio.h>
#include <linux/ioctl.h>
#include <linux/fcntl.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include <asm/dma.h>
#include <asm/system.h>

/* The driver prints some debugging information on the console if DEBUG
   is defined and non-zero. */
#define DEBUG 0

#if DEBUG
/* The message level for the debug messages is currently set to KERN_NOTICE
   so that people can easily see the messages. Later when the debugging messages
   in the drivers are more widely classified, this may be changed to KERN_DEBUG. */
#define ST_DEB_MSG  KERN_NOTICE
#define DEB(a) a
#define DEBC(a) if (debugging) { a ; }
#else
#define DEB(a)
#define DEBC(a)
#endif

#define MAJOR_NR SCSI_TAPE_MAJOR
#include <linux/blk.h>

#include "scsi.h"
#include "hosts.h"
#include <scsi/scsi_ioctl.h>

#define ST_KILOBYTE 1024

#include "st_options.h"
#include "st.h"

#include "constants.h"

static int buffer_kbs = 0;
static int write_threshold_kbs = 0;
static int max_buffers = (-1);
static int max_sg_segs = 0;
#ifdef MODULE
MODULE_AUTHOR("Kai Makisara");
MODULE_DESCRIPTION("SCSI Tape Driver");
MODULE_PARM(buffer_kbs, "i");
MODULE_PARM(write_threshold_kbs, "i");
MODULE_PARM(max_buffers, "i");
MODULE_PARM(max_sg_segs, "i");
#else

static struct st_dev_parm {
	char *name;
	int *val;
} parms[] __initdata = {
	{
		"buffer_kbs", &buffer_kbs
	},
	{
		"write_threshold_kbs", &write_threshold_kbs
	},
	{
		"max_buffers", &max_buffers
	},
	{
		"max_sg_segs", &max_sg_segs
	}
};

#endif


/* The default definitions have been moved to st_options.h */

#define ST_BUFFER_SIZE (ST_BUFFER_BLOCKS * ST_KILOBYTE)
#define ST_WRITE_THRESHOLD (ST_WRITE_THRESHOLD_BLOCKS * ST_KILOBYTE)

/* The buffer size should fit into the 24 bits for length in the
   6-byte SCSI read and write commands. */
#if ST_BUFFER_SIZE >= (2 << 24 - 1)
#error "Buffer size should not exceed (2 << 24 - 1) bytes!"
#endif

DEB( static int debugging = DEBUG; )

#define MAX_RETRIES 0
#define MAX_WRITE_RETRIES 0
#define MAX_READY_RETRIES 5
#define NO_TAPE  NOT_READY

#define ST_TIMEOUT (900 * HZ)
#define ST_LONG_TIMEOUT (14000 * HZ)

#define TAPE_NR(x) (MINOR(x) & ~(128 | ST_MODE_MASK))
#define TAPE_MODE(x) ((MINOR(x) & ST_MODE_MASK) >> ST_MODE_SHIFT)

/* Internal ioctl to set both density (uppermost 8 bits) and blocksize (lower
   24 bits) */
#define SET_DENS_AND_BLK 0x10001

static int st_nbr_buffers;
static ST_buffer **st_buffers;
static int st_buffer_size = ST_BUFFER_SIZE;
static int st_write_threshold = ST_WRITE_THRESHOLD;
static int st_max_buffers = ST_MAX_BUFFERS;
static int st_max_sg_segs = ST_MAX_SG;

static Scsi_Tape *scsi_tapes = NULL;

static int modes_defined = FALSE;

static ST_buffer *new_tape_buffer(int, int);
static int enlarge_buffer(ST_buffer *, int, int);
static void normalize_buffer(ST_buffer *);
static int append_to_buffer(const char *, ST_buffer *, int);
static int from_buffer(ST_buffer *, char *, int);

static int st_init(void);
static int st_attach(Scsi_Device *);
static int st_detect(Scsi_Device *);
static void st_detach(Scsi_Device *);

struct Scsi_Device_Template st_template =
{
	name:"tape", 
	tag:"st", 
	scsi_type:TYPE_TAPE,
	major:SCSI_TAPE_MAJOR, 
	detect:st_detect, 
	init:st_init,
	attach:st_attach, 
	detach:st_detach
};

static int st_compression(Scsi_Tape *, int);

static int find_partition(struct inode *);
static int update_partition(struct inode *);

static int st_int_ioctl(struct inode *inode, unsigned int cmd_in,
			unsigned long arg);




/* Convert the result to success code */
static int st_chk_result(Scsi_Cmnd * SCpnt)
{
	int dev = TAPE_NR(SCpnt->request.rq_dev);
	int result = SCpnt->result;
	unsigned char *sense = SCpnt->sense_buffer, scode;
	DEB(const char *stp;)

	if (!result /* && SCpnt->sense_buffer[0] == 0 */ )
		return 0;

	if (driver_byte(result) & DRIVER_SENSE)
		scode = sense[2] & 0x0f;
	else {
		sense[0] = 0;	/* We don't have sense data if this byte is zero */
		scode = 0;
	}

        DEB(
        if (debugging) {
                printk(ST_DEB_MSG "st%d: Error: %x, cmd: %x %x %x %x %x %x Len: %d\n",
		       dev, result,
		       SCpnt->data_cmnd[0], SCpnt->data_cmnd[1], SCpnt->data_cmnd[2],
		       SCpnt->data_cmnd[3], SCpnt->data_cmnd[4], SCpnt->data_cmnd[5],
		       SCpnt->request_bufflen);
		if (driver_byte(result) & DRIVER_SENSE)
			print_sense("st", SCpnt);
	} else ) /* end DEB */
		if (!(driver_byte(result) & DRIVER_SENSE) ||
		    ((sense[0] & 0x70) == 0x70 &&
		     scode != NO_SENSE &&
		     scode != RECOVERED_ERROR &&
                     /* scode != UNIT_ATTENTION && */
		     scode != BLANK_CHECK &&
		     scode != VOLUME_OVERFLOW &&
		     SCpnt->data_cmnd[0] != MODE_SENSE &&
		     SCpnt->data_cmnd[0] != TEST_UNIT_READY)) {	/* Abnormal conditions for tape */
		if (driver_byte(result) & DRIVER_SENSE) {
			printk(KERN_WARNING "st%d: Error with sense data: ", dev);
			print_sense("st", SCpnt);
		} else
			printk(KERN_WARNING
			       "st%d: Error %x (sugg. bt 0x%x, driver bt 0x%x, host bt 0x%x).\n",
			       dev, result, suggestion(result),
                               driver_byte(result) & DRIVER_MASK, host_byte(result));
	}

	if ((sense[0] & 0x70) == 0x70 &&
	    scode == RECOVERED_ERROR
#if ST_RECOVERED_WRITE_FATAL
	    && SCpnt->data_cmnd[0] != WRITE_6
	    && SCpnt->data_cmnd[0] != WRITE_FILEMARKS
#endif
	    ) {
		scsi_tapes[dev].recover_count++;
		scsi_tapes[dev].mt_status->mt_erreg += (1 << MT_ST_SOFTERR_SHIFT);

                DEB(
		if (debugging) {
			if (SCpnt->data_cmnd[0] == READ_6)
				stp = "read";
			else if (SCpnt->data_cmnd[0] == WRITE_6)
				stp = "write";
			else
				stp = "ioctl";
			printk(ST_DEB_MSG "st%d: Recovered %s error (%d).\n", dev, stp,
			       scsi_tapes[dev].recover_count);
		} ) /* end DEB */

		if ((sense[2] & 0xe0) == 0)
			return 0;
	}
	return (-EIO);
}


/* Wakeup from interrupt */
static void st_sleep_done(Scsi_Cmnd * SCpnt)
{
	unsigned int st_nbr;
	int remainder;
	Scsi_Tape *STp;

	if ((st_nbr = TAPE_NR(SCpnt->request.rq_dev)) < st_template.nr_dev) {
		STp = &(scsi_tapes[st_nbr]);
		if ((STp->buffer)->writing &&
		    (SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
		    (SCpnt->sense_buffer[2] & 0x40)) {
			/* EOM at write-behind, has all been written? */
			if ((SCpnt->sense_buffer[0] & 0x80) != 0)
				remainder = (SCpnt->sense_buffer[3] << 24) |
                                    (SCpnt->sense_buffer[4] << 16) |
				    (SCpnt->sense_buffer[5] << 8) |
                                    SCpnt->sense_buffer[6];
			else
				remainder = 0;
			if ((SCpnt->sense_buffer[2] & 0x0f) == VOLUME_OVERFLOW ||
			    remainder > 0)
				(STp->buffer)->last_result = SCpnt->result;	/* Error */
			else
				(STp->buffer)->last_result = INT_MAX;	/* OK */
		} else
			(STp->buffer)->last_result = SCpnt->result;
		SCpnt->request.rq_status = RQ_SCSI_DONE;
		(STp->buffer)->last_SCpnt = SCpnt;
		DEB( STp->write_pending = 0; )

		up(SCpnt->request.sem);
	}
        DEB(
	else if (debugging)
		printk(KERN_ERR "st?: Illegal interrupt device %x\n", st_nbr);
	) /* end DEB */
}


/* Do the scsi command. Waits until command performed if do_wait is true.
   Otherwise write_behind_check() is used to check that the command
   has finished. */
static Scsi_Cmnd *
 st_do_scsi(Scsi_Cmnd * SCpnt, Scsi_Tape * STp, unsigned char *cmd, int bytes,
	    int timeout, int retries, int do_wait)
{
	unsigned char *bp;

	if (SCpnt == NULL)
		SCpnt = scsi_allocate_device(STp->device, 1, TRUE);
		if (SCpnt == NULL) {
			DEBC( printk(KERN_ERR "st%d: Can't get SCSI request.\n",
				     TAPE_NR(STp->devt)); );
			if (signal_pending(current))
				(STp->buffer)->last_result_fatal = (-EINTR);
			else
				(STp->buffer)->last_result_fatal = (-EBUSY);
			return NULL;
		}

	cmd[1] |= (SCpnt->lun << 5) & 0xe0;
	init_MUTEX_LOCKED(&STp->sem);
	SCpnt->use_sg = (bytes > (STp->buffer)->sg[0].length) ?
	    (STp->buffer)->use_sg : 0;
	if (SCpnt->use_sg) {
		bp = (char *) &((STp->buffer)->sg[0]);
		if ((STp->buffer)->sg_segs < SCpnt->use_sg)
			SCpnt->use_sg = (STp->buffer)->sg_segs;
	} else
		bp = (STp->buffer)->b_data;
	SCpnt->cmd_len = 0;
	SCpnt->request.sem = &(STp->sem);
	SCpnt->request.rq_status = RQ_SCSI_BUSY;
	SCpnt->request.rq_dev = STp->devt;

	scsi_do_cmd(SCpnt, (void *) cmd, bp, bytes,
		    st_sleep_done, timeout, retries);

	if (do_wait) {
		down(SCpnt->request.sem);
		(STp->buffer)->last_result_fatal = st_chk_result(SCpnt);
	}
	return SCpnt;
}


/* Handle the write-behind checking (downs the semaphore) */
static void write_behind_check(Scsi_Tape * STp)
{
	ST_buffer *STbuffer;
	ST_partstat *STps;

	STbuffer = STp->buffer;

        DEB(
	if (STp->write_pending)
		STp->nbr_waits++;
	else
		STp->nbr_finished++;
        ) /* end DEB */

	down(&(STp->sem));

	(STp->buffer)->last_result_fatal = st_chk_result((STp->buffer)->last_SCpnt);
	scsi_release_command((STp->buffer)->last_SCpnt);

	if (STbuffer->writing < STbuffer->buffer_bytes)
#if 0
		memcpy(STbuffer->b_data,
		       STbuffer->b_data + STbuffer->writing,
		       STbuffer->buffer_bytes - STbuffer->writing);
#else
		printk(KERN_WARNING
                       "st: write_behind_check: something left in buffer!\n");
#endif
	STbuffer->buffer_bytes -= STbuffer->writing;
	STps = &(STp->ps[STp->partition]);
	if (STps->drv_block >= 0) {
		if (STp->block_size == 0)
			STps->drv_block++;
		else
			STps->drv_block += STbuffer->writing / STp->block_size;
	}
	STbuffer->writing = 0;

	return;
}


/* Step over EOF if it has been inadvertently crossed (ioctl not used because
   it messes up the block number). */
static int cross_eof(Scsi_Tape * STp, int forward)
{
	Scsi_Cmnd *SCpnt;
	unsigned char cmd[10];

	cmd[0] = SPACE;
	cmd[1] = 0x01;		/* Space FileMarks */
	if (forward) {
		cmd[2] = cmd[3] = 0;
		cmd[4] = 1;
	} else
		cmd[2] = cmd[3] = cmd[4] = 0xff;	/* -1 filemarks */
	cmd[5] = 0;

        DEBC(printk(ST_DEB_MSG "st%d: Stepping over filemark %s.\n",
		   TAPE_NR(STp->devt), forward ? "forward" : "backward"));

	SCpnt = st_do_scsi(NULL, STp, cmd, 0, STp->timeout, MAX_RETRIES, TRUE);
	if (!SCpnt)
		return (STp->buffer)->last_result_fatal;

	scsi_release_command(SCpnt);
	SCpnt = NULL;

	if ((STp->buffer)->last_result != 0)
		printk(KERN_ERR "st%d: Stepping over filemark %s failed.\n",
		   TAPE_NR(STp->devt), forward ? "forward" : "backward");

	return (STp->buffer)->last_result_fatal;
}


/* Flush the write buffer (never need to write if variable blocksize). */
static int flush_write_buffer(Scsi_Tape * STp)
{
	int offset, transfer, blks;
	int result;
	unsigned char cmd[10];
	Scsi_Cmnd *SCpnt;
	ST_partstat *STps;

	if ((STp->buffer)->writing) {
		write_behind_check(STp);
		if ((STp->buffer)->last_result_fatal) {
                        DEBC(printk(ST_DEB_MSG
                                       "st%d: Async write error (flush) %x.\n",
				       TAPE_NR(STp->devt), (STp->buffer)->last_result))
			if ((STp->buffer)->last_result == INT_MAX)
				return (-ENOSPC);
			return (-EIO);
		}
	}
	if (STp->block_size == 0)
		return 0;

	result = 0;
	if (STp->dirty == 1) {

		offset = (STp->buffer)->buffer_bytes;
		transfer = ((offset + STp->block_size - 1) /
			    STp->block_size) * STp->block_size;
                DEBC(printk(ST_DEB_MSG "st%d: Flushing %d bytes.\n",
                               TAPE_NR(STp->devt), transfer));

		memset((STp->buffer)->b_data + offset, 0, transfer - offset);

		memset(cmd, 0, 10);
		cmd[0] = WRITE_6;
		cmd[1] = 1;
		blks = transfer / STp->block_size;
		cmd[2] = blks >> 16;
		cmd[3] = blks >> 8;
		cmd[4] = blks;

		SCpnt = st_do_scsi(NULL, STp, cmd, transfer, STp->timeout,
                                   MAX_WRITE_RETRIES, TRUE);
		if (!SCpnt)
			return (STp->buffer)->last_result_fatal;

		STps = &(STp->ps[STp->partition]);
		if ((STp->buffer)->last_result_fatal != 0) {
			if ((SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
			    (SCpnt->sense_buffer[2] & 0x40) &&
			    (SCpnt->sense_buffer[2] & 0x0f) == NO_SENSE) {
				STp->dirty = 0;
				(STp->buffer)->buffer_bytes = 0;
				result = (-ENOSPC);
			} else {
				printk(KERN_ERR "st%d: Error on flush.\n",
                                       TAPE_NR(STp->devt));
				result = (-EIO);
			}
			STps->drv_block = (-1);
		} else {
			if (STps->drv_block >= 0)
				STps->drv_block += blks;
			STp->dirty = 0;
			(STp->buffer)->buffer_bytes = 0;
		}
		scsi_release_command(SCpnt);
		SCpnt = NULL;
	}
	return result;
}


/* Flush the tape buffer. The tape will be positioned correctly unless
   seek_next is true. */
static int flush_buffer(struct inode *inode, struct file *filp, int seek_next)
{
	int backspace, result;
	Scsi_Tape *STp;
	ST_buffer *STbuffer;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);
	STbuffer = STp->buffer;

	/*
	 * If there was a bus reset, block further access
	 * to this device.
	 */
	if (STp->device->was_reset)
		return (-EIO);

	if (STp->ready != ST_READY)
		return 0;

	STps = &(STp->ps[STp->partition]);
	if (STps->rw == ST_WRITING)	/* Writing */
		return flush_write_buffer(STp);

	if (STp->block_size == 0)
		return 0;

	backspace = ((STp->buffer)->buffer_bytes +
		     (STp->buffer)->read_pointer) / STp->block_size -
	    ((STp->buffer)->read_pointer + STp->block_size - 1) /
	    STp->block_size;
	(STp->buffer)->buffer_bytes = 0;
	(STp->buffer)->read_pointer = 0;
	result = 0;
	if (!seek_next) {
		if (STps->eof == ST_FM_HIT) {
			result = cross_eof(STp, FALSE);	/* Back over the EOF hit */
			if (!result)
				STps->eof = ST_NOEOF;
			else {
				if (STps->drv_file >= 0)
					STps->drv_file++;
				STps->drv_block = 0;
			}
		}
		if (!result && backspace > 0)
			result = st_int_ioctl(inode, MTBSR, backspace);
	} else if (STps->eof == ST_FM_HIT) {
		if (STps->drv_file >= 0)
			STps->drv_file++;
		STps->drv_block = 0;
		STps->eof = ST_NOEOF;
	}
	return result;

}

/* Set the mode parameters */
static int set_mode_densblk(struct inode *inode, Scsi_Tape * STp, ST_mode * STm)
{
	int set_it = FALSE;
	unsigned long arg;
	int dev = TAPE_NR(inode->i_rdev);

	if (!STp->density_changed &&
	    STm->default_density >= 0 &&
	    STm->default_density != STp->density) {
		arg = STm->default_density;
		set_it = TRUE;
	} else
		arg = STp->density;
	arg <<= MT_ST_DENSITY_SHIFT;
	if (!STp->blksize_changed &&
	    STm->default_blksize >= 0 &&
	    STm->default_blksize != STp->block_size) {
		arg |= STm->default_blksize;
		set_it = TRUE;
	} else
		arg |= STp->block_size;
	if (set_it &&
	    st_int_ioctl(inode, SET_DENS_AND_BLK, arg)) {
		printk(KERN_WARNING
		       "st%d: Can't set default block size to %d bytes and density %x.\n",
		       dev, STm->default_blksize, STm->default_density);
		if (modes_defined)
			return (-EINVAL);
	}
	return 0;
}


/* Open the device */
static int scsi_tape_open(struct inode *inode, struct file *filp)
{
	unsigned short flags;
	int i, need_dma_buffer, new_session = FALSE;
	unsigned char cmd[10];
	Scsi_Cmnd *SCpnt;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);
	int mode = TAPE_MODE(inode->i_rdev);

	if (dev >= st_template.dev_max || !scsi_tapes[dev].device)
		return (-ENXIO);

	if (!scsi_block_when_processing_errors(scsi_tapes[dev].device)) {
		return -ENXIO;
	}
	STp = &(scsi_tapes[dev]);
	if (STp->in_use) {
		DEB( printk(ST_DEB_MSG "st%d: Device already in use.\n", dev); )
		return (-EBUSY);
	}
	STp->rew_at_close = (MINOR(inode->i_rdev) & 0x80) == 0;

	if (mode != STp->current_mode) {
                DEBC(printk(ST_DEB_MSG "st%d: Mode change from %d to %d.\n",
			       dev, STp->current_mode, mode));
		new_session = TRUE;
		STp->current_mode = mode;
	}
	STm = &(STp->modes[STp->current_mode]);

	/* Allocate a buffer for this user */
	need_dma_buffer = STp->restr_dma;
	for (i = 0; i < st_nbr_buffers; i++)
		if (!st_buffers[i]->in_use &&
		    (!need_dma_buffer || st_buffers[i]->dma))
			break;
	if (i >= st_nbr_buffers) {
		STp->buffer = new_tape_buffer(FALSE, need_dma_buffer);
		if (STp->buffer == NULL) {
			printk(KERN_WARNING "st%d: Can't allocate tape buffer.\n", dev);
			return (-EBUSY);
		}
	} else
		STp->buffer = st_buffers[i];
	(STp->buffer)->in_use = 1;
	(STp->buffer)->writing = 0;
	(STp->buffer)->last_result_fatal = 0;
	(STp->buffer)->use_sg = STp->device->host->sg_tablesize;

	/* Compute the usable buffer size for this SCSI adapter */
	if (!(STp->buffer)->use_sg)
		(STp->buffer)->buffer_size = (STp->buffer)->sg[0].length;
	else {
		for (i = 0, (STp->buffer)->buffer_size = 0; i < (STp->buffer)->use_sg &&
		     i < (STp->buffer)->sg_segs; i++)
			(STp->buffer)->buffer_size += (STp->buffer)->sg[i].length;
	}

	flags = filp->f_flags;
	STp->write_prot = ((flags & O_ACCMODE) == O_RDONLY);

	STp->dirty = 0;
	for (i = 0; i < ST_NBR_PARTITIONS; i++) {
		STps = &(STp->ps[i]);
		STps->rw = ST_IDLE;
	}
	STp->ready = ST_READY;
	STp->recover_count = 0;
	DEB( STp->nbr_waits = STp->nbr_finished = 0; )

	if (scsi_tapes[dev].device->host->hostt->module)
		__MOD_INC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
	if (st_template.module)
		__MOD_INC_USE_COUNT(st_template.module);

	memset((void *) &cmd[0], 0, 10);
	cmd[0] = TEST_UNIT_READY;

	SCpnt = st_do_scsi(NULL, STp, cmd, 0, STp->long_timeout, MAX_READY_RETRIES,
			   TRUE);
	if (!SCpnt) {
		if (scsi_tapes[dev].device->host->hostt->module)
			__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
		if (st_template.module)
			__MOD_DEC_USE_COUNT(st_template.module);
		return (STp->buffer)->last_result_fatal;
	}

	if ((SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
	    (SCpnt->sense_buffer[2] & 0x0f) == UNIT_ATTENTION) {	/* New media? */

		/* Flush the queued UNIT ATTENTION sense data */
		for (i=0; i < 10; i++) {
                        memset((void *) &cmd[0], 0, 10);
                        cmd[0] = TEST_UNIT_READY;
                        SCpnt = st_do_scsi(SCpnt, STp, cmd, 0, STp->long_timeout,
                                           MAX_READY_RETRIES, TRUE);
                        if ((SCpnt->sense_buffer[0] & 0x70) != 0x70 ||
                            (SCpnt->sense_buffer[2] & 0x0f) != UNIT_ATTENTION)
                                break;
		}

		(STp->device)->was_reset = 0;
		STp->partition = STp->new_partition = 0;
		if (STp->can_partitions)
			STp->nbr_partitions = 1; /* This guess will be updated later
                                                    if necessary */
		for (i = 0; i < ST_NBR_PARTITIONS; i++) {
			STps = &(STp->ps[i]);
			STps->rw = ST_IDLE;
			STps->eof = ST_NOEOF;
			STps->at_sm = 0;
			STps->last_block_valid = FALSE;
			STps->drv_block = 0;
			STps->drv_file = 0;
		}
		new_session = TRUE;
	}

	if ((STp->buffer)->last_result_fatal != 0) {
		if ((STp->device)->scsi_level >= SCSI_2 &&
		    (SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
		    (SCpnt->sense_buffer[2] & 0x0f) == NOT_READY &&
		    SCpnt->sense_buffer[12] == 0x3a) {	/* Check ASC */
			STp->ready = ST_NO_TAPE;
		} else
			STp->ready = ST_NOT_READY;
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		STp->density = 0;	/* Clear the erroneous "residue" */
		STp->write_prot = 0;
		STp->block_size = 0;
		STp->ps[0].drv_file = STp->ps[0].drv_block = (-1);
		STp->partition = STp->new_partition = 0;
		STp->door_locked = ST_UNLOCKED;
		STp->in_use = 1;
		return 0;
	}

	if (STp->omit_blklims)
		STp->min_block = STp->max_block = (-1);
	else {
		memset((void *) &cmd[0], 0, 10);
		cmd[0] = READ_BLOCK_LIMITS;

		SCpnt = st_do_scsi(SCpnt, STp, cmd, 6, STp->timeout, MAX_READY_RETRIES,
                                   TRUE);

		if (!SCpnt->result && !SCpnt->sense_buffer[0]) {
			STp->max_block = ((STp->buffer)->b_data[1] << 16) |
			    ((STp->buffer)->b_data[2] << 8) | (STp->buffer)->b_data[3];
			STp->min_block = ((STp->buffer)->b_data[4] << 8) |
			    (STp->buffer)->b_data[5];
			if ( DEB( debugging || ) !STp->inited)
				printk(KERN_WARNING
                                       "st%d: Block limits %d - %d bytes.\n", dev,
                                       STp->min_block, STp->max_block);
		} else {
			STp->min_block = STp->max_block = (-1);
                        DEBC(printk(ST_DEB_MSG "st%d: Can't read block limits.\n",
                                       dev));
		}
	}

	memset((void *) &cmd[0], 0, 10);
	cmd[0] = MODE_SENSE;
	cmd[4] = 12;

	SCpnt = st_do_scsi(SCpnt, STp, cmd, 12, STp->timeout, MAX_READY_RETRIES, TRUE);

	if ((STp->buffer)->last_result_fatal != 0) {
                DEBC(printk(ST_DEB_MSG "st%d: No Mode Sense.\n", dev));
		STp->block_size = ST_DEFAULT_BLOCK;	/* Educated guess (?) */
		(STp->buffer)->last_result_fatal = 0;	/* Prevent error propagation */
		STp->drv_write_prot = 0;
	} else {
                DEBC(printk(ST_DEB_MSG
                            "st%d: Mode sense. Length %d, medium %x, WBS %x, BLL %d\n",
                            dev,
                            (STp->buffer)->b_data[0], (STp->buffer)->b_data[1],
                            (STp->buffer)->b_data[2], (STp->buffer)->b_data[3]));

		if ((STp->buffer)->b_data[3] >= 8) {
			STp->drv_buffer = ((STp->buffer)->b_data[2] >> 4) & 7;
			STp->density = (STp->buffer)->b_data[4];
			STp->block_size = (STp->buffer)->b_data[9] * 65536 +
			    (STp->buffer)->b_data[10] * 256 + (STp->buffer)->b_data[11];
                        DEBC(printk(ST_DEB_MSG
                                    "st%d: Density %x, tape length: %x, drv buffer: %d\n",
                                    dev, STp->density, (STp->buffer)->b_data[5] * 65536 +
                                    (STp->buffer)->b_data[6] * 256 + (STp->buffer)->b_data[7],
                                    STp->drv_buffer));
		}

		if (STp->block_size > (STp->buffer)->buffer_size &&
		    !enlarge_buffer(STp->buffer, STp->block_size, STp->restr_dma)) {
			printk(KERN_NOTICE "st%d: Blocksize %d too large for buffer.\n",
                               dev, STp->block_size);
			scsi_release_command(SCpnt);
			(STp->buffer)->in_use = 0;
			STp->buffer = NULL;
			if (scsi_tapes[dev].device->host->hostt->module)
				__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
			if (st_template.module)
				__MOD_DEC_USE_COUNT(st_template.module);
			return (-EIO);
		}
		STp->drv_write_prot = ((STp->buffer)->b_data[2] & 0x80) != 0;
	}
	scsi_release_command(SCpnt);
	SCpnt = NULL;
        STp->inited = TRUE;

	if (STp->block_size > 0)
		(STp->buffer)->buffer_blocks =
                        (STp->buffer)->buffer_size / STp->block_size;
	else
		(STp->buffer)->buffer_blocks = 1;
	(STp->buffer)->buffer_bytes = (STp->buffer)->read_pointer = 0;

        DEBC(printk(ST_DEB_MSG
                       "st%d: Block size: %d, buffer size: %d (%d blocks).\n", dev,
		       STp->block_size, (STp->buffer)->buffer_size,
		       (STp->buffer)->buffer_blocks));

	if (STp->drv_write_prot) {
		STp->write_prot = 1;

                DEBC(printk(ST_DEB_MSG "st%d: Write protected\n", dev));

		if ((flags & O_ACCMODE) == O_WRONLY || (flags & O_ACCMODE) == O_RDWR) {
			(STp->buffer)->in_use = 0;
			STp->buffer = NULL;
			if (scsi_tapes[dev].device->host->hostt->module)
				__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
			if (st_template.module)
				__MOD_DEC_USE_COUNT(st_template.module);
			return (-EROFS);
		}
	}

	if (STp->can_partitions && STp->nbr_partitions < 1) {
		/* This code is reached when the device is opened for the first time
		   after the driver has been initialized with tape in the drive and the
		   partition support has been enabled. */
                DEBC(printk(ST_DEB_MSG
                            "st%d: Updating partition number in status.\n", dev));
		if ((STp->partition = find_partition(inode)) < 0) {
			(STp->buffer)->in_use = 0;
			STp->buffer = NULL;
			if (scsi_tapes[dev].device->host->hostt->module)
				__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
			if (st_template.module)
				__MOD_DEC_USE_COUNT(st_template.module);
			return STp->partition;
		}
		STp->new_partition = STp->partition;
		STp->nbr_partitions = 1; /* This guess will be updated when necessary */
	}

	if (new_session) {	/* Change the drive parameters for the new mode */
		STp->density_changed = STp->blksize_changed = FALSE;
		STp->compression_changed = FALSE;
		if (!(STm->defaults_for_writes) &&
		    (i = set_mode_densblk(inode, STp, STm)) < 0) {
			(STp->buffer)->in_use = 0;
			STp->buffer = NULL;
			if (scsi_tapes[dev].device->host->hostt->module)
				__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
			if (st_template.module)
				__MOD_DEC_USE_COUNT(st_template.module);
			return i;
		}

		if (STp->default_drvbuffer != 0xff) {
			if (st_int_ioctl(inode, MTSETDRVBUFFER, STp->default_drvbuffer))
				printk(KERN_WARNING
                                       "st%d: Can't set default drive buffering to %d.\n",
				       dev, STp->default_drvbuffer);
		}
	}
	STp->in_use = 1;

	return 0;
}


/* Flush the tape buffer before close */
static int scsi_tape_flush(struct file *filp)
{
	int result = 0, result2;
	static unsigned char cmd[10];
	Scsi_Cmnd *SCpnt;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;

	struct inode *inode = filp->f_dentry->d_inode;
	kdev_t devt = inode->i_rdev;
	int dev;

	if (file_count(filp) > 1)
		return 0;

	dev = TAPE_NR(devt);
	STp = &(scsi_tapes[dev]);
	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);

	if (STp->can_partitions &&
	    (result = update_partition(inode)) < 0) {
                DEBC(printk(ST_DEB_MSG
                               "st%d: update_partition at close failed.\n", dev));
		goto out;
	}

	if (STps->rw == ST_WRITING && !(STp->device)->was_reset) {

		result = flush_write_buffer(STp);

                DEBC(printk(ST_DEB_MSG "st%d: File length %ld bytes.\n",
                            dev, (long) (filp->f_pos));
                     printk(ST_DEB_MSG "st%d: Async write waits %d, finished %d.\n",
                            dev, STp->nbr_waits, STp->nbr_finished);
		)

		if (result == 0 || result == (-ENOSPC)) {

			memset(cmd, 0, 10);
			cmd[0] = WRITE_FILEMARKS;
			cmd[4] = 1 + STp->two_fm;

			SCpnt = st_do_scsi(NULL, STp, cmd, 0, STp->timeout,
                                           MAX_WRITE_RETRIES, TRUE);
			if (!SCpnt) {
				result = (STp->buffer)->last_result_fatal;
				goto out;
			}

			if ((STp->buffer)->last_result_fatal != 0 &&
			    ((SCpnt->sense_buffer[0] & 0x70) != 0x70 ||
			     (SCpnt->sense_buffer[2] & 0x4f) != 0x40 ||
			     ((SCpnt->sense_buffer[0] & 0x80) != 0 &&
			(SCpnt->sense_buffer[3] | SCpnt->sense_buffer[4] |
			 SCpnt->sense_buffer[5] |
			 SCpnt->sense_buffer[6]) == 0))) {
				/* Filter out successful write at EOM */
				scsi_release_command(SCpnt);
				SCpnt = NULL;
				printk(KERN_ERR "st%d: Error on write filemark.\n", dev);
				if (result == 0)
					result = (-EIO);
			} else {
				scsi_release_command(SCpnt);
				SCpnt = NULL;
				if (STps->drv_file >= 0)
					STps->drv_file++;
				STps->drv_block = 0;
				if (STp->two_fm)
					cross_eof(STp, FALSE);
				STps->eof = ST_FM;
			}
		}

                DEBC(printk(ST_DEB_MSG "st%d: Buffer flushed, %d EOF(s) written\n",
                            dev, cmd[4]));
	} else if (!STp->rew_at_close) {
		STps = &(STp->ps[STp->partition]);
		if (!STm->sysv || STps->rw != ST_READING) {
			if (STp->can_bsr)
				result = flush_buffer(inode, filp, 0);
			else if (STps->eof == ST_FM_HIT) {
				result = cross_eof(STp, FALSE);
				if (result) {
					if (STps->drv_file >= 0)
						STps->drv_file++;
					STps->drv_block = 0;
					STps->eof = ST_FM;
				} else
					STps->eof = ST_NOEOF;
			}
		} else if ((STps->eof == ST_NOEOF &&
			    !(result = cross_eof(STp, TRUE))) ||
			   STps->eof == ST_FM_HIT) {
			if (STps->drv_file >= 0)
				STps->drv_file++;
			STps->drv_block = 0;
			STps->eof = ST_FM;
		}
	}

      out:
	if (STp->rew_at_close) {
		result2 = st_int_ioctl(inode, MTREW, 1);
		if (result == 0)
			result = result2;
	}
	return result;
}


/* Close the device and release it */
static int scsi_tape_close(struct inode *inode, struct file *filp)
{
	int result = 0;
	Scsi_Tape *STp;

	kdev_t devt = inode->i_rdev;
	int dev;

	dev = TAPE_NR(devt);
	STp = &(scsi_tapes[dev]);

	if (STp->door_locked == ST_LOCKED_AUTO)
		st_int_ioctl(inode, MTUNLOCK, 0);

	if (STp->buffer != NULL) {
		normalize_buffer(STp->buffer);
		(STp->buffer)->in_use = 0;
	}

	STp->in_use = 0;
	if (scsi_tapes[dev].device->host->hostt->module)
		__MOD_DEC_USE_COUNT(scsi_tapes[dev].device->host->hostt->module);
	if (st_template.module)
		__MOD_DEC_USE_COUNT(st_template.module);

	return result;
}


/* Write command */
static ssize_t
 st_write(struct file *filp, const char *buf, size_t count, loff_t * ppos)
{
	struct inode *inode = filp->f_dentry->d_inode;
	ssize_t total;
	ssize_t i, do_count, blks, retval, transfer;
	int write_threshold;
	int doing_write = 0;
	static unsigned char cmd[10];
	const char *b_point;
	Scsi_Cmnd *SCpnt = NULL;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);

	/*
	 * If we are in the middle of error recovery, don't let anyone
	 * else try and use this device.  Also, if error recovery fails, it
	 * may try and take the device offline, in which case all further
	 * access to the device is prohibited.
	 */
	if (!scsi_block_when_processing_errors(STp->device)) {
		return -ENXIO;
	}

	if (ppos != &filp->f_pos) {
		/* "A request was outside the capabilities of the device." */
		return -ENXIO;
	}

	if (STp->ready != ST_READY) {
		if (STp->ready == ST_NO_TAPE)
			return (-ENOMEDIUM);
		else
			return (-EIO);
	}

	STm = &(STp->modes[STp->current_mode]);
	if (!STm->defined)
		return (-ENXIO);
	if (count == 0)
		return 0;

	/*
	 * If there was a bus reset, block further access
	 * to this device.
	 */
	if (STp->device->was_reset)
		return (-EIO);

        DEB(
	if (!STp->in_use) {
		printk(ST_DEB_MSG "st%d: Incorrect device.\n", dev);
		return (-EIO);
	} ) /* end DEB */

	/* Write must be integral number of blocks */
	if (STp->block_size != 0 && (count % STp->block_size) != 0) {
		printk(KERN_WARNING "st%d: Write not multiple of tape block size.\n",
		       dev);
		return (-EIO);
	}

	if (STp->can_partitions &&
	    (retval = update_partition(inode)) < 0)
		return retval;
	STps = &(STp->ps[STp->partition]);

	if (STp->write_prot)
		return (-EACCES);

	if (STp->block_size == 0 &&
	    count > (STp->buffer)->buffer_size &&
	    !enlarge_buffer(STp->buffer, count, STp->restr_dma))
		return (-EOVERFLOW);

	if (STp->do_auto_lock && STp->door_locked == ST_UNLOCKED &&
	    !st_int_ioctl(inode, MTLOCK, 0))
		STp->door_locked = ST_LOCKED_AUTO;

	if (STps->rw == ST_READING) {
		retval = flush_buffer(inode, filp, 0);
		if (retval)
			return retval;
		STps->rw = ST_WRITING;
	} else if (STps->rw != ST_WRITING &&
		   STps->drv_file == 0 && STps->drv_block == 0) {
		if ((retval = set_mode_densblk(inode, STp, STm)) < 0)
			return retval;
		if (STm->default_compression != ST_DONT_TOUCH &&
		    !(STp->compression_changed)) {
			if (st_compression(STp, (STm->default_compression == ST_YES))) {
				printk(KERN_WARNING "st%d: Can't set default compression.\n",
				       dev);
				if (modes_defined)
					return (-EINVAL);
			}
		}
	}

	if ((STp->buffer)->writing) {
		write_behind_check(STp);
		if ((STp->buffer)->last_result_fatal) {
                        DEBC(printk(ST_DEB_MSG "st%d: Async write error (write) %x.\n",
                                    dev, (STp->buffer)->last_result));
			if ((STp->buffer)->last_result == INT_MAX)
				STps->eof = ST_EOM_OK;
			else
				STps->eof = ST_EOM_ERROR;
		}
	}

	if (STps->eof == ST_EOM_OK)
		return (-ENOSPC);
	else if (STps->eof == ST_EOM_ERROR)
		return (-EIO);

	/* Check the buffer readability in cases where copy_user might catch
	   the problems after some tape movement. */
	if (STp->block_size != 0 &&
	    (copy_from_user(&i, buf, 1) != 0 ||
	     copy_from_user(&i, buf + count - 1, 1) != 0))
		return (-EFAULT);

	if (!STm->do_buffer_writes) {
#if 0
		if (STp->block_size != 0 && (count % STp->block_size) != 0)
			return (-EIO);	/* Write must be integral number of blocks */
#endif
		write_threshold = 1;
	} else
		write_threshold = (STp->buffer)->buffer_blocks * STp->block_size;
	if (!STm->do_async_writes)
		write_threshold--;

	total = count;

	memset(cmd, 0, 10);
	cmd[0] = WRITE_6;
	cmd[1] = (STp->block_size != 0);

	STps->rw = ST_WRITING;

	b_point = buf;
	while ((STp->block_size == 0 && !STm->do_async_writes && count > 0) ||
	       (STp->block_size != 0 &&
		(STp->buffer)->buffer_bytes + count > write_threshold)) {
		doing_write = 1;
		if (STp->block_size == 0)
			do_count = count;
		else {
			do_count = (STp->buffer)->buffer_blocks * STp->block_size -
			    (STp->buffer)->buffer_bytes;
			if (do_count > count)
				do_count = count;
		}

		i = append_to_buffer(b_point, STp->buffer, do_count);
		if (i) {
			if (SCpnt != NULL) {
				scsi_release_command(SCpnt);
				SCpnt = NULL;
			}
			return i;
		}

		if (STp->block_size == 0)
			blks = transfer = do_count;
		else {
			blks = (STp->buffer)->buffer_bytes /
			    STp->block_size;
			transfer = blks * STp->block_size;
		}
		cmd[2] = blks >> 16;
		cmd[3] = blks >> 8;
		cmd[4] = blks;

		SCpnt = st_do_scsi(SCpnt, STp, cmd, transfer, STp->timeout,
				   MAX_WRITE_RETRIES, TRUE);
		if (!SCpnt)
			return (STp->buffer)->last_result_fatal;

		if ((STp->buffer)->last_result_fatal != 0) {
                        DEBC(printk(ST_DEB_MSG "st%d: Error on write:\n", dev));
			if ((SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
			    (SCpnt->sense_buffer[2] & 0x40)) {
				if (STp->block_size != 0 &&
                                    (SCpnt->sense_buffer[0] & 0x80) != 0)
					transfer = (SCpnt->sense_buffer[3] << 24) |
					    (SCpnt->sense_buffer[4] << 16) |
					    (SCpnt->sense_buffer[5] << 8) |
                                                SCpnt->sense_buffer[6];
				else if (STp->block_size == 0 &&
					 (SCpnt->sense_buffer[2] & 0x0f) ==
                                         VOLUME_OVERFLOW)
					transfer = do_count;
				else
					transfer = 0;
				if (STp->block_size != 0)
					transfer *= STp->block_size;
				if (transfer <= do_count) {
					filp->f_pos += do_count - transfer;
					count -= do_count - transfer;
					if (STps->drv_block >= 0) {
						if (STp->block_size == 0 &&
                                                    transfer < do_count)
							STps->drv_block++;
						else if (STp->block_size != 0)
							STps->drv_block +=
                                                                (do_count - transfer) /
                                                                STp->block_size;
					}
					STps->eof = ST_EOM_OK;
					retval = (-ENOSPC); /* EOM within current request */
                                        DEBC(printk(ST_DEB_MSG
                                                       "st%d: EOM with %d bytes unwritten.\n",
						       dev, transfer));
				} else {
					STps->eof = ST_EOM_ERROR;
					STps->drv_block = (-1); /* Too cautious? */
					retval = (-EIO);	/* EOM for old data */
					DEBC(printk(ST_DEB_MSG
                                                       "st%d: EOM with lost data.\n",
                                                       dev));
				}
			} else {
				STps->drv_block = (-1);		/* Too cautious? */
				retval = (-EIO);
			}

			scsi_release_command(SCpnt);
			SCpnt = NULL;
			(STp->buffer)->buffer_bytes = 0;
			STp->dirty = 0;
			if (count < total)
				return total - count;
			else
				return retval;
		}
		filp->f_pos += do_count;
		b_point += do_count;
		count -= do_count;
		if (STps->drv_block >= 0) {
			if (STp->block_size == 0)
				STps->drv_block++;
			else
				STps->drv_block += blks;
		}
		(STp->buffer)->buffer_bytes = 0;
		STp->dirty = 0;
	}
	if (count != 0) {
		STp->dirty = 1;
		i = append_to_buffer(b_point, STp->buffer, count);
		if (i) {
			if (SCpnt != NULL) {
				scsi_release_command(SCpnt);
				SCpnt = NULL;
			}
			return i;
		}
		filp->f_pos += count;
		count = 0;
	}

	if (doing_write && (STp->buffer)->last_result_fatal != 0) {
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		return (STp->buffer)->last_result_fatal;
	}

	if (STm->do_async_writes &&
	    (((STp->buffer)->buffer_bytes >= STp->write_threshold &&
	      (STp->buffer)->buffer_bytes >= STp->block_size) ||
	     STp->block_size == 0)) {
		/* Schedule an asynchronous write */
		if (STp->block_size == 0)
			(STp->buffer)->writing = (STp->buffer)->buffer_bytes;
		else
			(STp->buffer)->writing = ((STp->buffer)->buffer_bytes /
				      STp->block_size) * STp->block_size;
		STp->dirty = !((STp->buffer)->writing ==
			       (STp->buffer)->buffer_bytes);

		if (STp->block_size == 0)
			blks = (STp->buffer)->writing;
		else
			blks = (STp->buffer)->writing / STp->block_size;
		cmd[2] = blks >> 16;
		cmd[3] = blks >> 8;
		cmd[4] = blks;
		DEB( STp->write_pending = 1; )

		SCpnt = st_do_scsi(SCpnt, STp, cmd, (STp->buffer)->writing, STp->timeout,
				   MAX_WRITE_RETRIES, FALSE);
		if (SCpnt == NULL)
			return (STp->buffer)->last_result_fatal;

	} else if (SCpnt != NULL) {
		scsi_release_command(SCpnt);
		SCpnt = NULL;
	}
	STps->at_sm &= (total == 0);
	if (total > 0)
		STps->eof = ST_NOEOF;

	return (total);
}

/* Read data from the tape. Returns zero in the normal case, one if the
   eof status has changed, and the negative error code in case of a
   fatal error. Otherwise updates the buffer and the eof state. */
static long read_tape(struct inode *inode, long count, Scsi_Cmnd ** aSCpnt)
{
	int transfer, blks, bytes;
	static unsigned char cmd[10];
	Scsi_Cmnd *SCpnt;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);
	int retval = 0;

	if (count == 0)
		return 0;

	STp = &(scsi_tapes[dev]);
	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);
	if (STps->eof == ST_FM_HIT)
		return 1;

	memset(cmd, 0, 10);
	cmd[0] = READ_6;
	cmd[1] = (STp->block_size != 0);
	if (STp->block_size == 0)
		blks = bytes = count;
	else {
		if (STm->do_read_ahead) {
			blks = (STp->buffer)->buffer_blocks;
			bytes = blks * STp->block_size;
		} else {
			bytes = count;
			if (bytes > (STp->buffer)->buffer_size)
				bytes = (STp->buffer)->buffer_size;
			blks = bytes / STp->block_size;
			bytes = blks * STp->block_size;
		}
	}
	cmd[2] = blks >> 16;
	cmd[3] = blks >> 8;
	cmd[4] = blks;

	SCpnt = *aSCpnt;
	SCpnt = st_do_scsi(SCpnt, STp, cmd, bytes, STp->timeout, MAX_RETRIES, TRUE);
	*aSCpnt = SCpnt;
	if (!SCpnt)
		return (STp->buffer)->last_result_fatal;

	(STp->buffer)->read_pointer = 0;
	STps->at_sm = 0;

	/* Something to check */
	if ((STp->buffer)->last_result_fatal) {
		retval = 1;
		DEBC(printk(ST_DEB_MSG "st%d: Sense: %2x %2x %2x %2x %2x %2x %2x %2x\n",
                            dev,
                            SCpnt->sense_buffer[0], SCpnt->sense_buffer[1],
                            SCpnt->sense_buffer[2], SCpnt->sense_buffer[3],
                            SCpnt->sense_buffer[4], SCpnt->sense_buffer[5],
                            SCpnt->sense_buffer[6], SCpnt->sense_buffer[7]));
		if ((SCpnt->sense_buffer[0] & 0x70) == 0x70) {	/* extended sense */

			if ((SCpnt->sense_buffer[2] & 0x0f) == BLANK_CHECK)
				SCpnt->sense_buffer[2] &= 0xcf;	/* No need for EOM in this case */

			if ((SCpnt->sense_buffer[2] & 0xe0) != 0) { /* EOF, EOM, or ILI */
				/* Compute the residual count */
				if ((SCpnt->sense_buffer[0] & 0x80) != 0)
					transfer = (SCpnt->sense_buffer[3] << 24) |
					    (SCpnt->sense_buffer[4] << 16) |
					    (SCpnt->sense_buffer[5] << 8) | SCpnt->sense_buffer[6];
				else
					transfer = 0;
				if (STp->block_size == 0 &&
				    (SCpnt->sense_buffer[2] & 0x0f) == MEDIUM_ERROR)
					transfer = bytes;

				if (SCpnt->sense_buffer[2] & 0x20) {	/* ILI */
					if (STp->block_size == 0) {
						if (transfer <= 0)
							transfer = 0;
						(STp->buffer)->buffer_bytes = bytes - transfer;
					} else {
						scsi_release_command(SCpnt);
						SCpnt = *aSCpnt = NULL;
						if (transfer == blks) {	/* We did not get anything, error */
							printk(KERN_NOTICE "st%d: Incorrect block size.\n", dev);
							if (STps->drv_block >= 0)
								STps->drv_block += blks - transfer + 1;
							st_int_ioctl(inode, MTBSR, 1);
							return (-EIO);
						}
						/* We have some data, deliver it */
						(STp->buffer)->buffer_bytes = (blks - transfer) *
						    STp->block_size;
                                                DEBC(printk(ST_DEB_MSG
                                                            "st%d: ILI but enough data received %ld %d.\n",
                                                            dev, count, (STp->buffer)->buffer_bytes));
						if (STps->drv_block >= 0)
							STps->drv_block += 1;
						if (st_int_ioctl(inode, MTBSR, 1))
							return (-EIO);
					}
				} else if (SCpnt->sense_buffer[2] & 0x80) {	/* FM overrides EOM */
					if (STps->eof != ST_FM_HIT)
						STps->eof = ST_FM_HIT;
					else
						STps->eof = ST_EOD_2;
					if (STp->block_size == 0)
						(STp->buffer)->buffer_bytes = 0;
					else
						(STp->buffer)->buffer_bytes =
						    bytes - transfer * STp->block_size;
                                        DEBC(printk(ST_DEB_MSG
                                                    "st%d: EOF detected (%d bytes read).\n",
                                                    dev, (STp->buffer)->buffer_bytes));
				} else if (SCpnt->sense_buffer[2] & 0x40) {
					if (STps->eof == ST_FM)
						STps->eof = ST_EOD_1;
					else
						STps->eof = ST_EOM_OK;
					if (STp->block_size == 0)
						(STp->buffer)->buffer_bytes = bytes - transfer;
					else
						(STp->buffer)->buffer_bytes =
						    bytes - transfer * STp->block_size;

                                        DEBC(printk(ST_DEB_MSG "st%d: EOM detected (%d bytes read).\n",
                                                    dev, (STp->buffer)->buffer_bytes));
				}
			}
			/* end of EOF, EOM, ILI test */ 
			else {	/* nonzero sense key */
                                DEBC(printk(ST_DEB_MSG
                                            "st%d: Tape error while reading.\n", dev));
				STps->drv_block = (-1);
				if (STps->eof == ST_FM &&
				    (SCpnt->sense_buffer[2] & 0x0f) == BLANK_CHECK) {
                                        DEBC(printk(ST_DEB_MSG
                                                    "st%d: Zero returned for first BLANK CHECK after EOF.\n",
                                                    dev));
					STps->eof = ST_EOD_2;	/* First BLANK_CHECK after FM */
				} else	/* Some other extended sense code */
					retval = (-EIO);
			}
		}
		/* End of extended sense test */ 
		else {		/* Non-extended sense */
			retval = (STp->buffer)->last_result_fatal;
		}

	}
	/* End of error handling */ 
	else			/* Read successful */
		(STp->buffer)->buffer_bytes = bytes;

	if (STps->drv_block >= 0) {
		if (STp->block_size == 0)
			STps->drv_block++;
		else
			STps->drv_block += (STp->buffer)->buffer_bytes / STp->block_size;
	}
	return retval;
}


/* Read command */
static ssize_t
 st_read(struct file *filp, char *buf, size_t count, loff_t * ppos)
{
	struct inode *inode = filp->f_dentry->d_inode;
	ssize_t total;
	ssize_t i, transfer;
	int special;
	Scsi_Cmnd *SCpnt = NULL;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);

	/*
	 * If we are in the middle of error recovery, don't let anyone
	 * else try and use this device.  Also, if error recovery fails, it
	 * may try and take the device offline, in which case all further
	 * access to the device is prohibited.
	 */
	if (!scsi_block_when_processing_errors(STp->device)) {
		return -ENXIO;
	}

	if (ppos != &filp->f_pos) {
		/* "A request was outside the capabilities of the device." */
		return -ENXIO;
	}

	if (STp->ready != ST_READY) {
		if (STp->ready == ST_NO_TAPE)
			return (-ENOMEDIUM);
		else
			return (-EIO);
	}
	STm = &(STp->modes[STp->current_mode]);
	if (!STm->defined)
		return (-ENXIO);
        DEB(
	if (!STp->in_use) {
		printk(ST_DEB_MSG "st%d: Incorrect device.\n", dev);
		return (-EIO);
	} ) /* end DEB */

	if (STp->can_partitions &&
	    (total = update_partition(inode)) < 0)
		return total;

	if (STp->block_size == 0 &&
	    count > (STp->buffer)->buffer_size &&
	    !enlarge_buffer(STp->buffer, count, STp->restr_dma))
		return (-EOVERFLOW);

	if (!(STm->do_read_ahead) && STp->block_size != 0 &&
	    (count % STp->block_size) != 0)
		return (-EIO);	/* Read must be integral number of blocks */

	if (STp->do_auto_lock && STp->door_locked == ST_UNLOCKED &&
	    !st_int_ioctl(inode, MTLOCK, 0))
		STp->door_locked = ST_LOCKED_AUTO;

	STps = &(STp->ps[STp->partition]);
	if (STps->rw == ST_WRITING) {
		transfer = flush_buffer(inode, filp, 0);
		if (transfer)
			return transfer;
		STps->rw = ST_READING;
	}
        DEB(
	if (debugging && STps->eof != ST_NOEOF)
		printk(ST_DEB_MSG "st%d: EOF/EOM flag up (%d). Bytes %d\n", dev,
		       STps->eof, (STp->buffer)->buffer_bytes);
        ) /* end DEB */

	if ((STp->buffer)->buffer_bytes == 0 &&
	    STps->eof >= ST_EOD_1) {
		if (STps->eof < ST_EOD) {
			STps->eof += 1;
			return 0;
		}
		return (-EIO);	/* EOM or Blank Check */
	}

	/* Check the buffer writability before any tape movement. Don't alter
	   buffer data. */
	if (copy_from_user(&i, buf, 1) != 0 ||
	    copy_to_user(buf, &i, 1) != 0 ||
	    copy_from_user(&i, buf + count - 1, 1) != 0 ||
	    copy_to_user(buf + count - 1, &i, 1) != 0)
		return (-EFAULT);

	STps->rw = ST_READING;


	/* Loop until enough data in buffer or a special condition found */
	for (total = 0, special = 0; total < count && !special;) {

		/* Get new data if the buffer is empty */
		if ((STp->buffer)->buffer_bytes == 0) {
			special = read_tape(inode, count - total, &SCpnt);
			if (special < 0) {	/* No need to continue read */
				if (SCpnt != NULL) {
					scsi_release_command(SCpnt);
				}
				return special;
			}
		}

		/* Move the data from driver buffer to user buffer */
		if ((STp->buffer)->buffer_bytes > 0) {
                        DEB(
			if (debugging && STps->eof != ST_NOEOF)
				printk(ST_DEB_MSG
                                       "st%d: EOF up (%d). Left %d, needed %d.\n", dev,
				       STps->eof, (STp->buffer)->buffer_bytes,
                                       count - total);
                        ) /* end DEB */
			transfer = (STp->buffer)->buffer_bytes < count - total ?
			    (STp->buffer)->buffer_bytes : count - total;
			i = from_buffer(STp->buffer, buf, transfer);
			if (i) {
				if (SCpnt != NULL) {
					scsi_release_command(SCpnt);
					SCpnt = NULL;
				}
				return i;
			}
			filp->f_pos += transfer;
			buf += transfer;
			total += transfer;
		}

		if (STp->block_size == 0)
			break;	/* Read only one variable length block */

	}			/* for (total = 0, special = 0;
                                   total < count && !special; ) */

	if (SCpnt != NULL) {
		scsi_release_command(SCpnt);
		SCpnt = NULL;
	}

	/* Change the eof state if no data from tape or buffer */
	if (total == 0) {
		if (STps->eof == ST_FM_HIT) {
			STps->eof = ST_FM;
			STps->drv_block = 0;
			if (STps->drv_file >= 0)
				STps->drv_file++;
		} else if (STps->eof == ST_EOD_1) {
			STps->eof = ST_EOD_2;
			STps->drv_block = 0;
			if (STps->drv_file >= 0)
				STps->drv_file++;
		} else if (STps->eof == ST_EOD_2)
			STps->eof = ST_EOD;
	} else if (STps->eof == ST_FM)
		STps->eof = ST_NOEOF;

	return total;
}



/* Set the driver options */
static void st_log_options(Scsi_Tape * STp, ST_mode * STm, int dev)
{
	printk(KERN_INFO
	       "st%d: Mode %d options: buffer writes: %d, async writes: %d, read ahead: %d\n",
	       dev, STp->current_mode, STm->do_buffer_writes, STm->do_async_writes,
	       STm->do_read_ahead);
	printk(KERN_INFO
	       "st%d:    can bsr: %d, two FMs: %d, fast mteom: %d, auto lock: %d,\n",
	       dev, STp->can_bsr, STp->two_fm, STp->fast_mteom, STp->do_auto_lock);
	printk(KERN_INFO
	       "st%d:    defs for wr: %d, no block limits: %d, partitions: %d, s2 log: %d\n",
	       dev, STm->defaults_for_writes, STp->omit_blklims, STp->can_partitions,
	       STp->scsi2_logical);
	printk(KERN_INFO
	       "st%d:    sysv: %d\n", dev, STm->sysv);
        DEB(printk(KERN_INFO
                   "st%d:    debugging: %d\n",
                   dev, debugging);)
}


static int st_set_options(struct inode *inode, long options)
{
	int value;
	long code;
	Scsi_Tape *STp;
	ST_mode *STm;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);
	STm = &(STp->modes[STp->current_mode]);
	if (!STm->defined) {
		memcpy(STm, &(STp->modes[0]), sizeof(ST_mode));
		modes_defined = TRUE;
                DEBC(printk(ST_DEB_MSG
                            "st%d: Initialized mode %d definition from mode 0\n",
                            dev, STp->current_mode));
	}

	code = options & MT_ST_OPTIONS;
	if (code == MT_ST_BOOLEANS) {
		STm->do_buffer_writes = (options & MT_ST_BUFFER_WRITES) != 0;
		STm->do_async_writes = (options & MT_ST_ASYNC_WRITES) != 0;
		STm->defaults_for_writes = (options & MT_ST_DEF_WRITES) != 0;
		STm->do_read_ahead = (options & MT_ST_READ_AHEAD) != 0;
		STp->two_fm = (options & MT_ST_TWO_FM) != 0;
		STp->fast_mteom = (options & MT_ST_FAST_MTEOM) != 0;
		STp->do_auto_lock = (options & MT_ST_AUTO_LOCK) != 0;
		STp->can_bsr = (options & MT_ST_CAN_BSR) != 0;
		STp->omit_blklims = (options & MT_ST_NO_BLKLIMS) != 0;
		if ((STp->device)->scsi_level >= SCSI_2)
			STp->can_partitions = (options & MT_ST_CAN_PARTITIONS) != 0;
		STp->scsi2_logical = (options & MT_ST_SCSI2LOGICAL) != 0;
		STm->sysv = (options & MT_ST_SYSV) != 0;
		DEB( debugging = (options & MT_ST_DEBUGGING) != 0; )
		st_log_options(STp, STm, dev);
	} else if (code == MT_ST_SETBOOLEANS || code == MT_ST_CLEARBOOLEANS) {
		value = (code == MT_ST_SETBOOLEANS);
		if ((options & MT_ST_BUFFER_WRITES) != 0)
			STm->do_buffer_writes = value;
		if ((options & MT_ST_ASYNC_WRITES) != 0)
			STm->do_async_writes = value;
		if ((options & MT_ST_DEF_WRITES) != 0)
			STm->defaults_for_writes = value;
		if ((options & MT_ST_READ_AHEAD) != 0)
			STm->do_read_ahead = value;
		if ((options & MT_ST_TWO_FM) != 0)
			STp->two_fm = value;
		if ((options & MT_ST_FAST_MTEOM) != 0)
			STp->fast_mteom = value;
		if ((options & MT_ST_AUTO_LOCK) != 0)
			STp->do_auto_lock = value;
		if ((options & MT_ST_CAN_BSR) != 0)
			STp->can_bsr = value;
		if ((options & MT_ST_NO_BLKLIMS) != 0)
			STp->omit_blklims = value;
		if ((STp->device)->scsi_level >= SCSI_2 &&
		    (options & MT_ST_CAN_PARTITIONS) != 0)
			STp->can_partitions = value;
		if ((options & MT_ST_SCSI2LOGICAL) != 0)
			STp->scsi2_logical = value;
		if ((options & MT_ST_SYSV) != 0)
			STm->sysv = value;
                DEB(
		if ((options & MT_ST_DEBUGGING) != 0)
			debugging = value; )
		st_log_options(STp, STm, dev);
	} else if (code == MT_ST_WRITE_THRESHOLD) {
		value = (options & ~MT_ST_OPTIONS) * ST_KILOBYTE;
		if (value < 1 || value > st_buffer_size) {
			printk(KERN_WARNING
                               "st%d: Write threshold %d too small or too large.\n",
			       dev, value);
			return (-EIO);
		}
		STp->write_threshold = value;
		printk(KERN_INFO "st%d: Write threshold set to %d bytes.\n",
		       dev, value);
	} else if (code == MT_ST_DEF_BLKSIZE) {
		value = (options & ~MT_ST_OPTIONS);
		if (value == ~MT_ST_OPTIONS) {
			STm->default_blksize = (-1);
			printk(KERN_INFO "st%d: Default block size disabled.\n", dev);
		} else {
			STm->default_blksize = value;
			printk(KERN_INFO "st%d: Default block size set to %d bytes.\n",
			       dev, STm->default_blksize);
		}
	} else if (code == MT_ST_TIMEOUTS) {
		value = (options & ~MT_ST_OPTIONS);
		if ((value & MT_ST_SET_LONG_TIMEOUT) != 0) {
			STp->long_timeout = (value & ~MT_ST_SET_LONG_TIMEOUT) * HZ;
			printk(KERN_INFO "st%d: Long timeout set to %d seconds.\n", dev,
			       (value & ~MT_ST_SET_LONG_TIMEOUT));
		} else {
			STp->timeout = value * HZ;
			printk(KERN_INFO "st%d: Normal timeout set to %d seconds.\n",
                               dev, value);
		}
	} else if (code == MT_ST_DEF_OPTIONS) {
		code = (options & ~MT_ST_CLEAR_DEFAULT);
		value = (options & MT_ST_CLEAR_DEFAULT);
		if (code == MT_ST_DEF_DENSITY) {
			if (value == MT_ST_CLEAR_DEFAULT) {
				STm->default_density = (-1);
				printk(KERN_INFO "st%d: Density default disabled.\n",
                                       dev);
			} else {
				STm->default_density = value & 0xff;
				printk(KERN_INFO "st%d: Density default set to %x\n",
				       dev, STm->default_density);
			}
		} else if (code == MT_ST_DEF_DRVBUFFER) {
			if (value == MT_ST_CLEAR_DEFAULT) {
				STp->default_drvbuffer = 0xff;
				printk(KERN_INFO
                                       "st%d: Drive buffer default disabled.\n", dev);
			} else {
				STp->default_drvbuffer = value & 7;
				printk(KERN_INFO
                                       "st%d: Drive buffer default set to %x\n",
				       dev, STp->default_drvbuffer);
			}
		} else if (code == MT_ST_DEF_COMPRESSION) {
			if (value == MT_ST_CLEAR_DEFAULT) {
				STm->default_compression = ST_DONT_TOUCH;
				printk(KERN_INFO
                                       "st%d: Compression default disabled.\n", dev);
			} else {
				STm->default_compression = (value & 1 ? ST_YES : ST_NO);
				printk(KERN_INFO "st%d: Compression default set to %x\n",
				       dev, (value & 1));
			}
		}
	} else
		return (-EIO);

	return 0;
}


#define COMPRESSION_PAGE        0x0f
#define COMPRESSION_PAGE_LENGTH 16

#define MODE_HEADER_LENGTH  4

#define DCE_MASK  0x80
#define DCC_MASK  0x40
#define RED_MASK  0x60


/* Control the compression with mode page 15. Algorithm not changed if zero. */
static int st_compression(Scsi_Tape * STp, int state)
{
	int dev;
	unsigned char cmd[10];
	Scsi_Cmnd *SCpnt = NULL;

	if (STp->ready != ST_READY)
		return (-EIO);

	/* Read the current page contents */
	memset(cmd, 0, 10);
	cmd[0] = MODE_SENSE;
	cmd[1] = 8;
	cmd[2] = COMPRESSION_PAGE;
	cmd[4] = COMPRESSION_PAGE_LENGTH + MODE_HEADER_LENGTH;

	SCpnt = st_do_scsi(SCpnt, STp, cmd, cmd[4], STp->timeout, 0, TRUE);
	if (SCpnt == NULL)
		return (STp->buffer)->last_result_fatal;

	dev = TAPE_NR(SCpnt->request.rq_dev);

	if ((STp->buffer)->last_result_fatal != 0) {
                DEBC(printk(ST_DEB_MSG "st%d: Compression mode page not supported.\n",
                            dev));
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		return (-EIO);
	}
        DEBC(printk(ST_DEB_MSG "st%d: Compression state is %d.\n", dev,
                    ((STp->buffer)->b_data[MODE_HEADER_LENGTH + 2] & DCE_MASK ? 1 : 0)));

	/* Check if compression can be changed */
	if (((STp->buffer)->b_data[MODE_HEADER_LENGTH + 2] & DCC_MASK) == 0) {
                DEBC(printk(ST_DEB_MSG "st%d: Compression not supported.\n", dev));
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		return (-EIO);
	}

	/* Do the change */
	if (state)
		(STp->buffer)->b_data[MODE_HEADER_LENGTH + 2] |= DCE_MASK;
	else
		(STp->buffer)->b_data[MODE_HEADER_LENGTH + 2] &= ~DCE_MASK;

	memset(cmd, 0, 10);
	cmd[0] = MODE_SELECT;
	cmd[1] = 0x10;
	cmd[4] = COMPRESSION_PAGE_LENGTH + MODE_HEADER_LENGTH;

	(STp->buffer)->b_data[0] = 0;	/* Reserved data length */
	(STp->buffer)->b_data[1] = 0;	/* Reserved media type byte */
	(STp->buffer)->b_data[MODE_HEADER_LENGTH] &= 0x3f;
	SCpnt = st_do_scsi(SCpnt, STp, cmd, cmd[4], STp->timeout, 0, TRUE);

	if ((STp->buffer)->last_result_fatal != 0) {
                DEBC(printk(ST_DEB_MSG "st%d: Compression change failed.\n", dev));
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		return (-EIO);
	}
        DEBC(printk(ST_DEB_MSG "st%d: Compression state changed to %d.\n",
		       dev, state));

	scsi_release_command(SCpnt);
	SCpnt = NULL;
	STp->compression_changed = TRUE;
	return 0;
}


/* Internal ioctl function */
static int st_int_ioctl(struct inode *inode,
			unsigned int cmd_in, unsigned long arg)
{
	int timeout;
	long ltmp;
	int i, ioctl_result;
	int chg_eof = TRUE;
	unsigned char cmd[10];
	Scsi_Cmnd *SCpnt;
	Scsi_Tape *STp;
	ST_partstat *STps;
	int fileno, blkno, at_sm, undone, datalen;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);
	if (STp->ready != ST_READY && cmd_in != MTLOAD) {
		if (STp->ready == ST_NO_TAPE)
			return (-ENOMEDIUM);
		else
			return (-EIO);
	}
	timeout = STp->long_timeout;
	STps = &(STp->ps[STp->partition]);
	fileno = STps->drv_file;
	blkno = STps->drv_block;
	at_sm = STps->at_sm;

	memset(cmd, 0, 10);
	datalen = 0;
	switch (cmd_in) {
	case MTFSFM:
		chg_eof = FALSE;	/* Changed from the FSF after this */
	case MTFSF:
		cmd[0] = SPACE;
		cmd[1] = 0x01;	/* Space FileMarks */
		cmd[2] = (arg >> 16);
		cmd[3] = (arg >> 8);
		cmd[4] = arg;
                DEBC(printk(ST_DEB_MSG "st%d: Spacing tape forward over %d filemarks.\n",
			    dev, cmd[2] * 65536 + cmd[3] * 256 + cmd[4]));
		if (fileno >= 0)
			fileno += arg;
		blkno = 0;
		at_sm &= (arg == 0);
		break;
	case MTBSFM:
		chg_eof = FALSE;	/* Changed from the FSF after this */
	case MTBSF:
		cmd[0] = SPACE;
		cmd[1] = 0x01;	/* Space FileMarks */
		ltmp = (-arg);
		cmd[2] = (ltmp >> 16);
		cmd[3] = (ltmp >> 8);
		cmd[4] = ltmp;
                DEBC(
                     if (cmd[2] & 0x80)
                     	ltmp = 0xff000000;
                     ltmp = ltmp | (cmd[2] << 16) | (cmd[3] << 8) | cmd[4];
                     printk(ST_DEB_MSG
                            "st%d: Spacing tape backward over %ld filemarks.\n",
                            dev, (-ltmp));
		)
		if (fileno >= 0)
			fileno -= arg;
		blkno = (-1);	/* We can't know the block number */
		at_sm &= (arg == 0);
		break;
	case MTFSR:
		cmd[0] = SPACE;
		cmd[1] = 0x00;	/* Space Blocks */
		cmd[2] = (arg >> 16);
		cmd[3] = (arg >> 8);
		cmd[4] = arg;
                DEBC(printk(ST_DEB_MSG "st%d: Spacing tape forward %d blocks.\n", dev,
			       cmd[2] * 65536 + cmd[3] * 256 + cmd[4]));
		if (blkno >= 0)
			blkno += arg;
		at_sm &= (arg == 0);
		break;
	case MTBSR:
		cmd[0] = SPACE;
		cmd[1] = 0x00;	/* Space Blocks */
		ltmp = (-arg);
		cmd[2] = (ltmp >> 16);
		cmd[3] = (ltmp >> 8);
		cmd[4] = ltmp;
                DEBC(
                     if (cmd[2] & 0x80)
                          ltmp = 0xff000000;
                     ltmp = ltmp | (cmd[2] << 16) | (cmd[3] << 8) | cmd[4];
                     printk(ST_DEB_MSG
                            "st%d: Spacing tape backward %ld blocks.\n", dev, (-ltmp));
		)
		if (blkno >= 0)
			blkno -= arg;
		at_sm &= (arg == 0);
		break;
	case MTFSS:
		cmd[0] = SPACE;
		cmd[1] = 0x04;	/* Space Setmarks */
		cmd[2] = (arg >> 16);
		cmd[3] = (arg >> 8);
		cmd[4] = arg;
                DEBC(printk(ST_DEB_MSG "st%d: Spacing tape forward %d setmarks.\n", dev,
                            cmd[2] * 65536 + cmd[3] * 256 + cmd[4]));
		if (arg != 0) {
			blkno = fileno = (-1);
			at_sm = 1;
		}
		break;
	case MTBSS:
		cmd[0] = SPACE;
		cmd[1] = 0x04;	/* Space Setmarks */
		ltmp = (-arg);
		cmd[2] = (ltmp >> 16);
		cmd[3] = (ltmp >> 8);
		cmd[4] = ltmp;
                DEBC(
                     if (cmd[2] & 0x80)
				ltmp = 0xff000000;
                     ltmp = ltmp | (cmd[2] << 16) | (cmd[3] << 8) | cmd[4];
                     printk(ST_DEB_MSG "st%d: Spacing tape backward %ld setmarks.\n",
                            dev, (-ltmp));
		)
		if (arg != 0) {
			blkno = fileno = (-1);
			at_sm = 1;
		}
		break;
	case MTWEOF:
	case MTWSM:
		if (STp->write_prot)
			return (-EACCES);
		cmd[0] = WRITE_FILEMARKS;
		if (cmd_in == MTWSM)
			cmd[1] = 2;
		cmd[2] = (arg >> 16);
		cmd[3] = (arg >> 8);
		cmd[4] = arg;
		timeout = STp->timeout;
                DEBC(
                     if (cmd_in == MTWEOF)
                               printk(ST_DEB_MSG "st%d: Writing %d filemarks.\n", dev,
				 cmd[2] * 65536 + cmd[3] * 256 + cmd[4]);
                     else
				printk(ST_DEB_MSG "st%d: Writing %d setmarks.\n", dev,
				 cmd[2] * 65536 + cmd[3] * 256 + cmd[4]);
		)
		if (fileno >= 0)
			fileno += arg;
		blkno = 0;
		at_sm = (cmd_in == MTWSM);
		break;
	case MTREW:
		cmd[0] = REZERO_UNIT;
#if ST_NOWAIT
		cmd[1] = 1;	/* Don't wait for completion */
		timeout = STp->timeout;
#endif
                DEBC(printk(ST_DEB_MSG "st%d: Rewinding tape.\n", dev));
		fileno = blkno = at_sm = 0;
		break;
	case MTOFFL:
	case MTLOAD:
	case MTUNLOAD:
		cmd[0] = START_STOP;
		if (cmd_in == MTLOAD)
			cmd[4] |= 1;
		/*
		 * If arg >= 1 && arg <= 6 Enhanced load/unload in HP C1553A
		 */
		if (cmd_in != MTOFFL &&
		    arg >= 1 + MT_ST_HPLOADER_OFFSET
		    && arg <= 6 + MT_ST_HPLOADER_OFFSET) {
                        DEBC(printk(ST_DEB_MSG "st%d: Enhanced %sload slot %2ld.\n",
                                    dev, (cmd[4]) ? "" : "un",
                                    arg - MT_ST_HPLOADER_OFFSET));
			cmd[3] = arg - MT_ST_HPLOADER_OFFSET; /* MediaID field of C1553A */
		}
#if ST_NOWAIT
		cmd[1] = 1;	/* Don't wait for completion */
		timeout = STp->timeout;
#else
		timeout = STp->long_timeout;
#endif
                DEBC(
			if (cmd_in != MTLOAD)
				printk(ST_DEB_MSG "st%d: Unloading tape.\n", dev);
			else
				printk(ST_DEB_MSG "st%d: Loading tape.\n", dev);
		)
		fileno = blkno = at_sm = 0;
		break;
	case MTNOP:
                DEBC(printk(ST_DEB_MSG "st%d: No op on tape.\n", dev));
		return 0;	/* Should do something ? */
		break;
	case MTRETEN:
		cmd[0] = START_STOP;
#if ST_NOWAIT
		cmd[1] = 1;	/* Don't wait for completion */
		timeout = STp->timeout;
#endif
		cmd[4] = 3;
                DEBC(printk(ST_DEB_MSG "st%d: Retensioning tape.\n", dev));
		fileno = blkno = at_sm = 0;
		break;
	case MTEOM:
		if (!STp->fast_mteom) {
			/* space to the end of tape */
			ioctl_result = st_int_ioctl(inode, MTFSF, 0x3fff);
			fileno = STps->drv_file;
			if (STps->eof >= ST_EOD_1)
				return 0;
			/* The next lines would hide the number of spaced FileMarks
			   That's why I inserted the previous lines. I had no luck
			   with detecting EOM with FSF, so we go now to EOM.
			   Joerg Weule */
		} else
			fileno = (-1);
		cmd[0] = SPACE;
		cmd[1] = 3;
                DEBC(printk(ST_DEB_MSG "st%d: Spacing to end of recorded medium.\n",
                            dev));
		blkno = 0;
		at_sm = 0;
		break;
	case MTERASE:
		if (STp->write_prot)
			return (-EACCES);
		cmd[0] = ERASE;
		cmd[1] = 1;	/* To the end of tape */
#if ST_NOWAIT
		cmd[1] |= 2;	/* Don't wait for completion */
		timeout = STp->timeout;
#else
		timeout = STp->long_timeout * 8;
#endif
                DEBC(printk(ST_DEB_MSG "st%d: Erasing tape.\n", dev));
		fileno = blkno = at_sm = 0;
		break;
	case MTLOCK:
		chg_eof = FALSE;
		cmd[0] = ALLOW_MEDIUM_REMOVAL;
		cmd[4] = SCSI_REMOVAL_PREVENT;
                DEBC(printk(ST_DEB_MSG "st%d: Locking drive door.\n", dev));
		break;
	case MTUNLOCK:
		chg_eof = FALSE;
		cmd[0] = ALLOW_MEDIUM_REMOVAL;
		cmd[4] = SCSI_REMOVAL_ALLOW;
                DEBC(printk(ST_DEB_MSG "st%d: Unlocking drive door.\n", dev));
		break;
	case MTSETBLK:		/* Set block length */
	case MTSETDENSITY:	/* Set tape density */
	case MTSETDRVBUFFER:	/* Set drive buffering */
	case SET_DENS_AND_BLK:	/* Set density and block size */
		chg_eof = FALSE;
		if (STp->dirty || (STp->buffer)->buffer_bytes != 0)
			return (-EIO);	/* Not allowed if data in buffer */
		if ((cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK) &&
		    (arg & MT_ST_BLKSIZE_MASK) != 0 &&
		    ((arg & MT_ST_BLKSIZE_MASK) < STp->min_block ||
		     (arg & MT_ST_BLKSIZE_MASK) > STp->max_block ||
		     (arg & MT_ST_BLKSIZE_MASK) > st_buffer_size)) {
			printk(KERN_WARNING "st%d: Illegal block size.\n", dev);
			return (-EINVAL);
		}
		cmd[0] = MODE_SELECT;
		cmd[4] = datalen = 12;

		memset((STp->buffer)->b_data, 0, 12);
		if (cmd_in == MTSETDRVBUFFER)
			(STp->buffer)->b_data[2] = (arg & 7) << 4;
		else
			(STp->buffer)->b_data[2] =
			    STp->drv_buffer << 4;
		(STp->buffer)->b_data[3] = 8;	/* block descriptor length */
		if (cmd_in == MTSETDENSITY) {
			(STp->buffer)->b_data[4] = arg;
			STp->density_changed = TRUE;	/* At least we tried ;-) */
		} else if (cmd_in == SET_DENS_AND_BLK)
			(STp->buffer)->b_data[4] = arg >> 24;
		else
			(STp->buffer)->b_data[4] = STp->density;
		if (cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK) {
			ltmp = arg & MT_ST_BLKSIZE_MASK;
			if (cmd_in == MTSETBLK)
				STp->blksize_changed = TRUE; /* At least we tried ;-) */
		} else
			ltmp = STp->block_size;
		(STp->buffer)->b_data[9] = (ltmp >> 16);
		(STp->buffer)->b_data[10] = (ltmp >> 8);
		(STp->buffer)->b_data[11] = ltmp;
		timeout = STp->timeout;
                DEBC(
			if (cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK)
				printk(ST_DEB_MSG
                                       "st%d: Setting block size to %d bytes.\n", dev,
				       (STp->buffer)->b_data[9] * 65536 +
				       (STp->buffer)->b_data[10] * 256 +
				       (STp->buffer)->b_data[11]);
			if (cmd_in == MTSETDENSITY || cmd_in == SET_DENS_AND_BLK)
				printk(ST_DEB_MSG
                                       "st%d: Setting density code to %x.\n", dev,
				       (STp->buffer)->b_data[4]);
			if (cmd_in == MTSETDRVBUFFER)
				printk(ST_DEB_MSG
                                       "st%d: Setting drive buffer code to %d.\n", dev,
				    ((STp->buffer)->b_data[2] >> 4) & 7);
		)
		break;
	default:
		return (-ENOSYS);
	}

	SCpnt = st_do_scsi(NULL, STp, cmd, datalen, timeout, MAX_RETRIES, TRUE);
	if (!SCpnt)
		return (STp->buffer)->last_result_fatal;

	ioctl_result = (STp->buffer)->last_result_fatal;

	if (!ioctl_result) {	/* SCSI command successful */
		scsi_release_command(SCpnt);
		SCpnt = NULL;
		STps->drv_block = blkno;
		STps->drv_file = fileno;
		STps->at_sm = at_sm;

		if (cmd_in == MTLOCK)
			STp->door_locked = ST_LOCKED_EXPLICIT;
		else if (cmd_in == MTUNLOCK)
			STp->door_locked = ST_UNLOCKED;

		if (cmd_in == MTBSFM)
			ioctl_result = st_int_ioctl(inode, MTFSF, 1);
		else if (cmd_in == MTFSFM)
			ioctl_result = st_int_ioctl(inode, MTBSF, 1);

		if (cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK) {
			STp->block_size = arg & MT_ST_BLKSIZE_MASK;
			if (STp->block_size != 0)
				(STp->buffer)->buffer_blocks =
				    (STp->buffer)->buffer_size / STp->block_size;
			(STp->buffer)->buffer_bytes = (STp->buffer)->read_pointer = 0;
			if (cmd_in == SET_DENS_AND_BLK)
				STp->density = arg >> MT_ST_DENSITY_SHIFT;
		} else if (cmd_in == MTSETDRVBUFFER)
			STp->drv_buffer = (arg & 7);
		else if (cmd_in == MTSETDENSITY)
			STp->density = arg;

		if (cmd_in == MTEOM)
			STps->eof = ST_EOD;
		else if (cmd_in == MTFSF)
			STps->eof = ST_FM;
		else if (chg_eof)
			STps->eof = ST_NOEOF;


		if (cmd_in == MTOFFL || cmd_in == MTUNLOAD)
			STp->rew_at_close = 0;
		else if (cmd_in == MTLOAD) {
			STp->rew_at_close = (MINOR(inode->i_rdev) & 0x80) == 0;
			for (i = 0; i < ST_NBR_PARTITIONS; i++) {
				STp->ps[i].rw = ST_IDLE;
				STp->ps[i].last_block_valid = FALSE;
			}
			STp->partition = 0;
		}
	} else { /* SCSI command was not completely successful. Don't return
                    from this block without releasing the SCSI command block! */

		if (SCpnt->sense_buffer[2] & 0x40) {
			if (cmd_in != MTBSF && cmd_in != MTBSFM &&
			    cmd_in != MTBSR && cmd_in != MTBSS)
				STps->eof = ST_EOM_OK;
			STps->drv_block = 0;
		}

		undone = (
				 (SCpnt->sense_buffer[3] << 24) +
				 (SCpnt->sense_buffer[4] << 16) +
				 (SCpnt->sense_buffer[5] << 8) +
				 SCpnt->sense_buffer[6]);
		if (cmd_in == MTWEOF &&
		    (SCpnt->sense_buffer[0] & 0x70) == 0x70 &&
		    (SCpnt->sense_buffer[2] & 0x4f) == 0x40 &&
		 ((SCpnt->sense_buffer[0] & 0x80) == 0 || undone == 0)) {
			ioctl_result = 0;	/* EOF written succesfully at EOM */
			if (fileno >= 0)
				fileno++;
			STps->drv_file = fileno;
			STps->eof = ST_NOEOF;
		} else if ((cmd_in == MTFSF) || (cmd_in == MTFSFM)) {
			if (fileno >= 0)
				STps->drv_file = fileno - undone;
			else
				STps->drv_file = fileno;
			STps->drv_block = 0;
			STps->eof = ST_NOEOF;
		} else if ((cmd_in == MTBSF) || (cmd_in == MTBSFM)) {
			if (fileno >= 0)
				STps->drv_file = fileno + undone;
			else
				STps->drv_file = fileno;
			STps->drv_block = 0;
			STps->eof = ST_NOEOF;
		} else if (cmd_in == MTFSR) {
			if (SCpnt->sense_buffer[2] & 0x80) {	/* Hit filemark */
				if (STps->drv_file >= 0)
					STps->drv_file++;
				STps->drv_block = 0;
				STps->eof = ST_FM;
			} else {
				if (blkno >= undone)
					STps->drv_block = blkno - undone;
				else
					STps->drv_block = (-1);
				STps->eof = ST_NOEOF;
			}
		} else if (cmd_in == MTBSR) {
			if (SCpnt->sense_buffer[2] & 0x80) {	/* Hit filemark */
				STps->drv_file--;
				STps->drv_block = (-1);
			} else {
				if (blkno >= 0)
					STps->drv_block = blkno + undone;
				else
					STps->drv_block = (-1);
			}
			STps->eof = ST_NOEOF;
		} else if (cmd_in == MTEOM) {
			STps->drv_file = (-1);
			STps->drv_block = (-1);
			STps->eof = ST_EOD;
		} else if (chg_eof)
			STps->eof = ST_NOEOF;

		if ((SCpnt->sense_buffer[2] & 0x0f) == BLANK_CHECK)
			STps->eof = ST_EOD;

		if (cmd_in == MTLOCK)
			STp->door_locked = ST_LOCK_FAILS;

		scsi_release_command(SCpnt);
		SCpnt = NULL;
	}

	return ioctl_result;
}


/* Get the tape position. If bt == 2, arg points into a kernel space mt_loc
   structure. */

static int get_location(struct inode *inode, unsigned int *block, int *partition,
			int logical)
{
	Scsi_Tape *STp;
	int dev = TAPE_NR(inode->i_rdev);
	int result;
	unsigned char scmd[10];
	Scsi_Cmnd *SCpnt;

	STp = &(scsi_tapes[dev]);
	if (STp->ready != ST_READY)
		return (-EIO);

	memset(scmd, 0, 10);
	if ((STp->device)->scsi_level < SCSI_2) {
		scmd[0] = QFA_REQUEST_BLOCK;
		scmd[4] = 3;
	} else {
		scmd[0] = READ_POSITION;
		if (!logical && !STp->scsi2_logical)
			scmd[1] = 1;
	}
	SCpnt = st_do_scsi(NULL, STp, scmd, 20, STp->timeout, MAX_READY_RETRIES, TRUE);
	if (!SCpnt)
		return (STp->buffer)->last_result_fatal;

	if ((STp->buffer)->last_result_fatal != 0 ||
	    (STp->device->scsi_level >= SCSI_2 &&
	     ((STp->buffer)->b_data[0] & 4) != 0)) {
		*block = *partition = 0;
                DEBC(printk(ST_DEB_MSG "st%d: Can't read tape position.\n", dev));
		result = (-EIO);
	} else {
		result = 0;
		if ((STp->device)->scsi_level < SCSI_2) {
			*block = ((STp->buffer)->b_data[0] << 16)
			    + ((STp->buffer)->b_data[1] << 8)
			    + (STp->buffer)->b_data[2];
			*partition = 0;
		} else {
			*block = ((STp->buffer)->b_data[4] << 24)
			    + ((STp->buffer)->b_data[5] << 16)
			    + ((STp->buffer)->b_data[6] << 8)
			    + (STp->buffer)->b_data[7];
			*partition = (STp->buffer)->b_data[1];
			if (((STp->buffer)->b_data[0] & 0x80) &&
			    (STp->buffer)->b_data[1] == 0)	/* BOP of partition 0 */
				STp->ps[0].drv_block = STp->ps[0].drv_file = 0;
		}
                DEBC(printk(ST_DEB_MSG "st%d: Got tape pos. blk %d part %d.\n", dev,
                            *block, *partition));
	}
	scsi_release_command(SCpnt);
	SCpnt = NULL;

	return result;
}


/* Set the tape block and partition. Negative partition means that only the
   block should be set in vendor specific way. */
static int set_location(struct inode *inode, unsigned int block, int partition,
			int logical)
{
	Scsi_Tape *STp;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);
	int result, p;
	unsigned int blk;
	int timeout;
	unsigned char scmd[10];
	Scsi_Cmnd *SCpnt;

	STp = &(scsi_tapes[dev]);
	if (STp->ready != ST_READY)
		return (-EIO);
	timeout = STp->long_timeout;
	STps = &(STp->ps[STp->partition]);

        DEBC(printk(ST_DEB_MSG "st%d: Setting block to %d and partition to %d.\n",
                    dev, block, partition));
	DEB(if (partition < 0)
		return (-EIO); )

	/* Update the location at the partition we are leaving */
	if ((!STp->can_partitions && partition != 0) ||
	    partition >= ST_NBR_PARTITIONS)
		return (-EINVAL);
	if (partition != STp->partition) {
		if (get_location(inode, &blk, &p, 1))
			STps->last_block_valid = FALSE;
		else {
			STps->last_block_valid = TRUE;
			STps->last_block_visited = blk;
                        DEBC(printk(ST_DEB_MSG
                                    "st%d: Visited block %d for partition %d saved.\n",
                                    dev, blk, STp->partition));
		}
	}

	memset(scmd, 0, 10);
	if ((STp->device)->scsi_level < SCSI_2) {
		scmd[0] = QFA_SEEK_BLOCK;
		scmd[2] = (block >> 16);
		scmd[3] = (block >> 8);
		scmd[4] = block;
		scmd[5] = 0;
	} else {
		scmd[0] = SEEK_10;
		scmd[3] = (block >> 24);
		scmd[4] = (block >> 16);
		scmd[5] = (block >> 8);
		scmd[6] = block;
		if (!logical && !STp->scsi2_logical)
			scmd[1] = 4;
		if (STp->partition != partition) {
			scmd[1] |= 2;
			scmd[8] = partition;
                        DEBC(printk(ST_DEB_MSG
                                    "st%d: Trying to change partition from %d to %d\n",
                                    dev, STp->partition, partition));
		}
	}
#if ST_NOWAIT
	scmd[1] |= 1;		/* Don't wait for completion */
	timeout = STp->timeout;
#endif

	SCpnt = st_do_scsi(NULL, STp, scmd, 20, timeout, MAX_READY_RETRIES, TRUE);
	if (!SCpnt)
		return (STp->buffer)->last_result_fatal;

	STps->drv_block = STps->drv_file = (-1);
	STps->eof = ST_NOEOF;
	if ((STp->buffer)->last_result_fatal != 0) {
		result = (-EIO);
		if (STp->can_partitions &&
		    (STp->device)->scsi_level >= SCSI_2 &&
		    (p = find_partition(inode)) >= 0)
			STp->partition = p;
	} else {
		if (STp->can_partitions) {
			STp->partition = partition;
			STps = &(STp->ps[partition]);
			if (!STps->last_block_valid ||
			    STps->last_block_visited != block) {
				STps->at_sm = 0;
				STps->rw = ST_IDLE;
			}
		} else
			STps->at_sm = 0;
		if (block == 0)
			STps->drv_block = STps->drv_file = 0;
		result = 0;
	}

	scsi_release_command(SCpnt);
	SCpnt = NULL;

	return result;
}


/* Find the current partition number for the drive status. Called from open and
   returns either partition number of negative error code. */
static int find_partition(struct inode *inode)
{
	int i, partition;
	unsigned int block;

	if ((i = get_location(inode, &block, &partition, 1)) < 0)
		return i;
	if (partition >= ST_NBR_PARTITIONS)
		return (-EIO);
	return partition;
}


/* Change the partition if necessary */
static int update_partition(struct inode *inode)
{
	int dev = TAPE_NR(inode->i_rdev);
	Scsi_Tape *STp;
	ST_partstat *STps;

	STp = &(scsi_tapes[dev]);
	if (STp->partition == STp->new_partition)
		return 0;
	STps = &(STp->ps[STp->new_partition]);
	if (!STps->last_block_valid)
		STps->last_block_visited = 0;
	return set_location(inode, STps->last_block_visited, STp->new_partition, 1);
}

/* Functions for reading and writing the medium partition mode page. These
   seem to work with Wangtek 6200HS and HP C1533A. */

#define PART_PAGE   0x11
#define PART_PAGE_LENGTH 10

/* Get the number of partitions on the tape. As a side effect reads the
   mode page into the tape buffer. */
static int nbr_partitions(struct inode *inode)
{
	int dev = TAPE_NR(inode->i_rdev), result;
	Scsi_Tape *STp;
	Scsi_Cmnd *SCpnt = NULL;
	unsigned char cmd[10];

	STp = &(scsi_tapes[dev]);
	if (STp->ready != ST_READY)
		return (-EIO);

	memset((void *) &cmd[0], 0, 10);
	cmd[0] = MODE_SENSE;
	cmd[1] = 8;		/* Page format */
	cmd[2] = PART_PAGE;
	cmd[4] = 200;

	SCpnt = st_do_scsi(SCpnt, STp, cmd, 200, STp->timeout, MAX_READY_RETRIES, TRUE);
	if (SCpnt == NULL)
		return (STp->buffer)->last_result_fatal;

	scsi_release_command(SCpnt);
	SCpnt = NULL;

	if ((STp->buffer)->last_result_fatal != 0) {
                DEBC(printk(ST_DEB_MSG "st%d: Can't read medium partition page.\n",
                            dev));
		result = (-EIO);
	} else {
		result = (STp->buffer)->b_data[MODE_HEADER_LENGTH + 3] + 1;
                DEBC(printk(ST_DEB_MSG "st%d: Number of partitions %d.\n", dev, result));
	}

	return result;
}


/* Partition the tape into two partitions if size > 0 or one partition if
   size == 0 */
static int partition_tape(struct inode *inode, int size)
{
	int dev = TAPE_NR(inode->i_rdev), result;
	int length;
	Scsi_Tape *STp;
	Scsi_Cmnd *SCpnt = NULL;
	unsigned char cmd[10], *bp;

	if ((result = nbr_partitions(inode)) < 0)
		return result;
	STp = &(scsi_tapes[dev]);

	/* The mode page is in the buffer. Let's modify it and write it. */
	bp = &((STp->buffer)->b_data[0]);
	if (size <= 0) {
		length = 8;
		bp[MODE_HEADER_LENGTH + 3] = 0;
                DEBC(printk(ST_DEB_MSG "st%d: Formatting tape with one partition.\n",
                            dev));
	} else {
		length = 10;
		bp[MODE_HEADER_LENGTH + 3] = 1;
		bp[MODE_HEADER_LENGTH + 8] = (size >> 8) & 0xff;
		bp[MODE_HEADER_LENGTH + 9] = size & 0xff;
                DEBC(printk(ST_DEB_MSG
                            "st%d: Formatting tape with two partition (1 = %d MB).\n",
                            dev, size));
	}
	bp[MODE_HEADER_LENGTH + 6] = 0;
	bp[MODE_HEADER_LENGTH + 7] = 0;
	bp[MODE_HEADER_LENGTH + 4] = 0x30;	/* IDP | PSUM = MB */

	bp[0] = 0;
	bp[1] = 0;
	bp[MODE_HEADER_LENGTH] &= 0x3f;
	bp[MODE_HEADER_LENGTH + 1] = length - 2;

	memset(cmd, 0, 10);
	cmd[0] = MODE_SELECT;
	cmd[1] = 0x10;
	cmd[4] = length + MODE_HEADER_LENGTH;

	SCpnt = st_do_scsi(SCpnt, STp, cmd, cmd[4], STp->long_timeout,
			   MAX_READY_RETRIES, TRUE);
	if (SCpnt == NULL)
		return (STp->buffer)->last_result_fatal;

	scsi_release_command(SCpnt);
	SCpnt = NULL;

	if ((STp->buffer)->last_result_fatal != 0) {
		printk(KERN_INFO "st%d: Partitioning of tape failed.\n", dev);
		result = (-EIO);
	} else
		result = 0;

	return result;
}



/* The ioctl command */
static int st_ioctl(struct inode *inode, struct file *file,
		    unsigned int cmd_in, unsigned long arg)
{
	int i, cmd_nr, cmd_type, bt;
	unsigned int blk;
	struct mtop mtc;
	struct mtpos mt_pos;
	Scsi_Tape *STp;
	ST_mode *STm;
	ST_partstat *STps;
	int dev = TAPE_NR(inode->i_rdev);

	STp = &(scsi_tapes[dev]);
        DEB(
	if (debugging && !STp->in_use) {
		printk(ST_DEB_MSG "st%d: Incorrect device.\n", dev);
		return (-EIO);
	} ) /* end DEB */

	STm = &(STp->modes[STp->current_mode]);
	STps = &(STp->ps[STp->partition]);

	/*
	 * If we are in the middle of error recovery, don't let anyone
	 * else try and use this device.  Also, if error recovery fails, it
	 * may try and take the device offline, in which case all further
	 * access to the device is prohibited.
	 */
	if (!scsi_block_when_processing_errors(STp->device)) {
		return -ENXIO;
	}
	cmd_type = _IOC_TYPE(cmd_in);
	cmd_nr = _IOC_NR(cmd_in);

	if (cmd_type == _IOC_TYPE(MTIOCTOP) && cmd_nr == _IOC_NR(MTIOCTOP)) {
		if (_IOC_SIZE(cmd_in) != sizeof(mtc))
			return (-EINVAL);

		i = copy_from_user((char *) &mtc, (char *) arg, sizeof(struct mtop));
		if (i)
			return (-EFAULT);

		if (mtc.mt_op == MTSETDRVBUFFER && !capable(CAP_SYS_ADMIN)) {
			printk(KERN_WARNING
                               "st%d: MTSETDRVBUFFER only allowed for root.\n", dev);
			return (-EPERM);
		}
		if (!STm->defined &&
		    (mtc.mt_op != MTSETDRVBUFFER && (mtc.mt_count & MT_ST_OPTIONS) == 0))
			return (-ENXIO);

		if (!(STp->device)->was_reset) {

			if (STps->eof == ST_FM_HIT) {
				if (mtc.mt_op == MTFSF || mtc.mt_op == MTFSFM ||
                                    mtc.mt_op == MTEOM) {
					mtc.mt_count -= 1;
					if (STps->drv_file >= 0)
						STps->drv_file += 1;
				} else if (mtc.mt_op == MTBSF || mtc.mt_op == MTBSFM) {
					mtc.mt_count += 1;
					if (STps->drv_file >= 0)
						STps->drv_file += 1;
				}
			}

			if (mtc.mt_op == MTSEEK) {
				/* Old position must be restored if partition will be
                                   changed */
				i = !STp->can_partitions ||
				    (STp->new_partition != STp->partition);
			} else {
				i = mtc.mt_op == MTREW || mtc.mt_op == MTOFFL ||
				    mtc.mt_op == MTRETEN || mtc.mt_op == MTEOM ||
				    mtc.mt_op == MTLOCK || mtc.mt_op == MTLOAD ||
				    mtc.mt_op == MTCOMPRESSION;
			}
			i = flush_buffer(inode, file, i);
			if (i < 0)
				return i;
		} else {
			/*
			 * If there was a bus reset, block further access
			 * to this device.  If the user wants to rewind the tape,
			 * then reset the flag and allow access again.
			 */
			if (mtc.mt_op != MTREW &&
			    mtc.mt_op != MTOFFL &&
			    mtc.mt_op != MTRETEN &&
			    mtc.mt_op != MTERASE &&
			    mtc.mt_op != MTSEEK &&
			    mtc.mt_op != MTEOM)
				return (-EIO);
			STp->device->was_reset = 0;
			if (STp->door_locked != ST_UNLOCKED &&
			    STp->door_locked != ST_LOCK_FAILS) {
				if (st_int_ioctl(inode, MTLOCK, 0)) {
					printk(KERN_NOTICE
                                               "st%d: Could not relock door after bus reset.\n",
					       dev);
					STp->door_locked = ST_UNLOCKED;
				}
			}
		}

		if (mtc.mt_op != MTNOP && mtc.mt_op != MTSETBLK &&
		    mtc.mt_op != MTSETDENSITY && mtc.mt_op != MTWSM &&
		    mtc.mt_op != MTSETDRVBUFFER && mtc.mt_op != MTSETPART)
			STps->rw = ST_IDLE;	/* Prevent automatic WEOF and fsf */

		if (mtc.mt_op == MTOFFL && STp->door_locked != ST_UNLOCKED)
			st_int_ioctl(inode, MTUNLOCK, 0);	/* Ignore result! */

		if (mtc.mt_op == MTSETDRVBUFFER &&
		    (mtc.mt_count & MT_ST_OPTIONS) != 0)
			return st_set_options(inode, mtc.mt_count);

		if (mtc.mt_op == MTSETPART) {
			if (!STp->can_partitions ||
			    mtc.mt_count < 0 || mtc.mt_count >= ST_NBR_PARTITIONS)
				return (-EINVAL);
			if (mtc.mt_count >= STp->nbr_partitions &&
			(STp->nbr_partitions = nbr_partitions(inode)) < 0)
				return (-EIO);
			if (mtc.mt_count >= STp->nbr_partitions)
				return (-EINVAL);
			STp->new_partition = mtc.mt_count;
			return 0;
		}

		if (mtc.mt_op == MTMKPART) {
			if (!STp->can_partitions)
				return (-EINVAL);
			if ((i = st_int_ioctl(inode, MTREW, 0)) < 0 ||
			    (i = partition_tape(inode, mtc.mt_count)) < 0)
				return i;
			for (i = 0; i < ST_NBR_PARTITIONS; i++) {
				STp->ps[i].rw = ST_IDLE;
				STp->ps[i].at_sm = 0;
				STp->ps[i].last_block_valid = FALSE;
			}
			STp->partition = STp->new_partition = 0;
			STp->nbr_partitions = 1;	/* Bad guess ?-) */
			STps->drv_block = STps->drv_file = 0;
			return 0;
		}

		if (mtc.mt_op == MTSEEK) {
			i = set_location(inode, mtc.mt_count, STp->new_partition, 0);
			if (!STp->can_partitions)
				STp->ps[0].rw = ST_IDLE;
			return i;
		}

		if (STp->can_partitions && STp->ready == ST_READY &&
		    (i = update_partition(inode)) < 0)
			return i;

		if (mtc.mt_op == MTCOMPRESSION)
			return st_compression(STp, (mtc.mt_count & 1));
		else
			return st_int_ioctl(inode, mtc.mt_op, mtc.mt_count);
	}
	if (!STm->defined)
		return (-ENXIO);

	if ((i = flush_buffer(inode, file, FALSE)) < 0)
		return i;
	if (STp->can_partitions &&
	    (i = update_partition(inode)) < 0)
		return i;

	if (cmd_type == _IOC_TYPE(MTIOCGET) && cmd_nr == _IOC_NR(MTIOCGET)) {

		if (_IOC_SIZE(cmd_in) != sizeof(struct mtget))
			 return (-EINVAL);

		(STp->mt_status)->mt_dsreg =
		    ((STp->block_size << MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK) |
		    ((STp->density << MT_ST_DENSITY_SHIFT) & MT_ST_DENSITY_MASK);
		(STp->mt_status)->mt_blkno = STps->drv_block;
		(STp->mt_status)->mt_fileno = STps->drv_file;
		if (STp->block_size != 0) {
			if (STps->rw == ST_WRITING)
				(STp->mt_status)->mt_blkno +=
				    (STp->buffer)->buffer_bytes / STp->block_size;
			else if (STps->rw == ST_READING)
				(STp->mt_status)->mt_blkno -=
                                        ((STp->buffer)->buffer_bytes +
                                         STp->block_size - 1) / STp->block_size;
		}

		(STp->mt_status)->mt_gstat = 0;
		if (STp->drv_write_prot)
			(STp->mt_status)->mt_gstat |= GMT_WR_PROT(0xffffffff);
		if ((STp->mt_status)->mt_blkno == 0) {
			if ((STp->mt_status)->mt_fileno == 0)
				(STp->mt_status)->mt_gstat |= GMT_BOT(0xffffffff);
			else
				(STp->mt_status)->mt_gstat |= GMT_EOF(0xffffffff);
		}
		(STp->mt_status)->mt_resid = STp->partition;
		if (STps->eof == ST_EOM_OK || STps->eof == ST_EOM_ERROR)
			(STp->mt_status)->mt_gstat |= GMT_EOT(0xffffffff);
		else if (STps->eof >= ST_EOM_OK)
			(STp->mt_status)->mt_gstat |= GMT_EOD(0xffffffff);
		if (STp->density == 1)
			(STp->mt_status)->mt_gstat |= GMT_D_800(0xffffffff);
		else if (STp->density == 2)
			(STp->mt_status)->mt_gstat |= GMT_D_1600(0xffffffff);
		else if (STp->density == 3)
			(STp->mt_status)->mt_gstat |= GMT_D_6250(0xffffffff);
		if (STp->ready == ST_READY)
			(STp->mt_status)->mt_gstat |= GMT_ONLINE(0xffffffff);
		if (STp->ready == ST_NO_TAPE)
			(STp->mt_status)->mt_gstat |= GMT_DR_OPEN(0xffffffff);
		if (STps->at_sm)
			(STp->mt_status)->mt_gstat |= GMT_SM(0xffffffff);
		if (STm->do_async_writes ||
                    (STm->do_buffer_writes && STp->block_size != 0) ||
		    STp->drv_buffer != 0)
			(STp->mt_status)->mt_gstat |= GMT_IM_REP_EN(0xffffffff);

		i = copy_to_user((char *) arg, (char *) (STp->mt_status),
				 sizeof(struct mtget));
		if (i)
			return (-EFAULT);

		(STp->mt_status)->mt_erreg = 0;		/* Clear after read */
		return 0;
	}			/* End of MTIOCGET */
	if (cmd_type == _IOC_TYPE(MTIOCPOS) && cmd_nr == _IOC_NR(MTIOCPOS)) {
		if (_IOC_SIZE(cmd_in) != sizeof(struct mtpos))
			 return (-EINVAL);
		if ((i = get_location(inode, &blk, &bt, 0)) < 0)
			return i;
		mt_pos.mt_blkno = blk;
		i = copy_to_user((char *) arg, (char *) (&mt_pos), sizeof(struct mtpos));
		if (i)
			return (-EFAULT);
		return 0;
	}
	return scsi_ioctl(STp->device, cmd_in, (void *) arg);
}


/* Try to allocate a new tape buffer */
static ST_buffer *
 new_tape_buffer(int from_initialization, int need_dma)
{
	int i, priority, b_size, order, got = 0, segs = 0;
	ST_buffer *tb;

	if (st_nbr_buffers >= st_template.dev_max)
		return NULL;	/* Should never happen */

	if (from_initialization)
		priority = GFP_ATOMIC;
	else
		priority = GFP_KERNEL;

	i = sizeof(ST_buffer) + (st_max_sg_segs - 1) * sizeof(struct scatterlist);
	tb = (ST_buffer *) kmalloc(i, priority);
	if (tb) {
		if (need_dma)
			priority |= GFP_DMA;

		/* Try to allocate the first segment up to ST_FIRST_ORDER and the
		   others big enough to reach the goal */
		for (b_size = PAGE_SIZE, order=0;
		     b_size < st_buffer_size && order < ST_FIRST_ORDER;
		     order++, b_size *= 2)
			;
		for ( ; b_size >= PAGE_SIZE; order--, b_size /= 2) {
			tb->sg[0].address =
			    (unsigned char *) __get_free_pages(priority, order);
			if (tb->sg[0].address != NULL) {
				tb->sg[0].alt_address = NULL;
				tb->sg[0].length = b_size;
				break;
			}
		}
		if (tb->sg[segs].address == NULL) {
			kfree(tb);
			tb = NULL;
		} else {	/* Got something, continue */

			for (b_size = PAGE_SIZE, order=0;
			     st_buffer_size >
                                     tb->sg[0].length + (ST_FIRST_SG - 1) * b_size;
			     order++, b_size *= 2)
				;
			for (segs = 1, got = tb->sg[0].length;
			     got < st_buffer_size && segs < ST_FIRST_SG;) {
				tb->sg[segs].address =
					(unsigned char *) __get_free_pages(priority,
									   order);
				if (tb->sg[segs].address == NULL) {
					if (st_buffer_size - got <=
					    (ST_FIRST_SG - segs) * b_size / 2) {
						b_size /= 2; /* Large enough for the
                                                                rest of the buffers */
						order--;
						continue;
					}
					tb->sg_segs = segs;
					tb->orig_sg_segs = 0;
					DEB(tb->buffer_size = got);
					normalize_buffer(tb);
					kfree(tb);
					tb = NULL;
					break;
				}
				tb->sg[segs].alt_address = NULL;
				tb->sg[segs].length = b_size;
				got += b_size;
				segs++;
			}
		}
	}

	if (!tb) {
		printk(KERN_NOTICE "st: Can't allocate new tape buffer (nbr %d).\n",
		       st_nbr_buffers);
		return NULL;
	}
	tb->sg_segs = tb->orig_sg_segs = segs;
	tb->b_data = tb->sg[0].address;

        DEBC(printk(ST_DEB_MSG
                    "st: Allocated tape buffer %d (%d bytes, %d segments, dma: %d, a: %p).\n",
                    st_nbr_buffers, got, tb->sg_segs, need_dma, tb->b_data);
             printk(ST_DEB_MSG
                    "st: segment sizes: first %d, last %d bytes.\n",
                    tb->sg[0].length, tb->sg[segs - 1].length);
	)
	tb->in_use = 0;
	tb->dma = need_dma;
	tb->buffer_size = got;
	tb->writing = 0;
	st_buffers[st_nbr_buffers++] = tb;

	return tb;
}


/* Try to allocate a temporary enlarged tape buffer */
static int enlarge_buffer(ST_buffer * STbuffer, int new_size, int need_dma)
{
	int segs, nbr, max_segs, b_size, priority, order, got;

	normalize_buffer(STbuffer);

	max_segs = STbuffer->use_sg;
	if (max_segs > st_max_sg_segs)
		max_segs = st_max_sg_segs;
	nbr = max_segs - STbuffer->sg_segs;
	if (nbr <= 0)
		return FALSE;

	priority = GFP_KERNEL;
	if (need_dma)
		priority |= GFP_DMA;
	for (b_size = PAGE_SIZE, order=0;
	     b_size * nbr < new_size - STbuffer->buffer_size;
	     order++, b_size *= 2);

	for (segs = STbuffer->sg_segs, got = STbuffer->buffer_size;
	     segs < max_segs && got < new_size;) {
		STbuffer->sg[segs].address =
			(unsigned char *) __get_free_pages(priority, order);
		if (STbuffer->sg[segs].address == NULL) {
			if (new_size - got <= (max_segs - segs) * b_size / 2) {
				b_size /= 2; /* Large enough for the rest of the buffers */
				order--;
				continue;
			}
			printk(KERN_NOTICE "st: failed to enlarge buffer to %d bytes.\n",
			       new_size);
			DEB(STbuffer->buffer_size = got);
			normalize_buffer(STbuffer);
			return FALSE;
		}
		STbuffer->sg[segs].alt_address = NULL;
		STbuffer->sg[segs].length = b_size;
		STbuffer->sg_segs += 1;
		got += b_size;
		STbuffer->buffer_size = got;
		segs++;
	}
        DEBC(printk(ST_DEB_MSG
                    "st: Succeeded to enlarge buffer to %d bytes (segs %d->%d, %d).\n",
                    got, STbuffer->orig_sg_segs, STbuffer->sg_segs, b_size));

	return TRUE;
}


/* Release the extra buffer */
static void normalize_buffer(ST_buffer * STbuffer)
{
	int i, order, b_size;

	for (i = STbuffer->orig_sg_segs; i < STbuffer->sg_segs; i++) {
		for (b_size=PAGE_SIZE, order=0; b_size < STbuffer->sg[i].length;
		     order++, b_size *= 2)
			;
		free_pages((unsigned long)(STbuffer->sg[i].address), order);
		STbuffer->buffer_size -= STbuffer->sg[i].length;
	}
        DEB(
	if (debugging && STbuffer->orig_sg_segs < STbuffer->sg_segs)
		printk(ST_DEB_MSG "st: Buffer at %p normalized to %d bytes (segs %d).\n",
		       STbuffer->sg[0].address, STbuffer->buffer_size,
		       STbuffer->sg_segs);
        ) /* end DEB */
	STbuffer->sg_segs = STbuffer->orig_sg_segs;
}


/* Move data from the user buffer to the tape buffer. Returns zero (success) or
   negative error code. */
static int append_to_buffer(const char *ubp, ST_buffer * st_bp, int do_count)
{
	int i, cnt, res, offset;

	for (i = 0, offset = st_bp->buffer_bytes;
	     i < st_bp->sg_segs && offset >= st_bp->sg[i].length; i++)
		offset -= st_bp->sg[i].length;
	if (i == st_bp->sg_segs) {	/* Should never happen */
		printk(KERN_WARNING "st: append_to_buffer offset overflow.\n");
		return (-EIO);
	}
	for (; i < st_bp->sg_segs && do_count > 0; i++) {
		cnt = st_bp->sg[i].length - offset < do_count ?
		    st_bp->sg[i].length - offset : do_count;
		res = copy_from_user(st_bp->sg[i].address + offset, ubp, cnt);
		if (res)
			return (-EFAULT);
		do_count -= cnt;
		st_bp->buffer_bytes += cnt;
		ubp += cnt;
		offset = 0;
	}
	if (do_count) {		/* Should never happen */
		printk(KERN_WARNING "st: append_to_buffer overflow (left %d).\n",
		       do_count);
		return (-EIO);
	}
	return 0;
}


/* Move data from the tape buffer to the user buffer. Returns zero (success) or
   negative error code. */
static int from_buffer(ST_buffer * st_bp, char *ubp, int do_count)
{
	int i, cnt, res, offset;

	for (i = 0, offset = st_bp->read_pointer;
	     i < st_bp->sg_segs && offset >= st_bp->sg[i].length; i++)
		offset -= st_bp->sg[i].length;
	if (i == st_bp->sg_segs) {	/* Should never happen */
		printk(KERN_WARNING "st: from_buffer offset overflow.\n");
		return (-EIO);
	}
	for (; i < st_bp->sg_segs && do_count > 0; i++) {
		cnt = st_bp->sg[i].length - offset < do_count ?
		    st_bp->sg[i].length - offset : do_count;
		res = copy_to_user(ubp, st_bp->sg[i].address + offset, cnt);
		if (res)
			return (-EFAULT);
		do_count -= cnt;
		st_bp->buffer_bytes -= cnt;
		st_bp->read_pointer += cnt;
		ubp += cnt;
		offset = 0;
	}
	if (do_count) {		/* Should never happen */
		printk(KERN_WARNING "st: from_buffer overflow (left %d).\n",
		       do_count);
		return (-EIO);
	}
	return 0;
}


/* Validate the options from command line or module parameters */
static void validate_options(void)
{
	if (buffer_kbs > 0)
		st_buffer_size = buffer_kbs * ST_KILOBYTE;
	if (write_threshold_kbs > 0)
		st_write_threshold = write_threshold_kbs * ST_KILOBYTE;
	else if (buffer_kbs > 0)
		st_write_threshold = st_buffer_size - 2048;
	if (st_write_threshold > st_buffer_size) {
		st_write_threshold = st_buffer_size;
		printk(KERN_WARNING "st: write_threshold limited to %d bytes.\n",
		       st_write_threshold);
	}
	if (max_buffers >= 0)
		st_max_buffers = max_buffers;
	if (max_sg_segs >= ST_FIRST_SG)
		st_max_sg_segs = max_sg_segs;
}

#ifndef MODULE
/* Set the boot options. Syntax is defined in README.st.
 */
static int __init st_setup(char *str)
{
	int i, len, ints[5];
	char *stp;

	stp = get_options(str, ARRAY_SIZE(ints), ints);

	if (ints[0] > 0) {
		for (i = 0; i < ints[0] && i < ARRAY_SIZE(parms); i++)
			*parms[i].val = ints[i + 1];
	} else {
		while (stp != NULL) {
			for (i = 0; i < ARRAY_SIZE(parms); i++) {
				len = strlen(parms[i].name);
				if (!strncmp(stp, parms[i].name, len) &&
				    (*(stp + len) == ':' || *(stp + len) == '=')) {
					*parms[i].val =
                                                simple_strtoul(stp + len + 1, NULL, 0);
					break;
				}
			}
			if (i >= sizeof(parms) / sizeof(struct st_dev_parm))
				 printk(KERN_WARNING "st: illegal parameter in '%s'\n",
					stp);
			stp = strchr(stp, ',');
			if (stp)
				stp++;
		}
	}

	validate_options();

	return 1;
}

__setup("st=", st_setup);

#endif


static struct file_operations st_fops =
{
	NULL,			/* lseek - default */
	st_read,		/* read - general block-dev read */
	st_write,		/* write - general block-dev write */
	NULL,			/* readdir - bad */
	NULL,			/* select */
	st_ioctl,		/* ioctl */
	NULL,			/* mmap */
	scsi_tape_open,		/* open */
	scsi_tape_flush,	/* flush */
	scsi_tape_close,	/* release */
	NULL			/* fsync */
};

static int st_attach(Scsi_Device * SDp)
{
	Scsi_Tape *tpnt;
	ST_mode *STm;
	ST_partstat *STps;
	int i;

	if (SDp->type != TYPE_TAPE)
		return 1;

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

	for (tpnt = scsi_tapes, i = 0; i < st_template.dev_max; i++, tpnt++)
		if (!tpnt->device)
			break;

	if (i >= st_template.dev_max)
		panic("scsi_devices corrupt (st)");

	scsi_tapes[i].device = SDp;
	if (SDp->scsi_level <= 2)
		scsi_tapes[i].mt_status->mt_type = MT_ISSCSI1;
	else
		scsi_tapes[i].mt_status->mt_type = MT_ISSCSI2;

        tpnt->inited = 0;
	tpnt->devt = MKDEV(SCSI_TAPE_MAJOR, i);
	tpnt->dirty = 0;
	tpnt->in_use = 0;
	tpnt->drv_buffer = 1;	/* Try buffering if no mode sense */
	tpnt->restr_dma = (SDp->host)->unchecked_isa_dma;
	tpnt->density = 0;
	tpnt->do_auto_lock = ST_AUTO_LOCK;
	tpnt->can_bsr = ST_IN_FILE_POS;
	tpnt->can_partitions = 0;
	tpnt->two_fm = ST_TWO_FM;
	tpnt->fast_mteom = ST_FAST_MTEOM;
	tpnt->scsi2_logical = ST_SCSI2LOGICAL;
	tpnt->write_threshold = st_write_threshold;
	tpnt->default_drvbuffer = 0xff;		/* No forced buffering */
	tpnt->partition = 0;
	tpnt->new_partition = 0;
	tpnt->nbr_partitions = 0;
	tpnt->timeout = ST_TIMEOUT;
	tpnt->long_timeout = ST_LONG_TIMEOUT;

	for (i = 0; i < ST_NBR_MODES; i++) {
		STm = &(tpnt->modes[i]);
		STm->defined = FALSE;
		STm->sysv = ST_SYSV;
		STm->defaults_for_writes = 0;
		STm->do_async_writes = ST_ASYNC_WRITES;
		STm->do_buffer_writes = ST_BUFFER_WRITES;
		STm->do_read_ahead = ST_READ_AHEAD;
		STm->default_compression = ST_DONT_TOUCH;
		STm->default_blksize = (-1);	/* No forced size */
		STm->default_density = (-1);	/* No forced density */
	}

	for (i = 0; i < ST_NBR_PARTITIONS; i++) {
		STps = &(tpnt->ps[i]);
		STps->rw = ST_IDLE;
		STps->eof = ST_NOEOF;
		STps->at_sm = 0;
		STps->last_block_valid = FALSE;
		STps->drv_block = (-1);
		STps->drv_file = (-1);
	}

	tpnt->current_mode = 0;
	tpnt->modes[0].defined = TRUE;

	tpnt->density_changed = tpnt->compression_changed =
	    tpnt->blksize_changed = FALSE;

	st_template.nr_dev++;
	return 0;
};

static int st_detect(Scsi_Device * SDp)
{
	if (SDp->type != TYPE_TAPE)
		return 0;

	printk(KERN_WARNING
	"Detected scsi tape st%d at scsi%d, channel %d, id %d, lun %d\n",
	       st_template.dev_noticed++,
	       SDp->host->host_no, SDp->channel, SDp->id, SDp->lun);

	return 1;
}

static int st_registered = 0;

/* Driver initialization (not __init because may be called later) */
static int st_init()
{
	int i, j;
	Scsi_Tape *STp;
	int target_nbr;

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

	printk(KERN_INFO "st: bufsize %d, wrt %d, max init. buffers %d, s/g segs %d.\n",
	       st_buffer_size, st_write_threshold, st_max_buffers, st_max_sg_segs);

	if (!st_registered) {
		if (register_chrdev(SCSI_TAPE_MAJOR, "st", &st_fops)) {
			printk(KERN_ERR "Unable to get major %d for SCSI tapes\n",
                               MAJOR_NR);
			return 1;
		}
		st_registered++;
	}
	if (scsi_tapes)
		return 0;
	st_template.dev_max = st_template.dev_noticed + ST_EXTRA_DEVS;
	if (st_template.dev_max < ST_MAX_TAPES)
		st_template.dev_max = ST_MAX_TAPES;
	if (st_template.dev_max > 128 / ST_NBR_MODES)
		printk(KERN_INFO "st: Only %d tapes accessible.\n", 128 / ST_NBR_MODES);
	scsi_tapes =
		(Scsi_Tape *) kmalloc(st_template.dev_max * sizeof(Scsi_Tape),
				      GFP_ATOMIC);
	if (scsi_tapes == NULL) {
		printk(KERN_ERR "Unable to allocate descriptors for SCSI tapes.\n");
		unregister_chrdev(SCSI_TAPE_MAJOR, "st");
		return 1;
	}

        DEB(printk(ST_DEB_MSG "st: Buffer size %d bytes, write threshold %d bytes.\n",
                   st_buffer_size, st_write_threshold));

	memset(scsi_tapes, 0, st_template.dev_max * sizeof(Scsi_Tape));
	for (i = 0; i < st_template.dev_max; ++i) {
		STp = &(scsi_tapes[i]);
		STp->capacity = 0xfffff;
		STp->mt_status = (struct mtget *) kmalloc(sizeof(struct mtget),
							  GFP_ATOMIC);
		if (STp->mt_status == NULL) {
			for (j=0; j < i; j++)
				kfree(scsi_tapes[j].mt_status);
			kfree(scsi_tapes);
			unregister_chrdev(SCSI_TAPE_MAJOR, "st");
			return 1;
		}
		/* Initialize status */
		memset((void *) scsi_tapes[i].mt_status, 0, sizeof(struct mtget));
	}

	/* Allocate the buffers */
	st_buffers =
	    (ST_buffer **) kmalloc(st_template.dev_max * sizeof(ST_buffer *),
				   GFP_ATOMIC);
	if (st_buffers == NULL) {
		printk(KERN_ERR "Unable to allocate tape buffer pointers.\n");
		unregister_chrdev(SCSI_TAPE_MAJOR, "st");
		for (i=0; i < st_template.dev_max; i++)
			kfree(scsi_tapes[i].mt_status);
		kfree(scsi_tapes);
		unregister_chrdev(SCSI_TAPE_MAJOR, "st");
		return 1;
	}
	target_nbr = st_template.dev_noticed;
	if (target_nbr < ST_EXTRA_DEVS)
		target_nbr = ST_EXTRA_DEVS;
	if (target_nbr > st_max_buffers)
		target_nbr = st_max_buffers;

	for (i = st_nbr_buffers = 0; i < target_nbr; i++) {
		if (!new_tape_buffer(TRUE, TRUE)) {
			if (i == 0) {
				printk(KERN_INFO
                                       "No tape buffers allocated at initialization.\n");
				break;
			}
			printk(KERN_INFO "Number of tape buffers adjusted.\n");
			break;
		}
	}

	return 0;
}

static void st_detach(Scsi_Device * SDp)
{
	Scsi_Tape *tpnt;
	int i;

	for (tpnt = scsi_tapes, i = 0; i < st_template.dev_max; i++, tpnt++)
		if (tpnt->device == SDp) {
			tpnt->device = NULL;
			SDp->attached--;
			st_template.nr_dev--;
			st_template.dev_noticed--;
			return;
		}
	return;
}


#ifdef MODULE

int __init init_module(void)
{
	validate_options();

	st_template.module = &__this_module;
        return scsi_register_module(MODULE_SCSI_DEV, &st_template);
}

void cleanup_module(void)
{
	int i;

	scsi_unregister_module(MODULE_SCSI_DEV, &st_template);
	unregister_chrdev(SCSI_TAPE_MAJOR, "st");
	st_registered--;
	if (scsi_tapes != NULL) {
		for (i=0; i < st_template.dev_max; ++i)
			kfree(scsi_tapes[i].mt_status);
		kfree(scsi_tapes);
		if (st_buffers != NULL) {
			for (i = 0; i < st_nbr_buffers; i++) {
				if (st_buffers[i] != NULL) {
					st_buffers[i]->orig_sg_segs = 0;
					normalize_buffer(st_buffers[i]);
					kfree(st_buffers[i]);
				}
			}	
			kfree(st_buffers);
		}
	}
	st_template.dev_max = 0;
	printk(KERN_INFO "st: Unloaded.\n");
}
#endif				/* MODULE */