drivers/block/paride/pt.c

/* 
        pt.c    (c) 1998  Grant R. Guenther <grant@torque.net>
                          Under the terms of the GNU General Public License.

        This is the high-level driver for parallel port ATAPI tape
        drives based on chips supported by the paride module.

	The driver implements both rewinding and non-rewinding
	devices, filemarks, and the rewind ioctl.  It allocates
	a small internal "bounce buffer" for each open device, but
        otherwise expects buffering and blocking to be done at the
        user level.  As with most block-structured tapes, short
	writes are padded to full tape blocks, so reading back a file
        may return more data than was actually written.

        By default, the driver will autoprobe for a single parallel
        port ATAPI tape drive, but if their individual parameters are
        specified, the driver can handle up to 4 drives.

	The rewinding devices are named /dev/pt0, /dev/pt1, ...
	while the non-rewinding devices are /dev/npt0, /dev/npt1, etc.

        The behaviour of the pt driver can be altered by setting
        some parameters from the insmod command line.  The following
        parameters are adjustable:

            drive0      These four arguments can be arrays of       
            drive1      1-6 integers as follows:
            drive2
            drive3      <prt>,<pro>,<uni>,<mod>,<slv>,<dly>

                        Where,

                <prt>   is the base of the parallel port address for
                        the corresponding drive.  (required)

                <pro>   is the protocol number for the adapter that
                        supports this drive.  These numbers are
                        logged by 'paride' when the protocol modules
                        are initialised.  (0 if not given)

                <uni>   for those adapters that support chained
                        devices, this is the unit selector for the
                        chain of devices on the given port.  It should
                        be zero for devices that don't support chaining.
                        (0 if not given)

                <mod>   this can be -1 to choose the best mode, or one
                        of the mode numbers supported by the adapter.
                        (-1 if not given)

                <slv>   ATAPI devices can be jumpered to master or slave.
                        Set this to 0 to choose the master drive, 1 to
                        choose the slave, -1 (the default) to choose the
                        first drive found.

                <dly>   some parallel ports require the driver to 
                        go more slowly.  -1 sets a default value that
                        should work with the chosen protocol.  Otherwise,
                        set this to a small integer, the larger it is
                        the slower the port i/o.  In some cases, setting
                        this to zero will speed up the device. (default -1)

	    major	You may use this parameter to overide the
			default major number (96) that this driver
			will use.  Be sure to change the device
			name as well.

	    name	This parameter is a character string that
			contains the name the kernel will use for this
			device (in /proc output, for instance).
			(default "pt").

            verbose     This parameter controls the amount of logging
                        that the driver will do.  Set it to 0 for
                        normal operation, 1 to see autoprobe progress
                        messages, or 2 to see additional debugging
                        output.  (default 0)
 
        If this driver is built into the kernel, you can use 
        the following command line parameters, with the same values
        as the corresponding module parameters listed above:

            pt.drive0
            pt.drive1
            pt.drive2
            pt.drive3

        In addition, you can use the parameter pt.disable to disable
        the driver entirely.

*/

/*   Changes:

	1.01	GRG 1998.05.06	Round up transfer size, fix ready_wait,
			        loosed interpretation of ATAPI standard
				for clearing error status.
				Eliminate sti();
	1.02    GRG 1998.06.16  Eliminate an Ugh.
	1.03    GRG 1998.08.15  Adjusted PT_TMO, use HZ in loop timing,
				extra debugging
	1.04    GRG 1998.09.24  Repair minor coding error, added jumbo support
	
*/

#define PT_VERSION      "1.04"
#define PT_MAJOR	96
#define PT_NAME		"pt"
#define PT_UNITS	4

#include <linux/types.h>

/* Here are things one can override from the insmod command.
   Most are autoprobed by paride unless set here.  Verbose is on
   by default.

*/

static bool verbose = 0;
static int major = PT_MAJOR;
static char *name = PT_NAME;
static int disable = 0;

static int drive0[6] = { 0, 0, 0, -1, -1, -1 };
static int drive1[6] = { 0, 0, 0, -1, -1, -1 };
static int drive2[6] = { 0, 0, 0, -1, -1, -1 };
static int drive3[6] = { 0, 0, 0, -1, -1, -1 };

static int (*drives[4])[6] = {&drive0, &drive1, &drive2, &drive3};

#define D_PRT   0
#define D_PRO   1
#define D_UNI   2
#define D_MOD   3
#define D_SLV   4
#define D_DLY   5

#define DU              (*drives[unit])

/* end of parameters */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/mtio.h>
#include <linux/device.h>
#include <linux/sched.h>	/* current, TASK_*, schedule_timeout() */
#include <linux/mutex.h>

#include <asm/uaccess.h>

module_param(verbose, bool, 0);
module_param(major, int, 0);
module_param(name, charp, 0);
module_param_array(drive0, int, NULL, 0);
module_param_array(drive1, int, NULL, 0);
module_param_array(drive2, int, NULL, 0);
module_param_array(drive3, int, NULL, 0);

#include "paride.h"

#define PT_MAX_RETRIES  5
#define PT_TMO          3000	/* interrupt timeout in jiffies */
#define PT_SPIN_DEL     50	/* spin delay in micro-seconds  */
#define PT_RESET_TMO    30	/* 30 seconds */
#define PT_READY_TMO	60	/* 60 seconds */
#define PT_REWIND_TMO	1200	/* 20 minutes */

#define PT_SPIN         ((1000000/(HZ*PT_SPIN_DEL))*PT_TMO)

#define STAT_ERR        0x00001
#define STAT_INDEX      0x00002
#define STAT_ECC        0x00004
#define STAT_DRQ        0x00008
#define STAT_SEEK       0x00010
#define STAT_WRERR      0x00020
#define STAT_READY      0x00040
#define STAT_BUSY       0x00080
#define STAT_SENSE	0x1f000

#define ATAPI_TEST_READY	0x00
#define ATAPI_REWIND		0x01
#define ATAPI_REQ_SENSE		0x03
#define ATAPI_READ_6		0x08
#define ATAPI_WRITE_6		0x0a
#define ATAPI_WFM		0x10
#define ATAPI_IDENTIFY		0x12
#define ATAPI_MODE_SENSE	0x1a
#define ATAPI_LOG_SENSE		0x4d

static DEFINE_MUTEX(pt_mutex);
static int pt_open(struct inode *inode, struct file *file);
static long pt_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
static int pt_release(struct inode *inode, struct file *file);
static ssize_t pt_read(struct file *filp, char __user *buf,
		       size_t count, loff_t * ppos);
static ssize_t pt_write(struct file *filp, const char __user *buf,
			size_t count, loff_t * ppos);
static int pt_detect(void);

/* bits in tape->flags */

#define PT_MEDIA	1
#define PT_WRITE_OK	2
#define PT_REWIND	4
#define PT_WRITING      8
#define PT_READING     16
#define PT_EOF	       32

#define PT_NAMELEN      8
#define PT_BUFSIZE  16384

struct pt_unit {
	struct pi_adapter pia;	/* interface to paride layer */
	struct pi_adapter *pi;
	int flags;		/* various state flags */
	int last_sense;		/* result of last request sense */
	int drive;		/* drive */
	atomic_t available;	/* 1 if access is available 0 otherwise */
	int bs;			/* block size */
	int capacity;		/* Size of tape in KB */
	int present;		/* device present ? */
	char *bufptr;
	char name[PT_NAMELEN];	/* pf0, pf1, ... */
};

static int pt_identify(struct pt_unit *tape);

static struct pt_unit pt[PT_UNITS];

static char pt_scratch[512];	/* scratch block buffer */

/* kernel glue structures */

static const struct file_operations pt_fops = {
	.owner = THIS_MODULE,
	.read = pt_read,
	.write = pt_write,
	.unlocked_ioctl = pt_ioctl,
	.open = pt_open,
	.release = pt_release,
	.llseek = noop_llseek,
};

/* sysfs class support */
static struct class *pt_class;

static inline int status_reg(struct pi_adapter *pi)
{
	return pi_read_regr(pi, 1, 6);
}

static inline int read_reg(struct pi_adapter *pi, int reg)
{
	return pi_read_regr(pi, 0, reg);
}

static inline void write_reg(struct pi_adapter *pi, int reg, int val)
{
	pi_write_regr(pi, 0, reg, val);
}

static inline u8 DRIVE(struct pt_unit *tape)
{
	return 0xa0+0x10*tape->drive;
}

static int pt_wait(struct pt_unit *tape, int go, int stop, char *fun, char *msg)
{
	int j, r, e, s, p;
	struct pi_adapter *pi = tape->pi;

	j = 0;
	while ((((r = status_reg(pi)) & go) || (stop && (!(r & stop))))
	       && (j++ < PT_SPIN))
		udelay(PT_SPIN_DEL);

	if ((r & (STAT_ERR & stop)) || (j > PT_SPIN)) {
		s = read_reg(pi, 7);
		e = read_reg(pi, 1);
		p = read_reg(pi, 2);
		if (j > PT_SPIN)
			e |= 0x100;
		if (fun)
			printk("%s: %s %s: alt=0x%x stat=0x%x err=0x%x"
			       " loop=%d phase=%d\n",
			       tape->name, fun, msg, r, s, e, j, p);
		return (e << 8) + s;
	}
	return 0;
}

static int pt_command(struct pt_unit *tape, char *cmd, int dlen, char *fun)
{
	struct pi_adapter *pi = tape->pi;
	pi_connect(pi);

	write_reg(pi, 6, DRIVE(tape));

	if (pt_wait(tape, STAT_BUSY | STAT_DRQ, 0, fun, "before command")) {
		pi_disconnect(pi);
		return -1;
	}

	write_reg(pi, 4, dlen % 256);
	write_reg(pi, 5, dlen / 256);
	write_reg(pi, 7, 0xa0);	/* ATAPI packet command */

	if (pt_wait(tape, STAT_BUSY, STAT_DRQ, fun, "command DRQ")) {
		pi_disconnect(pi);
		return -1;
	}

	if (read_reg(pi, 2) != 1) {
		printk("%s: %s: command phase error\n", tape->name, fun);
		pi_disconnect(pi);
		return -1;
	}

	pi_write_block(pi, cmd, 12);

	return 0;
}

static int pt_completion(struct pt_unit *tape, char *buf, char *fun)
{
	struct pi_adapter *pi = tape->pi;
	int r, s, n, p;

	r = pt_wait(tape, STAT_BUSY, STAT_DRQ | STAT_READY | STAT_ERR,
		    fun, "completion");

	if (read_reg(pi, 7) & STAT_DRQ) {
		n = (((read_reg(pi, 4) + 256 * read_reg(pi, 5)) +
		      3) & 0xfffc);
		p = read_reg(pi, 2) & 3;
		if (p == 0)
			pi_write_block(pi, buf, n);
		if (p == 2)
			pi_read_block(pi, buf, n);
	}

	s = pt_wait(tape, STAT_BUSY, STAT_READY | STAT_ERR, fun, "data done");

	pi_disconnect(pi);

	return (r ? r : s);
}

static void pt_req_sense(struct pt_unit *tape, int quiet)
{
	char rs_cmd[12] = { ATAPI_REQ_SENSE, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0 };
	char buf[16];
	int r;

	r = pt_command(tape, rs_cmd, 16, "Request sense");
	mdelay(1);
	if (!r)
		pt_completion(tape, buf, "Request sense");

	tape->last_sense = -1;
	if (!r) {
		if (!quiet)
			printk("%s: Sense key: %x, ASC: %x, ASQ: %x\n",
			       tape->name, buf[2] & 0xf, buf[12], buf[13]);
		tape->last_sense = (buf[2] & 0xf) | ((buf[12] & 0xff) << 8)
		    | ((buf[13] & 0xff) << 16);
	}
}

static int pt_atapi(struct pt_unit *tape, char *cmd, int dlen, char *buf, char *fun)
{
	int r;

	r = pt_command(tape, cmd, dlen, fun);
	mdelay(1);
	if (!r)
		r = pt_completion(tape, buf, fun);
	if (r)
		pt_req_sense(tape, !fun);

	return r;
}

static void pt_sleep(int cs)
{
	schedule_timeout_interruptible(cs);
}

static int pt_poll_dsc(struct pt_unit *tape, int pause, int tmo, char *msg)
{
	struct pi_adapter *pi = tape->pi;
	int k, e, s;

	k = 0;
	e = 0;
	s = 0;
	while (k < tmo) {
		pt_sleep(pause);
		k++;
		pi_connect(pi);
		write_reg(pi, 6, DRIVE(tape));
		s = read_reg(pi, 7);
		e = read_reg(pi, 1);
		pi_disconnect(pi);
		if (s & (STAT_ERR | STAT_SEEK))
			break;
	}
	if ((k >= tmo) || (s & STAT_ERR)) {
		if (k >= tmo)
			printk("%s: %s DSC timeout\n", tape->name, msg);
		else
			printk("%s: %s stat=0x%x err=0x%x\n", tape->name, msg, s,
			       e);
		pt_req_sense(tape, 0);
		return 0;
	}
	return 1;
}

static void pt_media_access_cmd(struct pt_unit *tape, int tmo, char *cmd, char *fun)
{
	if (pt_command(tape, cmd, 0, fun)) {
		pt_req_sense(tape, 0);
		return;
	}
	pi_disconnect(tape->pi);
	pt_poll_dsc(tape, HZ, tmo, fun);
}

static void pt_rewind(struct pt_unit *tape)
{
	char rw_cmd[12] = { ATAPI_REWIND, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

	pt_media_access_cmd(tape, PT_REWIND_TMO, rw_cmd, "rewind");
}

static void pt_write_fm(struct pt_unit *tape)
{
	char wm_cmd[12] = { ATAPI_WFM, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0 };

	pt_media_access_cmd(tape, PT_TMO, wm_cmd, "write filemark");
}

#define DBMSG(msg)      ((verbose>1)?(msg):NULL)

static int pt_reset(struct pt_unit *tape)
{
	struct pi_adapter *pi = tape->pi;
	int i, k, flg;
	int expect[5] = { 1, 1, 1, 0x14, 0xeb };

	pi_connect(pi);
	write_reg(pi, 6, DRIVE(tape));
	write_reg(pi, 7, 8);

	pt_sleep(20 * HZ / 1000);

	k = 0;
	while ((k++ < PT_RESET_TMO) && (status_reg(pi) & STAT_BUSY))
		pt_sleep(HZ / 10);

	flg = 1;
	for (i = 0; i < 5; i++)
		flg &= (read_reg(pi, i + 1) == expect[i]);

	if (verbose) {
		printk("%s: Reset (%d) signature = ", tape->name, k);
		for (i = 0; i < 5; i++)
			printk("%3x", read_reg(pi, i + 1));
		if (!flg)
			printk(" (incorrect)");
		printk("\n");
	}

	pi_disconnect(pi);
	return flg - 1;
}

static int pt_ready_wait(struct pt_unit *tape, int tmo)
{
	char tr_cmd[12] = { ATAPI_TEST_READY, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
	int k, p;

	k = 0;
	while (k < tmo) {
		tape->last_sense = 0;
		pt_atapi(tape, tr_cmd, 0, NULL, DBMSG("test unit ready"));
		p = tape->last_sense;
		if (!p)
			return 0;
		if (!(((p & 0xffff) == 0x0402) || ((p & 0xff) == 6)))
			return p;
		k++;
		pt_sleep(HZ);
	}
	return 0x000020;	/* timeout */
}

static void xs(char *buf, char *targ, int offs, int len)
{
	int j, k, l;

	j = 0;
	l = 0;
	for (k = 0; k < len; k++)
		if ((buf[k + offs] != 0x20) || (buf[k + offs] != l))
			l = targ[j++] = buf[k + offs];
	if (l == 0x20)
		j--;
	targ[j] = 0;
}

static int xn(char *buf, int offs, int size)
{
	int v, k;

	v = 0;
	for (k = 0; k < size; k++)
		v = v * 256 + (buf[k + offs] & 0xff);
	return v;
}

static int pt_identify(struct pt_unit *tape)
{
	int dt, s;
	char *ms[2] = { "master", "slave" };
	char mf[10], id[18];
	char id_cmd[12] = { ATAPI_IDENTIFY, 0, 0, 0, 36, 0, 0, 0, 0, 0, 0, 0 };
	char ms_cmd[12] =
	    { ATAPI_MODE_SENSE, 0, 0x2a, 0, 36, 0, 0, 0, 0, 0, 0, 0 };
	char ls_cmd[12] =
	    { ATAPI_LOG_SENSE, 0, 0x71, 0, 0, 0, 0, 0, 36, 0, 0, 0 };
	char buf[36];

	s = pt_atapi(tape, id_cmd, 36, buf, "identify");
	if (s)
		return -1;

	dt = buf[0] & 0x1f;
	if (dt != 1) {
		if (verbose)
			printk("%s: Drive %d, unsupported type %d\n",
			       tape->name, tape->drive, dt);
		return -1;
	}

	xs(buf, mf, 8, 8);
	xs(buf, id, 16, 16);

	tape->flags = 0;
	tape->capacity = 0;
	tape->bs = 0;

	if (!pt_ready_wait(tape, PT_READY_TMO))
		tape->flags |= PT_MEDIA;

	if (!pt_atapi(tape, ms_cmd, 36, buf, "mode sense")) {
		if (!(buf[2] & 0x80))
			tape->flags |= PT_WRITE_OK;
		tape->bs = xn(buf, 10, 2);
	}

	if (!pt_atapi(tape, ls_cmd, 36, buf, "log sense"))
		tape->capacity = xn(buf, 24, 4);

	printk("%s: %s %s, %s", tape->name, mf, id, ms[tape->drive]);
	if (!(tape->flags & PT_MEDIA))
		printk(", no media\n");
	else {
		if (!(tape->flags & PT_WRITE_OK))
			printk(", RO");
		printk(", blocksize %d, %d MB\n", tape->bs, tape->capacity / 1024);
	}

	return 0;
}


/*
 * returns  0, with id set if drive is detected
 *	   -1, if drive detection failed
 */
static int pt_probe(struct pt_unit *tape)
{
	if (tape->drive == -1) {
		for (tape->drive = 0; tape->drive <= 1; tape->drive++)
			if (!pt_reset(tape))
				return pt_identify(tape);
	} else {
		if (!pt_reset(tape))
			return pt_identify(tape);
	}
	return -1;
}

static int pt_detect(void)
{
	struct pt_unit *tape;
	int specified = 0, found = 0;
	int unit;

	printk("%s: %s version %s, major %d\n", name, name, PT_VERSION, major);

	specified = 0;
	for (unit = 0; unit < PT_UNITS; unit++) {
		struct pt_unit *tape = &pt[unit];
		tape->pi = &tape->pia;
		atomic_set(&tape->available, 1);
		tape->flags = 0;
		tape->last_sense = 0;
		tape->present = 0;
		tape->bufptr = NULL;
		tape->drive = DU[D_SLV];
		snprintf(tape->name, PT_NAMELEN, "%s%d", name, unit);
		if (!DU[D_PRT])
			continue;
		specified++;
		if (pi_init(tape->pi, 0, DU[D_PRT], DU[D_MOD], DU[D_UNI],
		     DU[D_PRO], DU[D_DLY], pt_scratch, PI_PT,
		     verbose, tape->name)) {
			if (!pt_probe(tape)) {
				tape->present = 1;
				found++;
			} else
				pi_release(tape->pi);
		}
	}
	if (specified == 0) {
		tape = pt;
		if (pi_init(tape->pi, 1, -1, -1, -1, -1, -1, pt_scratch,
			    PI_PT, verbose, tape->name)) {
			if (!pt_probe(tape)) {
				tape->present = 1;
				found++;
			} else
				pi_release(tape->pi);
		}

	}
	if (found)
		return 0;

	printk("%s: No ATAPI tape drive detected\n", name);
	return -1;
}

static int pt_open(struct inode *inode, struct file *file)
{
	int unit = iminor(inode) & 0x7F;
	struct pt_unit *tape = pt + unit;
	int err;

	mutex_lock(&pt_mutex);
	if (unit >= PT_UNITS || (!tape->present)) {
		mutex_unlock(&pt_mutex);
		return -ENODEV;
	}

	err = -EBUSY;
	if (!atomic_dec_and_test(&tape->available))
		goto out;

	pt_identify(tape);

	err = -ENODEV;
	if (!(tape->flags & PT_MEDIA))
		goto out;

	err = -EROFS;
	if ((!(tape->flags & PT_WRITE_OK)) && (file->f_mode & FMODE_WRITE))
		goto out;

	if (!(iminor(inode) & 128))
		tape->flags |= PT_REWIND;

	err = -ENOMEM;
	tape->bufptr = kmalloc(PT_BUFSIZE, GFP_KERNEL);
	if (tape->bufptr == NULL) {
		printk("%s: buffer allocation failed\n", tape->name);
		goto out;
	}

	file->private_data = tape;
	mutex_unlock(&pt_mutex);
	return 0;

out:
	atomic_inc(&tape->available);
	mutex_unlock(&pt_mutex);
	return err;
}

static long pt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct pt_unit *tape = file->private_data;
	struct mtop __user *p = (void __user *)arg;
	struct mtop mtop;

	switch (cmd) {
	case MTIOCTOP:
		if (copy_from_user(&mtop, p, sizeof(struct mtop)))
			return -EFAULT;

		switch (mtop.mt_op) {

		case MTREW:
			mutex_lock(&pt_mutex);
			pt_rewind(tape);
			mutex_unlock(&pt_mutex);
			return 0;

		case MTWEOF:
			mutex_lock(&pt_mutex);
			pt_write_fm(tape);
			mutex_unlock(&pt_mutex);
			return 0;

		default:
			/* FIXME: rate limit ?? */
			printk(KERN_DEBUG "%s: Unimplemented mt_op %d\n", tape->name,
			       mtop.mt_op);
			return -EINVAL;
		}

	default:
		return -ENOTTY;
	}
}

static int
pt_release(struct inode *inode, struct file *file)
{
	struct pt_unit *tape = file->private_data;

	if (atomic_read(&tape->available) > 1)
		return -EINVAL;

	if (tape->flags & PT_WRITING)
		pt_write_fm(tape);

	if (tape->flags & PT_REWIND)
		pt_rewind(tape);

	kfree(tape->bufptr);
	tape->bufptr = NULL;

	atomic_inc(&tape->available);

	return 0;

}

static ssize_t pt_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
{
	struct pt_unit *tape = filp->private_data;
	struct pi_adapter *pi = tape->pi;
	char rd_cmd[12] = { ATAPI_READ_6, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
	int k, n, r, p, s, t, b;

	if (!(tape->flags & (PT_READING | PT_WRITING))) {
		tape->flags |= PT_READING;
		if (pt_atapi(tape, rd_cmd, 0, NULL, "start read-ahead"))
			return -EIO;
	} else if (tape->flags & PT_WRITING)
		return -EIO;

	if (tape->flags & PT_EOF)
		return 0;

	t = 0;

	while (count > 0) {

		if (!pt_poll_dsc(tape, HZ / 100, PT_TMO, "read"))
			return -EIO;

		n = count;
		if (n > 32768)
			n = 32768;	/* max per command */
		b = (n - 1 + tape->bs) / tape->bs;
		n = b * tape->bs;	/* rounded up to even block */

		rd_cmd[4] = b;

		r = pt_command(tape, rd_cmd, n, "read");

		mdelay(1);

		if (r) {
			pt_req_sense(tape, 0);
			return -EIO;
		}

		while (1) {

			r = pt_wait(tape, STAT_BUSY,
				    STAT_DRQ | STAT_ERR | STAT_READY,
				    DBMSG("read DRQ"), "");

			if (r & STAT_SENSE) {
				pi_disconnect(pi);
				pt_req_sense(tape, 0);
				return -EIO;
			}

			if (r)
				tape->flags |= PT_EOF;

			s = read_reg(pi, 7);

			if (!(s & STAT_DRQ))
				break;

			n = (read_reg(pi, 4) + 256 * read_reg(pi, 5));
			p = (read_reg(pi, 2) & 3);
			if (p != 2) {
				pi_disconnect(pi);
				printk("%s: Phase error on read: %d\n", tape->name,
				       p);
				return -EIO;
			}

			while (n > 0) {
				k = n;
				if (k > PT_BUFSIZE)
					k = PT_BUFSIZE;
				pi_read_block(pi, tape->bufptr, k);
				n -= k;
				b = k;
				if (b > count)
					b = count;
				if (copy_to_user(buf + t, tape->bufptr, b)) {
					pi_disconnect(pi);
					return -EFAULT;
				}
				t += b;
				count -= b;
			}

		}
		pi_disconnect(pi);
		if (tape->flags & PT_EOF)
			break;
	}

	return t;

}

static ssize_t pt_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
{
	struct pt_unit *tape = filp->private_data;
	struct pi_adapter *pi = tape->pi;
	char wr_cmd[12] = { ATAPI_WRITE_6, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
	int k, n, r, p, s, t, b;

	if (!(tape->flags & PT_WRITE_OK))
		return -EROFS;

	if (!(tape->flags & (PT_READING | PT_WRITING))) {
		tape->flags |= PT_WRITING;
		if (pt_atapi
		    (tape, wr_cmd, 0, NULL, "start buffer-available mode"))
			return -EIO;
	} else if (tape->flags & PT_READING)
		return -EIO;

	if (tape->flags & PT_EOF)
		return -ENOSPC;

	t = 0;

	while (count > 0) {

		if (!pt_poll_dsc(tape, HZ / 100, PT_TMO, "write"))
			return -EIO;

		n = count;
		if (n > 32768)
			n = 32768;	/* max per command */
		b = (n - 1 + tape->bs) / tape->bs;
		n = b * tape->bs;	/* rounded up to even block */

		wr_cmd[4] = b;

		r = pt_command(tape, wr_cmd, n, "write");

		mdelay(1);

		if (r) {	/* error delivering command only */
			pt_req_sense(tape, 0);
			return -EIO;
		}

		while (1) {

			r = pt_wait(tape, STAT_BUSY,
				    STAT_DRQ | STAT_ERR | STAT_READY,
				    DBMSG("write DRQ"), NULL);

			if (r & STAT_SENSE) {
				pi_disconnect(pi);
				pt_req_sense(tape, 0);
				return -EIO;
			}

			if (r)
				tape->flags |= PT_EOF;

			s = read_reg(pi, 7);

			if (!(s & STAT_DRQ))
				break;

			n = (read_reg(pi, 4) + 256 * read_reg(pi, 5));
			p = (read_reg(pi, 2) & 3);
			if (p != 0) {
				pi_disconnect(pi);
				printk("%s: Phase error on write: %d \n",
				       tape->name, p);
				return -EIO;
			}

			while (n > 0) {
				k = n;
				if (k > PT_BUFSIZE)
					k = PT_BUFSIZE;
				b = k;
				if (b > count)
					b = count;
				if (copy_from_user(tape->bufptr, buf + t, b)) {
					pi_disconnect(pi);
					return -EFAULT;
				}
				pi_write_block(pi, tape->bufptr, k);
				t += b;
				count -= b;
				n -= k;
			}

		}
		pi_disconnect(pi);
		if (tape->flags & PT_EOF)
			break;
	}

	return t;
}

static int __init pt_init(void)
{
	int unit;
	int err;

	if (disable) {
		err = -EINVAL;
		goto out;
	}

	if (pt_detect()) {
		err = -ENODEV;
		goto out;
	}

	err = register_chrdev(major, name, &pt_fops);
	if (err < 0) {
		printk("pt_init: unable to get major number %d\n", major);
		for (unit = 0; unit < PT_UNITS; unit++)
			if (pt[unit].present)
				pi_release(pt[unit].pi);
		goto out;
	}
	major = err;
	pt_class = class_create(THIS_MODULE, "pt");
	if (IS_ERR(pt_class)) {
		err = PTR_ERR(pt_class);
		goto out_chrdev;
	}

	for (unit = 0; unit < PT_UNITS; unit++)
		if (pt[unit].present) {
			device_create(pt_class, NULL, MKDEV(major, unit), NULL,
				      "pt%d", unit);
			device_create(pt_class, NULL, MKDEV(major, unit + 128),
				      NULL, "pt%dn", unit);
		}
	goto out;

out_chrdev:
	unregister_chrdev(major, "pt");
out:
	return err;
}

static void __exit pt_exit(void)
{
	int unit;
	for (unit = 0; unit < PT_UNITS; unit++)
		if (pt[unit].present) {
			device_destroy(pt_class, MKDEV(major, unit));
			device_destroy(pt_class, MKDEV(major, unit + 128));
		}
	class_destroy(pt_class);
	unregister_chrdev(major, name);
	for (unit = 0; unit < PT_UNITS; unit++)
		if (pt[unit].present)
			pi_release(pt[unit].pi);
}

MODULE_LICENSE("GPL");
module_init(pt_init)
module_exit(pt_exit)