xref: /openbsd/sys/scsi/st.c (revision d415bd75)
1 /*	$OpenBSD: st.c,v 1.190 2023/04/27 18:21:44 robert Exp $	*/
2 /*	$NetBSD: st.c,v 1.71 1997/02/21 23:03:49 thorpej Exp $	*/
3 
4 /*
5  * Copyright (c) 1994 Charles Hannum.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by Charles Hannum.
18  * 4. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 /*
34  * Originally written by Julian Elischer (julian@tfs.com)
35  * for TRW Financial Systems for use under the MACH(2.5) operating system.
36  *
37  * TRW Financial Systems, in accordance with their agreement with Carnegie
38  * Mellon University, makes this software available to CMU to distribute
39  * or use in any manner that they see fit as long as this message is kept with
40  * the software. For this reason TFS also grants any other persons or
41  * organisations permission to use or modify this software.
42  *
43  * TFS supplies this software to be publicly redistributed
44  * on the understanding that TFS is not responsible for the correct
45  * functioning of this software in any circumstances.
46  *
47  * Ported to run under 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
48  * major changes by Julian Elischer (julian@jules.dialix.oz.au) May 1993
49  */
50 
51 /*
52  * To do:
53  * work out some better way of guessing what a good timeout is going
54  * to be depending on whether we expect to retension or not.
55  */
56 
57 #include <sys/param.h>
58 #include <sys/systm.h>
59 #include <sys/timeout.h>
60 #include <sys/fcntl.h>
61 #include <sys/errno.h>
62 #include <sys/ioctl.h>
63 #include <sys/stat.h>
64 #include <sys/pool.h>
65 #include <sys/buf.h>
66 #include <sys/mtio.h>
67 #include <sys/device.h>
68 #include <sys/disk.h>
69 #include <sys/conf.h>
70 #include <sys/vnode.h>
71 
72 #include <scsi/scsi_all.h>
73 #include <scsi/scsi_debug.h>
74 #include <scsi/scsi_tape.h>
75 #include <scsi/scsiconf.h>
76 
77 /* Defines for device specific stuff */
78 #define DEF_FIXED_BSIZE  512
79 
80 #define STMODE(z)	( minor(z)	 & 0x03)
81 #define STUNIT(z)	((minor(z) >> 4)       )
82 
83 #define STMINOR(unit, mode)	(((unit) << 4) + (mode))
84 #define MAXSTMODES	16	/* Old max retained so minor's don't change. */
85 
86 #define	ST_IO_TIME	(3 * 60 * 1000)		/* 3 minutes */
87 #define	ST_CTL_TIME	(30 * 1000)		/* 30 seconds */
88 #define	ST_SPC_TIME	(4 * 60 * 60 * 1000)	/* 4 hours */
89 
90 /*
91  * Maximum density code allowed in SCSI spec (SSC2R08f, Section 8.3).
92  */
93 #define SCSI_MAX_DENSITY_CODE		0xff
94 
95 /*
96  * Define various devices that we know mis-behave in some way,
97  * and note how they are bad, so we can correct for them
98  */
99 struct mode {
100 	int blksize;
101 	u_int8_t density;
102 };
103 
104 struct quirkdata {
105 	u_int quirks;
106 #define	ST_Q_SENSE_HELP		0x0001	/* must do READ for good MODE SENSE */
107 #define	ST_Q_IGNORE_LOADS	0x0002
108 #define	ST_Q_UNIMODAL		0x0004	/* unimode drive rejects mode select */
109 	struct mode mode;
110 };
111 
112 struct st_quirk_inquiry_pattern {
113 	struct scsi_inquiry_pattern pattern;
114 	struct quirkdata quirkdata;
115 };
116 
117 const struct st_quirk_inquiry_pattern st_quirk_patterns[] = {
118 	{{T_SEQUENTIAL, T_REMOV,
119 		 "        ", "                ", "    "}, {0,
120 							   {512, 0}}},
121  	{{T_SEQUENTIAL, T_REMOV,
122 		 "TANDBERG", " TDC 3800       ", ""},     {0,
123 							   {512, 0}}},
124 	{{T_SEQUENTIAL, T_REMOV,
125 		 "ARCHIVE ", "VIPER 2525 25462", ""},     {ST_Q_SENSE_HELP,
126 							   {0, 0}}},
127 	{{T_SEQUENTIAL, T_REMOV,
128 		 "SANKYO  ", "CP525           ", ""},     {0,
129 							   {512, 0}}},
130 	{{T_SEQUENTIAL, T_REMOV,
131 		 "ANRITSU ", "DMT780          ", ""},     {0,
132 							   {512, 0}}},
133 	{{T_SEQUENTIAL, T_REMOV,
134 		 "ARCHIVE ", "VIPER 150  21531", ""},     {ST_Q_SENSE_HELP,
135 							   {0, 0}}},
136 	{{T_SEQUENTIAL, T_REMOV,
137 		 "WANGTEK ", "5099ES SCSI",	 ""},     {0,
138 							   {512, 0}}},
139 	{{T_SEQUENTIAL, T_REMOV,
140 		 "WANGTEK ", "5150ES SCSI",	 ""},     {0,
141 							   {512, 0}}},
142 	{{T_SEQUENTIAL, T_REMOV,
143 		 "HP      ", "T4000s          ", ""},     {ST_Q_UNIMODAL,
144 							   {0, QIC_3095}}},
145 	{{T_SEQUENTIAL, T_REMOV,
146 		 "WANGTEK ", "5150ES SCSI FA15", "01 A"}, {ST_Q_IGNORE_LOADS,
147 							   {0, 0}}},
148 	{{T_SEQUENTIAL, T_REMOV,
149 		 "TEAC    ", "MT-2ST/N50      ", ""},     {ST_Q_IGNORE_LOADS,
150 							   {0, 0}}},
151 };
152 
153 #define NOEJECT 0
154 #define EJECT 1
155 
156 #define NOREWIND 0
157 #define DOREWIND 1
158 
159 struct st_softc {
160 	struct device sc_dev;
161 	struct disk sc_dk;
162 
163 	int flags;
164 #define	ST_INFO_VALID		0x00000001
165 #define	ST_WRITTEN		0x00000004
166 #define	ST_FIXEDBLOCKS		0x00000008
167 #define	ST_AT_FILEMARK		0x00000010
168 #define	ST_EIO_PENDING		0x00000020
169 #define	ST_EOM_PENDING  	0x00000040
170 #define	ST_EOD_DETECTED		0x00000080
171 #define	ST_FM_WRITTEN		0x00000100
172 #define	ST_BLANK_READ		0x00000200
173 #define	ST_2FM_AT_EOD		0x00000400
174 #define	ST_MOUNTED		0x00000800
175 #define	ST_DONTBUFFER		0x00001000
176 #define	ST_DYING		0x00004000
177 #define	ST_BOD_DETECTED		0x00008000
178 #define	ST_MODE_DENSITY		0x00010000
179 #define	ST_MODE_BLKSIZE		0x00040000
180 
181 	u_int quirks;		/* quirks for the open mode           */
182 	int blksize;		/* blksize we are using               */
183 	u_int8_t density;	/* present density                    */
184 	short mt_resid;		/* last (short) resid                 */
185 	short mt_erreg;		/* last error (sense key) seen        */
186 
187 	struct scsi_link *sc_link;	/* our link to the adapter etc.       */
188 
189 	int blkmin;		/* min blk size                       */
190 	int blkmax;		/* max blk size                       */
191 
192 	u_int32_t media_blksize;	/* 0 if not ST_FIXEDBLOCKS            */
193 	u_int32_t media_density;	/* this is what it said when asked    */
194 	int media_fileno;		/* relative to BOT. -1 means unknown. */
195 	int media_blkno;		/* relative to BOF. -1 means unknown. */
196 	int media_eom;			/* relative to BOT. -1 means unknown. */
197 
198 	struct mode mode;
199 	struct bufq sc_bufq;
200 	struct scsi_xshandler sc_xsh;
201 };
202 
203 
204 int	stmatch(struct device *, void *, void *);
205 void	stattach(struct device *, struct device *, void *);
206 int	stactivate(struct device *, int);
207 int	stdetach(struct device *, int);
208 void	stminphys(struct buf *);
209 void	ststart(struct scsi_xfer *);
210 
211 int	st_mount_tape(struct st_softc *, int);
212 void	st_unmount(struct st_softc *, int, int);
213 int	st_decide_mode(struct st_softc *, int);
214 void	st_buf_done(struct scsi_xfer *);
215 int	st_read(struct st_softc *, char *, int, int);
216 int	st_read_block_limits(struct st_softc *, int);
217 int	st_mode_sense(struct st_softc *, int);
218 int	st_mode_select(struct st_softc *, int);
219 int	st_space(struct st_softc *, int, u_int, int);
220 int	st_write_filemarks(struct st_softc *, int, int);
221 int	st_check_eod(struct st_softc *, int, int *, int);
222 int	st_load(struct st_softc *, u_int, int);
223 int	st_rewind(struct st_softc *, u_int, int);
224 int	st_interpret_sense(struct scsi_xfer *);
225 int	st_touch_tape(struct st_softc *);
226 int	st_erase(struct st_softc *, int, int);
227 
228 const struct cfattach st_ca = {
229 	sizeof(struct st_softc), stmatch, stattach,
230 	stdetach, stactivate
231 };
232 
233 struct cfdriver st_cd = {
234 	NULL, "st", DV_TAPE
235 };
236 
237 #define	ST_PER_ACTION	(ST_AT_FILEMARK | ST_EIO_PENDING | ST_EOM_PENDING | \
238 			 ST_BLANK_READ)
239 
240 #define stlookup(unit) (struct st_softc *)device_lookup(&st_cd, (unit))
241 
242 const struct scsi_inquiry_pattern st_patterns[] = {
243 	{T_SEQUENTIAL, T_REMOV,
244 	 "",         "",                 ""},
245 };
246 
247 int
248 stmatch(struct device *parent, void *match, void *aux)
249 {
250 	struct scsi_attach_args *sa = aux;
251 	struct scsi_inquiry_data *inq = &sa->sa_sc_link->inqdata;
252 	int priority;
253 
254 	(void)scsi_inqmatch(inq, st_patterns, nitems(st_patterns),
255 	    sizeof(st_patterns[0]), &priority);
256 	return priority;
257 }
258 
259 /*
260  * The routine called by the low level scsi routine when it discovers
261  * a device suitable for this driver.
262  */
263 void
264 stattach(struct device *parent, struct device *self, void *aux)
265 {
266 	const struct st_quirk_inquiry_pattern *finger;
267 	struct st_softc *st = (void *)self;
268 	struct scsi_attach_args *sa = aux;
269 	struct scsi_link *link = sa->sa_sc_link;
270 	int priority;
271 
272 	SC_DEBUG(link, SDEV_DB2, ("stattach:\n"));
273 
274 	/*
275 	 * Store information needed to contact our base driver
276 	 */
277 	st->sc_link = link;
278 	link->interpret_sense = st_interpret_sense;
279 	link->device_softc = st;
280 
281 	/* Get any quirks and mode information. */
282 	finger = (const struct st_quirk_inquiry_pattern *)scsi_inqmatch(
283 	    &link->inqdata,
284 	    st_quirk_patterns,
285 	    nitems(st_quirk_patterns),
286 	    sizeof(st_quirk_patterns[0]), &priority);
287 	if (finger != NULL) {
288 		st->quirks = finger->quirkdata.quirks;
289 		st->mode = finger->quirkdata.mode;
290 		CLR(st->flags, ST_MODE_BLKSIZE | ST_MODE_DENSITY);
291 		if (st->mode.blksize != 0)
292 			SET(st->flags, ST_MODE_BLKSIZE);
293 		if (st->mode.density != 0)
294 			SET(st->flags, ST_MODE_DENSITY);
295 	}
296 	printf("\n");
297 
298 	scsi_xsh_set(&st->sc_xsh, link, ststart);
299 
300 	st->sc_dk.dk_name = st->sc_dev.dv_xname;
301 
302 	/* Set up the buf queue for this device. */
303 	bufq_init(&st->sc_bufq, BUFQ_FIFO);
304 
305 	/* Start up with media position unknown. */
306 	st->media_fileno = -1;
307 	st->media_blkno = -1;
308 	st->media_eom = -1;
309 
310 	/*
311 	 * Reset the media loaded flag, sometimes the data
312 	 * acquired at boot time is not quite accurate.  This
313 	 * will be checked again at the first open.
314 	 */
315 	CLR(link->flags, SDEV_MEDIA_LOADED);
316 
317 	st->sc_dk.dk_flags = DKF_NOLABELREAD;
318 	disk_attach(&st->sc_dev, &st->sc_dk);
319 }
320 
321 int
322 stactivate(struct device *self, int act)
323 {
324 	struct st_softc *st = (struct st_softc *)self;
325 
326 	switch (act) {
327 	case DVACT_DEACTIVATE:
328 		SET(st->flags, ST_DYING);
329 		scsi_xsh_del(&st->sc_xsh);
330 		break;
331 	}
332 
333 	return 0;
334 }
335 
336 int
337 stdetach(struct device *self, int flags)
338 {
339 	struct st_softc *st = (struct st_softc *)self;
340 	int cmaj, mn;
341 
342 	bufq_drain(&st->sc_bufq);
343 
344 	/* Locate the lowest minor number to be detached. */
345 	mn = STMINOR(self->dv_unit, 0);
346 
347 	for (cmaj = 0; cmaj < nchrdev; cmaj++)
348 		if (cdevsw[cmaj].d_open == stopen)
349 			vdevgone(cmaj, mn, mn + MAXSTMODES - 1, VCHR);
350 
351 	bufq_destroy(&st->sc_bufq);
352 
353 	disk_detach(&st->sc_dk);
354 
355 	return 0;
356 }
357 
358 /*
359  * open the device.
360  */
361 int
362 stopen(dev_t dev, int flags, int fmt, struct proc *p)
363 {
364 	struct scsi_link *link;
365 	struct st_softc *st;
366 	int error = 0;
367 
368 	st = stlookup(STUNIT(dev));
369 	if (st == NULL)
370 		return ENXIO;
371 	if (ISSET(st->flags, ST_DYING)) {
372 		device_unref(&st->sc_dev);
373 		return ENXIO;
374 	}
375 	link = st->sc_link;
376 
377 	if ((error = disk_lock(&st->sc_dk)) != 0) {
378 		device_unref(&st->sc_dev);
379 		return error;
380 	}
381 
382 	if (ISSET(flags, FWRITE) && ISSET(link->flags, SDEV_READONLY)) {
383 		error = EACCES;
384 		goto done;
385 	}
386 
387 	SC_DEBUG(link, SDEV_DB1, ("open: dev=0x%x (unit %d (of %d))\n", dev,
388 	    STUNIT(dev), st_cd.cd_ndevs));
389 
390 	/*
391 	 * Tape is an exclusive media. Only one open at a time.
392 	 */
393 	if (ISSET(link->flags, SDEV_OPEN)) {
394 		SC_DEBUG(link, SDEV_DB4, ("already open\n"));
395 		error = EBUSY;
396 		goto done;
397 	}
398 
399 	/* Use st_interpret_sense() now. */
400 	SET(link->flags, SDEV_OPEN);
401 
402 	/*
403 	 * Check the unit status. This clears any outstanding errors and
404 	 * will ensure that media is present.
405 	 */
406 	error = scsi_test_unit_ready(link, TEST_READY_RETRIES,
407 	    SCSI_SILENT | SCSI_IGNORE_MEDIA_CHANGE |
408 	    SCSI_IGNORE_ILLEGAL_REQUEST);
409 
410 	/*
411 	 * Terminate any existing mount session if there is no media.
412 	 */
413 	if (!ISSET(link->flags, SDEV_MEDIA_LOADED))
414 		st_unmount(st, NOEJECT, DOREWIND);
415 
416 	if (error != 0) {
417 		CLR(link->flags, SDEV_OPEN);
418 		goto done;
419 	}
420 
421 	error = st_mount_tape(st, flags);
422 	if (error != 0) {
423 		CLR(link->flags, SDEV_OPEN);
424 		goto done;
425 	}
426 
427 	/*
428 	 * Make sure that a tape opened in write-only mode will have
429 	 * file marks written on it when closed, even if not written to.
430 	 * This is for SUN compatibility
431 	 */
432 	if ((flags & O_ACCMODE) == FWRITE)
433 		SET(st->flags, ST_WRITTEN);
434 
435 done:
436 	SC_DEBUG(link, SDEV_DB2, ("open complete\n"));
437 	disk_unlock(&st->sc_dk);
438 	device_unref(&st->sc_dev);
439 	return error;
440 }
441 
442 /*
443  * close the device.. only called if we are the LAST
444  * occurrence of an open device
445  */
446 int
447 stclose(dev_t dev, int flags, int mode, struct proc *p)
448 {
449 	struct scsi_link *link;
450 	struct st_softc *st;
451 	int error = 0;
452 
453 	st = stlookup(STUNIT(dev));
454 	if (st == NULL)
455 		return ENXIO;
456 	if (ISSET(st->flags, ST_DYING)) {
457 		error = ENXIO;
458 		goto done;
459 	}
460 	link = st->sc_link;
461 
462 	disk_lock_nointr(&st->sc_dk);
463 
464 	SC_DEBUG(link, SDEV_DB1, ("closing\n"));
465 
466 	if (ISSET(st->flags, ST_WRITTEN) && !ISSET(st->flags, ST_FM_WRITTEN))
467 		st_write_filemarks(st, 1, 0);
468 
469 	switch (STMODE(dev)) {
470 	case 0:		/* /dev/rstN */
471 		st_unmount(st, NOEJECT, DOREWIND);
472 		break;
473 	case 1:		/* /dev/nrstN */
474 		st_unmount(st, NOEJECT, NOREWIND);
475 		break;
476 	case 2:		/* /dev/erstN */
477 		st_unmount(st, EJECT, DOREWIND);
478 		break;
479 	case 3:		/* /dev/enrstN */
480 		st_unmount(st, EJECT, NOREWIND);
481 		break;
482 	}
483 	CLR(link->flags, SDEV_OPEN);
484 	scsi_xsh_del(&st->sc_xsh);
485 
486 	disk_unlock(&st->sc_dk);
487 
488 done:
489 	device_unref(&st->sc_dev);
490 	return error;
491 }
492 
493 /*
494  * Start a new mount session if needed.
495  */
496 int
497 st_mount_tape(struct st_softc *st, int flags)
498 {
499 	struct scsi_link *link = st->sc_link;
500 	int error = 0;
501 
502 	if (ISSET(st->flags, ST_MOUNTED))
503 		return 0;
504 
505 	SC_DEBUG(link, SDEV_DB1, ("mounting\n"));
506 
507 	/*
508 	 * Assume the media is new and give it a chance to
509 	 * to do a 'load' instruction.
510 	 */
511 	if ((error = st_load(st, LD_LOAD, 0)) != 0)
512 		goto done;
513 
514 	/*
515 	 * Throw another dummy instruction to catch
516 	 * 'Unit attention' errors. Some drives appear to give
517 	 * these after doing a Load instruction.
518 	 * (notably some DAT drives)
519 	 */
520 	/* XXX */
521 	scsi_test_unit_ready(link, TEST_READY_RETRIES, SCSI_SILENT);
522 
523 	/*
524 	 * Some devices can't tell you much until they have been
525 	 * asked to look at the media. This quirk does this.
526 	 */
527 	if (ISSET(st->quirks, ST_Q_SENSE_HELP))
528 		if ((error = st_touch_tape(st)) != 0)
529 			return error;
530 	/*
531 	 * Load the physical device parameters
532 	 * loads: blkmin, blkmax
533 	 */
534 	if (!ISSET(link->flags, SDEV_ATAPI) &&
535 	    (error = st_read_block_limits(st, 0)) != 0)
536 		goto done;
537 
538 	/*
539 	 * Load the media dependent parameters
540 	 * includes: media_blksize,media_density
541 	 * As we have a tape in, it should be reflected here.
542 	 * If not you may need the "quirk" above.
543 	 */
544 	if ((error = st_mode_sense(st, 0)) != 0)
545 		goto done;
546 
547 	/*
548 	 * If we have gained a permanent density from somewhere,
549 	 * then use it in preference to the one supplied by
550 	 * default by the driver.
551 	 */
552 	if (ISSET(st->flags, ST_MODE_DENSITY))
553 		st->density = st->mode.density;
554 	else
555 		st->density = st->media_density;
556 	/*
557 	 * If we have gained a permanent blocksize
558 	 * then use it in preference to the one supplied by
559 	 * default by the driver.
560 	 */
561 	CLR(st->flags, ST_FIXEDBLOCKS);
562 	if (ISSET(st->flags, ST_MODE_BLKSIZE)) {
563 		st->blksize = st->mode.blksize;
564 		if (st->blksize)
565 			SET(st->flags, ST_FIXEDBLOCKS);
566 	} else {
567 		if ((error = st_decide_mode(st, 0)) != 0)
568 			goto done;
569 	}
570 	if ((error = st_mode_select(st, 0)) != 0) {
571 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
572 		goto done;
573 	}
574 	scsi_prevent(link, PR_PREVENT,
575 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
576 	SET(st->flags, ST_MOUNTED);
577 	SET(link->flags, SDEV_MEDIA_LOADED);	/* move earlier? */
578 	st->media_fileno = 0;
579 	st->media_blkno = 0;
580 	st->media_eom = -1;
581 
582 done:
583 	return error;
584 }
585 
586 /*
587  * End the present mount session.
588  * Rewind, and optionally eject the tape.
589  * Reset various flags to indicate that all new
590  * operations require another mount operation
591  */
592 void
593 st_unmount(struct st_softc *st, int eject, int rewind)
594 {
595 	struct scsi_link *link = st->sc_link;
596 	int nmarks;
597 
598 	if (eject == NOEJECT && rewind == NOREWIND) {
599 		if (ISSET(link->flags, SDEV_MEDIA_LOADED))
600 			return;
601 	}
602 
603 	st->media_fileno = -1;
604 	st->media_blkno = -1;
605 
606 	if (!ISSET(st->flags, ST_MOUNTED))
607 		return;
608 	SC_DEBUG(link, SDEV_DB1, ("unmounting\n"));
609 	st_check_eod(st, 0, &nmarks, SCSI_IGNORE_NOT_READY);
610 	if (rewind == DOREWIND)
611 		st_rewind(st, 0, SCSI_IGNORE_NOT_READY);
612 	scsi_prevent(link, PR_ALLOW,
613 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
614 	if (eject == EJECT)
615 		st_load(st, LD_UNLOAD, SCSI_IGNORE_NOT_READY);
616 	CLR(st->flags, ST_MOUNTED);
617 	CLR(link->flags, SDEV_MEDIA_LOADED);
618 }
619 
620 /*
621  * Given all we know about the device, media, mode, 'quirks' and
622  * initial operation, make a decision as to how we should be set
623  * to run (regarding blocking and EOD marks)
624  */
625 int
626 st_decide_mode(struct st_softc *st, int first_read)
627 {
628 	struct scsi_link *link = st->sc_link;
629 
630 	SC_DEBUG(link, SDEV_DB2, ("starting block mode decision\n"));
631 
632 	/* ATAPI tapes are always fixed blocksize. */
633 	if (ISSET(link->flags, SDEV_ATAPI)) {
634 		SET(st->flags, ST_FIXEDBLOCKS);
635 		if (st->media_blksize > 0)
636 			st->blksize = st->media_blksize;
637 		else
638 			st->blksize = DEF_FIXED_BSIZE;
639 		goto done;
640 	}
641 
642 	/*
643 	 * If the drive can only handle fixed-length blocks and only at
644 	 * one size, perhaps we should just do that.
645 	 */
646 	if (st->blkmin && (st->blkmin == st->blkmax)) {
647 		SET(st->flags, ST_FIXEDBLOCKS);
648 		st->blksize = st->blkmin;
649 		SC_DEBUG(link, SDEV_DB3,
650 		    ("blkmin == blkmax of %d\n", st->blkmin));
651 		goto done;
652 	}
653 	/*
654 	 * If the tape density mandates (or even suggests) use of fixed
655 	 * or variable-length blocks, comply.
656 	 */
657 	switch (st->density) {
658 	case HALFINCH_800:
659 	case HALFINCH_1600:
660 	case HALFINCH_6250:
661 	case DDS:
662 		CLR(st->flags, ST_FIXEDBLOCKS);
663 		st->blksize = 0;
664 		SC_DEBUG(link, SDEV_DB3, ("density specified variable\n"));
665 		goto done;
666 	case QIC_11:
667 	case QIC_24:
668 	case QIC_120:
669 	case QIC_150:
670 	case QIC_525:
671 	case QIC_1320:
672 		SET(st->flags, ST_FIXEDBLOCKS);
673 		if (st->media_blksize > 0)
674 			st->blksize = st->media_blksize;
675 		else
676 			st->blksize = DEF_FIXED_BSIZE;
677 		SC_DEBUG(link, SDEV_DB3, ("density specified fixed\n"));
678 		goto done;
679 	}
680 	/*
681 	 * If we're about to read the tape, perhaps we should choose
682 	 * fixed or variable-length blocks and block size according to
683 	 * what the drive found on the tape.
684 	 */
685 	if (first_read) {
686 		if (st->media_blksize > 0)
687 			SET(st->flags, ST_FIXEDBLOCKS);
688 		else
689 			CLR(st->flags, ST_FIXEDBLOCKS);
690 		st->blksize = st->media_blksize;
691 		SC_DEBUG(link, SDEV_DB3,
692 		    ("Used media_blksize of %d\n", st->media_blksize));
693 		goto done;
694 	}
695 	/*
696 	 * We're getting no hints from any direction.  Choose variable-
697 	 * length blocks arbitrarily.
698 	 */
699 	CLR(st->flags, ST_FIXEDBLOCKS);
700 	st->blksize = 0;
701 	SC_DEBUG(link, SDEV_DB3,
702 	    ("Give up and default to variable mode\n"));
703 
704 done:
705 	/*
706 	 * Decide whether or not to write two file marks to signify end-
707 	 * of-data.  Make the decision as a function of density.  If
708 	 * the decision is not to use a second file mark, the SCSI BLANK
709 	 * CHECK condition code will be recognized as end-of-data when
710 	 * first read.
711 	 * (I think this should be a by-product of fixed/variable..julian)
712 	 */
713 	switch (st->density) {
714 /*      case 8 mm:   What is the SCSI density code for 8 mm, anyway? */
715 	case QIC_11:
716 	case QIC_24:
717 	case QIC_120:
718 	case QIC_150:
719 	case QIC_525:
720 	case QIC_1320:
721 		CLR(st->flags, ST_2FM_AT_EOD);
722 		break;
723 	default:
724 		SET(st->flags, ST_2FM_AT_EOD);
725 	}
726 	return 0;
727 }
728 
729 /*
730  * Actually translate the requested transfer into
731  * one the physical driver can understand
732  * The transfer is described by a buf and will include
733  * only one physical transfer.
734  */
735 void
736 ststrategy(struct buf *bp)
737 {
738 	struct scsi_link *link;
739 	struct st_softc *st;
740 	int s;
741 
742 	st = stlookup(STUNIT(bp->b_dev));
743 	if (st == NULL) {
744 		bp->b_error = ENXIO;
745 		goto bad;
746 	}
747 	if (ISSET(st->flags, ST_DYING)) {
748 		bp->b_error = ENXIO;
749 		goto bad;
750 	}
751 	link = st->sc_link;
752 
753 	SC_DEBUG(link, SDEV_DB2, ("ststrategy: %ld bytes @ blk %lld\n",
754 	    bp->b_bcount, (long long)bp->b_blkno));
755 
756 	/*
757 	 * If it's a null transfer, return immediately.
758 	 */
759 	if (bp->b_bcount == 0)
760 		goto done;
761 	/*
762 	 * Odd sized request on fixed drives are verboten
763 	 */
764 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
765 		if (bp->b_bcount % st->blksize) {
766 			printf("%s: bad request, must be multiple of %d\n",
767 			    st->sc_dev.dv_xname, st->blksize);
768 			bp->b_error = EIO;
769 			goto bad;
770 		}
771 	}
772 	/*
773 	 * as are out-of-range requests on variable drives.
774 	 */
775 	else if (bp->b_bcount < st->blkmin ||
776 	    (st->blkmax && bp->b_bcount > st->blkmax)) {
777 		printf("%s: bad request, must be between %d and %d\n",
778 		    st->sc_dev.dv_xname, st->blkmin, st->blkmax);
779 		bp->b_error = EIO;
780 		goto bad;
781 	}
782 
783 	/*
784 	 * Place it in the queue of activities for this tape
785 	 * at the end (a bit silly because we only have on user..
786 	 * (but it could fork()))
787 	 */
788 	bufq_queue(&st->sc_bufq, bp);
789 
790 	/*
791 	 * Tell the device to get going on the transfer if it's
792 	 * not doing anything, otherwise just wait for completion
793 	 * (All a bit silly if we're only allowing 1 open but..)
794 	 */
795 	scsi_xsh_add(&st->sc_xsh);
796 
797 	device_unref(&st->sc_dev);
798 	return;
799 bad:
800 	SET(bp->b_flags, B_ERROR);
801 done:
802 	/* Set b_resid to indicate no xfer was done. */
803 	bp->b_resid = bp->b_bcount;
804 	s = splbio();
805 	biodone(bp);
806 	splx(s);
807 	if (st)
808 		device_unref(&st->sc_dev);
809 }
810 
811 void
812 ststart(struct scsi_xfer *xs)
813 {
814 	struct scsi_link *link = xs->sc_link;
815 	struct st_softc *st = link->device_softc;
816 	struct buf *bp;
817 	struct scsi_rw_tape *cmd;
818 	int s;
819 
820 	SC_DEBUG(link, SDEV_DB2, ("ststart\n"));
821 
822 	if (ISSET(st->flags, ST_DYING)) {
823 		scsi_xs_put(xs);
824 		return;
825 	}
826 
827 	/*
828 	 * if the device has been unmounted by the user
829 	 * then throw away all requests until done
830 	 */
831 	if (!ISSET(st->flags, ST_MOUNTED) ||
832 	    !ISSET(link->flags, SDEV_MEDIA_LOADED)) {
833 		/* make sure that one implies the other.. */
834 		CLR(link->flags, SDEV_MEDIA_LOADED);
835 		bufq_drain(&st->sc_bufq);
836 		scsi_xs_put(xs);
837 		return;
838 	}
839 
840 	for (;;) {
841 		bp = bufq_dequeue(&st->sc_bufq);
842 		if (bp == NULL) {
843 			scsi_xs_put(xs);
844 			return;
845 		}
846 
847 		/*
848 		 * Only FIXEDBLOCK devices have pending I/O or space
849 		 * operations.
850 		 */
851 		if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
852 			/*
853 			 * If we are at a filemark but have not reported it yet
854 			 * then we should report it now
855 			 */
856 			if (ISSET(st->flags, ST_AT_FILEMARK)) {
857 				if ((bp->b_flags & B_READ) == B_WRITE) {
858 					/*
859 					 * Handling of ST_AT_FILEMARK in
860 					 * st_space will fill in the right file
861 					 * mark count.
862 					 * Back up over filemark
863 					 */
864 					if (st_space(st, 0, SP_FILEMARKS, 0)) {
865 						SET(bp->b_flags, B_ERROR);
866 						bp->b_resid = bp->b_bcount;
867 						bp->b_error = EIO;
868 						s = splbio();
869 						biodone(bp);
870 						splx(s);
871 						continue;
872 					}
873 				} else {
874 					bp->b_resid = bp->b_bcount;
875 					bp->b_error = 0;
876 					CLR(bp->b_flags, B_ERROR);
877 					CLR(st->flags, ST_AT_FILEMARK);
878 					s = splbio();
879 					biodone(bp);
880 					splx(s);
881 					continue;	/* seek more work */
882 				}
883 			}
884 		}
885 
886 		/*
887 		 * If we are at EIO or EOM but have not reported it
888 		 * yet then we should report it now.
889 		 */
890 		if (ISSET(st->flags, ST_EOM_PENDING | ST_EIO_PENDING)) {
891 			bp->b_resid = bp->b_bcount;
892 			if (ISSET(st->flags, ST_EIO_PENDING)) {
893 				bp->b_error = EIO;
894 				SET(bp->b_flags, B_ERROR);
895 			}
896 			CLR(st->flags, ST_EOM_PENDING | ST_EIO_PENDING);
897 			s = splbio();
898 			biodone(bp);
899 			splx(s);
900 			continue;	/* seek more work */
901 		}
902 		break;
903 	}
904 
905 	/*
906 	 *  Fill out the scsi command
907 	 */
908 	cmd = (struct scsi_rw_tape *)&xs->cmd;
909 	bzero(cmd, sizeof(*cmd));
910 	if ((bp->b_flags & B_READ) == B_WRITE) {
911 		cmd->opcode = WRITE;
912 		CLR(st->flags, ST_FM_WRITTEN);
913 		SET(st->flags, ST_WRITTEN);
914 		SET(xs->flags, SCSI_DATA_OUT);
915 	} else {
916 		cmd->opcode = READ;
917 		SET(xs->flags, SCSI_DATA_IN);
918 	}
919 
920 	/*
921 	 * Handle "fixed-block-mode" tape drives by using the
922 	 * block count instead of the length.
923 	 */
924 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
925 		SET(cmd->byte2, SRW_FIXED);
926 		_lto3b(bp->b_bcount / st->blksize, cmd->len);
927 	} else
928 		_lto3b(bp->b_bcount, cmd->len);
929 
930 	if (st->media_blkno != -1) {
931 		/* Update block count now, errors will set it to -1. */
932 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
933 			st->media_blkno += _3btol(cmd->len);
934 		else if (_3btol(cmd->len) != 0)
935 			st->media_blkno++;
936 	}
937 
938 	xs->cmdlen = sizeof(*cmd);
939 	xs->timeout = ST_IO_TIME;
940 	xs->data = bp->b_data;
941 	xs->datalen = bp->b_bcount;
942 	xs->done = st_buf_done;
943 	xs->cookie = bp;
944 	xs->bp = bp;
945 
946 	/* Instrumentation. */
947 	disk_busy(&st->sc_dk);
948 
949 	/*
950 	 * go ask the adapter to do all this for us
951 	 */
952 	scsi_xs_exec(xs);
953 
954 	/*
955 	 * should we try do more work now?
956 	 */
957 	if (bufq_peek(&st->sc_bufq))
958 		scsi_xsh_add(&st->sc_xsh);
959 }
960 
961 void
962 st_buf_done(struct scsi_xfer *xs)
963 {
964 	struct st_softc *st = xs->sc_link->device_softc;
965 	struct buf *bp = xs->cookie;
966 	int error, s;
967 
968 	switch (xs->error) {
969 	case XS_NOERROR:
970 		bp->b_error = 0;
971 		CLR(bp->b_flags, B_ERROR);
972 		bp->b_resid = xs->resid;
973 		break;
974 
975 	case XS_SENSE:
976 	case XS_SHORTSENSE:
977 		SC_DEBUG_SENSE(xs);
978 		error = st_interpret_sense(xs);
979 		if (error == 0) {
980 			bp->b_error = 0;
981 			CLR(bp->b_flags, B_ERROR);
982 			bp->b_resid = xs->resid;
983 			break;
984 		}
985 		if (error != ERESTART)
986 			xs->retries = 0;
987 		goto retry;
988 
989 	case XS_BUSY:
990 		if (xs->retries) {
991 			if (scsi_delay(xs, 1) != ERESTART)
992 				xs->retries = 0;
993 		}
994 		goto retry;
995 
996 	case XS_TIMEOUT:
997  retry:
998 		if (xs->retries--) {
999 			scsi_xs_exec(xs);
1000 			return;
1001 		}
1002 		/* FALLTHROUGH */
1003 
1004 	default:
1005 		bp->b_error = EIO;
1006 		SET(bp->b_flags, B_ERROR);
1007 		bp->b_resid = bp->b_bcount;
1008 		break;
1009 	}
1010 
1011 	disk_unbusy(&st->sc_dk, bp->b_bcount - xs->resid, bp->b_blkno,
1012 		bp->b_flags & B_READ);
1013 
1014 	s = splbio();
1015 	biodone(bp);
1016 	splx(s);
1017 	scsi_xs_put(xs);
1018 }
1019 
1020 void
1021 stminphys(struct buf *bp)
1022 {
1023 	struct scsi_link	*link;
1024 	struct st_softc		*sc;
1025 
1026 	sc = stlookup(STUNIT(bp->b_dev));
1027 	if (sc == NULL)
1028 		return;
1029 	link = sc->sc_link;
1030 
1031 	if (link->bus->sb_adapter->dev_minphys != NULL)
1032 		(*link->bus->sb_adapter->dev_minphys)(bp, link);
1033 	else
1034 		minphys(bp);
1035 
1036 	device_unref(&sc->sc_dev);
1037 }
1038 
1039 int
1040 stread(dev_t dev, struct uio *uio, int iomode)
1041 {
1042 	return physio(ststrategy, dev, B_READ, stminphys, uio);
1043 }
1044 
1045 int
1046 stwrite(dev_t dev, struct uio *uio, int iomode)
1047 {
1048 	return physio(ststrategy, dev, B_WRITE, stminphys, uio);
1049 }
1050 
1051 /*
1052  * Perform special action on behalf of the user;
1053  * knows about the internals of this device
1054  */
1055 int
1056 stioctl(dev_t dev, u_long cmd, caddr_t arg, int flag, struct proc *p)
1057 {
1058 	int error = 0;
1059 	int nmarks;
1060 	int flags = 0;
1061 	struct st_softc *st;
1062 	int hold_blksize;
1063 	u_int8_t hold_density;
1064 	struct mtop *mt = (struct mtop *) arg;
1065 	int number;
1066 
1067 	/*
1068 	 * Find the device that the user is talking about
1069 	 */
1070 	st = stlookup(STUNIT(dev));
1071 	if (st == NULL)
1072 		return ENXIO;
1073 
1074 	if (ISSET(st->flags, ST_DYING)) {
1075 		error = ENXIO;
1076 		goto done;
1077 	}
1078 
1079 	hold_blksize = st->blksize;
1080 	hold_density = st->density;
1081 
1082 	switch (cmd) {
1083 
1084 	case MTIOCGET: {
1085 		struct mtget *g = (struct mtget *) arg;
1086 
1087 		/*
1088 		 * (to get the current state of READONLY)
1089 		 */
1090 		error = st_mode_sense(st, SCSI_SILENT);
1091 		if (error != 0)
1092 			break;
1093 
1094 		SC_DEBUG(st->sc_link, SDEV_DB1, ("[ioctl: get status]\n"));
1095 		bzero(g, sizeof(struct mtget));
1096 		g->mt_type = 0x7;	/* Ultrix compat *//*? */
1097 		g->mt_blksiz = st->blksize;
1098 		g->mt_density = st->density;
1099 		g->mt_mblksiz = st->mode.blksize;
1100 		g->mt_mdensity = st->mode.density;
1101 		if (ISSET(st->sc_link->flags, SDEV_READONLY))
1102 			SET(g->mt_dsreg, MT_DS_RDONLY);
1103 		if (ISSET(st->flags, ST_MOUNTED))
1104 			SET(g->mt_dsreg, MT_DS_MOUNTED);
1105 		g->mt_resid = st->mt_resid;
1106 		g->mt_erreg = st->mt_erreg;
1107 		g->mt_fileno = st->media_fileno;
1108 		g->mt_blkno = st->media_blkno;
1109 		/*
1110 		 * clear latched errors.
1111 		 */
1112 		st->mt_resid = 0;
1113 		st->mt_erreg = 0;
1114 		break;
1115 	}
1116 	case MTIOCTOP: {
1117 
1118 		SC_DEBUG(st->sc_link, SDEV_DB1,
1119 		    ("[ioctl: op=0x%x count=0x%x]\n", mt->mt_op, mt->mt_count));
1120 
1121 		number = mt->mt_count;
1122 		switch (mt->mt_op) {
1123 		case MTWEOF:	/* write an end-of-file record */
1124 			error = st_write_filemarks(st, number, flags);
1125 			break;
1126 		case MTBSF:	/* backward space file */
1127 			number = -number;
1128 		case MTFSF:	/* forward space file */
1129 			error = st_check_eod(st, 0, &nmarks, flags);
1130 			if (error == 0)
1131 				error = st_space(st, number - nmarks,
1132 				    SP_FILEMARKS, flags);
1133 			break;
1134 		case MTBSR:	/* backward space record */
1135 			number = -number;
1136 		case MTFSR:	/* forward space record */
1137 			error = st_check_eod(st, 1, &nmarks, flags);
1138 			if (error == 0)
1139 				error = st_space(st, number, SP_BLKS, flags);
1140 			break;
1141 		case MTREW:	/* rewind */
1142 			error = st_rewind(st, 0, flags);
1143 			break;
1144 		case MTOFFL:	/* rewind and put the drive offline */
1145 			st_unmount(st, EJECT, DOREWIND);
1146 			break;
1147 		case MTNOP:	/* no operation, sets status only */
1148 			break;
1149 		case MTRETEN:	/* retension the tape */
1150 			error = st_load(st, LD_RETENSION, flags);
1151 			if (error == 0)
1152 				error = st_load(st, LD_LOAD, flags);
1153 			break;
1154 		case MTEOM:	/* forward space to end of media */
1155 			error = st_check_eod(st, 0, &nmarks, flags);
1156 			if (error == 0)
1157 				error = st_space(st, 1, SP_EOM, flags);
1158 			break;
1159 		case MTCACHE:	/* enable controller cache */
1160 			CLR(st->flags, ST_DONTBUFFER);
1161 			goto try_new_value;
1162 		case MTNOCACHE:	/* disable controller cache */
1163 			SET(st->flags, ST_DONTBUFFER);
1164 			goto try_new_value;
1165 		case MTERASE:	/* erase volume */
1166 			error = st_erase(st, number, flags);
1167 			break;
1168 		case MTSETBSIZ:	/* Set block size for device and mode. */
1169 			if (number == 0) {
1170 				CLR(st->flags, ST_FIXEDBLOCKS);
1171 			} else {
1172 				if ((st->blkmin || st->blkmax) &&
1173 				    (number < st->blkmin ||
1174 				    number > st->blkmax)) {
1175 					error = EINVAL;
1176 					break;
1177 				}
1178 				SET(st->flags, ST_FIXEDBLOCKS);
1179 			}
1180 			st->blksize = number;
1181 			goto try_new_value;
1182 
1183 		case MTSETDNSTY:	/* Set density for device and mode. */
1184 			if (number < 0 || number > SCSI_MAX_DENSITY_CODE) {
1185 				error = EINVAL;
1186 				break;
1187 			}
1188 			st->density = number;
1189 			goto try_new_value;
1190 
1191 		default:
1192 			error = EINVAL;
1193 		}
1194 		break;
1195 	}
1196 	case MTIOCIEOT:
1197 	case MTIOCEEOT:
1198 		break;
1199 
1200 #if 0
1201 	case MTIOCRDSPOS:
1202 		error = st_rdpos(st, 0, (u_int32_t *) arg);
1203 		break;
1204 
1205 	case MTIOCRDHPOS:
1206 		error = st_rdpos(st, 1, (u_int32_t *) arg);
1207 		break;
1208 
1209 	case MTIOCSLOCATE:
1210 		error = st_setpos(st, 0, (u_int32_t *) arg);
1211 		break;
1212 
1213 	case MTIOCHLOCATE:
1214 		error = st_setpos(st, 1, (u_int32_t *) arg);
1215 		break;
1216 #endif /* 0 */
1217 
1218 	default:
1219 		error = scsi_do_ioctl(st->sc_link, cmd, arg, flag);
1220 		break;
1221 	}
1222 	goto done;
1223 
1224 try_new_value:
1225 	/*
1226 	 * Check that the mode being asked for is aggreeable to the
1227 	 * drive. If not, put it back the way it was.
1228 	 */
1229 	if ((error = st_mode_select(st, 0)) != 0) {/* put it back as it was */
1230 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
1231 		st->density = hold_density;
1232 		st->blksize = hold_blksize;
1233 		if (st->blksize)
1234 			SET(st->flags, ST_FIXEDBLOCKS);
1235 		else
1236 			CLR(st->flags, ST_FIXEDBLOCKS);
1237 		goto done;
1238 	}
1239 	/*
1240 	 * As the drive liked it, if we are setting a new default,
1241 	 * set it into the structures as such.
1242 	 */
1243 	switch (mt->mt_op) {
1244 	case MTSETBSIZ:
1245 		st->mode.blksize = st->blksize;
1246 		SET(st->flags, ST_MODE_BLKSIZE);
1247 		break;
1248 	case MTSETDNSTY:
1249 		st->mode.density = st->density;
1250 		SET(st->flags, ST_MODE_DENSITY);
1251 		break;
1252 	}
1253 
1254 done:
1255 	device_unref(&st->sc_dev);
1256 	return error;
1257 }
1258 
1259 /*
1260  * Do a synchronous read.
1261  */
1262 int
1263 st_read(struct st_softc *st, char *buf, int size, int flags)
1264 {
1265 	struct scsi_rw_tape *cmd;
1266 	struct scsi_xfer *xs;
1267 	int error;
1268 
1269 	if (size == 0)
1270 		return 0;
1271 
1272 	xs = scsi_xs_get(st->sc_link, flags | SCSI_DATA_IN);
1273 	if (xs == NULL)
1274 		return ENOMEM;
1275 	xs->cmdlen = sizeof(*cmd);
1276 	xs->data = buf;
1277 	xs->datalen = size;
1278 	xs->retries = 0;
1279 	xs->timeout = ST_IO_TIME;
1280 
1281 	cmd = (struct scsi_rw_tape *)&xs->cmd;
1282 	cmd->opcode = READ;
1283 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
1284 		SET(cmd->byte2, SRW_FIXED);
1285 		_lto3b(size / (st->blksize ? st->blksize : DEF_FIXED_BSIZE),
1286 		    cmd->len);
1287 	} else
1288 		_lto3b(size, cmd->len);
1289 
1290 	error = scsi_xs_sync(xs);
1291 	scsi_xs_put(xs);
1292 
1293 	return error;
1294 }
1295 
1296 /*
1297  * Ask the drive what its min and max blk sizes are.
1298  */
1299 int
1300 st_read_block_limits(struct st_softc *st, int flags)
1301 {
1302 	struct scsi_block_limits_data *block_limits = NULL;
1303 	struct scsi_block_limits *cmd;
1304 	struct scsi_link *link = st->sc_link;
1305 	struct scsi_xfer *xs;
1306 	int error = 0;
1307 
1308 	if (ISSET(link->flags, SDEV_MEDIA_LOADED))
1309 		return 0;
1310 
1311 	block_limits = dma_alloc(sizeof(*block_limits), PR_NOWAIT);
1312 	if (block_limits == NULL)
1313 		return ENOMEM;
1314 
1315 	xs = scsi_xs_get(link, flags | SCSI_DATA_IN);
1316 	if (xs == NULL) {
1317 		error = ENOMEM;
1318 		goto done;
1319 	}
1320 
1321 	xs->cmdlen = sizeof(*cmd);
1322 	xs->data = (void *)block_limits;
1323 	xs->datalen = sizeof(*block_limits);
1324 	xs->timeout = ST_CTL_TIME;
1325 
1326 	cmd = (struct scsi_block_limits *)&xs->cmd;
1327 	cmd->opcode = READ_BLOCK_LIMITS;
1328 
1329 	error = scsi_xs_sync(xs);
1330 	scsi_xs_put(xs);
1331 
1332 	if (error == 0) {
1333 		st->blkmin = _2btol(block_limits->min_length);
1334 		st->blkmax = _3btol(block_limits->max_length);
1335 		SC_DEBUG(link, SDEV_DB3,
1336 		    ("(%d <= blksize <= %d)\n", st->blkmin, st->blkmax));
1337 	}
1338 
1339 done:
1340 	if (block_limits)
1341 		dma_free(block_limits, sizeof(*block_limits));
1342 	return error;
1343 }
1344 
1345 /*
1346  * Get the scsi driver to send a full inquiry to the
1347  * device and use the results to fill out the global
1348  * parameter structure.
1349  *
1350  * called from:
1351  * attach
1352  * open
1353  * ioctl (to reset original blksize)
1354  */
1355 int
1356 st_mode_sense(struct st_softc *st, int flags)
1357 {
1358 	union scsi_mode_sense_buf *data = NULL;
1359 	struct scsi_link *link = st->sc_link;
1360 	u_int64_t block_count;
1361 	u_int32_t density, block_size;
1362 	u_char *page0 = NULL;
1363 	u_int8_t dev_spec;
1364 	int error = 0, big;
1365 
1366 	data = dma_alloc(sizeof(*data), PR_NOWAIT);
1367 	if (data == NULL)
1368 		return ENOMEM;
1369 
1370 	/*
1371 	 * Ask for page 0 (vendor specific) mode sense data.
1372 	 */
1373 	density = 0;
1374 	block_count = 0;
1375 	block_size = 0;
1376 	error = scsi_do_mode_sense(link, 0, data, (void **)&page0, 1,
1377 	    flags | SCSI_SILENT, &big);
1378 	if (error != 0)
1379 		goto done;
1380 	scsi_parse_blkdesc(link, data, big, &density, &block_count,
1381 	    &block_size);
1382 
1383 	/* It is valid for no page0 to be available. */
1384 
1385 	if (big)
1386 		dev_spec = data->hdr_big.dev_spec;
1387 	else
1388 		dev_spec = data->hdr.dev_spec;
1389 
1390 	if (ISSET(dev_spec, SMH_DSP_WRITE_PROT))
1391 		SET(link->flags, SDEV_READONLY);
1392 	else
1393 		CLR(link->flags, SDEV_READONLY);
1394 
1395 	st->media_blksize = block_size;
1396 	st->media_density = density;
1397 
1398 	SC_DEBUG(link, SDEV_DB3,
1399 	    ("density code 0x%x, %d-byte blocks, write-%s, %sbuffered\n",
1400 	    st->media_density, st->media_blksize,
1401 	    ISSET(link->flags, SDEV_READONLY) ? "protected" : "enabled",
1402 	    ISSET(dev_spec, SMH_DSP_BUFF_MODE) ? "" : "un"));
1403 
1404 	SET(link->flags, SDEV_MEDIA_LOADED);
1405 
1406  done:
1407 	if (data)
1408 		dma_free(data, sizeof(*data));
1409 	return error;
1410 }
1411 
1412 /*
1413  * Send a filled out parameter structure to the drive to
1414  * set it into the desire mode etc.
1415  */
1416 int
1417 st_mode_select(struct st_softc *st, int flags)
1418 {
1419 	union scsi_mode_sense_buf *inbuf = NULL, *outbuf = NULL;
1420 	struct scsi_blk_desc general;
1421 	struct scsi_link *link = st->sc_link;
1422 	u_int8_t *page0 = NULL;
1423 	int error = 0, big, page0_size;
1424 
1425 	inbuf = dma_alloc(sizeof(*inbuf), PR_NOWAIT);
1426 	if (inbuf == NULL) {
1427 		error = ENOMEM;
1428 		goto done;
1429 	}
1430 	outbuf = dma_alloc(sizeof(*outbuf), PR_NOWAIT | PR_ZERO);
1431 	if (outbuf == NULL) {
1432 		error = ENOMEM;
1433 		goto done;
1434 	}
1435 
1436 	/*
1437 	 * This quirk deals with drives that have only one valid mode and think
1438 	 * this gives them license to reject all mode selects, even if the
1439 	 * selected mode is the one that is supported.
1440 	 */
1441 	if (ISSET(st->quirks, ST_Q_UNIMODAL)) {
1442 		SC_DEBUG(link, SDEV_DB3,
1443 		    ("not setting density 0x%x blksize 0x%x\n",
1444 		    st->density, st->blksize));
1445 		error = 0;
1446 		goto done;
1447 	}
1448 
1449 	if (ISSET(link->flags, SDEV_ATAPI)) {
1450 		error = 0;
1451 		goto done;
1452 	}
1453 
1454 	bzero(&general, sizeof(general));
1455 
1456 	general.density = st->density;
1457 	if (ISSET(st->flags, ST_FIXEDBLOCKS))
1458 		_lto3b(st->blksize, general.blklen);
1459 
1460 	/*
1461 	 * Ask for page 0 (vendor specific) mode sense data.
1462 	 *
1463 	 * page0 == NULL is a valid situation.
1464 	 */
1465 	error = scsi_do_mode_sense(link, 0, inbuf, (void **)&page0, 1,
1466 	    flags | SCSI_SILENT, &big);
1467 	if (error != 0)
1468 		goto done;
1469 
1470 	if (page0 == NULL) {
1471 		page0_size = 0;
1472 	} else if (big == 0) {
1473 		page0_size = inbuf->hdr.data_length +
1474 		    sizeof(inbuf->hdr.data_length) - sizeof(inbuf->hdr) -
1475 		    inbuf->hdr.blk_desc_len;
1476 		memcpy(&outbuf->buf[sizeof(outbuf->hdr)+ sizeof(general)],
1477 		    page0, page0_size);
1478 	} else {
1479 		page0_size = _2btol(inbuf->hdr_big.data_length) +
1480 		    sizeof(inbuf->hdr_big.data_length) -
1481 		    sizeof(inbuf->hdr_big) -
1482 		    _2btol(inbuf->hdr_big.blk_desc_len);
1483 		memcpy(&outbuf->buf[sizeof(outbuf->hdr_big) + sizeof(general)],
1484 		    page0, page0_size);
1485 	}
1486 
1487 	/*
1488 	 * Set up for a mode select.
1489 	 */
1490 	if (big == 0) {
1491 		outbuf->hdr.data_length = sizeof(outbuf->hdr) +
1492 		    sizeof(general) + page0_size -
1493 		    sizeof(outbuf->hdr.data_length);
1494 		if (!ISSET(st->flags, ST_DONTBUFFER))
1495 			outbuf->hdr.dev_spec = SMH_DSP_BUFF_MODE_ON;
1496 		outbuf->hdr.blk_desc_len = sizeof(general);
1497 		memcpy(&outbuf->buf[sizeof(outbuf->hdr)],
1498 		    &general, sizeof(general));
1499 		error = scsi_mode_select(st->sc_link, 0, &outbuf->hdr,
1500 		    flags, ST_CTL_TIME);
1501 		goto done;
1502 	}
1503 
1504 	/* MODE SENSE (10) header was returned, so use MODE SELECT (10). */
1505 	_lto2b((sizeof(outbuf->hdr_big) + sizeof(general) + page0_size -
1506 	    sizeof(outbuf->hdr_big.data_length)), outbuf->hdr_big.data_length);
1507 	if (!ISSET(st->flags, ST_DONTBUFFER))
1508 		outbuf->hdr_big.dev_spec = SMH_DSP_BUFF_MODE_ON;
1509 	_lto2b(sizeof(general), outbuf->hdr_big.blk_desc_len);
1510 	memcpy(&outbuf->buf[sizeof(outbuf->hdr_big)], &general,
1511 	    sizeof(general));
1512 
1513 	error = scsi_mode_select_big(st->sc_link, 0, &outbuf->hdr_big,
1514 	    flags, ST_CTL_TIME);
1515 done:
1516 	if (inbuf)
1517 		dma_free(inbuf, sizeof(*inbuf));
1518 	if (outbuf)
1519 		dma_free(outbuf, sizeof(*outbuf));
1520 	return error;
1521 }
1522 
1523 /*
1524  * issue an erase command
1525  */
1526 int
1527 st_erase(struct st_softc *st, int full, int flags)
1528 {
1529 	struct scsi_erase *cmd;
1530 	struct scsi_xfer *xs;
1531 	int error;
1532 
1533 	xs = scsi_xs_get(st->sc_link, flags);
1534 	if (xs == NULL)
1535 		return ENOMEM;
1536 	xs->cmdlen = sizeof(*cmd);
1537 
1538 	/*
1539 	 * Full erase means set LONG bit in erase command, which asks
1540 	 * the drive to erase the entire unit.  Without this bit, we're
1541 	 * asking the drive to write an erase gap.
1542 	 */
1543 	cmd = (struct scsi_erase *)&xs->cmd;
1544 	cmd->opcode = ERASE;
1545 	if (full) {
1546 		cmd->byte2 = SE_IMMED|SE_LONG;
1547 		xs->timeout = ST_SPC_TIME;
1548 	} else {
1549 		cmd->byte2 = SE_IMMED;
1550 		xs->timeout = ST_IO_TIME;
1551 	}
1552 
1553 	/*
1554 	 * XXX We always do this asynchronously, for now.  How long should
1555 	 * we wait if we want to (eventually) to it synchronously?
1556 	 */
1557 	error = scsi_xs_sync(xs);
1558 	scsi_xs_put(xs);
1559 
1560 	return error;
1561 }
1562 
1563 /*
1564  * skip N blocks/filemarks/seq filemarks/eom
1565  */
1566 int
1567 st_space(struct st_softc *st, int number, u_int what, int flags)
1568 {
1569 	struct scsi_space *cmd;
1570 	struct scsi_xfer *xs;
1571 	int error;
1572 
1573 	switch (what) {
1574 	case SP_BLKS:
1575 		if (ISSET(st->flags, ST_PER_ACTION)) {
1576 			if (number > 0) {
1577 				CLR(st->flags, ST_PER_ACTION);
1578 				return EIO;
1579 			} else if (number < 0) {
1580 				if (ISSET(st->flags, ST_AT_FILEMARK)) {
1581 					/*
1582 					 * Handling of ST_AT_FILEMARK
1583 					 * in st_space will fill in the
1584 					 * right file mark count.
1585 					 */
1586 					error = st_space(st, 0, SP_FILEMARKS,
1587 					    flags);
1588 					if (error != 0)
1589 						return error;
1590 				}
1591 				if (ISSET(st->flags, ST_BLANK_READ)) {
1592 					CLR(st->flags, ST_BLANK_READ);
1593 					return EIO;
1594 				}
1595 				CLR(st->flags, ST_EIO_PENDING | ST_EOM_PENDING);
1596 			}
1597 		}
1598 		break;
1599 	case SP_FILEMARKS:
1600 		if (ISSET(st->flags,  ST_EIO_PENDING)) {
1601 			if (number > 0) {
1602 				/* pretend we just discovered the error */
1603 				CLR(st->flags, ST_EIO_PENDING);
1604 				return EIO;
1605 			} else if (number < 0) {
1606 				/* back away from the error */
1607 				CLR(st->flags, ST_EIO_PENDING);
1608 			}
1609 		}
1610 		if (ISSET(st->flags, ST_AT_FILEMARK)) {
1611 			CLR(st->flags, ST_AT_FILEMARK);
1612 			number--;
1613 		}
1614 		if (ISSET(st->flags, ST_BLANK_READ) && (number < 0)) {
1615 			/* back away from unwritten tape */
1616 			CLR(st->flags, ST_BLANK_READ);
1617 			number++;	/* XXX dubious */
1618 		}
1619 		break;
1620 	case SP_EOM:
1621 		if (ISSET(st->flags, ST_EOM_PENDING)) {
1622 			/* We are already there. */
1623 			CLR(st->flags, ST_EOM_PENDING);
1624 			return 0;
1625 		}
1626 		if (ISSET(st->flags, ST_EIO_PENDING)) {
1627 			/* pretend we just discovered the error */
1628 			CLR(st->flags, ST_EIO_PENDING);
1629 			return EIO;
1630 		}
1631 		if (ISSET(st->flags, ST_AT_FILEMARK))
1632 			CLR(st->flags, ST_AT_FILEMARK);
1633 		break;
1634 	}
1635 	if (number == 0)
1636 		return 0;
1637 
1638 	xs = scsi_xs_get(st->sc_link, flags);
1639 	if (xs == NULL)
1640 		return ENOMEM;
1641 
1642 	cmd = (struct scsi_space *)&xs->cmd;
1643 	cmd->opcode = SPACE;
1644 	cmd->byte2 = what;
1645 	_lto3b(number, cmd->number);
1646 	xs->cmdlen = sizeof(*cmd);
1647 	xs->timeout = ST_SPC_TIME;
1648 
1649 	CLR(st->flags, ST_EOD_DETECTED);
1650 
1651 	error = scsi_xs_sync(xs);
1652 	scsi_xs_put(xs);
1653 
1654 	if (error != 0) {
1655 		st->media_fileno = -1;
1656 		st->media_blkno = -1;
1657 	} else {
1658 		switch (what) {
1659 		case SP_BLKS:
1660 			if (st->media_blkno != -1) {
1661 				st->media_blkno += number;
1662 				if (st->media_blkno < 0)
1663 					st->media_blkno = -1;
1664 			}
1665 			break;
1666 		case SP_FILEMARKS:
1667 			if (st->media_fileno != -1) {
1668 				if (!ISSET(st->flags, ST_EOD_DETECTED))
1669 					st->media_fileno += number;
1670 				if (st->media_fileno > st->media_eom)
1671 					st->media_eom = st->media_fileno;
1672 				st->media_blkno = 0;
1673 			}
1674 			break;
1675 		case SP_EOM:
1676 			if (st->media_eom != -1) {
1677 				st->media_fileno = st->media_eom;
1678 				st->media_blkno = 0;
1679 			} else {
1680 				st->media_fileno = -1;
1681 				st->media_blkno = -1;
1682 			}
1683 			break;
1684 		default:
1685 			st->media_fileno = -1;
1686 			st->media_blkno = -1;
1687 			break;
1688 		}
1689 	}
1690 
1691 	return error;
1692 }
1693 
1694 /*
1695  * write N filemarks
1696  */
1697 int
1698 st_write_filemarks(struct st_softc *st, int number, int flags)
1699 {
1700 	struct scsi_write_filemarks *cmd;
1701 	struct scsi_xfer *xs;
1702 	int error;
1703 
1704 	if (number < 0)
1705 		return EINVAL;
1706 
1707 	xs = scsi_xs_get(st->sc_link, flags);
1708 	if (xs == NULL)
1709 		return ENOMEM;
1710 
1711 	xs->cmdlen = sizeof(*cmd);
1712 	xs->timeout = ST_IO_TIME * 4;
1713 
1714 	switch (number) {
1715 	case 0:		/* really a command to sync the drive's buffers */
1716 		break;
1717 	case 1:
1718 		if (ISSET(st->flags, ST_FM_WRITTEN))	/* already have one down */
1719 			CLR(st->flags, ST_WRITTEN);
1720 		else
1721 			SET(st->flags, ST_FM_WRITTEN);
1722 		CLR(st->flags, ST_PER_ACTION);
1723 		break;
1724 	default:
1725 		CLR(st->flags, ST_PER_ACTION | ST_WRITTEN);
1726 		break;
1727 	}
1728 
1729 	cmd = (struct scsi_write_filemarks *)&xs->cmd;
1730 	cmd->opcode = WRITE_FILEMARKS;
1731 	_lto3b(number, cmd->number);
1732 
1733 	error = scsi_xs_sync(xs);
1734 	scsi_xs_put(xs);
1735 
1736 	if (error != 0) {
1737 		st->media_fileno = -1;
1738 		st->media_blkno = -1;
1739 		st->media_eom = -1;
1740 	} else if (st->media_fileno != -1) {
1741 		st->media_fileno += number;
1742 		st->media_eom = st->media_fileno;
1743 		st->media_blkno = 0;
1744 	}
1745 
1746 	return error;
1747 }
1748 
1749 /*
1750  * Make sure the right number of file marks is on tape if the
1751  * tape has been written.  If the position argument is true,
1752  * leave the tape positioned where it was originally.
1753  *
1754  * nmarks returns the number of marks to skip (or, if position
1755  * true, which were skipped) to get back original position.
1756  */
1757 int
1758 st_check_eod(struct st_softc *st, int position, int *nmarks, int flags)
1759 {
1760 	int error;
1761 
1762 	switch (st->flags & (ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD)) {
1763 	default:
1764 		*nmarks = 0;
1765 		return 0;
1766 	case ST_WRITTEN:
1767 	case ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD:
1768 		*nmarks = 1;
1769 		break;
1770 	case ST_WRITTEN | ST_2FM_AT_EOD:
1771 		*nmarks = 2;
1772 	}
1773 	error = st_write_filemarks(st, *nmarks, flags);
1774 	if (error == 0 && position != 0)
1775 		error = st_space(st, -*nmarks, SP_FILEMARKS, flags);
1776 	return error;
1777 }
1778 
1779 /*
1780  * load/unload/retension
1781  */
1782 int
1783 st_load(struct st_softc *st, u_int type, int flags)
1784 {
1785 	struct scsi_load *cmd;
1786 	struct scsi_xfer *xs;
1787 	int error, nmarks;
1788 
1789 	st->media_fileno = -1;
1790 	st->media_blkno = -1;
1791 	st->media_eom = -1;
1792 
1793 	if (type != LD_LOAD) {
1794 		error = st_check_eod(st, 0, &nmarks, flags);
1795 		if (error != 0)
1796 			return error;
1797 	}
1798 
1799 	if (ISSET(st->quirks, ST_Q_IGNORE_LOADS)) {
1800 		if (type == LD_LOAD) {
1801 			/*
1802 			 * If we ignore loads, at least we should try a rewind.
1803 			 */
1804 			return st_rewind(st, 0, flags);
1805 		}
1806 		return 0;
1807 	}
1808 
1809 
1810 	xs = scsi_xs_get(st->sc_link, flags);
1811 	if (xs == NULL)
1812 		return ENOMEM;
1813 	xs->cmdlen = sizeof(*cmd);
1814 	xs->timeout = ST_SPC_TIME;
1815 
1816 	cmd = (struct scsi_load *)&xs->cmd;
1817 	cmd->opcode = LOAD;
1818 	cmd->how = type;
1819 
1820 	error = scsi_xs_sync(xs);
1821 	scsi_xs_put(xs);
1822 
1823 	return error;
1824 }
1825 
1826 /*
1827  *  Rewind the device
1828  */
1829 int
1830 st_rewind(struct st_softc *st, u_int immediate, int flags)
1831 {
1832 	struct scsi_rewind *cmd;
1833 	struct scsi_xfer *xs;
1834 	int error, nmarks;
1835 
1836 	error = st_check_eod(st, 0, &nmarks, flags);
1837 	if (error != 0)
1838 		return error;
1839 	CLR(st->flags, ST_PER_ACTION);
1840 
1841 	xs = scsi_xs_get(st->sc_link, flags);
1842 	if (xs == NULL)
1843 		return ENOMEM;
1844 	xs->cmdlen = sizeof(*cmd);
1845 	xs->timeout = immediate ? ST_CTL_TIME : ST_SPC_TIME;
1846 
1847 	cmd = (struct scsi_rewind *)&xs->cmd;
1848 	cmd->opcode = REWIND;
1849 	cmd->byte2 = immediate;
1850 
1851 	error = scsi_xs_sync(xs);
1852 	scsi_xs_put(xs);
1853 
1854 	if (error == 0) {
1855 		st->media_fileno = 0;
1856 		st->media_blkno = 0;
1857 	}
1858 
1859 	return error;
1860 }
1861 
1862 /*
1863  * Look at the returned sense and act on the error to determine
1864  * the unix error number to pass back... (0 = report no error)
1865  *                            (-1 = continue processing)
1866  */
1867 int
1868 st_interpret_sense(struct scsi_xfer *xs)
1869 {
1870 	struct scsi_sense_data *sense = &xs->sense;
1871 	struct scsi_link *link = xs->sc_link;
1872 	struct scsi_space *space;
1873 	struct st_softc *st = link->device_softc;
1874 	u_int8_t serr = sense->error_code & SSD_ERRCODE;
1875 	u_int8_t skey = sense->flags & SSD_KEY;
1876 	int32_t resid, info, number;
1877 	int datalen;
1878 
1879 	if (!ISSET(link->flags, SDEV_OPEN) ||
1880 	    (serr != SSD_ERRCODE_CURRENT && serr != SSD_ERRCODE_DEFERRED))
1881 		return scsi_interpret_sense(xs);
1882 
1883 	info = (int32_t)_4btol(sense->info);
1884 
1885 	switch (skey) {
1886 
1887 	/*
1888 	 * We do custom processing in st for the unit becoming ready case.
1889 	 * in this case we do not allow xs->retries to be decremented
1890 	 * only on the "Unit Becoming Ready" case. This is because tape
1891 	 * drives report "Unit Becoming Ready" when loading media, etc.
1892 	 * and can take a long time.  Rather than having a massive timeout
1893 	 * for all operations (which would cause other problems) we allow
1894 	 * operations to wait (but be interruptible with Ctrl-C) forever
1895 	 * as long as the drive is reporting that it is becoming ready.
1896 	 * all other cases are handled as per the default.
1897 	 */
1898 
1899 	case SKEY_NOT_READY:
1900 		if (ISSET(xs->flags, SCSI_IGNORE_NOT_READY))
1901 			return 0;
1902 		switch (ASC_ASCQ(sense)) {
1903 		case SENSE_NOT_READY_BECOMING_READY:
1904 			SC_DEBUG(link, SDEV_DB1, ("not ready: busy (%#x)\n",
1905 			    sense->add_sense_code_qual));
1906 			/* don't count this as a retry */
1907 			xs->retries++;
1908 			return scsi_delay(xs, 1);
1909 		default:
1910 			return scsi_interpret_sense(xs);
1911 		}
1912 		break;
1913 	case SKEY_BLANK_CHECK:
1914 		if (sense->error_code & SSD_ERRCODE_VALID &&
1915 		    xs->cmd.opcode == SPACE) {
1916 			switch (ASC_ASCQ(sense)) {
1917 			case SENSE_END_OF_DATA_DETECTED:
1918 				SET(st->flags, ST_EOD_DETECTED);
1919 				space = (struct scsi_space *)&xs->cmd;
1920 				number = _3btol(space->number);
1921 				st->media_fileno = number - info;
1922 				st->media_eom = st->media_fileno;
1923 				return 0;
1924 			case SENSE_BEGINNING_OF_MEDIUM_DETECTED:
1925 				/* Standard says: Position is undefined! */
1926 				SET(st->flags, ST_BOD_DETECTED);
1927 				st->media_fileno = -1;
1928 				st->media_blkno = -1;
1929 				return 0;
1930 			}
1931 		}
1932 		break;
1933 	case SKEY_NO_SENSE:
1934 	case SKEY_RECOVERED_ERROR:
1935 	case SKEY_MEDIUM_ERROR:
1936 	case SKEY_VOLUME_OVERFLOW:
1937 		break;
1938 	default:
1939 		return scsi_interpret_sense(xs);
1940 	}
1941 
1942 	/*
1943 	 * 'resid' can be in units of st->blksize or bytes. xs->resid and
1944 	 * xs->datalen are always in units of bytes. So we need a variable
1945 	 * to store datalen in the same units as resid and to adjust
1946 	 * xs->resid to be in bytes.
1947 	 */
1948 	if (ISSET(sense->error_code, SSD_ERRCODE_VALID)) {
1949 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
1950 			resid = info * st->blksize; /* XXXX overflow? */
1951 		else
1952 			resid = info;
1953 	} else {
1954 		resid = xs->datalen;
1955 	}
1956 
1957 	if (resid < 0 || resid > xs->datalen)
1958 		xs->resid = xs->datalen;
1959 	else
1960 		xs->resid = resid;
1961 
1962 	datalen = xs->datalen;
1963 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
1964 		resid /= st->blksize;
1965 		datalen /= st->blksize;
1966 	}
1967 
1968 	if (ISSET(sense->flags, SSD_FILEMARK)) {
1969 		if (st->media_fileno != -1) {
1970 			st->media_fileno++;
1971 			if (st->media_fileno > st->media_eom)
1972 				st->media_eom = st->media_fileno;
1973 			st->media_blkno = 0;
1974 		}
1975 		if (!ISSET(st->flags, ST_FIXEDBLOCKS))
1976 			return 0;
1977 		SET(st->flags, ST_AT_FILEMARK);
1978 	}
1979 
1980 	if (ISSET(sense->flags, SSD_EOM)) {
1981 		SET(st->flags, ST_EOM_PENDING);
1982 		xs->resid = 0;
1983 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
1984 			return 0;
1985 	}
1986 
1987 	if (ISSET(sense->flags, SSD_ILI)) {
1988 		if (!ISSET(st->flags, ST_FIXEDBLOCKS)) {
1989 			if (resid >= 0 && resid <= datalen)
1990 				return 0;
1991 			if (!ISSET(xs->flags, SCSI_SILENT))
1992 				printf( "%s: bad residual %d out of "
1993 				    "%d\n", st->sc_dev.dv_xname, resid,
1994 				    datalen);
1995 			return EIO;
1996 		}
1997 
1998 		/* Fixed size blocks. */
1999 		if (ISSET(sense->error_code, SSD_ERRCODE_VALID))
2000 			if (!ISSET(xs->flags, SCSI_SILENT))
2001 				printf("%s: block wrong size, %d blocks "
2002 				    "residual\n", st->sc_dev.dv_xname, resid);
2003 		SET(st->flags, ST_EIO_PENDING);
2004 		/*
2005 		 * This quirk code helps the drive read the first tape block,
2006 		 * regardless of format.  That is required for these drives to
2007 		 * return proper MODE SENSE information.
2008 		 */
2009 		if (ISSET(st->quirks, ST_Q_SENSE_HELP) &&
2010 		    !ISSET(link->flags, SDEV_MEDIA_LOADED))
2011 			st->blksize -= 512;
2012 	}
2013 
2014 	if (ISSET(st->flags, ST_FIXEDBLOCKS) && xs->resid == xs->datalen) {
2015 		if (ISSET(st->flags, ST_EIO_PENDING))
2016 			return EIO;
2017 		if (ISSET(st->flags, ST_AT_FILEMARK))
2018 			return 0;
2019 	}
2020 
2021 	if (skey == SKEY_BLANK_CHECK) {
2022 		/*
2023 		 * This quirk code helps the drive read the first tape block,
2024 		 * regardless of format.  That is required for these drives to
2025 		 * return proper MODE SENSE information.
2026 		 */
2027 		if (ISSET(st->quirks, ST_Q_SENSE_HELP) &&
2028 		    !ISSET(link->flags, SDEV_MEDIA_LOADED)) {
2029 			/* still starting */
2030 			st->blksize -= 512;
2031 		} else if (!ISSET(st->flags, ST_2FM_AT_EOD | ST_BLANK_READ)) {
2032 			SET(st->flags, ST_BLANK_READ);
2033 			SET(st->flags, ST_EOM_PENDING);
2034 			xs->resid = xs->datalen;
2035 			return 0;
2036 		}
2037 	}
2038 
2039 	return scsi_interpret_sense(xs);
2040 }
2041 
2042 /*
2043  * The quirk here is that the drive returns some value to st_mode_sense
2044  * incorrectly until the tape has actually passed by the head.
2045  *
2046  * The method is to set the drive to large fixed-block state (user-specified
2047  * density and 1024-byte blocks), then read and rewind to get it to sense the
2048  * tape.  If that doesn't work, try 512-byte fixed blocks.  If that doesn't
2049  * work, as a last resort, try variable- length blocks.  The result will be
2050  * the ability to do an accurate st_mode_sense.
2051  *
2052  * We know we can do a rewind because we just did a load, which implies rewind.
2053  * Rewind seems preferable to space backward if we have a virgin tape.
2054  *
2055  * The rest of the code for this quirk is in ILI processing and BLANK CHECK
2056  * error processing, both part of st_interpret_sense.
2057  */
2058 int
2059 st_touch_tape(struct st_softc *st)
2060 {
2061 	char *buf = NULL;
2062 	int readsize, maxblksize = 1024;
2063 	int error = 0;
2064 
2065 	if ((error = st_mode_sense(st, 0)) != 0)
2066 		goto done;
2067 	buf = dma_alloc(maxblksize, PR_NOWAIT);
2068 	if (buf == NULL) {
2069 		error = ENOMEM;
2070 		goto done;
2071 	}
2072 
2073 	st->blksize = 1024;
2074 	do {
2075 		switch (st->blksize) {
2076 		case 512:
2077 		case 1024:
2078 			readsize = st->blksize;
2079 			SET(st->flags, ST_FIXEDBLOCKS);
2080 			break;
2081 		default:
2082 			readsize = 1;
2083 			CLR(st->flags, ST_FIXEDBLOCKS);
2084 		}
2085 		if ((error = st_mode_select(st, 0)) != 0)
2086 			goto done;
2087 		st_read(st, buf, readsize, SCSI_SILENT);	/* XXX */
2088 		if ((error = st_rewind(st, 0, 0)) != 0)
2089 			goto done;
2090 	} while (readsize != 1 && readsize > st->blksize);
2091 done:
2092 	dma_free(buf, maxblksize);
2093 	return error;
2094 }
2095