xref: /openbsd-src/sys/scsi/st.c (revision 99fd087599a8791921855f21bd7e36130f39aadc)
1 /*	$OpenBSD: st.c,v 1.177 2020/02/20 16:26:02 krw 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/conf.h>
69 #include <sys/vnode.h>
70 
71 #include <scsi/scsi_all.h>
72 #include <scsi/scsi_tape.h>
73 #include <scsi/scsiconf.h>
74 
75 /* Defines for device specific stuff */
76 #define DEF_FIXED_BSIZE  512
77 
78 #define STMODE(z)	( minor(z)	 & 0x03)
79 #define STUNIT(z)	((minor(z) >> 4)       )
80 
81 #define STMINOR(unit, mode)	(((unit) << 4) + (mode))
82 #define MAXSTMODES	16	/* Old max retained so minor's don't change. */
83 
84 #define	ST_IO_TIME	(3 * 60 * 1000)		/* 3 minutes */
85 #define	ST_CTL_TIME	(30 * 1000)		/* 30 seconds */
86 #define	ST_SPC_TIME	(4 * 60 * 60 * 1000)	/* 4 hours */
87 
88 /*
89  * Maximum density code allowed in SCSI spec (SSC2R08f, Section 8.3).
90  */
91 #define SCSI_MAX_DENSITY_CODE		0xff
92 
93 /*
94  * Define various devices that we know mis-behave in some way,
95  * and note how they are bad, so we can correct for them
96  */
97 struct mode {
98 	int blksize;
99 	u_int8_t density;
100 };
101 
102 struct quirkdata {
103 	u_int quirks;
104 #define	ST_Q_SENSE_HELP		0x0001	/* must do READ for good MODE SENSE */
105 #define	ST_Q_IGNORE_LOADS	0x0002
106 #define	ST_Q_UNIMODAL		0x0004	/* unimode drive rejects mode select */
107 	struct mode mode;
108 };
109 
110 struct st_quirk_inquiry_pattern {
111 	struct scsi_inquiry_pattern pattern;
112 	struct quirkdata quirkdata;
113 };
114 
115 const struct st_quirk_inquiry_pattern st_quirk_patterns[] = {
116 	{{T_SEQUENTIAL, T_REMOV,
117 		 "        ", "                ", "    "}, {0,
118 							   {512, 0}}},
119  	{{T_SEQUENTIAL, T_REMOV,
120 		 "TANDBERG", " TDC 3800       ", ""},     {0,
121 							   {512, 0}}},
122 	{{T_SEQUENTIAL, T_REMOV,
123 		 "ARCHIVE ", "VIPER 2525 25462", ""},     {ST_Q_SENSE_HELP,
124 							   {0, 0}}},
125 	{{T_SEQUENTIAL, T_REMOV,
126 		 "SANKYO  ", "CP525           ", ""},     {0,
127 							   {512, 0}}},
128 	{{T_SEQUENTIAL, T_REMOV,
129 		 "ANRITSU ", "DMT780          ", ""},     {0,
130 							   {512, 0}}},
131 	{{T_SEQUENTIAL, T_REMOV,
132 		 "ARCHIVE ", "VIPER 150  21531", ""},     {ST_Q_SENSE_HELP,
133 							   {0, 0}}},
134 	{{T_SEQUENTIAL, T_REMOV,
135 		 "WANGTEK ", "5099ES SCSI",	 ""},     {0,
136 							   {512, 0}}},
137 	{{T_SEQUENTIAL, T_REMOV,
138 		 "WANGTEK ", "5150ES SCSI",	 ""},     {0,
139 							   {512, 0}}},
140 	{{T_SEQUENTIAL, T_REMOV,
141 		 "HP      ", "T4000s          ", ""},     {ST_Q_UNIMODAL,
142 							   {0, QIC_3095}}},
143 	{{T_SEQUENTIAL, T_REMOV,
144 		 "WANGTEK ", "5150ES SCSI FA15", "01 A"}, {ST_Q_IGNORE_LOADS,
145 							   {0, 0}}},
146 	{{T_SEQUENTIAL, T_REMOV,
147 		 "TEAC    ", "MT-2ST/N50      ", ""},     {ST_Q_IGNORE_LOADS,
148 							   {0, 0}}},
149 };
150 
151 #define NOEJECT 0
152 #define EJECT 1
153 
154 #define NOREWIND 0
155 #define DOREWIND 1
156 
157 struct st_softc {
158 	struct device sc_dev;
159 
160 	int flags;
161 #define	ST_INFO_VALID		0x00000001
162 #define	ST_WRITTEN		0x00000004
163 #define	ST_FIXEDBLOCKS		0x00000008
164 #define	ST_AT_FILEMARK		0x00000010
165 #define	ST_EIO_PENDING		0x00000020
166 #define	ST_EOM_PENDING  	0x00000040
167 #define	ST_EOD_DETECTED		0x00000080
168 #define	ST_FM_WRITTEN		0x00000100
169 #define	ST_BLANK_READ		0x00000200
170 #define	ST_2FM_AT_EOD		0x00000400
171 #define	ST_MOUNTED		0x00000800
172 #define	ST_DONTBUFFER		0x00001000
173 #define	ST_WAITING		0x00002000
174 #define	ST_DYING		0x00004000
175 #define	ST_BOD_DETECTED		0x00008000
176 #define	ST_MODE_DENSITY		0x00010000
177 #define	ST_MODE_BLKSIZE		0x00040000
178 
179 	u_int quirks;		/* quirks for the open mode           */
180 	int blksize;		/* blksize we are using               */
181 	u_int8_t density;	/* present density                    */
182 	short mt_resid;		/* last (short) resid                 */
183 	short mt_erreg;		/* last error (sense key) seen        */
184 
185 	struct scsi_link *sc_link;	/* our link to the adpter etc.        */
186 
187 	int blkmin;		/* min blk size                       */
188 	int blkmax;		/* max blk size                       */
189 
190 	u_int32_t media_blksize;	/* 0 if not ST_FIXEDBLOCKS            */
191 	u_int32_t media_density;	/* this is what it said when asked    */
192 	int media_fileno;		/* relative to BOT. -1 means unknown. */
193 	int media_blkno;		/* relative to BOF. -1 means unknown. */
194 	int media_eom;			/* relative to BOT. -1 means unknown. */
195 
196 	struct mode mode;
197 	struct bufq sc_bufq;
198 	struct timeout sc_timeout;
199 	struct scsi_xshandler sc_xsh;
200 };
201 
202 
203 int	stmatch(struct device *, void *, void *);
204 void	stattach(struct device *, struct device *, void *);
205 int	stactivate(struct device *, int);
206 int	stdetach(struct device *, int);
207 void	stminphys(struct buf *);
208 void	ststart(struct scsi_xfer *);
209 
210 int	st_mount_tape(struct st_softc *, int);
211 void	st_unmount(struct st_softc *, int, int);
212 int	st_decide_mode(struct st_softc *, int);
213 void	st_buf_done(struct scsi_xfer *);
214 int	st_read(struct st_softc *, char *, int, int);
215 int	st_read_block_limits(struct st_softc *, int);
216 int	st_mode_sense(struct st_softc *, int);
217 int	st_mode_select(struct st_softc *, int);
218 int	st_space(struct st_softc *, int, u_int, int);
219 int	st_write_filemarks(struct st_softc *, int, int);
220 int	st_check_eod(struct st_softc *, int, int *, int);
221 int	st_load(struct st_softc *, u_int, int);
222 int	st_rewind(struct st_softc *, u_int, int);
223 int	st_interpret_sense(struct scsi_xfer *);
224 int	st_touch_tape(struct st_softc *);
225 int	st_erase(struct st_softc *, int, int);
226 
227 struct cfattach st_ca = {
228 	sizeof(struct st_softc), stmatch, stattach,
229 	stdetach, stactivate
230 };
231 
232 struct cfdriver st_cd = {
233 	NULL, "st", DV_TAPE
234 };
235 
236 #define	ST_PER_ACTION	(ST_AT_FILEMARK | ST_EIO_PENDING | ST_EOM_PENDING | \
237 			 ST_BLANK_READ)
238 
239 #define stlookup(unit) (struct st_softc *)device_lookup(&st_cd, (unit))
240 
241 const struct scsi_inquiry_pattern st_patterns[] = {
242 	{T_SEQUENTIAL, T_REMOV,
243 	 "",         "",                 ""},
244 };
245 
246 int
247 stmatch(struct device *parent, void *match, void *aux)
248 {
249 	struct scsi_attach_args *sa = aux;
250 	int priority;
251 
252 	(void)scsi_inqmatch(sa->sa_inqbuf,
253 	    st_patterns, nitems(st_patterns),
254 	    sizeof(st_patterns[0]), &priority);
255 	return priority;
256 }
257 
258 /*
259  * The routine called by the low level scsi routine when it discovers
260  * a device suitable for this driver.
261  */
262 void
263 stattach(struct device *parent, struct device *self, void *aux)
264 {
265 	const struct st_quirk_inquiry_pattern *finger;
266 	struct st_softc *st = (void *)self;
267 	struct scsi_attach_args *sa = aux;
268 	struct scsi_link *link = sa->sa_sc_link;
269 	int priority;
270 
271 	SC_DEBUG(link, SDEV_DB2, ("stattach:\n"));
272 
273 	/*
274 	 * Store information needed to contact our base driver
275 	 */
276 	st->sc_link = link;
277 	link->interpret_sense = st_interpret_sense;
278 	link->device_softc = st;
279 
280 	/* Get any quirks and mode information. */
281 	finger = (const struct st_quirk_inquiry_pattern *)scsi_inqmatch(
282 	    &link->inqdata,
283 	    st_quirk_patterns,
284 	    nitems(st_quirk_patterns),
285 	    sizeof(st_quirk_patterns[0]), &priority);
286 	if (finger != NULL) {
287 		st->quirks = finger->quirkdata.quirks;
288 		st->mode = finger->quirkdata.mode;
289 		CLR(st->flags, ST_MODE_BLKSIZE | ST_MODE_DENSITY);
290 		if (st->mode.blksize != 0)
291 			SET(st->flags, ST_MODE_BLKSIZE);
292 		if (st->mode.density != 0)
293 			SET(st->flags, ST_MODE_DENSITY);
294 	}
295 	printf("\n");
296 
297 	scsi_xsh_set(&st->sc_xsh, link, ststart);
298 	timeout_set(&st->sc_timeout, (void (*)(void *))scsi_xsh_set,
299 	    &st->sc_xsh);
300 
301 	/* Set up the buf queue for this device. */
302 	bufq_init(&st->sc_bufq, BUFQ_FIFO);
303 
304 	/* Start up with media position unknown. */
305 	st->media_fileno = -1;
306 	st->media_blkno = -1;
307 	st->media_eom = -1;
308 
309 	/*
310 	 * Reset the media loaded flag, sometimes the data
311 	 * acquired at boot time is not quite accurate.  This
312 	 * will be checked again at the first open.
313 	 */
314 	CLR(link->flags, SDEV_MEDIA_LOADED);
315 }
316 
317 int
318 stactivate(struct device *self, int act)
319 {
320 	struct st_softc *st = (struct st_softc *)self;
321 
322 	switch (act) {
323 	case DVACT_DEACTIVATE:
324 		SET(st->flags, ST_DYING);
325 		scsi_xsh_del(&st->sc_xsh);
326 		break;
327 	}
328 
329 	return 0;
330 }
331 
332 int
333 stdetach(struct device *self, int flags)
334 {
335 	struct st_softc *st = (struct st_softc *)self;
336 	int cmaj, mn;
337 
338 	bufq_drain(&st->sc_bufq);
339 
340 	/* Locate the lowest minor number to be detached. */
341 	mn = STMINOR(self->dv_unit, 0);
342 
343 	for (cmaj = 0; cmaj < nchrdev; cmaj++)
344 		if (cdevsw[cmaj].d_open == stopen)
345 			vdevgone(cmaj, mn, mn + MAXSTMODES - 1, VCHR);
346 
347 	bufq_destroy(&st->sc_bufq);
348 
349 	return 0;
350 }
351 
352 /*
353  * open the device.
354  */
355 int
356 stopen(dev_t dev, int flags, int fmt, struct proc *p)
357 {
358 	struct scsi_link *link;
359 	struct st_softc *st;
360 	int error = 0;
361 
362 	st = stlookup(STUNIT(dev));
363 	if (st == NULL)
364 		return ENXIO;
365 	if (ISSET(st->flags, ST_DYING)) {
366 		error = ENXIO;
367 		goto done;
368 	}
369 	link = st->sc_link;
370 
371 	if (ISSET(flags, FWRITE) && ISSET(link->flags, SDEV_READONLY)) {
372 		error = EACCES;
373 		goto done;
374 	}
375 
376 	SC_DEBUG(link, SDEV_DB1, ("open: dev=0x%x (unit %d (of %d))\n", dev,
377 	    STUNIT(dev), st_cd.cd_ndevs));
378 
379 	/*
380 	 * Tape is an exclusive media. Only one open at a time.
381 	 */
382 	if (ISSET(link->flags, SDEV_OPEN)) {
383 		SC_DEBUG(link, SDEV_DB4, ("already open\n"));
384 		error = EBUSY;
385 		goto done;
386 	}
387 
388 	/* Use st_interpret_sense() now. */
389 	SET(link->flags, SDEV_OPEN);
390 
391 	/*
392 	 * Check the unit status. This clears any outstanding errors and
393 	 * will ensure that media is present.
394 	 */
395 	error = scsi_test_unit_ready(link, TEST_READY_RETRIES,
396 	    SCSI_SILENT | SCSI_IGNORE_MEDIA_CHANGE |
397 	    SCSI_IGNORE_ILLEGAL_REQUEST);
398 
399 	/*
400 	 * Terminate any exising mount session if there is no media.
401 	 */
402 	if (!ISSET(link->flags, SDEV_MEDIA_LOADED))
403 		st_unmount(st, NOEJECT, DOREWIND);
404 
405 	if (error != 0) {
406 		CLR(link->flags, SDEV_OPEN);
407 		goto done;
408 	}
409 
410 	error = st_mount_tape(st, flags);
411 	if (error != 0) {
412 		CLR(link->flags, SDEV_OPEN);
413 		goto done;
414 	}
415 
416 	/*
417 	 * Make sure that a tape opened in write-only mode will have
418 	 * file marks written on it when closed, even if not written to.
419 	 * This is for SUN compatibility
420 	 */
421 	if ((flags & O_ACCMODE) == FWRITE)
422 		SET(st->flags, ST_WRITTEN);
423 
424 done:
425 	SC_DEBUG(link, SDEV_DB2, ("open complete\n"));
426 	device_unref(&st->sc_dev);
427 	return error;
428 }
429 
430 /*
431  * close the device.. only called if we are the LAST
432  * occurrence of an open device
433  */
434 int
435 stclose(dev_t dev, int flags, int mode, struct proc *p)
436 {
437 	struct scsi_link *link;
438 	struct st_softc *st;
439 	int error = 0;
440 
441 	st = stlookup(STUNIT(dev));
442 	if (st == NULL)
443 		return ENXIO;
444 	if (ISSET(st->flags, ST_DYING)) {
445 		error = ENXIO;
446 		goto done;
447 	}
448 	link = st->sc_link;
449 
450 	SC_DEBUG(link, SDEV_DB1, ("closing\n"));
451 
452 	if (ISSET(st->flags, ST_WRITTEN) && !ISSET(st->flags, ST_FM_WRITTEN))
453 		st_write_filemarks(st, 1, 0);
454 
455 	switch (STMODE(dev)) {
456 	case 0:		/* /dev/rstN */
457 		st_unmount(st, NOEJECT, DOREWIND);
458 		break;
459 	case 1:		/* /dev/nrstN */
460 		st_unmount(st, NOEJECT, NOREWIND);
461 		break;
462 	case 2:		/* /dev/erstN */
463 		st_unmount(st, EJECT, DOREWIND);
464 		break;
465 	case 3:		/* /dev/enrstN */
466 		st_unmount(st, EJECT, NOREWIND);
467 		break;
468 	}
469 	CLR(link->flags, SDEV_OPEN);
470 	timeout_del(&st->sc_timeout);
471 	scsi_xsh_del(&st->sc_xsh);
472 
473 done:
474 	device_unref(&st->sc_dev);
475 	return error;
476 }
477 
478 /*
479  * Start a new mount session if needed.
480  */
481 int
482 st_mount_tape(struct st_softc *st, int flags)
483 {
484 	struct scsi_link *link = st->sc_link;
485 	int error = 0;
486 
487 	if (ISSET(st->flags, ST_MOUNTED))
488 		return 0;
489 
490 	SC_DEBUG(link, SDEV_DB1, ("mounting\n"));
491 
492 	/*
493 	 * Assume the media is new and give it a chance to
494 	 * to do a 'load' instruction.
495 	 */
496 	if ((error = st_load(st, LD_LOAD, 0)) != 0)
497 		goto done;
498 
499 	/*
500 	 * Throw another dummy instruction to catch
501 	 * 'Unit attention' errors. Some drives appear to give
502 	 * these after doing a Load instruction.
503 	 * (noteably some DAT drives)
504 	 */
505 	/* XXX */
506 	scsi_test_unit_ready(link, TEST_READY_RETRIES, SCSI_SILENT);
507 
508 	/*
509 	 * Some devices can't tell you much until they have been
510 	 * asked to look at the media. This quirk does this.
511 	 */
512 	if (ISSET(st->quirks, ST_Q_SENSE_HELP))
513 		if ((error = st_touch_tape(st)) != 0)
514 			return error;
515 	/*
516 	 * Load the physical device parameters
517 	 * loads: blkmin, blkmax
518 	 */
519 	if (!ISSET(link->flags, SDEV_ATAPI) &&
520 	    (error = st_read_block_limits(st, 0)) != 0)
521 		goto done;
522 
523 	/*
524 	 * Load the media dependent parameters
525 	 * includes: media_blksize,media_density
526 	 * As we have a tape in, it should be reflected here.
527 	 * If not you may need the "quirk" above.
528 	 */
529 	if ((error = st_mode_sense(st, 0)) != 0)
530 		goto done;
531 
532 	/*
533 	 * If we have gained a permanent density from somewhere,
534 	 * then use it in preference to the one supplied by
535 	 * default by the driver.
536 	 */
537 	if (ISSET(st->flags, ST_MODE_DENSITY))
538 		st->density = st->mode.density;
539 	else
540 		st->density = st->media_density;
541 	/*
542 	 * If we have gained a permanent blocksize
543 	 * then use it in preference to the one supplied by
544 	 * default by the driver.
545 	 */
546 	CLR(st->flags, ST_FIXEDBLOCKS);
547 	if (ISSET(st->flags, ST_MODE_BLKSIZE)) {
548 		st->blksize = st->mode.blksize;
549 		if (st->blksize)
550 			SET(st->flags, ST_FIXEDBLOCKS);
551 	} else {
552 		if ((error = st_decide_mode(st, 0)) != 0)
553 			goto done;
554 	}
555 	if ((error = st_mode_select(st, 0)) != 0) {
556 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
557 		goto done;
558 	}
559 	scsi_prevent(link, PR_PREVENT,
560 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
561 	SET(st->flags, ST_MOUNTED);
562 	SET(link->flags, SDEV_MEDIA_LOADED);	/* move earlier? */
563 	st->media_fileno = 0;
564 	st->media_blkno = 0;
565 	st->media_eom = -1;
566 
567 done:
568 	return error;
569 }
570 
571 /*
572  * End the present mount session.
573  * Rewind, and optionally eject the tape.
574  * Reset various flags to indicate that all new
575  * operations require another mount operation
576  */
577 void
578 st_unmount(struct st_softc *st, int eject, int rewind)
579 {
580 	struct scsi_link *link = st->sc_link;
581 	int nmarks;
582 
583 	if (eject == NOEJECT && rewind == NOREWIND) {
584 		if (ISSET(link->flags, SDEV_MEDIA_LOADED))
585 			return;
586 	}
587 
588 	st->media_fileno = -1;
589 	st->media_blkno = -1;
590 
591 	if (!ISSET(st->flags, ST_MOUNTED))
592 		return;
593 	SC_DEBUG(link, SDEV_DB1, ("unmounting\n"));
594 	st_check_eod(st, 0, &nmarks, SCSI_IGNORE_NOT_READY);
595 	if (rewind == DOREWIND)
596 		st_rewind(st, 0, SCSI_IGNORE_NOT_READY);
597 	scsi_prevent(link, PR_ALLOW,
598 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
599 	if (eject == EJECT)
600 		st_load(st, LD_UNLOAD, SCSI_IGNORE_NOT_READY);
601 	CLR(st->flags, ST_MOUNTED);
602 	CLR(link->flags, SDEV_MEDIA_LOADED);
603 }
604 
605 /*
606  * Given all we know about the device, media, mode, 'quirks' and
607  * initial operation, make a decision as to how we should be set
608  * to run (regarding blocking and EOD marks)
609  */
610 int
611 st_decide_mode(struct st_softc *st, int first_read)
612 {
613 	struct scsi_link *link = st->sc_link;
614 
615 	SC_DEBUG(link, SDEV_DB2, ("starting block mode decision\n"));
616 
617 	/* ATAPI tapes are always fixed blocksize. */
618 	if (ISSET(link->flags, SDEV_ATAPI)) {
619 		SET(st->flags, ST_FIXEDBLOCKS);
620 		if (st->media_blksize > 0)
621 			st->blksize = st->media_blksize;
622 		else
623 			st->blksize = DEF_FIXED_BSIZE;
624 		goto done;
625 	}
626 
627 	/*
628 	 * If the drive can only handle fixed-length blocks and only at
629 	 * one size, perhaps we should just do that.
630 	 */
631 	if (st->blkmin && (st->blkmin == st->blkmax)) {
632 		SET(st->flags, ST_FIXEDBLOCKS);
633 		st->blksize = st->blkmin;
634 		SC_DEBUG(link, SDEV_DB3,
635 		    ("blkmin == blkmax of %d\n", st->blkmin));
636 		goto done;
637 	}
638 	/*
639 	 * If the tape density mandates (or even suggests) use of fixed
640 	 * or variable-length blocks, comply.
641 	 */
642 	switch (st->density) {
643 	case HALFINCH_800:
644 	case HALFINCH_1600:
645 	case HALFINCH_6250:
646 	case DDS:
647 		CLR(st->flags, ST_FIXEDBLOCKS);
648 		st->blksize = 0;
649 		SC_DEBUG(link, SDEV_DB3, ("density specified variable\n"));
650 		goto done;
651 	case QIC_11:
652 	case QIC_24:
653 	case QIC_120:
654 	case QIC_150:
655 	case QIC_525:
656 	case QIC_1320:
657 		SET(st->flags, ST_FIXEDBLOCKS);
658 		if (st->media_blksize > 0)
659 			st->blksize = st->media_blksize;
660 		else
661 			st->blksize = DEF_FIXED_BSIZE;
662 		SC_DEBUG(link, SDEV_DB3, ("density specified fixed\n"));
663 		goto done;
664 	}
665 	/*
666 	 * If we're about to read the tape, perhaps we should choose
667 	 * fixed or variable-length blocks and block size according to
668 	 * what the drive found on the tape.
669 	 */
670 	if (first_read) {
671 		if (st->media_blksize > 0)
672 			SET(st->flags, ST_FIXEDBLOCKS);
673 		else
674 			CLR(st->flags, ST_FIXEDBLOCKS);
675 		st->blksize = st->media_blksize;
676 		SC_DEBUG(link, SDEV_DB3,
677 		    ("Used media_blksize of %d\n", st->media_blksize));
678 		goto done;
679 	}
680 	/*
681 	 * We're getting no hints from any direction.  Choose variable-
682 	 * length blocks arbitrarily.
683 	 */
684 	CLR(st->flags, ST_FIXEDBLOCKS);
685 	st->blksize = 0;
686 	SC_DEBUG(link, SDEV_DB3,
687 	    ("Give up and default to variable mode\n"));
688 
689 done:
690 	/*
691 	 * Decide whether or not to write two file marks to signify end-
692 	 * of-data.  Make the decision as a function of density.  If
693 	 * the decision is not to use a second file mark, the SCSI BLANK
694 	 * CHECK condition code will be recognized as end-of-data when
695 	 * first read.
696 	 * (I think this should be a by-product of fixed/variable..julian)
697 	 */
698 	switch (st->density) {
699 /*      case 8 mm:   What is the SCSI density code for 8 mm, anyway? */
700 	case QIC_11:
701 	case QIC_24:
702 	case QIC_120:
703 	case QIC_150:
704 	case QIC_525:
705 	case QIC_1320:
706 		CLR(st->flags, ST_2FM_AT_EOD);
707 		break;
708 	default:
709 		SET(st->flags, ST_2FM_AT_EOD);
710 	}
711 	return 0;
712 }
713 
714 /*
715  * Actually translate the requested transfer into
716  * one the physical driver can understand
717  * The transfer is described by a buf and will include
718  * only one physical transfer.
719  */
720 void
721 ststrategy(struct buf *bp)
722 {
723 	struct scsi_link *link;
724 	struct st_softc *st;
725 	int s;
726 
727 	st = stlookup(STUNIT(bp->b_dev));
728 	if (st == NULL) {
729 		bp->b_error = ENXIO;
730 		goto bad;
731 	}
732 	if (ISSET(st->flags, ST_DYING)) {
733 		bp->b_error = ENXIO;
734 		goto bad;
735 	}
736 	link = st->sc_link;
737 
738 	SC_DEBUG(link, SDEV_DB2, ("ststrategy: %ld bytes @ blk %lld\n",
739 	    bp->b_bcount, (long long)bp->b_blkno));
740 
741 	/*
742 	 * If it's a null transfer, return immediately.
743 	 */
744 	if (bp->b_bcount == 0)
745 		goto done;
746 	/*
747 	 * Odd sized request on fixed drives are verboten
748 	 */
749 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
750 		if (bp->b_bcount % st->blksize) {
751 			printf("%s: bad request, must be multiple of %d\n",
752 			    st->sc_dev.dv_xname, st->blksize);
753 			bp->b_error = EIO;
754 			goto bad;
755 		}
756 	}
757 	/*
758 	 * as are out-of-range requests on variable drives.
759 	 */
760 	else if (bp->b_bcount < st->blkmin ||
761 	    (st->blkmax && bp->b_bcount > st->blkmax)) {
762 		printf("%s: bad request, must be between %d and %d\n",
763 		    st->sc_dev.dv_xname, st->blkmin, st->blkmax);
764 		bp->b_error = EIO;
765 		goto bad;
766 	}
767 
768 	/*
769 	 * Place it in the queue of activities for this tape
770 	 * at the end (a bit silly because we only have on user..
771 	 * (but it could fork()))
772 	 */
773 	bufq_queue(&st->sc_bufq, bp);
774 
775 	/*
776 	 * Tell the device to get going on the transfer if it's
777 	 * not doing anything, otherwise just wait for completion
778 	 * (All a bit silly if we're only allowing 1 open but..)
779 	 */
780 	scsi_xsh_add(&st->sc_xsh);
781 
782 	device_unref(&st->sc_dev);
783 	return;
784 bad:
785 	SET(bp->b_flags, B_ERROR);
786 done:
787 	/* Set b_resid to indicate no xfer was done. */
788 	bp->b_resid = bp->b_bcount;
789 	s = splbio();
790 	biodone(bp);
791 	splx(s);
792 	if (st)
793 		device_unref(&st->sc_dev);
794 }
795 
796 void
797 ststart(struct scsi_xfer *xs)
798 {
799 	struct scsi_link *link = xs->sc_link;
800 	struct st_softc *st = link->device_softc;
801 	struct buf *bp;
802 	struct scsi_rw_tape *cmd;
803 	int s;
804 
805 	SC_DEBUG(link, SDEV_DB2, ("ststart\n"));
806 
807 	if (ISSET(st->flags, ST_DYING)) {
808 		scsi_xs_put(xs);
809 		return;
810 	}
811 
812 	/*
813 	 * if the device has been unmounted by the user
814 	 * then throw away all requests until done
815 	 */
816 	if (!ISSET(st->flags, ST_MOUNTED) ||
817 	    !ISSET(link->flags, SDEV_MEDIA_LOADED)) {
818 		/* make sure that one implies the other.. */
819 		CLR(link->flags, SDEV_MEDIA_LOADED);
820 		bufq_drain(&st->sc_bufq);
821 		scsi_xs_put(xs);
822 		return;
823 	}
824 
825 	for (;;) {
826 		bp = bufq_dequeue(&st->sc_bufq);
827 		if (bp == NULL) {
828 			scsi_xs_put(xs);
829 			return;
830 		}
831 
832 		/*
833 		 * Only FIXEDBLOCK devices have pending I/O or space
834 		 * operations.
835 		 */
836 		if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
837 			/*
838 			 * If we are at a filemark but have not reported it yet
839 			 * then we should report it now
840 			 */
841 			if (ISSET(st->flags, ST_AT_FILEMARK)) {
842 				if ((bp->b_flags & B_READ) == B_WRITE) {
843 					/*
844 					 * Handling of ST_AT_FILEMARK in
845 					 * st_space will fill in the right file
846 					 * mark count.
847 					 * Back up over filemark
848 					 */
849 					if (st_space(st, 0, SP_FILEMARKS, 0)) {
850 						SET(bp->b_flags, B_ERROR);
851 						bp->b_resid = bp->b_bcount;
852 						bp->b_error = EIO;
853 						s = splbio();
854 						biodone(bp);
855 						splx(s);
856 						continue;
857 					}
858 				} else {
859 					bp->b_resid = bp->b_bcount;
860 					bp->b_error = 0;
861 					CLR(bp->b_flags, B_ERROR);
862 					CLR(st->flags, ST_AT_FILEMARK);
863 					s = splbio();
864 					biodone(bp);
865 					splx(s);
866 					continue;	/* seek more work */
867 				}
868 			}
869 		}
870 
871 		/*
872 		 * If we are at EIO or EOM but have not reported it
873 		 * yet then we should report it now.
874 		 */
875 		if (ISSET(st->flags, ST_EOM_PENDING | ST_EIO_PENDING)) {
876 			bp->b_resid = bp->b_bcount;
877 			if (ISSET(st->flags, ST_EIO_PENDING)) {
878 				bp->b_error = EIO;
879 				SET(bp->b_flags, B_ERROR);
880 			}
881 			CLR(st->flags, ST_EOM_PENDING | ST_EIO_PENDING);
882 			s = splbio();
883 			biodone(bp);
884 			splx(s);
885 			continue;	/* seek more work */
886 		}
887 		break;
888 	}
889 
890 	/*
891 	 *  Fill out the scsi command
892 	 */
893 	cmd = (struct scsi_rw_tape *)xs->cmd;
894 	bzero(cmd, sizeof(*cmd));
895 	if ((bp->b_flags & B_READ) == B_WRITE) {
896 		cmd->opcode = WRITE;
897 		CLR(st->flags, ST_FM_WRITTEN);
898 		SET(st->flags, ST_WRITTEN);
899 		SET(xs->flags, SCSI_DATA_OUT);
900 	} else {
901 		cmd->opcode = READ;
902 		SET(xs->flags, SCSI_DATA_IN);
903 	}
904 
905 	/*
906 	 * Handle "fixed-block-mode" tape drives by using the
907 	 * block count instead of the length.
908 	 */
909 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
910 		SET(cmd->byte2, SRW_FIXED);
911 		_lto3b(bp->b_bcount / st->blksize, cmd->len);
912 	} else
913 		_lto3b(bp->b_bcount, cmd->len);
914 
915 	if (st->media_blkno != -1) {
916 		/* Update block count now, errors will set it to -1. */
917 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
918 			st->media_blkno += _3btol(cmd->len);
919 		else if (_3btol(cmd->len) != 0)
920 			st->media_blkno++;
921 	}
922 
923 	xs->cmdlen = sizeof(*cmd);
924 	xs->timeout = ST_IO_TIME;
925 	xs->data = bp->b_data;
926 	xs->datalen = bp->b_bcount;
927 	xs->done = st_buf_done;
928 	xs->cookie = bp;
929 	xs->bp = bp;
930 
931 	/*
932 	 * go ask the adapter to do all this for us
933 	 */
934 	scsi_xs_exec(xs);
935 
936 	/*
937 	 * should we try do more work now?
938 	 */
939 	if (ISSET(st->flags, ST_WAITING))
940 		CLR(st->flags, ST_WAITING);
941 	else if (bufq_peek(&st->sc_bufq))
942 		scsi_xsh_add(&st->sc_xsh);
943 }
944 
945 void
946 st_buf_done(struct scsi_xfer *xs)
947 {
948 	struct buf *bp = xs->cookie;
949 	int error, s;
950 
951 	switch (xs->error) {
952 	case XS_NOERROR:
953 		bp->b_error = 0;
954 		CLR(bp->b_flags, B_ERROR);
955 		bp->b_resid = xs->resid;
956 		break;
957 
958 	case XS_SENSE:
959 	case XS_SHORTSENSE:
960 		SC_DEBUG_SENSE(xs);
961 		error = st_interpret_sense(xs);
962 		if (error == 0) {
963 			bp->b_error = 0;
964 			CLR(bp->b_flags, B_ERROR);
965 			bp->b_resid = xs->resid;
966 			break;
967 		}
968 		if (error != ERESTART)
969 			xs->retries = 0;
970 		goto retry;
971 
972 	case XS_BUSY:
973 		if (xs->retries) {
974 			if (scsi_delay(xs, 1) != ERESTART)
975 				xs->retries = 0;
976 		}
977 		goto retry;
978 
979 	case XS_TIMEOUT:
980  retry:
981 		if (xs->retries--) {
982 			scsi_xs_exec(xs);
983 			return;
984 		}
985 		/* FALLTHROUGH */
986 
987 	default:
988 		bp->b_error = EIO;
989 		SET(bp->b_flags, B_ERROR);
990 		bp->b_resid = bp->b_bcount;
991 		break;
992 	}
993 
994 	s = splbio();
995 	biodone(bp);
996 	splx(s);
997 	scsi_xs_put(xs);
998 }
999 
1000 void
1001 stminphys(struct buf *bp)
1002 {
1003 	struct scsi_link	*link;
1004 	struct st_softc		*sc;
1005 
1006 	sc = stlookup(STUNIT(bp->b_dev));
1007 	if (sc == NULL)
1008 		return;
1009 	link = sc->sc_link;
1010 
1011 	if (link->adapter->dev_minphys != NULL)
1012 		(*link->adapter->dev_minphys)(bp, link);
1013 	else
1014 		minphys(bp);
1015 
1016 	device_unref(&sc->sc_dev);
1017 }
1018 
1019 int
1020 stread(dev_t dev, struct uio *uio, int iomode)
1021 {
1022 	return physio(ststrategy, dev, B_READ, stminphys, uio);
1023 }
1024 
1025 int
1026 stwrite(dev_t dev, struct uio *uio, int iomode)
1027 {
1028 	return physio(ststrategy, dev, B_WRITE, stminphys, uio);
1029 }
1030 
1031 /*
1032  * Perform special action on behalf of the user;
1033  * knows about the internals of this device
1034  */
1035 int
1036 stioctl(dev_t dev, u_long cmd, caddr_t arg, int flag, struct proc *p)
1037 {
1038 	int error = 0;
1039 	int nmarks;
1040 	int flags = 0;
1041 	struct st_softc *st;
1042 	int hold_blksize;
1043 	u_int8_t hold_density;
1044 	struct mtop *mt = (struct mtop *) arg;
1045 	int number;
1046 
1047 	/*
1048 	 * Find the device that the user is talking about
1049 	 */
1050 	st = stlookup(STUNIT(dev));
1051 	if (st == NULL)
1052 		return ENXIO;
1053 
1054 	if (ISSET(st->flags, ST_DYING)) {
1055 		error = ENXIO;
1056 		goto done;
1057 	}
1058 
1059 	hold_blksize = st->blksize;
1060 	hold_density = st->density;
1061 
1062 	switch (cmd) {
1063 
1064 	case MTIOCGET: {
1065 		struct mtget *g = (struct mtget *) arg;
1066 
1067 		/*
1068 		 * (to get the current state of READONLY)
1069 		 */
1070 		error = st_mode_sense(st, SCSI_SILENT);
1071 		if (error != 0)
1072 			break;
1073 
1074 		SC_DEBUG(st->sc_link, SDEV_DB1, ("[ioctl: get status]\n"));
1075 		bzero(g, sizeof(struct mtget));
1076 		g->mt_type = 0x7;	/* Ultrix compat *//*? */
1077 		g->mt_blksiz = st->blksize;
1078 		g->mt_density = st->density;
1079 		g->mt_mblksiz = st->mode.blksize;
1080 		g->mt_mdensity = st->mode.density;
1081 		if (ISSET(st->sc_link->flags, SDEV_READONLY))
1082 			SET(g->mt_dsreg, MT_DS_RDONLY);
1083 		if (ISSET(st->flags, ST_MOUNTED))
1084 			SET(g->mt_dsreg, MT_DS_MOUNTED);
1085 		g->mt_resid = st->mt_resid;
1086 		g->mt_erreg = st->mt_erreg;
1087 		g->mt_fileno = st->media_fileno;
1088 		g->mt_blkno = st->media_blkno;
1089 		/*
1090 		 * clear latched errors.
1091 		 */
1092 		st->mt_resid = 0;
1093 		st->mt_erreg = 0;
1094 		break;
1095 	}
1096 	case MTIOCTOP: {
1097 
1098 		SC_DEBUG(st->sc_link, SDEV_DB1,
1099 		    ("[ioctl: op=0x%x count=0x%x]\n", mt->mt_op, mt->mt_count));
1100 
1101 		number = mt->mt_count;
1102 		switch (mt->mt_op) {
1103 		case MTWEOF:	/* write an end-of-file record */
1104 			error = st_write_filemarks(st, number, flags);
1105 			break;
1106 		case MTBSF:	/* backward space file */
1107 			number = -number;
1108 		case MTFSF:	/* forward space file */
1109 			error = st_check_eod(st, 0, &nmarks, flags);
1110 			if (error == 0)
1111 				error = st_space(st, number - nmarks,
1112 				    SP_FILEMARKS, flags);
1113 			break;
1114 		case MTBSR:	/* backward space record */
1115 			number = -number;
1116 		case MTFSR:	/* forward space record */
1117 			error = st_check_eod(st, 1, &nmarks, flags);
1118 			if (error == 0)
1119 				error = st_space(st, number, SP_BLKS, flags);
1120 			break;
1121 		case MTREW:	/* rewind */
1122 			error = st_rewind(st, 0, flags);
1123 			break;
1124 		case MTOFFL:	/* rewind and put the drive offline */
1125 			st_unmount(st, EJECT, DOREWIND);
1126 			break;
1127 		case MTNOP:	/* no operation, sets status only */
1128 			break;
1129 		case MTRETEN:	/* retension the tape */
1130 			error = st_load(st, LD_RETENSION, flags);
1131 			if (error == 0)
1132 				error = st_load(st, LD_LOAD, flags);
1133 			break;
1134 		case MTEOM:	/* forward space to end of media */
1135 			error = st_check_eod(st, 0, &nmarks, flags);
1136 			if (error == 0)
1137 				error = st_space(st, 1, SP_EOM, flags);
1138 			break;
1139 		case MTCACHE:	/* enable controller cache */
1140 			CLR(st->flags, ST_DONTBUFFER);
1141 			goto try_new_value;
1142 		case MTNOCACHE:	/* disable controller cache */
1143 			SET(st->flags, ST_DONTBUFFER);
1144 			goto try_new_value;
1145 		case MTERASE:	/* erase volume */
1146 			error = st_erase(st, number, flags);
1147 			break;
1148 		case MTSETBSIZ:	/* Set block size for device and mode. */
1149 			if (number == 0) {
1150 				CLR(st->flags, ST_FIXEDBLOCKS);
1151 			} else {
1152 				if ((st->blkmin || st->blkmax) &&
1153 				    (number < st->blkmin ||
1154 				    number > st->blkmax)) {
1155 					error = EINVAL;
1156 					break;
1157 				}
1158 				SET(st->flags, ST_FIXEDBLOCKS);
1159 			}
1160 			st->blksize = number;
1161 			goto try_new_value;
1162 
1163 		case MTSETDNSTY:	/* Set density for device and mode. */
1164 			if (number < 0 || number > SCSI_MAX_DENSITY_CODE) {
1165 				error = EINVAL;
1166 				break;
1167 			}
1168 			st->density = number;
1169 			goto try_new_value;
1170 
1171 		default:
1172 			error = EINVAL;
1173 		}
1174 		break;
1175 	}
1176 	case MTIOCIEOT:
1177 	case MTIOCEEOT:
1178 		break;
1179 
1180 #if 0
1181 	case MTIOCRDSPOS:
1182 		error = st_rdpos(st, 0, (u_int32_t *) arg);
1183 		break;
1184 
1185 	case MTIOCRDHPOS:
1186 		error = st_rdpos(st, 1, (u_int32_t *) arg);
1187 		break;
1188 
1189 	case MTIOCSLOCATE:
1190 		error = st_setpos(st, 0, (u_int32_t *) arg);
1191 		break;
1192 
1193 	case MTIOCHLOCATE:
1194 		error = st_setpos(st, 1, (u_int32_t *) arg);
1195 		break;
1196 #endif /* 0 */
1197 
1198 	default:
1199 		error = scsi_do_ioctl(st->sc_link, cmd, arg, flag);
1200 		break;
1201 	}
1202 	goto done;
1203 
1204 try_new_value:
1205 	/*
1206 	 * Check that the mode being asked for is aggreeable to the
1207 	 * drive. If not, put it back the way it was.
1208 	 */
1209 	if ((error = st_mode_select(st, 0)) != 0) {/* put it back as it was */
1210 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
1211 		st->density = hold_density;
1212 		st->blksize = hold_blksize;
1213 		if (st->blksize)
1214 			SET(st->flags, ST_FIXEDBLOCKS);
1215 		else
1216 			CLR(st->flags, ST_FIXEDBLOCKS);
1217 		goto done;
1218 	}
1219 	/*
1220 	 * As the drive liked it, if we are setting a new default,
1221 	 * set it into the structures as such.
1222 	 */
1223 	switch (mt->mt_op) {
1224 	case MTSETBSIZ:
1225 		st->mode.blksize = st->blksize;
1226 		SET(st->flags, ST_MODE_BLKSIZE);
1227 		break;
1228 	case MTSETDNSTY:
1229 		st->mode.density = st->density;
1230 		SET(st->flags, ST_MODE_DENSITY);
1231 		break;
1232 	}
1233 
1234 done:
1235 	device_unref(&st->sc_dev);
1236 	return error;
1237 }
1238 
1239 /*
1240  * Do a synchronous read.
1241  */
1242 int
1243 st_read(struct st_softc *st, char *buf, int size, int flags)
1244 {
1245 	struct scsi_rw_tape *cmd;
1246 	struct scsi_xfer *xs;
1247 	int error;
1248 
1249 	if (size == 0)
1250 		return 0;
1251 
1252 	xs = scsi_xs_get(st->sc_link, flags | SCSI_DATA_IN);
1253 	if (xs == NULL)
1254 		return ENOMEM;
1255 	xs->cmdlen = sizeof(*cmd);
1256 	xs->data = buf;
1257 	xs->datalen = size;
1258 	xs->retries = 0;
1259 	xs->timeout = ST_IO_TIME;
1260 
1261 	cmd = (struct scsi_rw_tape *)xs->cmd;
1262 	cmd->opcode = READ;
1263 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
1264 		SET(cmd->byte2, SRW_FIXED);
1265 		_lto3b(size / (st->blksize ? st->blksize : DEF_FIXED_BSIZE),
1266 		    cmd->len);
1267 	} else
1268 		_lto3b(size, cmd->len);
1269 
1270 	error = scsi_xs_sync(xs);
1271 	scsi_xs_put(xs);
1272 
1273 	return error;
1274 }
1275 
1276 /*
1277  * Ask the drive what its min and max blk sizes are.
1278  */
1279 int
1280 st_read_block_limits(struct st_softc *st, int flags)
1281 {
1282 	struct scsi_block_limits_data *block_limits = NULL;
1283 	struct scsi_block_limits *cmd;
1284 	struct scsi_link *link = st->sc_link;
1285 	struct scsi_xfer *xs;
1286 	int error = 0;
1287 
1288 	if (ISSET(link->flags, SDEV_MEDIA_LOADED))
1289 		return 0;
1290 
1291 	block_limits = dma_alloc(sizeof(*block_limits), PR_NOWAIT);
1292 	if (block_limits == NULL)
1293 		return ENOMEM;
1294 
1295 	xs = scsi_xs_get(link, flags | SCSI_DATA_IN);
1296 	if (xs == NULL) {
1297 		error = ENOMEM;
1298 		goto done;
1299 	}
1300 
1301 	xs->cmdlen = sizeof(*cmd);
1302 	xs->data = (void *)block_limits;
1303 	xs->datalen = sizeof(*block_limits);
1304 	xs->timeout = ST_CTL_TIME;
1305 
1306 	cmd = (struct scsi_block_limits *)xs->cmd;
1307 	cmd->opcode = READ_BLOCK_LIMITS;
1308 
1309 	error = scsi_xs_sync(xs);
1310 	scsi_xs_put(xs);
1311 
1312 	if (error == 0) {
1313 		st->blkmin = _2btol(block_limits->min_length);
1314 		st->blkmax = _3btol(block_limits->max_length);
1315 		SC_DEBUG(link, SDEV_DB3,
1316 		    ("(%d <= blksize <= %d)\n", st->blkmin, st->blkmax));
1317 	}
1318 
1319 done:
1320 	if (block_limits)
1321 		dma_free(block_limits, sizeof(*block_limits));
1322 	return error;
1323 }
1324 
1325 /*
1326  * Get the scsi driver to send a full inquiry to the
1327  * device and use the results to fill out the global
1328  * parameter structure.
1329  *
1330  * called from:
1331  * attach
1332  * open
1333  * ioctl (to reset original blksize)
1334  */
1335 int
1336 st_mode_sense(struct st_softc *st, int flags)
1337 {
1338 	union scsi_mode_sense_buf *data = NULL;
1339 	struct scsi_link *link = st->sc_link;
1340 	u_int64_t block_count;
1341 	u_int32_t density, block_size;
1342 	u_char *page0 = NULL;
1343 	u_int8_t dev_spec;
1344 	int error = 0, big;
1345 
1346 	data = dma_alloc(sizeof(*data), PR_NOWAIT);
1347 	if (data == NULL)
1348 		return ENOMEM;
1349 
1350 	/*
1351 	 * Ask for page 0 (vendor specific) mode sense data.
1352 	 */
1353 	density = 0;
1354 	block_count = 0;
1355 	block_size = 0;
1356 	error = scsi_do_mode_sense(link, 0, data, (void **)&page0, 1,
1357 	    flags | SCSI_SILENT, &big);
1358 	if (error != 0)
1359 		goto done;
1360 	scsi_parse_blkdesc(link, data, big, &density, &block_count,
1361 	    &block_size);
1362 
1363 	/* It is valid for no page0 to be available. */
1364 
1365 	if (big)
1366 		dev_spec = data->hdr_big.dev_spec;
1367 	else
1368 		dev_spec = data->hdr.dev_spec;
1369 
1370 	if (ISSET(dev_spec, SMH_DSP_WRITE_PROT))
1371 		SET(link->flags, SDEV_READONLY);
1372 	else
1373 		CLR(link->flags, SDEV_READONLY);
1374 
1375 	st->media_blksize = block_size;
1376 	st->media_density = density;
1377 
1378 	SC_DEBUG(link, SDEV_DB3,
1379 	    ("density code 0x%x, %d-byte blocks, write-%s, %sbuffered\n",
1380 	    st->media_density, st->media_blksize,
1381 	    ISSET(link->flags, SDEV_READONLY) ? "protected" : "enabled",
1382 	    ISSET(dev_spec, SMH_DSP_BUFF_MODE) ? "" : "un"));
1383 
1384 	SET(link->flags, SDEV_MEDIA_LOADED);
1385 
1386  done:
1387 	if (data)
1388 		dma_free(data, sizeof(*data));
1389 	return error;
1390 }
1391 
1392 /*
1393  * Send a filled out parameter structure to the drive to
1394  * set it into the desire mode etc.
1395  */
1396 int
1397 st_mode_select(struct st_softc *st, int flags)
1398 {
1399 	union scsi_mode_sense_buf *inbuf = NULL, *outbuf = NULL;
1400 	struct scsi_blk_desc general;
1401 	struct scsi_link *link = st->sc_link;
1402 	u_int8_t *page0 = NULL;
1403 	int error = 0, big, page0_size;
1404 
1405 	inbuf = dma_alloc(sizeof(*inbuf), PR_NOWAIT);
1406 	if (inbuf == NULL) {
1407 		error = ENOMEM;
1408 		goto done;
1409 	}
1410 	outbuf = dma_alloc(sizeof(*outbuf), PR_NOWAIT | PR_ZERO);
1411 	if (outbuf == NULL) {
1412 		error = ENOMEM;
1413 		goto done;
1414 	}
1415 
1416 	/*
1417 	 * This quirk deals with drives that have only one valid mode and think
1418 	 * this gives them license to reject all mode selects, even if the
1419 	 * selected mode is the one that is supported.
1420 	 */
1421 	if (ISSET(st->quirks, ST_Q_UNIMODAL)) {
1422 		SC_DEBUG(link, SDEV_DB3,
1423 		    ("not setting density 0x%x blksize 0x%x\n",
1424 		    st->density, st->blksize));
1425 		error = 0;
1426 		goto done;
1427 	}
1428 
1429 	if (ISSET(link->flags, SDEV_ATAPI)) {
1430 		error = 0;
1431 		goto done;
1432 	}
1433 
1434 	bzero(&general, sizeof(general));
1435 
1436 	general.density = st->density;
1437 	if (ISSET(st->flags, ST_FIXEDBLOCKS))
1438 		_lto3b(st->blksize, general.blklen);
1439 
1440 	/*
1441 	 * Ask for page 0 (vendor specific) mode sense data.
1442 	 *
1443 	 * page0 == NULL is a valid situation.
1444 	 */
1445 	error = scsi_do_mode_sense(link, 0, inbuf, (void **)&page0, 1,
1446 	    flags | SCSI_SILENT, &big);
1447 	if (error != 0)
1448 		goto done;
1449 
1450 	if (page0 == NULL) {
1451 		page0_size = 0;
1452 	} else if (big == 0) {
1453 		page0_size = inbuf->hdr.data_length +
1454 		    sizeof(inbuf->hdr.data_length) - sizeof(inbuf->hdr) -
1455 		    inbuf->hdr.blk_desc_len;
1456 		memcpy(&outbuf->buf[sizeof(outbuf->hdr)+ sizeof(general)],
1457 		    page0, page0_size);
1458 	} else {
1459 		page0_size = _2btol(inbuf->hdr_big.data_length) +
1460 		    sizeof(inbuf->hdr_big.data_length) -
1461 		    sizeof(inbuf->hdr_big) -
1462 		    _2btol(inbuf->hdr_big.blk_desc_len);
1463 		memcpy(&outbuf->buf[sizeof(outbuf->hdr_big) + sizeof(general)],
1464 		    page0, page0_size);
1465 	}
1466 
1467 	/*
1468 	 * Set up for a mode select.
1469 	 */
1470 	if (big == 0) {
1471 		outbuf->hdr.data_length = sizeof(outbuf->hdr) +
1472 		    sizeof(general) + page0_size -
1473 		    sizeof(outbuf->hdr.data_length);
1474 		if (!ISSET(st->flags, ST_DONTBUFFER))
1475 			outbuf->hdr.dev_spec = SMH_DSP_BUFF_MODE_ON;
1476 		outbuf->hdr.blk_desc_len = sizeof(general);
1477 		memcpy(&outbuf->buf[sizeof(outbuf->hdr)],
1478 		    &general, sizeof(general));
1479 		error = scsi_mode_select(st->sc_link, 0, &outbuf->hdr,
1480 		    flags, ST_CTL_TIME);
1481 		goto done;
1482 	}
1483 
1484 	/* MODE SENSE (10) header was returned, so use MODE SELECT (10). */
1485 	_lto2b((sizeof(outbuf->hdr_big) + sizeof(general) + page0_size -
1486 	    sizeof(outbuf->hdr_big.data_length)), outbuf->hdr_big.data_length);
1487 	if (!ISSET(st->flags, ST_DONTBUFFER))
1488 		outbuf->hdr_big.dev_spec = SMH_DSP_BUFF_MODE_ON;
1489 	_lto2b(sizeof(general), outbuf->hdr_big.blk_desc_len);
1490 	memcpy(&outbuf->buf[sizeof(outbuf->hdr_big)], &general,
1491 	    sizeof(general));
1492 
1493 	error = scsi_mode_select_big(st->sc_link, 0, &outbuf->hdr_big,
1494 	    flags, ST_CTL_TIME);
1495 done:
1496 	if (inbuf)
1497 		dma_free(inbuf, sizeof(*inbuf));
1498 	if (outbuf)
1499 		dma_free(outbuf, sizeof(*outbuf));
1500 	return error;
1501 }
1502 
1503 /*
1504  * issue an erase command
1505  */
1506 int
1507 st_erase(struct st_softc *st, int full, int flags)
1508 {
1509 	struct scsi_erase *cmd;
1510 	struct scsi_xfer *xs;
1511 	int error;
1512 
1513 	xs = scsi_xs_get(st->sc_link, flags);
1514 	if (xs == NULL)
1515 		return ENOMEM;
1516 	xs->cmdlen = sizeof(*cmd);
1517 
1518 	/*
1519 	 * Full erase means set LONG bit in erase command, which asks
1520 	 * the drive to erase the entire unit.  Without this bit, we're
1521 	 * asking the drive to write an erase gap.
1522 	 */
1523 	cmd = (struct scsi_erase *)xs->cmd;
1524 	cmd->opcode = ERASE;
1525 	if (full) {
1526 		cmd->byte2 = SE_IMMED|SE_LONG;
1527 		xs->timeout = ST_SPC_TIME;
1528 	} else {
1529 		cmd->byte2 = SE_IMMED;
1530 		xs->timeout = ST_IO_TIME;
1531 	}
1532 
1533 	/*
1534 	 * XXX We always do this asynchronously, for now.  How long should
1535 	 * we wait if we want to (eventually) to it synchronously?
1536 	 */
1537 	error = scsi_xs_sync(xs);
1538 	scsi_xs_put(xs);
1539 
1540 	return error;
1541 }
1542 
1543 /*
1544  * skip N blocks/filemarks/seq filemarks/eom
1545  */
1546 int
1547 st_space(struct st_softc *st, int number, u_int what, int flags)
1548 {
1549 	struct scsi_space *cmd;
1550 	struct scsi_xfer *xs;
1551 	int error;
1552 
1553 	switch (what) {
1554 	case SP_BLKS:
1555 		if (ISSET(st->flags, ST_PER_ACTION)) {
1556 			if (number > 0) {
1557 				CLR(st->flags, ST_PER_ACTION);
1558 				return EIO;
1559 			} else if (number < 0) {
1560 				if (ISSET(st->flags, ST_AT_FILEMARK)) {
1561 					/*
1562 					 * Handling of ST_AT_FILEMARK
1563 					 * in st_space will fill in the
1564 					 * right file mark count.
1565 					 */
1566 					error = st_space(st, 0, SP_FILEMARKS,
1567 					    flags);
1568 					if (error != 0)
1569 						return error;
1570 				}
1571 				if (ISSET(st->flags, ST_BLANK_READ)) {
1572 					CLR(st->flags, ST_BLANK_READ);
1573 					return EIO;
1574 				}
1575 				CLR(st->flags, ST_EIO_PENDING | ST_EOM_PENDING);
1576 			}
1577 		}
1578 		break;
1579 	case SP_FILEMARKS:
1580 		if (ISSET(st->flags,  ST_EIO_PENDING)) {
1581 			if (number > 0) {
1582 				/* pretend we just discovered the error */
1583 				CLR(st->flags, ST_EIO_PENDING);
1584 				return EIO;
1585 			} else if (number < 0) {
1586 				/* back away from the error */
1587 				CLR(st->flags, ST_EIO_PENDING);
1588 			}
1589 		}
1590 		if (ISSET(st->flags, ST_AT_FILEMARK)) {
1591 			CLR(st->flags, ST_AT_FILEMARK);
1592 			number--;
1593 		}
1594 		if (ISSET(st->flags, ST_BLANK_READ) && (number < 0)) {
1595 			/* back away from unwritten tape */
1596 			CLR(st->flags, ST_BLANK_READ);
1597 			number++;	/* XXX dubious */
1598 		}
1599 		break;
1600 	case SP_EOM:
1601 		if (ISSET(st->flags, ST_EOM_PENDING)) {
1602 			/* We are already there. */
1603 			CLR(st->flags, ST_EOM_PENDING);
1604 			return 0;
1605 		}
1606 		if (ISSET(st->flags, ST_EIO_PENDING)) {
1607 			/* pretend we just discovered the error */
1608 			CLR(st->flags, ST_EIO_PENDING);
1609 			return EIO;
1610 		}
1611 		if (ISSET(st->flags, ST_AT_FILEMARK))
1612 			CLR(st->flags, ST_AT_FILEMARK);
1613 		break;
1614 	}
1615 	if (number == 0)
1616 		return 0;
1617 
1618 	xs = scsi_xs_get(st->sc_link, flags);
1619 	if (xs == NULL)
1620 		return ENOMEM;
1621 
1622 	cmd = (struct scsi_space *)xs->cmd;
1623 	cmd->opcode = SPACE;
1624 	cmd->byte2 = what;
1625 	_lto3b(number, cmd->number);
1626 	xs->cmdlen = sizeof(*cmd);
1627 	xs->timeout = ST_SPC_TIME;
1628 
1629 	CLR(st->flags, ST_EOD_DETECTED);
1630 
1631 	error = scsi_xs_sync(xs);
1632 	scsi_xs_put(xs);
1633 
1634 	if (error != 0) {
1635 		st->media_fileno = -1;
1636 		st->media_blkno = -1;
1637 	} else {
1638 		switch (what) {
1639 		case SP_BLKS:
1640 			if (st->media_blkno != -1) {
1641 				st->media_blkno += number;
1642 				if (st->media_blkno < 0)
1643 					st->media_blkno = -1;
1644 			}
1645 			break;
1646 		case SP_FILEMARKS:
1647 			if (st->media_fileno != -1) {
1648 				if (!ISSET(st->flags, ST_EOD_DETECTED))
1649 					st->media_fileno += number;
1650 				if (st->media_fileno > st->media_eom)
1651 					st->media_eom = st->media_fileno;
1652 				st->media_blkno = 0;
1653 			}
1654 			break;
1655 		case SP_EOM:
1656 			if (st->media_eom != -1) {
1657 				st->media_fileno = st->media_eom;
1658 				st->media_blkno = 0;
1659 			} else {
1660 				st->media_fileno = -1;
1661 				st->media_blkno = -1;
1662 			}
1663 			break;
1664 		default:
1665 			st->media_fileno = -1;
1666 			st->media_blkno = -1;
1667 			break;
1668 		}
1669 	}
1670 
1671 	return error;
1672 }
1673 
1674 /*
1675  * write N filemarks
1676  */
1677 int
1678 st_write_filemarks(struct st_softc *st, int number, int flags)
1679 {
1680 	struct scsi_write_filemarks *cmd;
1681 	struct scsi_xfer *xs;
1682 	int error;
1683 
1684 	if (number < 0)
1685 		return EINVAL;
1686 
1687 	xs = scsi_xs_get(st->sc_link, flags);
1688 	if (xs == NULL)
1689 		return ENOMEM;
1690 
1691 	xs->cmdlen = sizeof(*cmd);
1692 	xs->timeout = ST_IO_TIME * 4;
1693 
1694 	switch (number) {
1695 	case 0:		/* really a command to sync the drive's buffers */
1696 		break;
1697 	case 1:
1698 		if (ISSET(st->flags, ST_FM_WRITTEN))	/* already have one down */
1699 			CLR(st->flags, ST_WRITTEN);
1700 		else
1701 			SET(st->flags, ST_FM_WRITTEN);
1702 		CLR(st->flags, ST_PER_ACTION);
1703 		break;
1704 	default:
1705 		CLR(st->flags, ST_PER_ACTION | ST_WRITTEN);
1706 		break;
1707 	}
1708 
1709 	cmd = (struct scsi_write_filemarks *)xs->cmd;
1710 	cmd->opcode = WRITE_FILEMARKS;
1711 	_lto3b(number, cmd->number);
1712 
1713 	error = scsi_xs_sync(xs);
1714 	scsi_xs_put(xs);
1715 
1716 	if (error != 0) {
1717 		st->media_fileno = -1;
1718 		st->media_blkno = -1;
1719 		st->media_eom = -1;
1720 	} else if (st->media_fileno != -1) {
1721 		st->media_fileno += number;
1722 		st->media_eom = st->media_fileno;
1723 		st->media_blkno = 0;
1724 	}
1725 
1726 	return error;
1727 }
1728 
1729 /*
1730  * Make sure the right number of file marks is on tape if the
1731  * tape has been written.  If the position argument is true,
1732  * leave the tape positioned where it was originally.
1733  *
1734  * nmarks returns the number of marks to skip (or, if position
1735  * true, which were skipped) to get back original position.
1736  */
1737 int
1738 st_check_eod(struct st_softc *st, int position, int *nmarks, int flags)
1739 {
1740 	int error;
1741 
1742 	switch (st->flags & (ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD)) {
1743 	default:
1744 		*nmarks = 0;
1745 		return 0;
1746 	case ST_WRITTEN:
1747 	case ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD:
1748 		*nmarks = 1;
1749 		break;
1750 	case ST_WRITTEN | ST_2FM_AT_EOD:
1751 		*nmarks = 2;
1752 	}
1753 	error = st_write_filemarks(st, *nmarks, flags);
1754 	if (error == 0 && position != 0)
1755 		error = st_space(st, -*nmarks, SP_FILEMARKS, flags);
1756 	return error;
1757 }
1758 
1759 /*
1760  * load/unload/retension
1761  */
1762 int
1763 st_load(struct st_softc *st, u_int type, int flags)
1764 {
1765 	struct scsi_load *cmd;
1766 	struct scsi_xfer *xs;
1767 	int error, nmarks;
1768 
1769 	st->media_fileno = -1;
1770 	st->media_blkno = -1;
1771 	st->media_eom = -1;
1772 
1773 	if (type != LD_LOAD) {
1774 		error = st_check_eod(st, 0, &nmarks, flags);
1775 		if (error != 0)
1776 			return error;
1777 	}
1778 
1779 	if (ISSET(st->quirks, ST_Q_IGNORE_LOADS)) {
1780 		if (type == LD_LOAD) {
1781 			/*
1782 			 * If we ignore loads, at least we should try a rewind.
1783 			 */
1784 			return st_rewind(st, 0, flags);
1785 		}
1786 		return 0;
1787 	}
1788 
1789 
1790 	xs = scsi_xs_get(st->sc_link, flags);
1791 	if (xs == NULL)
1792 		return ENOMEM;
1793 	xs->cmdlen = sizeof(*cmd);
1794 	xs->timeout = ST_SPC_TIME;
1795 
1796 	cmd = (struct scsi_load *)xs->cmd;
1797 	cmd->opcode = LOAD;
1798 	cmd->how = type;
1799 
1800 	error = scsi_xs_sync(xs);
1801 	scsi_xs_put(xs);
1802 
1803 	return error;
1804 }
1805 
1806 /*
1807  *  Rewind the device
1808  */
1809 int
1810 st_rewind(struct st_softc *st, u_int immediate, int flags)
1811 {
1812 	struct scsi_rewind *cmd;
1813 	struct scsi_xfer *xs;
1814 	int error, nmarks;
1815 
1816 	error = st_check_eod(st, 0, &nmarks, flags);
1817 	if (error != 0)
1818 		return error;
1819 	CLR(st->flags, ST_PER_ACTION);
1820 
1821 	xs = scsi_xs_get(st->sc_link, flags);
1822 	if (xs == NULL)
1823 		return ENOMEM;
1824 	xs->cmdlen = sizeof(*cmd);
1825 	xs->timeout = immediate ? ST_CTL_TIME : ST_SPC_TIME;
1826 
1827 	cmd = (struct scsi_rewind *)xs->cmd;
1828 	cmd->opcode = REWIND;
1829 	cmd->byte2 = immediate;
1830 
1831 	error = scsi_xs_sync(xs);
1832 	scsi_xs_put(xs);
1833 
1834 	if (error == 0) {
1835 		st->media_fileno = 0;
1836 		st->media_blkno = 0;
1837 	}
1838 
1839 	return error;
1840 }
1841 
1842 /*
1843  * Look at the returned sense and act on the error and detirmine
1844  * The unix error number to pass back... (0 = report no error)
1845  *                            (-1 = continue processing)
1846  */
1847 int
1848 st_interpret_sense(struct scsi_xfer *xs)
1849 {
1850 	struct scsi_sense_data *sense = &xs->sense;
1851 	struct scsi_link *link = xs->sc_link;
1852 	struct scsi_space *space;
1853 	struct st_softc *st = link->device_softc;
1854 	u_int8_t serr = sense->error_code & SSD_ERRCODE;
1855 	u_int8_t skey = sense->flags & SSD_KEY;
1856 	int32_t resid, info, number;
1857 	int datalen;
1858 
1859 	if (!ISSET(link->flags, SDEV_OPEN) ||
1860 	    (serr != SSD_ERRCODE_CURRENT && serr != SSD_ERRCODE_DEFERRED))
1861 		return scsi_interpret_sense(xs);
1862 
1863 	info = (int32_t)_4btol(sense->info);
1864 
1865 	switch (skey) {
1866 
1867 	/*
1868 	 * We do custom processing in st for the unit becoming ready case.
1869 	 * in this case we do not allow xs->retries to be decremented
1870 	 * only on the "Unit Becoming Ready" case. This is because tape
1871 	 * drives report "Unit Becoming Ready" when loading media, etc.
1872 	 * and can take a long time.  Rather than having a massive timeout
1873 	 * for all operations (which would cause other problems) we allow
1874 	 * operations to wait (but be interruptable with Ctrl-C) forever
1875 	 * as long as the drive is reporting that it is becoming ready.
1876 	 * all other cases are handled as per the default.
1877 	 */
1878 
1879 	case SKEY_NOT_READY:
1880 		if (ISSET(xs->flags, SCSI_IGNORE_NOT_READY))
1881 			return 0;
1882 		switch (ASC_ASCQ(sense)) {
1883 		case SENSE_NOT_READY_BECOMING_READY:
1884 			SC_DEBUG(link, SDEV_DB1, ("not ready: busy (%#x)\n",
1885 			    sense->add_sense_code_qual));
1886 			/* don't count this as a retry */
1887 			xs->retries++;
1888 			return scsi_delay(xs, 1);
1889 		default:
1890 			return scsi_interpret_sense(xs);
1891 		}
1892 		break;
1893 	case SKEY_BLANK_CHECK:
1894 		if (sense->error_code & SSD_ERRCODE_VALID &&
1895 		    xs->cmd->opcode == SPACE) {
1896 			switch (ASC_ASCQ(sense)) {
1897 			case SENSE_END_OF_DATA_DETECTED:
1898 				SET(st->flags, ST_EOD_DETECTED);
1899 				space = (struct scsi_space *)xs->cmd;
1900 				number = _3btol(space->number);
1901 				st->media_fileno = number - info;
1902 				st->media_eom = st->media_fileno;
1903 				return 0;
1904 			case SENSE_BEGINNING_OF_MEDIUM_DETECTED:
1905 				/* Standard says: Position is undefined! */
1906 				SET(st->flags, ST_BOD_DETECTED);
1907 				st->media_fileno = -1;
1908 				st->media_blkno = -1;
1909 				return 0;
1910 			}
1911 		}
1912 		break;
1913 	case SKEY_NO_SENSE:
1914 	case SKEY_RECOVERED_ERROR:
1915 	case SKEY_MEDIUM_ERROR:
1916 	case SKEY_VOLUME_OVERFLOW:
1917 		break;
1918 	default:
1919 		return scsi_interpret_sense(xs);
1920 	}
1921 
1922 	/*
1923 	 * 'resid' can be in units of st->blksize or bytes. xs->resid and
1924 	 * xs->datalen are always in units of bytes. So we need a variable
1925 	 * to store datalen in the same units as resid and to adjust
1926 	 * xs->resid to be in bytes.
1927 	 */
1928 	if (ISSET(sense->error_code, SSD_ERRCODE_VALID)) {
1929 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
1930 			resid = info * st->blksize; /* XXXX overflow? */
1931 		else
1932 			resid = info;
1933 	} else {
1934 		resid = xs->datalen;
1935 	}
1936 
1937 	if (resid < 0 || resid > xs->datalen)
1938 		xs->resid = xs->datalen;
1939 	else
1940 		xs->resid = resid;
1941 
1942 	datalen = xs->datalen;
1943 	if (ISSET(st->flags, ST_FIXEDBLOCKS)) {
1944 		resid /= st->blksize;
1945 		datalen /= st->blksize;
1946 	}
1947 
1948 	if (ISSET(sense->flags, SSD_FILEMARK)) {
1949 		if (st->media_fileno != -1) {
1950 			st->media_fileno++;
1951 			if (st->media_fileno > st->media_eom)
1952 				st->media_eom = st->media_fileno;
1953 			st->media_blkno = 0;
1954 		}
1955 		if (!ISSET(st->flags, ST_FIXEDBLOCKS))
1956 			return 0;
1957 		SET(st->flags, ST_AT_FILEMARK);
1958 	}
1959 
1960 	if (ISSET(sense->flags, SSD_EOM)) {
1961 		SET(st->flags, ST_EOM_PENDING);
1962 		xs->resid = 0;
1963 		if (ISSET(st->flags, ST_FIXEDBLOCKS))
1964 			return 0;
1965 	}
1966 
1967 	if (ISSET(sense->flags, SSD_ILI)) {
1968 		if (!ISSET(st->flags, ST_FIXEDBLOCKS)) {
1969 			if (resid >= 0 && resid <= datalen)
1970 				return 0;
1971 			if (!ISSET(xs->flags, SCSI_SILENT))
1972 				printf( "%s: bad residual %d out of "
1973 				    "%d\n", st->sc_dev.dv_xname, resid,
1974 				    datalen);
1975 			return EIO;
1976 		}
1977 
1978 		/* Fixed size blocks. */
1979 		if (ISSET(sense->error_code, SSD_ERRCODE_VALID))
1980 			if (!ISSET(xs->flags, SCSI_SILENT))
1981 				printf("%s: block wrong size, %d blocks "
1982 				    "residual\n", st->sc_dev.dv_xname, resid);
1983 		SET(st->flags, ST_EIO_PENDING);
1984 		/*
1985 		 * This quirk code helps the drive read the first tape block,
1986 		 * regardless of format.  That is required for these drives to
1987 		 * return proper MODE SENSE information.
1988 		 */
1989 		if (ISSET(st->quirks, ST_Q_SENSE_HELP) &&
1990 		    !ISSET(link->flags, SDEV_MEDIA_LOADED))
1991 			st->blksize -= 512;
1992 	}
1993 
1994 	if (ISSET(st->flags, ST_FIXEDBLOCKS) && xs->resid == xs->datalen) {
1995 		if (ISSET(st->flags, ST_EIO_PENDING))
1996 			return EIO;
1997 		if (ISSET(st->flags, ST_AT_FILEMARK))
1998 			return 0;
1999 	}
2000 
2001 	if (skey == SKEY_BLANK_CHECK) {
2002 		/*
2003 		 * This quirk code helps the drive read the first tape block,
2004 		 * regardless of format.  That is required for these drives to
2005 		 * return proper MODE SENSE information.
2006 		 */
2007 		if (ISSET(st->quirks, ST_Q_SENSE_HELP) &&
2008 		    !ISSET(link->flags, SDEV_MEDIA_LOADED)) {
2009 			/* still starting */
2010 			st->blksize -= 512;
2011 		} else if (!ISSET(st->flags, ST_2FM_AT_EOD | ST_BLANK_READ)) {
2012 			SET(st->flags, ST_BLANK_READ);
2013 			SET(st->flags, ST_EOM_PENDING);
2014 			xs->resid = xs->datalen;
2015 			return 0;
2016 		}
2017 	}
2018 
2019 	return scsi_interpret_sense(xs);
2020 }
2021 
2022 /*
2023  * The quirk here is that the drive returns some value to st_mode_sense
2024  * incorrectly until the tape has actually passed by the head.
2025  *
2026  * The method is to set the drive to large fixed-block state (user-specified
2027  * density and 1024-byte blocks), then read and rewind to get it to sense the
2028  * tape.  If that doesn't work, try 512-byte fixed blocks.  If that doesn't
2029  * work, as a last resort, try variable- length blocks.  The result will be
2030  * the ability to do an accurate st_mode_sense.
2031  *
2032  * We know we can do a rewind because we just did a load, which implies rewind.
2033  * Rewind seems preferable to space backward if we have a virgin tape.
2034  *
2035  * The rest of the code for this quirk is in ILI processing and BLANK CHECK
2036  * error processing, both part of st_interpret_sense.
2037  */
2038 int
2039 st_touch_tape(struct st_softc *st)
2040 {
2041 	char *buf = NULL;
2042 	int readsize, maxblksize = 1024;
2043 	int error = 0;
2044 
2045 	if ((error = st_mode_sense(st, 0)) != 0)
2046 		goto done;
2047 	buf = dma_alloc(maxblksize, PR_NOWAIT);
2048 	if (buf == NULL) {
2049 		error = ENOMEM;
2050 		goto done;
2051 	}
2052 
2053 	st->blksize = 1024;
2054 	do {
2055 		switch (st->blksize) {
2056 		case 512:
2057 		case 1024:
2058 			readsize = st->blksize;
2059 			SET(st->flags, ST_FIXEDBLOCKS);
2060 			break;
2061 		default:
2062 			readsize = 1;
2063 			CLR(st->flags, ST_FIXEDBLOCKS);
2064 		}
2065 		if ((error = st_mode_select(st, 0)) != 0)
2066 			goto done;
2067 		st_read(st, buf, readsize, SCSI_SILENT);	/* XXX */
2068 		if ((error = st_rewind(st, 0, 0)) != 0)
2069 			goto done;
2070 	} while (readsize != 1 && readsize > st->blksize);
2071 done:
2072 	dma_free(buf, maxblksize);
2073 	return error;
2074 }
2075