xref: /netbsd-src/sys/dev/scsipi/st.c (revision 1394f01b4a9e99092957ca5d824d67219565d9b5)
1 /*	$NetBSD: st.c,v 1.71 1997/02/21 23:03:49 thorpej Exp $	*/
2 
3 /*
4  * Copyright (c) 1994 Charles Hannum.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by Charles Hannum.
17  * 4. The name of the author may not be used to endorse or promote products
18  *    derived from this software without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 /*
33  * Originally written by Julian Elischer (julian@tfs.com)
34  * for TRW Financial Systems for use under the MACH(2.5) operating system.
35  *
36  * TRW Financial Systems, in accordance with their agreement with Carnegie
37  * Mellon University, makes this software available to CMU to distribute
38  * or use in any manner that they see fit as long as this message is kept with
39  * the software. For this reason TFS also grants any other persons or
40  * organisations permission to use or modify this software.
41  *
42  * TFS supplies this software to be publicly redistributed
43  * on the understanding that TFS is not responsible for the correct
44  * functioning of this software in any circumstances.
45  *
46  * Ported to run under 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
47  * major changes by Julian Elischer (julian@jules.dialix.oz.au) May 1993
48  */
49 
50 /*
51  * To do:
52  * work out some better way of guessing what a good timeout is going
53  * to be depending on whether we expect to retension or not.
54  */
55 
56 #include <sys/types.h>
57 #include <sys/param.h>
58 #include <sys/systm.h>
59 #include <sys/fcntl.h>
60 #include <sys/errno.h>
61 #include <sys/ioctl.h>
62 #include <sys/malloc.h>
63 #include <sys/buf.h>
64 #include <sys/proc.h>
65 #include <sys/user.h>
66 #include <sys/mtio.h>
67 #include <sys/device.h>
68 #include <sys/conf.h>
69 
70 #include <scsi/scsi_all.h>
71 #include <scsi/scsi_tape.h>
72 #include <scsi/scsiconf.h>
73 
74 /* Defines for device specific stuff */
75 #define DEF_FIXED_BSIZE  512
76 #define	ST_RETRIES	4	/* only on non IO commands */
77 
78 #define STMODE(z)	( minor(z)       & 0x03)
79 #define STDSTY(z)	((minor(z) >> 2) & 0x03)
80 #define STUNIT(z)	((minor(z) >> 4)       )
81 #define CTLMODE	3
82 
83 /*
84  * Maximum density code known.
85  */
86 #define SCSI_2_MAX_DENSITY_CODE	0x45
87 
88 /*
89  * Define various devices that we know mis-behave in some way,
90  * and note how they are bad, so we can correct for them
91  */
92 struct modes {
93 	u_int quirks;			/* same definitions as in quirkdata */
94 	int blksize;
95 	u_int8_t density;
96 };
97 
98 struct quirkdata {
99 	u_int quirks;
100 #define	ST_Q_FORCE_BLKSIZE	0x0001
101 #define	ST_Q_SENSE_HELP		0x0002	/* must do READ for good MODE SENSE */
102 #define	ST_Q_IGNORE_LOADS	0x0004
103 #define	ST_Q_BLKSIZE		0x0008	/* variable-block media_blksize > 0 */
104 #define	ST_Q_UNIMODAL		0x0010	/* unimode drive rejects mode select */
105 	u_int page_0_size;
106 #define	MAX_PAGE_0_SIZE	64
107 	struct modes modes[4];
108 };
109 
110 struct st_quirk_inquiry_pattern {
111 	struct scsi_inquiry_pattern pattern;
112 	struct quirkdata quirkdata;
113 };
114 
115 struct st_quirk_inquiry_pattern st_quirk_patterns[] = {
116 	{{T_SEQUENTIAL, T_REMOV,
117 	 "        ", "                ", "    "}, {0, 0, {
118 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
119 		{ST_Q_FORCE_BLKSIZE, 512, QIC_24},	/* minor 4-7 */
120 		{ST_Q_FORCE_BLKSIZE, 0, HALFINCH_1600},	/* minor 8-11 */
121 		{ST_Q_FORCE_BLKSIZE, 0, HALFINCH_6250}	/* minor 12-15 */
122 	}}},
123 	{{T_SEQUENTIAL, T_REMOV,
124 	 "TANDBERG", " TDC 3600       ", ""},     {0, 12, {
125 		{0, 0, 0},				/* minor 0-3 */
126 		{ST_Q_FORCE_BLKSIZE, 0, QIC_525},	/* minor 4-7 */
127 		{0, 0, QIC_150},			/* minor 8-11 */
128 		{0, 0, QIC_120}				/* minor 12-15 */
129 	}}},
130  	{{T_SEQUENTIAL, T_REMOV,
131  	 "TANDBERG", " TDC 3800       ", ""},     {0, 0, {
132 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
133 		{0, 0, QIC_525},			/* minor 4-7 */
134 		{0, 0, QIC_150},			/* minor 8-11 */
135 		{0, 0, QIC_120}				/* minor 12-15 */
136 	}}},
137 	/*
138 	 * At least -005 and -007 need this.  I'll assume they all do unless I
139 	 * hear otherwise.  - mycroft, 31MAR1994
140 	 */
141 	{{T_SEQUENTIAL, T_REMOV,
142 	 "ARCHIVE ", "VIPER 2525 25462", ""},     {0, 0, {
143 		{ST_Q_SENSE_HELP, 0, 0},		/* minor 0-3 */
144 		{ST_Q_SENSE_HELP, 0, QIC_525},		/* minor 4-7 */
145 		{0, 0, QIC_150},			/* minor 8-11 */
146 		{0, 0, QIC_120}				/* minor 12-15 */
147 	}}},
148 	/*
149 	 * One user reports that this works for his tape drive.  It probably
150 	 * needs more work.  - mycroft, 09APR1994
151 	 */
152 	{{T_SEQUENTIAL, T_REMOV,
153 	 "SANKYO  ", "CP525           ", ""},    {0, 0, {
154 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
155 		{ST_Q_FORCE_BLKSIZE, 512, QIC_525},	/* minor 4-7 */
156 		{0, 0, QIC_150},			/* minor 8-11 */
157 		{0, 0, QIC_120}				/* minor 12-15 */
158 	}}},
159 	{{T_SEQUENTIAL, T_REMOV,
160 	 "ANRITSU ", "DMT780          ", ""},     {0, 0, {
161 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
162 		{ST_Q_FORCE_BLKSIZE, 512, QIC_525},	/* minor 4-7 */
163 		{0, 0, QIC_150},			/* minor 8-11 */
164 		{0, 0, QIC_120}				/* minor 12-15 */
165 	}}},
166 	{{T_SEQUENTIAL, T_REMOV,
167 	 "ARCHIVE ", "VIPER 150  21247", ""},     {0, 12, {
168 		{0, 0, 0},				/* minor 0-3 */
169 		{0, 0, QIC_150},			/* minor 4-7 */
170 		{0, 0, QIC_120},			/* minor 8-11 */
171 		{0, 0, QIC_24}				/* minor 12-15 */
172 	}}},
173 	{{T_SEQUENTIAL, T_REMOV,
174 	 "WANGTEK ", "5099ES SCSI", ""},          {0, 0, {
175 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
176 		{0, 0, QIC_11},				/* minor 4-7 */
177 		{0, 0, QIC_24},				/* minor 8-11 */
178 		{0, 0, QIC_24}				/* minor 12-15 */
179 	}}},
180 	{{T_SEQUENTIAL, T_REMOV,
181 	 "WANGTEK ", "5150ES SCSI", ""},          {0, 0, {
182 		{ST_Q_FORCE_BLKSIZE, 512, 0},		/* minor 0-3 */
183 		{0, 0, QIC_24},				/* minor 4-7 */
184 		{0, 0, QIC_120},			/* minor 8-11 */
185 		{0, 0, QIC_150}				/* minor 12-15 */
186 	}}},
187 	{{T_SEQUENTIAL, T_REMOV,
188 	 "WANGTEK ", "5525ES SCSI REV7", ""},     {0, 0, {
189 		{0, 0, 0},				/* minor 0-3 */
190 		{ST_Q_BLKSIZE, 0, QIC_525},		/* minor 4-7 */
191 		{0, 0, QIC_150},			/* minor 8-11 */
192 		{0, 0, QIC_120}				/* minor 12-15 */
193 	}}},
194 	{{T_SEQUENTIAL, T_REMOV,
195 	 "WangDAT ", "Model 1300      ", ""},     {0, 0, {
196 		{0, 0, 0},				/* minor 0-3 */
197 		{ST_Q_FORCE_BLKSIZE, 512, DDS},		/* minor 4-7 */
198 		{ST_Q_FORCE_BLKSIZE, 1024, DDS},	/* minor 8-11 */
199 		{ST_Q_FORCE_BLKSIZE, 0, DDS}		/* minor 12-15 */
200 	}}},
201 	{{T_SEQUENTIAL, T_REMOV,
202 	 "EXABYTE ", "EXB-8200        ", "263H"}, {0, 5, {
203 		{0, 0, 0},				/* minor 0-3 */
204 		{0, 0, 0},				/* minor 4-7 */
205 		{0, 0, 0},				/* minor 8-11 */
206 		{0, 0, 0}				/* minor 12-15 */
207 	}}},
208 	{{T_SEQUENTIAL, T_REMOV,
209 	 "HP      ", "T4000s          ", ""},     {ST_Q_UNIMODAL, 0, {
210 		{0, 0, QIC_3095},			/* minor 0-3 */
211 		{0, 0, QIC_3095},			/* minor 4-7 */
212 		{0, 0, QIC_3095},			/* minor 8-11 */
213 		{0, 0, QIC_3095},			/* minor 12-15 */
214 	}}},
215 #if 0
216 	{{T_SEQUENTIAL, T_REMOV,
217 	 "EXABYTE ", "EXB-8200        ", ""},     {0, 12, {
218 		{0, 0, 0},				/* minor 0-3 */
219 		{0, 0, 0},				/* minor 4-7 */
220 		{0, 0, 0},				/* minor 8-11 */
221 		{0, 0, 0}				/* minor 12-15 */
222 	}}},
223 #endif
224 };
225 
226 #define NOEJECT 0
227 #define EJECT 1
228 
229 struct st_softc {
230 	struct device sc_dev;
231 /*--------------------present operating parameters, flags etc.----------------*/
232 	int flags;		/* see below                          */
233 	u_int quirks;		/* quirks for the open mode           */
234 	int blksize;		/* blksize we are using                */
235 	u_int8_t density;	/* present density                    */
236 	u_int page_0_size;	/* size of page 0 data		      */
237 	u_int last_dsty;	/* last density opened               */
238 /*--------------------device/scsi parameters----------------------------------*/
239 	struct scsi_link *sc_link;	/* our link to the adpter etc.        */
240 /*--------------------parameters reported by the device ----------------------*/
241 	int blkmin;		/* min blk size                       */
242 	int blkmax;		/* max blk size                       */
243 	struct quirkdata *quirkdata;	/* if we have a rogue entry           */
244 /*--------------------parameters reported by the device for this media--------*/
245 	u_long numblks;		/* nominal blocks capacity            */
246 	int media_blksize;	/* 0 if not ST_FIXEDBLOCKS            */
247 	u_int8_t media_density;	/* this is what it said when asked    */
248 /*--------------------quirks for the whole drive------------------------------*/
249 	u_int drive_quirks;	/* quirks of this drive               */
250 /*--------------------How we should set up when opening each minor device----*/
251 	struct modes modes[4];	/* plus more for each mode            */
252 	u_int8_t  modeflags[4];	/* flags for the modes                */
253 #define DENSITY_SET_BY_USER	0x01
254 #define DENSITY_SET_BY_QUIRK	0x02
255 #define BLKSIZE_SET_BY_USER	0x04
256 #define BLKSIZE_SET_BY_QUIRK	0x08
257 /*--------------------storage for sense data returned by the drive------------*/
258 	u_char sense_data[MAX_PAGE_0_SIZE];	/*
259 						 * additional sense data needed
260 						 * for mode sense/select.
261 						 */
262 	struct buf buf_queue;		/* the queue of pending IO operations */
263 };
264 
265 
266 #ifdef __BROKEN_INDIRECT_CONFIG
267 int	stmatch __P((struct device *, void *, void *));
268 #else
269 int	stmatch __P((struct device *, struct cfdata *, void *));
270 #endif
271 void	stattach __P((struct device *, struct device *, void *));
272 void	st_identify_drive __P((struct st_softc *, struct scsi_inquiry_data *));
273 void	st_loadquirks __P((struct st_softc *));
274 int	st_mount_tape __P((dev_t, int));
275 void	st_unmount __P((struct st_softc *, boolean));
276 int	st_decide_mode __P((struct st_softc *, boolean));
277 void	ststart __P((void *));
278 int	st_read __P((struct st_softc *, char *, int, int));
279 int	st_read_block_limits __P((struct st_softc *, int));
280 int	st_mode_sense __P((struct st_softc *, int));
281 int	st_mode_select __P((struct st_softc *, int));
282 int	st_space __P((struct st_softc *, int, u_int, int));
283 int	st_write_filemarks __P((struct st_softc *, int, int));
284 int	st_check_eod __P((struct st_softc *, boolean, int *, int));
285 int	st_load __P((struct st_softc *, u_int, int));
286 int	st_rewind __P((struct st_softc *, u_int, int));
287 int	st_interpret_sense __P((struct scsi_xfer *));
288 int	st_touch_tape __P((struct st_softc *));
289 int	st_erase __P((struct st_softc *, int full, int flags));
290 
291 struct cfattach st_ca = {
292 	sizeof(struct st_softc), stmatch, stattach
293 };
294 
295 struct cfdriver st_cd = {
296 	NULL, "st", DV_TAPE
297 };
298 
299 struct scsi_device st_switch = {
300 	st_interpret_sense,
301 	ststart,
302 	NULL,
303 	NULL,
304 };
305 
306 #define	ST_INFO_VALID	0x0001
307 #define	ST_BLOCK_SET	0x0002	/* block size, mode set by ioctl      */
308 #define	ST_WRITTEN	0x0004	/* data have been written, EOD needed */
309 #define	ST_FIXEDBLOCKS	0x0008
310 #define	ST_AT_FILEMARK	0x0010
311 #define	ST_EIO_PENDING	0x0020	/* we couldn't report it then (had data) */
312 #define	ST_NEW_MOUNT	0x0040	/* still need to decide mode              */
313 #define	ST_READONLY	0x0080	/* st_mode_sense says write protected */
314 #define	ST_FM_WRITTEN	0x0100	/*
315 				 * EOF file mark written  -- used with
316 				 * ~ST_WRITTEN to indicate that multiple file
317 				 * marks have been written
318 				 */
319 #define	ST_BLANK_READ	0x0200	/* BLANK CHECK encountered already */
320 #define	ST_2FM_AT_EOD	0x0400	/* write 2 file marks at EOD */
321 #define	ST_MOUNTED	0x0800	/* Device is presently mounted */
322 #define	ST_DONTBUFFER	0x1000	/* Disable buffering/caching */
323 
324 #define	ST_PER_ACTION	(ST_AT_FILEMARK | ST_EIO_PENDING | ST_BLANK_READ)
325 #define	ST_PER_MOUNT	(ST_INFO_VALID | ST_BLOCK_SET | ST_WRITTEN | \
326 			 ST_FIXEDBLOCKS | ST_READONLY | ST_FM_WRITTEN | \
327 			 ST_2FM_AT_EOD | ST_PER_ACTION)
328 
329 struct scsi_inquiry_pattern st_patterns[] = {
330 	{T_SEQUENTIAL, T_REMOV,
331 	 "",         "",                 ""},
332 };
333 
334 int
335 stmatch(parent, match, aux)
336 	struct device *parent;
337 #ifdef __BROKEN_INDIRECT_CONFIG
338 	void *match;
339 #else
340 	struct cfdata *match;
341 #endif
342 	void *aux;
343 {
344 	struct scsibus_attach_args *sa = aux;
345 	int priority;
346 
347 	(void)scsi_inqmatch(sa->sa_inqbuf,
348 	    (caddr_t)st_patterns, sizeof(st_patterns)/sizeof(st_patterns[0]),
349 	    sizeof(st_patterns[0]), &priority);
350 	return (priority);
351 }
352 
353 /*
354  * The routine called by the low level scsi routine when it discovers
355  * A device suitable for this driver
356  */
357 void
358 stattach(parent, self, aux)
359 	struct device *parent, *self;
360 	void *aux;
361 {
362 	struct st_softc *st = (void *)self;
363 	struct scsibus_attach_args *sa = aux;
364 	struct scsi_link *sc_link = sa->sa_sc_link;
365 
366 	SC_DEBUG(sc_link, SDEV_DB2, ("stattach: "));
367 
368 	/*
369 	 * Store information needed to contact our base driver
370 	 */
371 	st->sc_link = sc_link;
372 	sc_link->device = &st_switch;
373 	sc_link->device_softc = st;
374 	sc_link->openings = 1;
375 
376 	/*
377 	 * Check if the drive is a known criminal and take
378 	 * Any steps needed to bring it into line
379 	 */
380 	st_identify_drive(st, sa->sa_inqbuf);
381 
382 	/*
383 	 * Use the subdriver to request information regarding
384 	 * the drive. We cannot use interrupts yet, so the
385 	 * request must specify this.
386 	 */
387 	printf("\n");
388 	printf("%s: %s", st->sc_dev.dv_xname, st->quirkdata ? "rogue, " : "");
389 	if (scsi_test_unit_ready(sc_link,
390 	    SCSI_AUTOCONF | SCSI_SILENT | SCSI_IGNORE_MEDIA_CHANGE) ||
391 	    st_mode_sense(st,
392 	    SCSI_AUTOCONF | SCSI_SILENT | SCSI_IGNORE_MEDIA_CHANGE))
393 		printf("drive empty\n");
394 	else {
395 		printf("density code 0x%x, ", st->media_density);
396 		if (st->media_blksize > 0)
397 			printf("%d-byte", st->media_blksize);
398 		else
399 			printf("variable");
400 		printf(" blocks, write-%s\n",
401 		    (st->flags & ST_READONLY) ? "protected" : "enabled");
402 	}
403 
404 	/*
405 	 * Set up the buf queue for this device
406 	 */
407 	st->buf_queue.b_active = 0;
408 	st->buf_queue.b_actf = 0;
409 	st->buf_queue.b_actb = &st->buf_queue.b_actf;
410 }
411 
412 /*
413  * Use the inquiry routine in 'scsi_base' to get drive info so we can
414  * Further tailor our behaviour.
415  */
416 void
417 st_identify_drive(st, inqbuf)
418 	struct st_softc *st;
419 	struct scsi_inquiry_data *inqbuf;
420 {
421 	struct st_quirk_inquiry_pattern *finger;
422 	int priority;
423 
424 	finger = (struct st_quirk_inquiry_pattern *)scsi_inqmatch(inqbuf,
425 	    (caddr_t)st_quirk_patterns,
426 	    sizeof(st_quirk_patterns)/sizeof(st_quirk_patterns[0]),
427 	    sizeof(st_quirk_patterns[0]), &priority);
428 	if (priority != 0) {
429 		st->quirkdata = &finger->quirkdata;
430 		st->drive_quirks = finger->quirkdata.quirks;
431 		st->quirks = finger->quirkdata.quirks;	/* start value */
432 		st->page_0_size = finger->quirkdata.page_0_size;
433 		st_loadquirks(st);
434 	}
435 }
436 
437 /*
438  * initialise the subdevices to the default (QUIRK) state.
439  * this will remove any setting made by the system operator or previous
440  * operations.
441  */
442 void
443 st_loadquirks(st)
444 	struct st_softc *st;
445 {
446 	int i;
447 	struct	modes *mode;
448 	struct	modes *mode2;
449 
450 	mode = st->quirkdata->modes;
451 	mode2 = st->modes;
452 	for (i = 0; i < 4; i++) {
453 		bzero(mode2, sizeof(struct modes));
454 		st->modeflags[i] &= ~(BLKSIZE_SET_BY_QUIRK |
455 		    DENSITY_SET_BY_QUIRK | BLKSIZE_SET_BY_USER |
456 		    DENSITY_SET_BY_USER);
457 		if ((mode->quirks | st->drive_quirks) & ST_Q_FORCE_BLKSIZE) {
458 			mode2->blksize = mode->blksize;
459 			st->modeflags[i] |= BLKSIZE_SET_BY_QUIRK;
460 		}
461 		if (mode->density) {
462 			mode2->density = mode->density;
463 			st->modeflags[i] |= DENSITY_SET_BY_QUIRK;
464 		}
465 		mode++;
466 		mode2++;
467 	}
468 }
469 
470 /*
471  * open the device.
472  */
473 int
474 stopen(dev, flags, mode, p)
475 	dev_t dev;
476 	int flags;
477 	int mode;
478 	struct proc *p;
479 {
480 	int unit;
481 	u_int stmode, dsty;
482 	int error = 0;
483 	struct st_softc *st;
484 	struct scsi_link *sc_link;
485 
486 	unit = STUNIT(dev);
487 	if (unit >= st_cd.cd_ndevs)
488 		return ENXIO;
489 	st = st_cd.cd_devs[unit];
490 	if (!st)
491 		return ENXIO;
492 
493 	stmode = STMODE(dev);
494 	dsty = STDSTY(dev);
495 	sc_link = st->sc_link;
496 
497 	SC_DEBUG(sc_link, SDEV_DB1, ("open: dev=0x%x (unit %d (of %d))\n", dev,
498 	    unit, st_cd.cd_ndevs));
499 
500 	/*
501 	 * Only allow one at a time
502 	 */
503 	if (sc_link->flags & SDEV_OPEN) {
504 		printf("%s: already open\n", st->sc_dev.dv_xname);
505 		return EBUSY;
506 	}
507 
508 	/*
509 	 * Catch any unit attention errors.
510 	 */
511 	error = scsi_test_unit_ready(sc_link,
512 				     SCSI_IGNORE_MEDIA_CHANGE |
513 				     (stmode == CTLMODE ?
514 					SCSI_IGNORE_NOT_READY : 0));
515 	if (error)
516 		goto bad;
517 
518 	sc_link->flags |= SDEV_OPEN;	/* unit attn are now errors */
519 
520 	/*
521 	 * If the mode is 3 (e.g. minor = 3,7,11,15)
522 	 * then the device has been opened to set defaults
523 	 * This mode does NOT ALLOW I/O, only ioctls
524 	 */
525 	if (stmode == CTLMODE)
526 		return 0;
527 
528 	/*
529 	 * if it's a different mode, or if the media has been
530 	 * invalidated, unmount the tape from the previous
531 	 * session but continue with open processing
532 	 */
533 	if (st->last_dsty != dsty || !(sc_link->flags & SDEV_MEDIA_LOADED))
534 		st_unmount(st, NOEJECT);
535 
536 	/*
537 	 * If we are not mounted, then we should start a new
538 	 * mount session.
539 	 */
540 	if (!(st->flags & ST_MOUNTED)) {
541 		st_mount_tape(dev, flags);
542 		st->last_dsty = dsty;
543 	}
544 
545 	/*
546 	 * Make sure that a tape opened in write-only mode will have
547 	 * file marks written on it when closed, even if not written to.
548 	 * This is for SUN compatibility
549 	 */
550 	if ((flags & O_ACCMODE) == FWRITE)
551 		st->flags |= ST_WRITTEN;
552 
553 	SC_DEBUG(sc_link, SDEV_DB2, ("open complete\n"));
554 	return 0;
555 
556 bad:
557 	st_unmount(st, NOEJECT);
558 	sc_link->flags &= ~SDEV_OPEN;
559 	return error;
560 }
561 
562 /*
563  * close the device.. only called if we are the LAST
564  * occurence of an open device
565  */
566 int
567 stclose(dev, flags, mode, p)
568 	dev_t dev;
569 	int flags;
570 	int mode;
571 	struct proc *p;
572 {
573 	struct st_softc *st = st_cd.cd_devs[STUNIT(dev)];
574 
575 	SC_DEBUG(st->sc_link, SDEV_DB1, ("closing\n"));
576 	if ((st->flags & (ST_WRITTEN | ST_FM_WRITTEN)) == ST_WRITTEN)
577 		st_write_filemarks(st, 1, 0);
578 	switch (STMODE(dev)) {
579 	case 0:
580 	case 3:		/* for now */
581 		st_unmount(st, NOEJECT);
582 		break;
583 	case 1:
584 		/* leave mounted unless media seems to have been removed */
585 		if (!(st->sc_link->flags & SDEV_MEDIA_LOADED))
586 			st_unmount(st, NOEJECT);
587 		break;
588 	case 2:
589 		st_unmount(st, EJECT);
590 		break;
591 	}
592 	st->sc_link->flags &= ~SDEV_OPEN;
593 
594 	return 0;
595 }
596 
597 /*
598  * Start a new mount session.
599  * Copy in all the default parameters from the selected device mode.
600  * and try guess any that seem to be defaulted.
601  */
602 int
603 st_mount_tape(dev, flags)
604 	dev_t dev;
605 	int flags;
606 {
607 	int unit;
608 	u_int mode, dsty;
609 	struct st_softc *st;
610 	struct scsi_link *sc_link;
611 	int error = 0;
612 
613 	unit = STUNIT(dev);
614 	mode = STMODE(dev);
615 	dsty = STDSTY(dev);
616 	st = st_cd.cd_devs[unit];
617 	sc_link = st->sc_link;
618 
619 	if (st->flags & ST_MOUNTED)
620 		return 0;
621 
622 	SC_DEBUG(sc_link, SDEV_DB1, ("mounting\n "));
623 	st->flags |= ST_NEW_MOUNT;
624 	st->quirks = st->drive_quirks | st->modes[dsty].quirks;
625 	/*
626 	 * If the media is new, then make sure we give it a chance to
627 	 * to do a 'load' instruction.  (We assume it is new.)
628 	 */
629 	if ((error = st_load(st, LD_LOAD, 0)) != 0)
630 		return error;
631 	/*
632 	 * Throw another dummy instruction to catch
633 	 * 'Unit attention' errors. Some drives appear to give
634 	 * these after doing a Load instruction.
635 	 * (noteably some DAT drives)
636 	 */
637 	scsi_test_unit_ready(sc_link, SCSI_SILENT);	/* XXX */
638 
639 	/*
640 	 * Some devices can't tell you much until they have been
641 	 * asked to look at the media. This quirk does this.
642 	 */
643 	if (st->quirks & ST_Q_SENSE_HELP)
644 		if ((error = st_touch_tape(st)) != 0)
645 			return error;
646 	/*
647 	 * Load the physical device parameters
648 	 * loads: blkmin, blkmax
649 	 */
650 	if ((error = st_read_block_limits(st, 0)) != 0)
651 		return error;
652 	/*
653 	 * Load the media dependent parameters
654 	 * includes: media_blksize,media_density,numblks
655 	 * As we have a tape in, it should be reflected here.
656 	 * If not you may need the "quirk" above.
657 	 */
658 	if ((error = st_mode_sense(st, 0)) != 0)
659 		return error;
660 	/*
661 	 * If we have gained a permanent density from somewhere,
662 	 * then use it in preference to the one supplied by
663 	 * default by the driver.
664 	 */
665 	if (st->modeflags[dsty] & (DENSITY_SET_BY_QUIRK | DENSITY_SET_BY_USER))
666 		st->density = st->modes[dsty].density;
667 	else
668 		st->density = st->media_density;
669 	/*
670 	 * If we have gained a permanent blocksize
671 	 * then use it in preference to the one supplied by
672 	 * default by the driver.
673 	 */
674 	st->flags &= ~ST_FIXEDBLOCKS;
675 	if (st->modeflags[dsty] & (BLKSIZE_SET_BY_QUIRK | BLKSIZE_SET_BY_USER)) {
676 		st->blksize = st->modes[dsty].blksize;
677 		if (st->blksize)
678 			st->flags |= ST_FIXEDBLOCKS;
679 	} else {
680 		if ((error = st_decide_mode(st, FALSE)) != 0)
681 			return error;
682 	}
683 	if ((error = st_mode_select(st, 0)) != 0) {
684 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
685 		return error;
686 	}
687 	scsi_prevent(sc_link, PR_PREVENT,
688 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
689 	st->flags &= ~ST_NEW_MOUNT;
690 	st->flags |= ST_MOUNTED;
691 	sc_link->flags |= SDEV_MEDIA_LOADED;	/* move earlier? */
692 
693 	return 0;
694 }
695 
696 /*
697  * End the present mount session.
698  * Rewind, and optionally eject the tape.
699  * Reset various flags to indicate that all new
700  * operations require another mount operation
701  */
702 void
703 st_unmount(st, eject)
704 	struct st_softc *st;
705 	boolean eject;
706 {
707 	struct scsi_link *sc_link = st->sc_link;
708 	int nmarks;
709 
710 	if (!(st->flags & ST_MOUNTED))
711 		return;
712 	SC_DEBUG(sc_link, SDEV_DB1, ("unmounting\n"));
713 	st_check_eod(st, FALSE, &nmarks, SCSI_IGNORE_NOT_READY);
714 	st_rewind(st, 0, SCSI_IGNORE_NOT_READY);
715 	scsi_prevent(sc_link, PR_ALLOW,
716 	    SCSI_IGNORE_ILLEGAL_REQUEST | SCSI_IGNORE_NOT_READY);
717 	if (eject)
718 		st_load(st, LD_UNLOAD, SCSI_IGNORE_NOT_READY);
719 	st->flags &= ~(ST_MOUNTED | ST_NEW_MOUNT);
720 	sc_link->flags &= ~SDEV_MEDIA_LOADED;
721 }
722 
723 /*
724  * Given all we know about the device, media, mode, 'quirks' and
725  * initial operation, make a decision as to how we should be set
726  * to run (regarding blocking and EOD marks)
727  */
728 int
729 st_decide_mode(st, first_read)
730 	struct st_softc *st;
731 	boolean	first_read;
732 {
733 #ifdef SCSIDEBUG
734 	struct scsi_link *sc_link = st->sc_link;
735 #endif
736 
737 	SC_DEBUG(sc_link, SDEV_DB2, ("starting block mode decision\n"));
738 
739 	/*
740 	 * If the drive can only handle fixed-length blocks and only at
741 	 * one size, perhaps we should just do that.
742 	 */
743 	if (st->blkmin && (st->blkmin == st->blkmax)) {
744 		st->flags |= ST_FIXEDBLOCKS;
745 		st->blksize = st->blkmin;
746 		SC_DEBUG(sc_link, SDEV_DB3,
747 		    ("blkmin == blkmax of %d\n", st->blkmin));
748 		goto done;
749 	}
750 	/*
751 	 * If the tape density mandates (or even suggests) use of fixed
752 	 * or variable-length blocks, comply.
753 	 */
754 	switch (st->density) {
755 	case HALFINCH_800:
756 	case HALFINCH_1600:
757 	case HALFINCH_6250:
758 	case DDS:
759 		st->flags &= ~ST_FIXEDBLOCKS;
760 		st->blksize = 0;
761 		SC_DEBUG(sc_link, SDEV_DB3, ("density specified variable\n"));
762 		goto done;
763 	case QIC_11:
764 	case QIC_24:
765 	case QIC_120:
766 	case QIC_150:
767 	case QIC_525:
768 	case QIC_1320:
769 		st->flags |= ST_FIXEDBLOCKS;
770 		if (st->media_blksize > 0)
771 			st->blksize = st->media_blksize;
772 		else
773 			st->blksize = DEF_FIXED_BSIZE;
774 		SC_DEBUG(sc_link, SDEV_DB3, ("density specified fixed\n"));
775 		goto done;
776 	}
777 	/*
778 	 * If we're about to read the tape, perhaps we should choose
779 	 * fixed or variable-length blocks and block size according to
780 	 * what the drive found on the tape.
781 	 */
782 	if (first_read &&
783 	    (!(st->quirks & ST_Q_BLKSIZE) || (st->media_blksize == 0) ||
784 	    (st->media_blksize == DEF_FIXED_BSIZE) ||
785 	    (st->media_blksize == 1024))) {
786 		if (st->media_blksize > 0)
787 			st->flags |= ST_FIXEDBLOCKS;
788 		else
789 			st->flags &= ~ST_FIXEDBLOCKS;
790 		st->blksize = st->media_blksize;
791 		SC_DEBUG(sc_link, SDEV_DB3,
792 		    ("Used media_blksize of %d\n", st->media_blksize));
793 		goto done;
794 	}
795 	/*
796 	 * We're getting no hints from any direction.  Choose variable-
797 	 * length blocks arbitrarily.
798 	 */
799 	st->flags &= ~ST_FIXEDBLOCKS;
800 	st->blksize = 0;
801 	SC_DEBUG(sc_link, SDEV_DB3,
802 	    ("Give up and default to variable mode\n"));
803 
804 done:
805 	/*
806 	 * Decide whether or not to write two file marks to signify end-
807 	 * of-data.  Make the decision as a function of density.  If
808 	 * the decision is not to use a second file mark, the SCSI BLANK
809 	 * CHECK condition code will be recognized as end-of-data when
810 	 * first read.
811 	 * (I think this should be a by-product of fixed/variable..julian)
812 	 */
813 	switch (st->density) {
814 /*      case 8 mm:   What is the SCSI density code for 8 mm, anyway? */
815 	case QIC_11:
816 	case QIC_24:
817 	case QIC_120:
818 	case QIC_150:
819 	case QIC_525:
820 	case QIC_1320:
821 		st->flags &= ~ST_2FM_AT_EOD;
822 		break;
823 	default:
824 		st->flags |= ST_2FM_AT_EOD;
825 	}
826 	return 0;
827 }
828 
829 /*
830  * Actually translate the requested transfer into
831  * one the physical driver can understand
832  * The transfer is described by a buf and will include
833  * only one physical transfer.
834  */
835 void
836 ststrategy(bp)
837 	struct buf *bp;
838 {
839 	struct st_softc *st = st_cd.cd_devs[STUNIT(bp->b_dev)];
840 	struct buf *dp;
841 	int s;
842 
843 	SC_DEBUG(st->sc_link, SDEV_DB1,
844 	    ("ststrategy %ld bytes @ blk %d\n", bp->b_bcount, bp->b_blkno));
845 	/*
846 	 * If it's a null transfer, return immediatly
847 	 */
848 	if (bp->b_bcount == 0)
849 		goto done;
850 	/*
851 	 * Odd sized request on fixed drives are verboten
852 	 */
853 	if (st->flags & ST_FIXEDBLOCKS) {
854 		if (bp->b_bcount % st->blksize) {
855 			printf("%s: bad request, must be multiple of %d\n",
856 			    st->sc_dev.dv_xname, st->blksize);
857 			bp->b_error = EIO;
858 			goto bad;
859 		}
860 	}
861 	/*
862 	 * as are out-of-range requests on variable drives.
863 	 */
864 	else if (bp->b_bcount < st->blkmin ||
865 		 (st->blkmax && bp->b_bcount > st->blkmax)) {
866 		printf("%s: bad request, must be between %d and %d\n",
867 		    st->sc_dev.dv_xname, st->blkmin, st->blkmax);
868 		bp->b_error = EIO;
869 		goto bad;
870 	}
871 	s = splbio();
872 
873 	/*
874 	 * Place it in the queue of activities for this tape
875 	 * at the end (a bit silly because we only have on user..
876 	 * (but it could fork()))
877 	 */
878 	dp = &st->buf_queue;
879 	bp->b_actf = NULL;
880 	bp->b_actb = dp->b_actb;
881 	*dp->b_actb = bp;
882 	dp->b_actb = &bp->b_actf;
883 
884 	/*
885 	 * Tell the device to get going on the transfer if it's
886 	 * not doing anything, otherwise just wait for completion
887 	 * (All a bit silly if we're only allowing 1 open but..)
888 	 */
889 	ststart(st);
890 
891 	splx(s);
892 	return;
893 bad:
894 	bp->b_flags |= B_ERROR;
895 done:
896 	/*
897 	 * Correctly set the buf to indicate a completed xfer
898 	 */
899 	bp->b_resid = bp->b_bcount;
900 	biodone(bp);
901 	return;
902 }
903 
904 /*
905  * ststart looks to see if there is a buf waiting for the device
906  * and that the device is not already busy. If both are true,
907  * It dequeues the buf and creates a scsi command to perform the
908  * transfer required. The transfer request will call scsi_done
909  * on completion, which will in turn call this routine again
910  * so that the next queued transfer is performed.
911  * The bufs are queued by the strategy routine (ststrategy)
912  *
913  * This routine is also called after other non-queued requests
914  * have been made of the scsi driver, to ensure that the queue
915  * continues to be drained.
916  * ststart() is called at splbio
917  */
918 void
919 ststart(v)
920 	void *v;
921 {
922 	struct st_softc *st = v;
923 	struct scsi_link *sc_link = st->sc_link;
924 	register struct buf *bp, *dp;
925 	struct scsi_rw_tape cmd;
926 	int flags;
927 
928 	SC_DEBUG(sc_link, SDEV_DB2, ("ststart "));
929 	/*
930 	 * See if there is a buf to do and we are not already
931 	 * doing one
932 	 */
933 	while (sc_link->openings > 0) {
934 		/* if a special awaits, let it proceed first */
935 		if (sc_link->flags & SDEV_WAITING) {
936 			sc_link->flags &= ~SDEV_WAITING;
937 			wakeup((caddr_t)sc_link);
938 			return;
939 		}
940 
941 		dp = &st->buf_queue;
942 		if ((bp = dp->b_actf) == NULL)
943 			return;
944 		if ((dp = bp->b_actf) != NULL)
945 			dp->b_actb = bp->b_actb;
946 		else
947 			st->buf_queue.b_actb = bp->b_actb;
948 		*bp->b_actb = dp;
949 
950 		/*
951 		 * if the device has been unmounted byt the user
952 		 * then throw away all requests until done
953 		 */
954 		if (!(st->flags & ST_MOUNTED) ||
955 		    !(sc_link->flags & SDEV_MEDIA_LOADED)) {
956 			/* make sure that one implies the other.. */
957 			sc_link->flags &= ~SDEV_MEDIA_LOADED;
958 			bp->b_flags |= B_ERROR;
959 			bp->b_error = EIO;
960 			bp->b_resid = bp->b_bcount;
961 			biodone(bp);
962 			continue;
963 		}
964 		/*
965 		 * only FIXEDBLOCK devices have pending operations
966 		 */
967 		if (st->flags & ST_FIXEDBLOCKS) {
968 			/*
969 			 * If we are at a filemark but have not reported it yet
970 			 * then we should report it now
971 			 */
972 			if (st->flags & ST_AT_FILEMARK) {
973 				if ((bp->b_flags & B_READ) == B_WRITE) {
974 					/*
975 					 * Handling of ST_AT_FILEMARK in
976 					 * st_space will fill in the right file
977 					 * mark count.
978 					 * Back up over filemark
979 					 */
980 					if (st_space(st, 0, SP_FILEMARKS, 0)) {
981 						bp->b_flags |= B_ERROR;
982 						bp->b_error = EIO;
983 						biodone(bp);
984 						continue;
985 					}
986 				} else {
987 					bp->b_resid = bp->b_bcount;
988 					bp->b_error = 0;
989 					bp->b_flags &= ~B_ERROR;
990 					st->flags &= ~ST_AT_FILEMARK;
991 					biodone(bp);
992 					continue;	/* seek more work */
993 				}
994 			}
995 			/*
996 			 * If we are at EIO (e.g. EOM) but have not reported it
997 			 * yet then we should report it now
998 			 */
999 			if (st->flags & ST_EIO_PENDING) {
1000 				bp->b_resid = bp->b_bcount;
1001 				bp->b_error = EIO;
1002 				bp->b_flags |= B_ERROR;
1003 				st->flags &= ~ST_EIO_PENDING;
1004 				biodone(bp);
1005 				continue;	/* seek more work */
1006 			}
1007 		}
1008 
1009 		/*
1010 		 *  Fill out the scsi command
1011 		 */
1012 		bzero(&cmd, sizeof(cmd));
1013 		if ((bp->b_flags & B_READ) == B_WRITE) {
1014 			cmd.opcode = WRITE;
1015 			st->flags &= ~ST_FM_WRITTEN;
1016 			st->flags |= ST_WRITTEN;
1017 			flags = SCSI_DATA_OUT;
1018 		} else {
1019 			cmd.opcode = READ;
1020 			flags = SCSI_DATA_IN;
1021 		}
1022 
1023 		/*
1024 		 * Handle "fixed-block-mode" tape drives by using the
1025 		 * block count instead of the length.
1026 		 */
1027 		if (st->flags & ST_FIXEDBLOCKS) {
1028 			cmd.byte2 |= SRW_FIXED;
1029 			_lto3b(bp->b_bcount / st->blksize, cmd.len);
1030 		} else
1031 			_lto3b(bp->b_bcount, cmd.len);
1032 
1033 		/*
1034 		 * go ask the adapter to do all this for us
1035 		 */
1036 		if (scsi_scsi_cmd(sc_link, (struct scsi_generic *) &cmd,
1037 		    sizeof(cmd), (u_char *) bp->b_data, bp->b_bcount, 0,
1038 		    100000, bp, flags | SCSI_NOSLEEP))
1039 			printf("%s: not queued\n", st->sc_dev.dv_xname);
1040 	} /* go back and see if we can cram more work in.. */
1041 }
1042 
1043 int
1044 stread(dev, uio, iomode)
1045 	dev_t dev;
1046 	struct uio *uio;
1047 	int iomode;
1048 {
1049 	struct st_softc *st = st_cd.cd_devs[STUNIT(dev)];
1050 
1051 	return (physio(ststrategy, NULL, dev, B_READ,
1052 		       st->sc_link->adapter->scsi_minphys, uio));
1053 }
1054 
1055 int
1056 stwrite(dev, uio, iomode)
1057 	dev_t dev;
1058 	struct uio *uio;
1059 	int iomode;
1060 {
1061 	struct st_softc *st = st_cd.cd_devs[STUNIT(dev)];
1062 
1063 	return (physio(ststrategy, NULL, dev, B_WRITE,
1064 		       st->sc_link->adapter->scsi_minphys, uio));
1065 }
1066 
1067 /*
1068  * Perform special action on behalf of the user;
1069  * knows about the internals of this device
1070  */
1071 int
1072 stioctl(dev, cmd, arg, flag, p)
1073 	dev_t dev;
1074 	u_long cmd;
1075 	caddr_t arg;
1076 	int flag;
1077 	struct proc *p;
1078 {
1079 	int error = 0;
1080 	int unit;
1081 	int number, nmarks, dsty;
1082 	int flags;
1083 	struct st_softc *st;
1084 	int hold_blksize;
1085 	u_int8_t hold_density;
1086 	struct mtop *mt = (struct mtop *) arg;
1087 
1088 	/*
1089 	 * Find the device that the user is talking about
1090 	 */
1091 	flags = 0;		/* give error messages, act on errors etc. */
1092 	unit = STUNIT(dev);
1093 	dsty = STDSTY(dev);
1094 	st = st_cd.cd_devs[unit];
1095 	hold_blksize = st->blksize;
1096 	hold_density = st->density;
1097 
1098 	switch (cmd) {
1099 
1100 	case MTIOCGET: {
1101 		struct mtget *g = (struct mtget *) arg;
1102 
1103 		SC_DEBUG(st->sc_link, SDEV_DB1, ("[ioctl: get status]\n"));
1104 		bzero(g, sizeof(struct mtget));
1105 		g->mt_type = 0x7;	/* Ultrix compat *//*? */
1106 		g->mt_blksiz = st->blksize;
1107 		g->mt_density = st->density;
1108 		g->mt_mblksiz[0] = st->modes[0].blksize;
1109 		g->mt_mblksiz[1] = st->modes[1].blksize;
1110 		g->mt_mblksiz[2] = st->modes[2].blksize;
1111 		g->mt_mblksiz[3] = st->modes[3].blksize;
1112 		g->mt_mdensity[0] = st->modes[0].density;
1113 		g->mt_mdensity[1] = st->modes[1].density;
1114 		g->mt_mdensity[2] = st->modes[2].density;
1115 		g->mt_mdensity[3] = st->modes[3].density;
1116 		break;
1117 	}
1118 	case MTIOCTOP: {
1119 
1120 		SC_DEBUG(st->sc_link, SDEV_DB1,
1121 		    ("[ioctl: op=0x%x count=0x%x]\n", mt->mt_op, mt->mt_count));
1122 
1123 		/* compat: in U*x it is a short */
1124 		number = mt->mt_count;
1125 		switch ((short) (mt->mt_op)) {
1126 		case MTWEOF:	/* write an end-of-file record */
1127 			error = st_write_filemarks(st, number, flags);
1128 			break;
1129 		case MTBSF:	/* backward space file */
1130 			number = -number;
1131 		case MTFSF:	/* forward space file */
1132 			error = st_check_eod(st, FALSE, &nmarks, flags);
1133 			if (!error)
1134 				error = st_space(st, number - nmarks,
1135 				    SP_FILEMARKS, flags);
1136 			break;
1137 		case MTBSR:	/* backward space record */
1138 			number = -number;
1139 		case MTFSR:	/* forward space record */
1140 			error = st_check_eod(st, TRUE, &nmarks, flags);
1141 			if (!error)
1142 				error = st_space(st, number, SP_BLKS, flags);
1143 			break;
1144 		case MTREW:	/* rewind */
1145 			error = st_rewind(st, 0, flags);
1146 			break;
1147 		case MTOFFL:	/* rewind and put the drive offline */
1148 			st_unmount(st, EJECT);
1149 			break;
1150 		case MTNOP:	/* no operation, sets status only */
1151 			break;
1152 		case MTRETEN:	/* retension the tape */
1153 			error = st_load(st, LD_RETENSION, flags);
1154 			if (!error)
1155 				error = st_load(st, LD_LOAD, flags);
1156 			break;
1157 		case MTEOM:	/* forward space to end of media */
1158 			error = st_check_eod(st, FALSE, &nmarks, flags);
1159 			if (!error)
1160 				error = st_space(st, 1, SP_EOM, flags);
1161 			break;
1162 		case MTCACHE:	/* enable controller cache */
1163 			st->flags &= ~ST_DONTBUFFER;
1164 			goto try_new_value;
1165 		case MTNOCACHE:	/* disable controller cache */
1166 			st->flags |= ST_DONTBUFFER;
1167 			goto try_new_value;
1168 		case MTERASE:	/* erase volume */
1169 			error = st_erase(st, number, flags);
1170 			break;
1171 		case MTSETBSIZ:	/* Set block size for device */
1172 #ifdef	NOTYET
1173 			if (!(st->flags & ST_NEW_MOUNT)) {
1174 				uprintf("re-mount tape before changing blocksize");
1175 				error = EINVAL;
1176 				break;
1177 			}
1178 #endif
1179 			if (number == 0) {
1180 				st->flags &= ~ST_FIXEDBLOCKS;
1181 			} else {
1182 				if ((st->blkmin || st->blkmax) &&
1183 				    (number < st->blkmin ||
1184 				    number > st->blkmax)) {
1185 					error = EINVAL;
1186 					break;
1187 				}
1188 				st->flags |= ST_FIXEDBLOCKS;
1189 			}
1190 			st->blksize = number;
1191 			st->flags |= ST_BLOCK_SET;	/*XXX */
1192 			goto try_new_value;
1193 
1194 		case MTSETDNSTY:	/* Set density for device and mode */
1195 			if (number > SCSI_2_MAX_DENSITY_CODE) {
1196 				error = EINVAL;
1197 				break;
1198 			} else
1199 				st->density = number;
1200 			goto try_new_value;
1201 
1202 		default:
1203 			error = EINVAL;
1204 		}
1205 		break;
1206 	}
1207 	case MTIOCIEOT:
1208 	case MTIOCEEOT:
1209 		break;
1210 	default:
1211 		if (STMODE(dev) == CTLMODE)
1212 			error = scsi_do_ioctl(st->sc_link, dev, cmd, arg, flag, p);
1213 		else
1214 			error = ENOTTY;
1215 		break;
1216 	}
1217 	return error;
1218 /*-----------------------------*/
1219 try_new_value:
1220 	/*
1221 	 * Check that the mode being asked for is aggreeable to the
1222 	 * drive. If not, put it back the way it was.
1223 	 */
1224 	if ((error = st_mode_select(st, 0)) != 0) {/* put it back as it was */
1225 		printf("%s: cannot set selected mode\n", st->sc_dev.dv_xname);
1226 		st->density = hold_density;
1227 		st->blksize = hold_blksize;
1228 		if (st->blksize)
1229 			st->flags |= ST_FIXEDBLOCKS;
1230 		else
1231 			st->flags &= ~ST_FIXEDBLOCKS;
1232 		return error;
1233 	}
1234 	/*
1235 	 * As the drive liked it, if we are setting a new default,
1236 	 * set it into the structures as such.
1237 	 *
1238 	 * The means for deciding this are not finalised yet
1239 	 */
1240 	if (STMODE(dev) == 0x03) {
1241 		/* special mode */
1242 		/* XXX */
1243 		switch ((short) (mt->mt_op)) {
1244 		case MTSETBSIZ:
1245 			st->modes[dsty].blksize = st->blksize;
1246 			st->modeflags[dsty] |= BLKSIZE_SET_BY_USER;
1247 			break;
1248 		case MTSETDNSTY:
1249 			st->modes[dsty].density = st->density;
1250 			st->modeflags[dsty] |= DENSITY_SET_BY_USER;
1251 			break;
1252 		}
1253 	}
1254 	return 0;
1255 }
1256 
1257 /*
1258  * Do a synchronous read.
1259  */
1260 int
1261 st_read(st, buf, size, flags)
1262 	struct st_softc *st;
1263 	int size;
1264 	int flags;
1265 	char *buf;
1266 {
1267 	struct scsi_rw_tape cmd;
1268 
1269 	/*
1270 	 * If it's a null transfer, return immediatly
1271 	 */
1272 	if (size == 0)
1273 		return 0;
1274 	bzero(&cmd, sizeof(cmd));
1275 	cmd.opcode = READ;
1276 	if (st->flags & ST_FIXEDBLOCKS) {
1277 		cmd.byte2 |= SRW_FIXED;
1278 		_lto3b(size / (st->blksize ? st->blksize : DEF_FIXED_BSIZE),
1279 		    cmd.len);
1280 	} else
1281 		_lto3b(size, cmd.len);
1282 	return scsi_scsi_cmd(st->sc_link, (struct scsi_generic *) &cmd,
1283 	    sizeof(cmd), (u_char *) buf, size, 0, 100000, NULL,
1284 	    flags | SCSI_DATA_IN);
1285 }
1286 
1287 /*
1288  * Ask the drive what it's min and max blk sizes are.
1289  */
1290 int
1291 st_read_block_limits(st, flags)
1292 	struct st_softc *st;
1293 	int flags;
1294 {
1295 	struct scsi_block_limits cmd;
1296 	struct scsi_block_limits_data block_limits;
1297 	struct scsi_link *sc_link = st->sc_link;
1298 	int error;
1299 
1300 	/*
1301 	 * First check if we have it all loaded
1302 	 */
1303 	if ((sc_link->flags & SDEV_MEDIA_LOADED))
1304 		return 0;
1305 
1306 	/*
1307 	 * do a 'Read Block Limits'
1308 	 */
1309 	bzero(&cmd, sizeof(cmd));
1310 	cmd.opcode = READ_BLOCK_LIMITS;
1311 
1312 	/*
1313 	 * do the command, update the global values
1314 	 */
1315 	error = scsi_scsi_cmd(sc_link, (struct scsi_generic *) &cmd,
1316 			      sizeof(cmd), (u_char *) &block_limits,
1317 			      sizeof(block_limits), ST_RETRIES, 5000,
1318 			      NULL, flags | SCSI_DATA_IN);
1319 	if (error)
1320 		return error;
1321 
1322 	st->blkmin = _2btol(block_limits.min_length);
1323 	st->blkmax = _3btol(block_limits.max_length);
1324 
1325 	SC_DEBUG(sc_link, SDEV_DB3,
1326 	    ("(%d <= blksize <= %d)\n", st->blkmin, st->blkmax));
1327 	return 0;
1328 }
1329 
1330 /*
1331  * Get the scsi driver to send a full inquiry to the
1332  * device and use the results to fill out the global
1333  * parameter structure.
1334  *
1335  * called from:
1336  * attach
1337  * open
1338  * ioctl (to reset original blksize)
1339  */
1340 int
1341 st_mode_sense(st, flags)
1342 	struct st_softc *st;
1343 	int flags;
1344 {
1345 	u_int scsi_sense_len;
1346 	int error;
1347 	struct scsi_mode_sense cmd;
1348 	struct scsi_sense {
1349 		struct scsi_mode_header header;
1350 		struct scsi_blk_desc blk_desc;
1351 		u_char sense_data[MAX_PAGE_0_SIZE];
1352 	} scsi_sense;
1353 	struct scsi_link *sc_link = st->sc_link;
1354 
1355 	scsi_sense_len = 12 + st->page_0_size;
1356 
1357 	/*
1358 	 * Set up a mode sense
1359 	 */
1360 	bzero(&cmd, sizeof(cmd));
1361 	cmd.opcode = MODE_SENSE;
1362 	cmd.length = scsi_sense_len;
1363 
1364 	/*
1365 	 * do the command, but we don't need the results
1366 	 * just print them for our interest's sake, if asked,
1367 	 * or if we need it as a template for the mode select
1368 	 * store it away.
1369 	 */
1370 	error = scsi_scsi_cmd(sc_link, (struct scsi_generic *) &cmd,
1371 			      sizeof(cmd), (u_char *) &scsi_sense,
1372 			      scsi_sense_len, ST_RETRIES, 5000, NULL,
1373 			      flags | SCSI_DATA_IN);
1374 	if (error)
1375 		return error;
1376 
1377 	st->numblks = _3btol(scsi_sense.blk_desc.nblocks);
1378 	st->media_blksize = _3btol(scsi_sense.blk_desc.blklen);
1379 	st->media_density = scsi_sense.blk_desc.density;
1380 	if (scsi_sense.header.dev_spec & SMH_DSP_WRITE_PROT)
1381 		st->flags |= ST_READONLY;
1382 	SC_DEBUG(sc_link, SDEV_DB3,
1383 	    ("density code 0x%x, %d-byte blocks, write-%s, ",
1384 	    st->media_density, st->media_blksize,
1385 	    st->flags & ST_READONLY ? "protected" : "enabled"));
1386 	SC_DEBUG(sc_link, SDEV_DB3,
1387 	    ("%sbuffered\n",
1388 	    scsi_sense.header.dev_spec & SMH_DSP_BUFF_MODE ? "" : "un"));
1389 	if (st->page_0_size)
1390 		bcopy(scsi_sense.sense_data, st->sense_data, st->page_0_size);
1391 	sc_link->flags |= SDEV_MEDIA_LOADED;
1392 	return 0;
1393 }
1394 
1395 /*
1396  * Send a filled out parameter structure to the drive to
1397  * set it into the desire modes etc.
1398  */
1399 int
1400 st_mode_select(st, flags)
1401 	struct st_softc *st;
1402 	int flags;
1403 {
1404 	u_int scsi_select_len;
1405 	struct scsi_mode_select cmd;
1406 	struct scsi_select {
1407 		struct scsi_mode_header header;
1408 		struct scsi_blk_desc blk_desc;
1409 		u_char sense_data[MAX_PAGE_0_SIZE];
1410 	} scsi_select;
1411 	struct scsi_link *sc_link = st->sc_link;
1412 
1413 	scsi_select_len = 12 + st->page_0_size;
1414 
1415 	/*
1416 	 * This quirk deals with drives that have only one valid mode
1417 	 * and think this gives them license to reject all mode selects,
1418 	 * even if the selected mode is the one that is supported.
1419 	 */
1420 	if (st->quirks & ST_Q_UNIMODAL) {
1421 		SC_DEBUG(sc_link, SDEV_DB3,
1422 		    ("not setting density 0x%x blksize 0x%x\n",
1423 		    st->density, st->blksize));
1424 		return 0;
1425 	}
1426 
1427 	/*
1428 	 * Set up for a mode select
1429 	 */
1430 	bzero(&cmd, sizeof(cmd));
1431 	cmd.opcode = MODE_SELECT;
1432 	cmd.length = scsi_select_len;
1433 
1434 	bzero(&scsi_select, scsi_select_len);
1435 	scsi_select.header.blk_desc_len = sizeof(struct scsi_blk_desc);
1436 	scsi_select.header.dev_spec &= ~SMH_DSP_BUFF_MODE;
1437 	scsi_select.blk_desc.density = st->density;
1438 	if (st->flags & ST_DONTBUFFER)
1439 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_OFF;
1440 	else
1441 		scsi_select.header.dev_spec |= SMH_DSP_BUFF_MODE_ON;
1442 	if (st->flags & ST_FIXEDBLOCKS)
1443 		_lto3b(st->blksize, scsi_select.blk_desc.blklen);
1444 	if (st->page_0_size)
1445 		bcopy(st->sense_data, scsi_select.sense_data, st->page_0_size);
1446 
1447 	/*
1448 	 * do the command
1449 	 */
1450 	return scsi_scsi_cmd(sc_link, (struct scsi_generic *) &cmd,
1451 	    sizeof(cmd), (u_char *) &scsi_select, scsi_select_len,
1452 	    ST_RETRIES, 5000, NULL, flags | SCSI_DATA_OUT);
1453 }
1454 
1455 /*
1456  * issue an erase command
1457  */
1458 int
1459 st_erase(st, full, flags)
1460 	struct st_softc *st;
1461 	int full, flags;
1462 {
1463 	struct scsi_erase cmd;
1464 
1465 	/*
1466 	 * Full erase means set LONG bit in erase command, which asks
1467 	 * the drive to erase the entire unit.  Without this bit, we're
1468 	 * asking the drive to write an erase gap.
1469 	 */
1470 	bzero(&cmd, sizeof(cmd));
1471 	cmd.opcode = ERASE;
1472 	if (full)
1473 		cmd.byte2 = SE_IMMED|SE_LONG;
1474 	else
1475 		cmd.byte2 = SE_IMMED;
1476 
1477 	/*
1478 	 * XXX We always do this asynchronously, for now.  How long should
1479 	 * we wait if we want to (eventually) to it synchronously?
1480 	 */
1481 	return (scsi_scsi_cmd(st->sc_link, (struct scsi_generic *)&cmd,
1482 	    sizeof(cmd), 0, 0, ST_RETRIES, 5000, NULL, flags));
1483 }
1484 
1485 /*
1486  * skip N blocks/filemarks/seq filemarks/eom
1487  */
1488 int
1489 st_space(st, number, what, flags)
1490 	struct st_softc *st;
1491 	u_int what;
1492 	int flags;
1493 	int number;
1494 {
1495 	struct scsi_space cmd;
1496 	int error;
1497 
1498 	switch (what) {
1499 	case SP_BLKS:
1500 		if (st->flags & ST_PER_ACTION) {
1501 			if (number > 0) {
1502 				st->flags &= ~ST_PER_ACTION;
1503 				return EIO;
1504 			} else if (number < 0) {
1505 				if (st->flags & ST_AT_FILEMARK) {
1506 					/*
1507 					 * Handling of ST_AT_FILEMARK
1508 					 * in st_space will fill in the
1509 					 * right file mark count.
1510 					 */
1511 					error = st_space(st, 0, SP_FILEMARKS,
1512 						flags);
1513 					if (error)
1514 						return error;
1515 				}
1516 				if (st->flags & ST_BLANK_READ) {
1517 					st->flags &= ~ST_BLANK_READ;
1518 					return EIO;
1519 				}
1520 				st->flags &= ~ST_EIO_PENDING;
1521 			}
1522 		}
1523 		break;
1524 	case SP_FILEMARKS:
1525 		if (st->flags & ST_EIO_PENDING) {
1526 			if (number > 0) {
1527 				/* pretend we just discovered the error */
1528 				st->flags &= ~ST_EIO_PENDING;
1529 				return EIO;
1530 			} else if (number < 0) {
1531 				/* back away from the error */
1532 				st->flags &= ~ST_EIO_PENDING;
1533 			}
1534 		}
1535 		if (st->flags & ST_AT_FILEMARK) {
1536 			st->flags &= ~ST_AT_FILEMARK;
1537 			number--;
1538 		}
1539 		if ((st->flags & ST_BLANK_READ) && (number < 0)) {
1540 			/* back away from unwritten tape */
1541 			st->flags &= ~ST_BLANK_READ;
1542 			number++;	/* XXX dubious */
1543 		}
1544 		break;
1545 	case SP_EOM:
1546 		if (st->flags & ST_EIO_PENDING) {
1547 			/* pretend we just discovered the error */
1548 			st->flags &= ~ST_EIO_PENDING;
1549 			return EIO;
1550 		}
1551 		if (st->flags & ST_AT_FILEMARK)
1552 			st->flags &= ~ST_AT_FILEMARK;
1553 		break;
1554 	}
1555 	if (number == 0)
1556 		return 0;
1557 
1558 	bzero(&cmd, sizeof(cmd));
1559 	cmd.opcode = SPACE;
1560 	cmd.byte2 = what;
1561 	_lto3b(number, cmd.number);
1562 
1563 	return scsi_scsi_cmd(st->sc_link, (struct scsi_generic *) &cmd,
1564 	    sizeof(cmd), 0, 0, 0, 900000, NULL, flags);
1565 }
1566 
1567 /*
1568  * write N filemarks
1569  */
1570 int
1571 st_write_filemarks(st, number, flags)
1572 	struct st_softc *st;
1573 	int flags;
1574 	int number;
1575 {
1576 	struct scsi_write_filemarks cmd;
1577 
1578 	/*
1579 	 * It's hard to write a negative number of file marks.
1580 	 * Don't try.
1581 	 */
1582 	if (number < 0)
1583 		return EINVAL;
1584 	switch (number) {
1585 	case 0:		/* really a command to sync the drive's buffers */
1586 		break;
1587 	case 1:
1588 		if (st->flags & ST_FM_WRITTEN)	/* already have one down */
1589 			st->flags &= ~ST_WRITTEN;
1590 		else
1591 			st->flags |= ST_FM_WRITTEN;
1592 		st->flags &= ~ST_PER_ACTION;
1593 		break;
1594 	default:
1595 		st->flags &= ~(ST_PER_ACTION | ST_WRITTEN);
1596 	}
1597 
1598 	bzero(&cmd, sizeof(cmd));
1599 	cmd.opcode = WRITE_FILEMARKS;
1600 	_lto3b(number, cmd.number);
1601 
1602 	return scsi_scsi_cmd(st->sc_link, (struct scsi_generic *) &cmd,
1603 	    sizeof(cmd), 0, 0, 0, 100000, NULL, flags);
1604 }
1605 
1606 /*
1607  * Make sure the right number of file marks is on tape if the
1608  * tape has been written.  If the position argument is true,
1609  * leave the tape positioned where it was originally.
1610  *
1611  * nmarks returns the number of marks to skip (or, if position
1612  * true, which were skipped) to get back original position.
1613  */
1614 int
1615 st_check_eod(st, position, nmarks, flags)
1616 	struct st_softc *st;
1617 	boolean position;
1618 	int *nmarks;
1619 	int flags;
1620 {
1621 	int error;
1622 
1623 	switch (st->flags & (ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD)) {
1624 	default:
1625 		*nmarks = 0;
1626 		return 0;
1627 	case ST_WRITTEN:
1628 	case ST_WRITTEN | ST_FM_WRITTEN | ST_2FM_AT_EOD:
1629 		*nmarks = 1;
1630 		break;
1631 	case ST_WRITTEN | ST_2FM_AT_EOD:
1632 		*nmarks = 2;
1633 	}
1634 	error = st_write_filemarks(st, *nmarks, flags);
1635 	if (position && !error)
1636 		error = st_space(st, -*nmarks, SP_FILEMARKS, flags);
1637 	return error;
1638 }
1639 
1640 /*
1641  * load/unload/retension
1642  */
1643 int
1644 st_load(st, type, flags)
1645 	struct st_softc *st;
1646 	u_int type;
1647 	int flags;
1648 {
1649 	struct scsi_load cmd;
1650 
1651 	if (type != LD_LOAD) {
1652 		int error;
1653 		int nmarks;
1654 
1655 		error = st_check_eod(st, FALSE, &nmarks, flags);
1656 		if (error)
1657 			return error;
1658 	}
1659 	if (st->quirks & ST_Q_IGNORE_LOADS)
1660 		return 0;
1661 
1662 	bzero(&cmd, sizeof(cmd));
1663 	cmd.opcode = LOAD;
1664 	cmd.how = type;
1665 
1666 	return scsi_scsi_cmd(st->sc_link, (struct scsi_generic *) &cmd,
1667 	    sizeof(cmd), 0, 0, ST_RETRIES, 300000, NULL, flags);
1668 }
1669 
1670 /*
1671  *  Rewind the device
1672  */
1673 int
1674 st_rewind(st, immediate, flags)
1675 	struct st_softc *st;
1676 	u_int immediate;
1677 	int flags;
1678 {
1679 	struct scsi_rewind cmd;
1680 	int error;
1681 	int nmarks;
1682 
1683 	error = st_check_eod(st, FALSE, &nmarks, flags);
1684 	if (error)
1685 		return error;
1686 	st->flags &= ~ST_PER_ACTION;
1687 
1688 	bzero(&cmd, sizeof(cmd));
1689 	cmd.opcode = REWIND;
1690 	cmd.byte2 = immediate;
1691 
1692 	return scsi_scsi_cmd(st->sc_link, (struct scsi_generic *) &cmd,
1693 	    sizeof(cmd), 0, 0, ST_RETRIES, immediate ? 5000 : 300000, NULL,
1694 	    flags);
1695 }
1696 
1697 /*
1698  * Look at the returned sense and act on the error and detirmine
1699  * The unix error number to pass back... (0 = report no error)
1700  *                            (-1 = continue processing)
1701  */
1702 int
1703 st_interpret_sense(xs)
1704 	struct scsi_xfer *xs;
1705 {
1706 	struct scsi_link *sc_link = xs->sc_link;
1707 	struct scsi_sense_data *sense = &xs->sense;
1708 	struct buf *bp = xs->bp;
1709 	struct st_softc *st = sc_link->device_softc;
1710 	u_int8_t key;
1711 	int32_t info;
1712 
1713 	/*
1714 	 * Get the sense fields and work out what code
1715 	 */
1716 	if (sense->error_code & SSD_ERRCODE_VALID)
1717 		info = _4btol(sense->info);
1718 	else
1719 		info = xs->datalen;	/* bad choice if fixed blocks */
1720 	if ((sense->error_code & SSD_ERRCODE) != 0x70)
1721 		return -1;	/* let the generic code handle it */
1722 	if (st->flags & ST_FIXEDBLOCKS) {
1723 		xs->resid = info * st->blksize;
1724 		if (sense->flags & SSD_EOM) {
1725 			st->flags |= ST_EIO_PENDING;
1726 			if (bp)
1727 				bp->b_resid = xs->resid;
1728 		}
1729 		if (sense->flags & SSD_FILEMARK) {
1730 			st->flags |= ST_AT_FILEMARK;
1731 			if (bp)
1732 				bp->b_resid = xs->resid;
1733 		}
1734 		if (sense->flags & SSD_ILI) {
1735 			st->flags |= ST_EIO_PENDING;
1736 			if (bp)
1737 				bp->b_resid = xs->resid;
1738 			if (sense->error_code & SSD_ERRCODE_VALID &&
1739 			    (xs->flags & SCSI_SILENT) == 0)
1740 				printf("%s: block wrong size, %d blocks residual\n",
1741 				    st->sc_dev.dv_xname, info);
1742 
1743 			/*
1744 			 * This quirk code helps the drive read
1745 			 * the first tape block, regardless of
1746 			 * format.  That is required for these
1747 			 * drives to return proper MODE SENSE
1748 			 * information.
1749 			 */
1750 			if ((st->quirks & ST_Q_SENSE_HELP) &&
1751 			    !(sc_link->flags & SDEV_MEDIA_LOADED))
1752 				st->blksize -= 512;
1753 		}
1754 		/*
1755 		 * If no data was tranfered, do it immediatly
1756 		 */
1757 		if (xs->resid >= xs->datalen) {
1758 			if (st->flags & ST_EIO_PENDING)
1759 				return EIO;
1760 			if (st->flags & ST_AT_FILEMARK) {
1761 				if (bp)
1762 					bp->b_resid = xs->resid;
1763 				return 0;
1764 			}
1765 		}
1766 	} else {		/* must be variable mode */
1767 		xs->resid = xs->datalen;	/* to be sure */
1768 		if (sense->flags & SSD_EOM)
1769 			return EIO;
1770 		if (sense->flags & SSD_FILEMARK) {
1771 			if (bp)
1772 				bp->b_resid = bp->b_bcount;
1773 			return 0;
1774 		}
1775 		if (sense->flags & SSD_ILI) {
1776 			if (info < 0) {
1777 				/*
1778 				 * the record was bigger than the read
1779 				 */
1780 				if ((xs->flags & SCSI_SILENT) == 0)
1781 					printf("%s: %d-byte record too big\n",
1782 					    st->sc_dev.dv_xname,
1783 					    xs->datalen - info);
1784 				return EIO;
1785 			}
1786 			xs->resid = info;
1787 			if (bp)
1788 				bp->b_resid = info;
1789 		}
1790 	}
1791 	key = sense->flags & SSD_KEY;
1792 
1793 	if (key == 0x8) {
1794 		/*
1795 		 * This quirk code helps the drive read the
1796 		 * first tape block, regardless of format.  That
1797 		 * is required for these drives to return proper
1798 		 * MODE SENSE information.
1799 		 */
1800 		if ((st->quirks & ST_Q_SENSE_HELP) &&
1801 		    !(sc_link->flags & SDEV_MEDIA_LOADED)) {
1802 			/* still starting */
1803 			st->blksize -= 512;
1804 		} else if (!(st->flags & (ST_2FM_AT_EOD | ST_BLANK_READ))) {
1805 			st->flags |= ST_BLANK_READ;
1806 			xs->resid = xs->datalen;
1807 			if (bp) {
1808 				bp->b_resid = xs->resid;
1809 				/* return an EOF */
1810 			}
1811 			return 0;
1812 		}
1813 	}
1814 	return -1;		/* let the default/generic handler handle it */
1815 }
1816 
1817 /*
1818  * The quirk here is that the drive returns some value to st_mode_sense
1819  * incorrectly until the tape has actually passed by the head.
1820  *
1821  * The method is to set the drive to large fixed-block state (user-specified
1822  * density and 1024-byte blocks), then read and rewind to get it to sense the
1823  * tape.  If that doesn't work, try 512-byte fixed blocks.  If that doesn't
1824  * work, as a last resort, try variable- length blocks.  The result will be
1825  * the ability to do an accurate st_mode_sense.
1826  *
1827  * We know we can do a rewind because we just did a load, which implies rewind.
1828  * Rewind seems preferable to space backward if we have a virgin tape.
1829  *
1830  * The rest of the code for this quirk is in ILI processing and BLANK CHECK
1831  * error processing, both part of st_interpret_sense.
1832  */
1833 int
1834 st_touch_tape(st)
1835 	struct st_softc *st;
1836 {
1837 	char *buf;
1838 	int readsize;
1839 	int error;
1840 
1841 	buf = malloc(1024, M_TEMP, M_NOWAIT);
1842 	if (!buf)
1843 		return ENOMEM;
1844 
1845 	if ((error = st_mode_sense(st, 0)) != 0)
1846 		goto bad;
1847 	st->blksize = 1024;
1848 	do {
1849 		switch (st->blksize) {
1850 		case 512:
1851 		case 1024:
1852 			readsize = st->blksize;
1853 			st->flags |= ST_FIXEDBLOCKS;
1854 			break;
1855 		default:
1856 			readsize = 1;
1857 			st->flags &= ~ST_FIXEDBLOCKS;
1858 		}
1859 		if ((error = st_mode_select(st, 0)) != 0)
1860 			goto bad;
1861 		st_read(st, buf, readsize, SCSI_SILENT);	/* XXX */
1862 		if ((error = st_rewind(st, 0, 0)) != 0) {
1863 bad:			free(buf, M_TEMP);
1864 			return error;
1865 		}
1866 	} while (readsize != 1 && readsize > st->blksize);
1867 
1868 	free(buf, M_TEMP);
1869 	return 0;
1870 }
1871 
1872 int
1873 stdump(dev, blkno, va, size)
1874 	dev_t dev;
1875 	daddr_t blkno;
1876 	caddr_t va;
1877 	size_t size;
1878 {
1879 
1880 	/* Not implemented. */
1881 	return ENXIO;
1882 }
1883