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*/
1 /*
2 * Copyright (C) 1993-1995 Bas Laarhoven.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
7 any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; see the file COPYING. If not, write to
16 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
17
18 $Source: /home/bas/distr/ftape-2.03b/RCS/ftape-rw.c,v $
19 $Author: bas $
20 *
21 $Revision: 1.54 $
22 $Date: 1995/05/27 08:55:27 $
23 $State: Beta $
24 *
25 * This file contains some common code for the segment read and segment
26 * write routines for the QIC-117 floppy-tape driver for Linux.
27 */
28
29 #include <linux/string.h>
30 #include <linux/errno.h>
31 #include <linux/ftape.h>
32
33 #include "tracing.h"
34 #include "ftape-rw.h"
35 #include "fdc-io.h"
36 #include "kernel-interface.h"
37 #include "qic117.h"
38 #include "ftape-io.h"
39 #include "ftape-ctl.h"
40 #include "ftape-read.h"
41 #include "ftape-eof.h"
42 #include "ecc.h"
43 #include "ftape-bsm.h"
44
45 /* Global vars.
46 */
47 volatile enum runner_status_enum runner_status = idle;
48 byte deblock_buffer[(SECTORS_PER_SEGMENT - 3) * SECTOR_SIZE];
49 byte scratch_buffer[(SECTORS_PER_SEGMENT - 3) * SECTOR_SIZE];
50 buffer_struct buffer[NR_BUFFERS];
51 struct wait_queue *wait_intr = NULL;
52 volatile int head;
53 volatile int tail; /* not volatile but need same type as head */
54 int fdc_setup_error;
55 ftape_last_segment_struct ftape_last_segment;
56 int header_segment_1 = -1;
57 int header_segment_2 = -1;
58 int used_header_segment = -1;
59 location_record location =
60 {-1, 0};
61 volatile int tape_running = 0;
62 format_type format_code;
63
64 /* Local vars.
65 */
66 static int overrun_count_offset = 0;
67 static int inhibit_correction = 0;
68
69
70 /* Increment cyclic buffer nr.
71 */
72 buffer_struct *
73 next_buffer(volatile int *x)
/* ![[next]](../icons/right.png)
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*/
74 {
75 if (++*x >= NR_BUFFERS) {
76 *x = 0;
77 }
78 return &buffer[*x];
79 }
80
81 int valid_segment_no(unsigned segment)
/* ![[previous]](../icons/left.png)
*/
82 {
83 return (segment >= first_data_segment && segment <= ftape_last_segment.id);
84 }
85
86 /* Count nr of 1's in pattern.
87 */
88 int count_ones(unsigned long mask)
/* */
89 {
90 int bits;
91
92 for (bits = 0; mask != 0; mask >>= 1) {
93 if (mask & 1) {
94 ++bits;
95 }
96 }
97 return bits;
98 }
99
100 /* Calculate Floppy Disk Controller and DMA parameters for a segment.
101 * head: selects buffer struct in array.
102 * offset: number of physical sectors to skip (including bad ones).
103 * count: number of physical sectors to handle (including bad ones).
104 */
105 static int setup_segment(buffer_struct * buff, unsigned int segment_id,
/* */
106 unsigned int sector_offset, unsigned int sector_count, int retry)
107 {
108 TRACE_FUN(8, "setup_segment");
109 unsigned long offset_mask;
110 unsigned long mask;
111
112 buff->segment_id = segment_id;
113 buff->sector_offset = sector_offset;
114 buff->remaining = sector_count;
115 buff->head = segment_id / segments_per_head;
116 buff->cyl = (segment_id % segments_per_head) / segments_per_cylinder;
117 buff->sect = (segment_id % segments_per_cylinder) * SECTORS_PER_SEGMENT + 1;
118 buff->deleted = 0;
119 offset_mask = (1 << buff->sector_offset) - 1;
120 mask = get_bad_sector_entry(segment_id) & offset_mask;
121 while (mask) {
122 if (mask & 1) {
123 offset_mask >>= 1; /* don't count bad sector */
124 }
125 mask >>= 1;
126 }
127 buff->data_offset = count_ones(offset_mask); /* good sectors to skip */
128 buff->ptr = buff->address + buff->data_offset * SECTOR_SIZE;
129 TRACEx1(5, "data offset = %d sectors", buff->data_offset);
130 if (retry) {
131 buff->soft_error_map &= offset_mask; /* keep skipped part */
132 } else {
133 buff->hard_error_map = buff->soft_error_map = 0;
134 }
135 buff->bad_sector_map = get_bad_sector_entry(buff->segment_id);
136 if (buff->bad_sector_map != 0) {
137 TRACEx2(4, "segment: %d, bad sector map: %08lx",
138 buff->segment_id, buff->bad_sector_map);
139 } else {
140 TRACEx1(5, "segment: %d", buff->segment_id);
141 }
142 if (buff->sector_offset > 0) {
143 buff->bad_sector_map >>= buff->sector_offset;
144 }
145 if (buff->sector_offset != 0 || buff->remaining != SECTORS_PER_SEGMENT) {
146 TRACEx2(5, "sector offset = %d, count = %d",
147 buff->sector_offset, buff->remaining);
148 }
149 /*
150 * Segments with 3 or less sectors are not written with
151 * valid data because there is no space left for the ecc.
152 * The data written is whatever happens to be in the buffer.
153 * Reading such a segment will return a zero byte-count.
154 * To allow us to read/write segments with all bad sectors
155 * we fake one readable sector in the segment. This prevents
156 * having to handle these segments in a very special way.
157 * It is not important if the reading of this bad sector
158 * fails or not (the data is ignored). It is only read to
159 * keep the driver running.
160 * The QIC-40/80 spec. has no information on how to handle
161 * this case, so this is my interpretation.
162 */
163 if (buff->bad_sector_map == EMPTY_SEGMENT) {
164 TRACE(5, "empty segment, fake first sector good");
165 buff->bad_sector_map = FAKE_SEGMENT;
166 }
167 fdc_setup_error = 0;
168 buff->next_segment = segment_id + 1;
169 TRACE_EXIT;
170 return 0;
171 }
172
173 /* Calculate Floppy Disk Controller and DMA parameters for a new segment.
174 */
175 int setup_new_segment(buffer_struct * buff, unsigned int segment_id, int skip)
/* */
176 {
177 TRACE_FUN(5, "setup_new_segment");
178 int result = 0;
179 static int old_segment_id = -1;
180 static int old_ftape_state = idle;
181 int retry = 0;
182 unsigned offset = 0;
183 int count = SECTORS_PER_SEGMENT;
184
185 TRACEx3(5, "%s segment %d (old = %d)",
186 (ftape_state == reading) ? "reading" : "writing",
187 segment_id, old_segment_id);
188 if (ftape_state != old_ftape_state) { /* when verifying */
189 old_segment_id = -1;
190 old_ftape_state = ftape_state;
191 }
192 if (segment_id == old_segment_id) {
193 ++buff->retry;
194 ++history.retries;
195 TRACEx1(5, "setting up for retry nr %d", buff->retry);
196 retry = 1;
197 if (skip && buff->skip > 0) { /* allow skip on retry */
198 offset = buff->skip;
199 count -= offset;
200 TRACEx1(5, "skipping %d sectors", offset);
201 }
202 } else {
203 buff->retry = 0;
204 buff->skip = 0;
205 old_segment_id = segment_id;
206 }
207 result = setup_segment(buff, segment_id, offset, count, retry);
208 TRACE_EXIT;
209 return result;
210 }
211
212 /* Determine size of next cluster of good sectors.
213 */
214 int calc_next_cluster(buffer_struct * buff)
/* */
215 {
216 /* Skip bad sectors.
217 */
218 while (buff->remaining > 0 && (buff->bad_sector_map & 1) != 0) {
219 buff->bad_sector_map >>= 1;
220 ++buff->sector_offset;
221 --buff->remaining;
222 }
223 /* Find next cluster of good sectors
224 */
225 if (buff->bad_sector_map == 0) { /* speed up */
226 buff->sector_count = buff->remaining;
227 } else {
228 unsigned long map = buff->bad_sector_map;
229
230 buff->sector_count = 0;
231 while (buff->sector_count < buff->remaining && (map & 1) == 0) {
232 ++buff->sector_count;
233 map >>= 1;
234 }
235 }
236 return buff->sector_count;
237 }
238
239 int check_bot_eot(int status)
/* */
240 {
241 TRACE_FUN(5, "check_bot_eot");
242
243 if (status & (QIC_STATUS_AT_BOT | QIC_STATUS_AT_EOT)) {
244 location.bot = ((location.track & 1) == 0 ?
245 (status & QIC_STATUS_AT_BOT) :
246 (status & QIC_STATUS_AT_EOT));
247 location.eot = !location.bot;
248 location.segment = (location.track +
249 (location.bot ? 0 : 1)) * segments_per_track - 1;
250 location.sector = -1;
251 location.known = 1;
252 TRACEx1(5, "tape at logical %s", location.bot ? "bot" : "eot");
253 TRACEx1(5, "segment = %d", location.segment);
254 } else {
255 location.known = 0;
256 }
257 TRACE_EXIT;
258 return location.known;
259 }
260
261 /* Read Id of first sector passing tape head.
262 */
263 int ftape_read_id(void)
/* */
264 {
265 TRACE_FUN(8, "ftape_read_id");
266 int result;
267 int status;
268 byte out[2];
269
270 /* Assume tape is running on entry, be able to handle
271 * situation where it stopped or is stopping.
272 */
273 location.known = 0; /* default is location not known */
274 out[0] = FDC_READID;
275 out[1] = FTAPE_UNIT;
276 result = fdc_command(out, 2);
277 if (result < 0) {
278 TRACE(1, "fdc_command failed");
279 } else {
280 result = fdc_interrupt_wait(20 * SECOND);
281 if (result == 0) {
282 if (fdc_sect == 0) {
283 result = ftape_report_drive_status(&status);
284 if (result == 0) {
285 if (status & QIC_STATUS_READY) {
286 tape_running = 0;
287 TRACE(5, "tape has stopped");
288 check_bot_eot(status);
289 if (!location.known) {
290 result = -EIO;
291 }
292 } else {
293 /* If read-id failed because of a hard or soft
294 * error, return an error. Higher level must retry!
295 */
296 result = -EIO;
297 }
298 }
299 } else {
300 location.known = 1;
301 location.segment = (segments_per_head * fdc_head
302 + segments_per_cylinder * fdc_cyl
303 + (fdc_sect - 1) / SECTORS_PER_SEGMENT);
304 location.sector = (fdc_sect - 1) % SECTORS_PER_SEGMENT;
305 location.eot =
306 location.bot = 0;
307 }
308 } else if (result == -ETIME) {
309 /* Didn't find id on tape, must be near end: Wait until stopped.
310 */
311 result = ftape_ready_wait(FOREVER, &status);
312 if (result >= 0) {
313 tape_running = 0;
314 TRACE(5, "tape has stopped");
315 check_bot_eot(status);
316 if (!location.known) {
317 result = -EIO;
318 }
319 }
320 } else {
321 /* Interrupted or otherwise failing fdc_interrupt_wait()
322 */
323 TRACE(1, "fdc_interrupt_wait failed :(");
324 result = -EIO;
325 }
326 }
327 if (!location.known) {
328 TRACE(5, "no id found");
329 } else {
330 if (location.sector == 0) {
331 TRACEx2(5, "passing segment %d/%d", location.segment, location.sector);
332 } else {
333 TRACEx2(6, "passing segment %d/%d", location.segment, location.sector);
334 }
335 }
336 TRACE_EXIT;
337 return result;
338 }
339
340 static int logical_forward(void)
/* */
341 {
342 tape_running = 1;
343 return ftape_command(QIC_LOGICAL_FORWARD);
344 }
345
346 static int stop_tape(int *pstatus)
/* */
347 {
348 TRACE_FUN(5, "stop_tape");
349 int retry = 0;
350 int result;
351
352 do {
353 result = ftape_command_wait(QIC_STOP_TAPE, timeout.stop, pstatus);
354 if (result == 0) {
355 if ((*pstatus & QIC_STATUS_READY) == 0) {
356 result = -EIO;
357 } else {
358 tape_running = 0;
359 }
360 }
361 } while (result < 0 && ++retry <= 3);
362 if (result < 0) {
363 TRACE(1, "failed ! (fatal)");
364 }
365 TRACE_EXIT;
366 return result;
367 }
368
369 int ftape_dumb_stop(void)
/* */
370 {
371 TRACE_FUN(5, "ftape_dumb_stop");
372 int result;
373 int status;
374
375 /* Abort current fdc operation if it's busy (probably read
376 * or write operation pending) with a reset.
377 */
378 result = fdc_ready_wait(100 /* usec */ );
379 if (result < 0) {
380 TRACE(1, "aborting fdc operation");
381 fdc_reset();
382 }
383 /* Reading id's after the last segment on a track may fail
384 * but eventually the drive will become ready (logical eot).
385 */
386 result = ftape_report_drive_status(&status);
387 location.known = 0;
388 do {
389 if (result == 0 && status & QIC_STATUS_READY) {
390 /* Tape is not running any more.
391 */
392 TRACE(5, "tape already halted");
393 check_bot_eot(status);
394 tape_running = 0;
395 } else if (tape_running) {
396 /* Tape is (was) still moving.
397 */
398 #ifdef TESTING
399 ftape_read_id();
400 #endif
401 result = stop_tape(&status);
402 } else {
403 /* Tape not yet ready but stopped.
404 */
405 result = ftape_ready_wait(timeout.pause, &status);
406 }
407 } while (tape_running);
408 #ifndef TESTING
409 location.known = 0;
410 #endif
411 TRACE_EXIT;
412 return result;
413 }
414
415 /* Wait until runner has finished tail buffer.
416 */
417 int wait_segment(buffer_state_enum state)
/* */
418 {
419 TRACE_FUN(5, "wait_segment");
420 int result = 0;
421
422 while (buffer[tail].status == state) {
423 /* First buffer still being worked on, wait up to timeout.
424 */
425 result = fdc_interrupt_wait(50 * SECOND);
426 if (result < 0) {
427 if (result != -EINTR) {
428 TRACE(1, "fdc_interrupt_wait failed");
429 result = -ETIME;
430 }
431 break;
432 }
433 if (fdc_setup_error) {
434 TRACE(1, "setup error");
435 /* recover... */
436 result = -EIO;
437 break;
438 }
439 }
440 TRACE_EXIT;
441 return result;
442 }
443
444 /* forward */ static int seek_forward(int segment_id);
445
446 int fast_seek(int count, int reverse)
/* */
447 {
448 TRACE_FUN(5, "fast_seek");
449 int result = 0;
450 int status;
451
452 if (count > 0) {
453 /* If positioned at begin or end of tape, fast seeking needs
454 * special treatment.
455 * Starting from logical bot needs a (slow) seek to the first
456 * segment before the high speed seek. Most drives do this
457 * automatically but some older don't, so we treat them
458 * all the same.
459 * Starting from logical eot is even more difficult because
460 * we cannot (slow) reverse seek to the last segment.
461 * TO BE IMPLEMENTED.
462 */
463 inhibit_correction = 0;
464 if (location.known &&
465 ((location.bot && !reverse) ||
466 (location.eot && reverse))) {
467 if (!reverse) {
468 /* (slow) skip to first segment on a track
469 */
470 seek_forward(location.track * segments_per_track);
471 --count;
472 } else {
473 /* When seeking backwards from end-of-tape the number
474 * of erased gaps found seems to be higher than expected.
475 * Therefor the drive must skip some more segments than
476 * calculated, but we don't know how many.
477 * Thus we will prevent the re-calculation of offset
478 * and overshoot when seeking backwards.
479 */
480 inhibit_correction = 1;
481 count += 3; /* best guess */
482 }
483 }
484 } else {
485 TRACEx1(5, "warning: zero or negative count: %d", count);
486 }
487 if (count > 0) {
488 int i;
489 int nibbles = count > 255 ? 3 : 2;
490
491 if (count > 4095) {
492 TRACE(4, "skipping clipped at 4095 segment");
493 count = 4095;
494 }
495 /* Issue this tape command first. */
496 if (!reverse) {
497 TRACEx1(4, "skipping %d segment(s)", count);
498 result = ftape_command(nibbles == 3 ?
499 QIC_SKIP_EXTENDED_FORWARD : QIC_SKIP_FORWARD);
500 } else {
501 TRACEx1(4, "backing up %d segment(s)", count);
502 result = ftape_command(nibbles == 3 ?
503 QIC_SKIP_EXTENDED_REVERSE : QIC_SKIP_REVERSE);
504 }
505 if (result < 0) {
506 TRACE(4, "Skip command failed");
507 } else {
508 --count; /* 0 means one gap etc. */
509 for (i = 0; i < nibbles; ++i) {
510 if (result >= 0) {
511 result = ftape_parameter(count & 15);
512 count /= 16;
513 }
514 }
515 result = ftape_ready_wait(timeout.rewind, &status);
516 if (result >= 0) {
517 tape_running = 0;
518 }
519 }
520 }
521 TRACE_EXIT;
522 return result;
523 }
524
525 static int validate(int id)
/* */
526 {
527 /* Check to see if position found is off-track as reported once.
528 * Because all tracks in one direction lie next to each other,
529 * if off-track the error will be approximately 2 * segments_per_track.
530 */
531 if (location.track == -1) {
532 return 1; /* unforeseen situation, don't generate error */
533 } else {
534 /* Use margin of segments_per_track on both sides because ftape
535 * needs some margin and the error we're looking for is much larger !
536 */
537 int lo = (location.track - 1) * segments_per_track;
538 int hi = (location.track + 2) * segments_per_track;
539
540 return (id >= lo && id < hi);
541 }
542 }
543
544 static int seek_forward(int segment_id)
/* */
545 {
546 TRACE_FUN(5, "seek_forward");
547 int failures = 0;
548 int result = 0;
549 int count;
550 static int margin = 1; /* fixed: stop this before target */
551 static int overshoot = 1;
552 static int min_count = 8;
553 int expected = -1;
554 int target = segment_id - margin;
555 int fast_seeking;
556
557 if (!location.known) {
558 TRACE(1, "fatal: cannot seek from unknown location");
559 result = -EIO;
560 } else if (!validate(segment_id)) {
561 TRACE(1, "fatal: head off track (bad hardware?)");
562 ftape_sleep(1 * SECOND);
563 ftape_failure = 1;
564 result = -EIO;
565 } else {
566 int prev_segment = location.segment;
567
568 TRACEx4(4, "from %d/%d to %d/0 - %d", location.segment,
569 location.sector, segment_id, margin);
570 count = target - location.segment - overshoot;
571 fast_seeking = (count > min_count + (location.bot ? 1 : 0));
572 if (fast_seeking) {
573 TRACEx1(5, "fast skipping %d segments", count);
574 expected = segment_id - margin;
575 fast_seek(count, 0);
576 }
577 if (!tape_running) {
578 logical_forward();
579 }
580 while (location.segment < segment_id) {
581 /* This requires at least one sector in a (bad) segment to
582 * have a valid and readable sector id !
583 * It looks like this is not guaranteed, so we must try
584 * to find a way to skip an EMPTY_SEGMENT. !!! FIXME !!!
585 */
586 if (ftape_read_id() < 0 || !location.known) {
587 location.known = 0;
588 if (!tape_running || ++failures > SECTORS_PER_SEGMENT ||
589 (current->signal & _DONT_BLOCK)) {
590 TRACE(1, "read_id failed completely");
591 result = -EIO;
592 break;
593 } else {
594 TRACEx1(5, "read_id failed, retry (%d)", failures);
595 }
596 } else if (fast_seeking) {
597 TRACEx4(4, "ended at %d/%d (%d,%d)", location.segment,
598 location.sector, overshoot, inhibit_correction);
599 if (!inhibit_correction &&
600 (location.segment < expected ||
601 location.segment > expected + margin)) {
602 int error = location.segment - expected;
603 TRACEx2(4, "adjusting overshoot from %d to %d",
604 overshoot, overshoot + error);
605 overshoot += error;
606 /* All overshoots have the same direction, so it should
607 * never become negative, but who knows.
608 */
609 if (overshoot < -5 || overshoot > 10) {
610 if (overshoot < 0) {
611 overshoot = -5; /* keep sane value */
612 } else {
613 overshoot = 10; /* keep sane value */
614 }
615 TRACEx1(4, "clipped overshoot to %d", overshoot);
616 }
617 }
618 fast_seeking = 0;
619 }
620 if (location.known) {
621 if (location.segment > prev_segment + 1) {
622 TRACEx1(4, "missed segment %d while skipping", prev_segment + 1);
623 }
624 prev_segment = location.segment;
625 }
626 }
627 if (location.segment > segment_id) {
628 TRACEx2(4, "failed: skip ended at segment %d/%d",
629 location.segment, location.sector);
630 result = -EIO;
631 }
632 }
633 TRACE_EXIT;
634 return result;
635 }
636
637 static int skip_reverse(int segment_id, int *pstatus)
/* */
638 {
639 TRACE_FUN(5, "skip_reverse");
640 int result = 0;
641 int failures = 0;
642 static int overshoot = 1;
643 static int min_rewind = 2; /* 1 + overshoot */
644 static const int margin = 1; /* stop this before target */
645 int expected = 0;
646 int count;
647 int short_seek;
648 int target = segment_id - margin;
649
650 if (location.known && !validate(segment_id)) {
651 TRACE(1, "fatal: head off track (bad hardware?)");
652 ftape_sleep(1 * SECOND);
653 ftape_failure = 1;
654 result = -EIO;
655 } else
656 do {
657 if (!location.known) {
658 TRACE(-1, "warning: location not known");
659 }
660 TRACEx4(4, "from %d/%d to %d/0 - %d",
661 location.segment, location.sector, segment_id, margin);
662 /* min_rewind == 1 + overshoot_when_doing_minimum_rewind
663 * overshoot == overshoot_when_doing_larger_rewind
664 * Initially min_rewind == 1 + overshoot, optimization
665 * of both values will be done separately.
666 * overshoot and min_rewind can be negative as both are
667 * sums of three components:
668 * any_overshoot == rewind_overshoot - stop_overshoot - start_overshoot
669 */
670 if (location.segment - target - (min_rewind - 1) < 1) {
671 short_seek = 1;
672 } else {
673 count = location.segment - target - overshoot;
674 short_seek = (count < 1);
675 }
676 if (short_seek) {
677 count = 1; /* do shortest rewind */
678 expected = location.segment - min_rewind;
679 if (expected / segments_per_track != location.track) {
680 expected = location.track * segments_per_track;
681 }
682 } else {
683 expected = target;
684 }
685 fast_seek(count, 1);
686 logical_forward();
687 result = ftape_read_id();
688 if (result == 0 && location.known) {
689 TRACEx5(4, "ended at %d/%d (%d,%d,%d)", location.segment,
690 location.sector, min_rewind, overshoot, inhibit_correction);
691 if (!inhibit_correction &&
692 (location.segment < expected ||
693 location.segment > expected + margin)) {
694 int error = expected - location.segment;
695 if (short_seek) {
696 TRACEx2(4, "adjusting min_rewind from %d to %d",
697 min_rewind, min_rewind + error);
698 min_rewind += error;
699 if (min_rewind < -5) { /* is this right ? FIXME ! */
700 min_rewind = -5; /* keep sane value */
701 TRACEx1(4, "clipped min_rewind to %d", min_rewind);
702 }
703 } else {
704 TRACEx2(4, "adjusting overshoot from %d to %d",
705 overshoot, overshoot + error);
706 overshoot += error;
707 if (overshoot < -5 || overshoot > 10) {
708 if (overshoot < 0) {
709 overshoot = -5; /* keep sane value */
710 } else {
711 overshoot = 10; /* keep sane value */
712 }
713 TRACEx1(4, "clipped overshoot to %d", overshoot);
714 }
715 }
716 }
717 } else {
718 if ((!tape_running && !location.known) ||
719 ++failures > SECTORS_PER_SEGMENT) {
720 TRACE(1, "read_id failed completely");
721 result = -EIO;
722 break;
723 } else {
724 TRACEx1(5, "ftape_read_id failed, retry (%d)", failures);
725 }
726 result = ftape_report_drive_status(pstatus);
727 if (result < 0) {
728 TRACEi(1, "ftape_report_drive_status failed with code", result);
729 break;
730 }
731 }
732 } while (location.segment > segment_id &&
733 (current->signal & _DONT_BLOCK) == 0);
734 if (location.known) {
735 TRACEx2(4, "current location: %d/%d", location.segment, location.sector);
736 }
737 TRACE_EXIT;
738 return result;
739 }
740
741 static int determine_position(void)
/* */
742 {
743 TRACE_FUN(5, "determine_position");
744 int retry = 0;
745 int fatal = 0;
746 int status;
747 int result;
748
749 if (!tape_running) {
750 /* This should only happen if tape is stopped by isr.
751 */
752 TRACE(5, "waiting for tape stop");
753 result = ftape_ready_wait(timeout.pause, &status);
754 if (result < 0) {
755 TRACE(5, "drive still running (fatal)");
756 tape_running = 1; /* ? */
757 }
758 } else {
759 ftape_report_drive_status(&status);
760 }
761 if (status & QIC_STATUS_READY) {
762 /* Drive must be ready to check error state !
763 */
764 TRACE(5, "drive is ready");
765 if (status & QIC_STATUS_ERROR) {
766 int error;
767 int command;
768
769 /* Report and clear error state, try to continue.
770 */
771 TRACE(5, "error status set");
772 ftape_report_error(&error, &command, 1);
773 ftape_ready_wait(timeout.reset, &status);
774 tape_running = 0; /* ? */
775 }
776 if (check_bot_eot(status)) {
777 if (location.bot) {
778 if ((status & QIC_STATUS_READY) == 0) {
779 /* tape moving away from bot/eot, let's see if we
780 * can catch up with the first segment on this track.
781 */
782 } else {
783 TRACE(5, "start tape from logical bot");
784 logical_forward(); /* start moving */
785 }
786 } else {
787 if ((status & QIC_STATUS_READY) == 0) {
788 TRACE(4, "waiting for logical end of track");
789 result = ftape_ready_wait(timeout.reset, &status);
790 /* error handling needed ? */
791 } else {
792 TRACE(4, "tape at logical end of track");
793 }
794 }
795 } else {
796 TRACE(5, "start tape");
797 logical_forward(); /* start moving */
798 location.known = 0; /* not cleared by logical forward ! */
799 }
800 }
801 if (!location.known) {
802 /* tape should be moving now, start reading id's
803 */
804 TRACE(5, "location unknown");
805 do {
806 result = ftape_read_id();
807 if (result < 0) {
808 /* read-id somehow failed, tape may have reached end
809 * or some other error happened.
810 */
811 TRACE(5, "read-id failed");
812 ftape_report_drive_status(&status);
813 if (status & QIC_STATUS_READY) {
814 tape_running = 0;
815 TRACEx1(4, "tape stopped for unknown reason ! status = 0x%02x",
816 status);
817 if (status & QIC_STATUS_ERROR) {
818 fatal = 1;
819 } else {
820 if (check_bot_eot(status)) {
821 result = 0;
822 } else {
823 fatal = 1; /* oops, tape stopped but not at end ! */
824 }
825 }
826 }
827 result = -EIO;
828 }
829 } while (result < 0 && !fatal && ++retry < SECTORS_PER_SEGMENT);
830 } else {
831 result = 0;
832 }
833 TRACEx1(5, "tape is positioned at segment %d", location.segment);
834 TRACE_EXIT;
835 return result;
836 }
837
838 /* Get the tape running and position it just before the
839 * requested segment.
840 * Seek tape-track and reposition as needed.
841 */
842 int ftape_start_tape(int segment_id, int sector_offset)
/* ![[last]](../icons/n_last.png)
*/
843 {
844 TRACE_FUN(5, "ftape_start_tape");
845 int track = segment_id / segments_per_track;
846 int result = -EIO;
847 int status;
848 static int last_segment = -1;
849 static int bad_bus_timing = 0;
850 /* number of segments passing the head between starting the tape
851 * and being able to access the first sector.
852 */
853 static int start_offset = 1;
854 int retry = 0;
855
856 /* If sector_offset > 0, seek into wanted segment instead of
857 * into previous.
858 * This allows error recovery if a part of the segment is bad
859 * (erased) causing the tape drive to generate an index pulse
860 * thus causing a no-data error before the requested sector
861 * is reached.
862 */
863 tape_running = 0;
864 TRACEx3(4, "target segment: %d/%d%s", segment_id, sector_offset,
865 buffer[head].retry > 0 ? " retry" : "");
866 if (buffer[head].retry > 0) { /* this is a retry */
867 if (!bad_bus_timing && ftape_data_rate == 1 &&
868 history.overrun_errors - overrun_count_offset >= 8) {
869 ftape_set_data_rate(ftape_data_rate + 1);
870 bad_bus_timing = 1;
871 TRACE(2, "reduced datarate because of excessive overrun errors");
872 }
873 }
874 last_segment = segment_id;
875 if (location.track != track || (might_be_off_track &&
876 buffer[head].retry == 0)) {
877 /* current track unknown or not equal to destination
878 */
879 ftape_ready_wait(timeout.seek, &status);
880 ftape_seek_head_to_track(track);
881 overrun_count_offset = history.overrun_errors;
882 }
883 do {
884 if (!location.known) {
885 determine_position();
886 }
887 /* Check if we are able to catch the requested segment in time.
888 */
889 if (location.known && location.segment >= segment_id -
890 ((tape_running || location.bot) ? 0 : start_offset)) {
891 /* Too far ahead (in or past target segment).
892 */
893 if (tape_running) {
894 result = stop_tape(&status);
895 if (result < 0) {
896 TRACEi(1, "stop tape failed with code", result);
897 break;
898 }
899 TRACE(5, "tape stopped");
900 tape_running = 0;
901 }
902 TRACE(5, "repositioning");
903 ++history.rewinds;
904 if (segment_id % segments_per_track < start_offset) {
905 /* If seeking to first segments on track better do a complete
906 * rewind to logical begin of track to get a more steady tape
907 * motion.
908 */
909 result = ftape_command_wait((location.track & 1) ?
910 QIC_PHYSICAL_FORWARD :
911 QIC_PHYSICAL_REVERSE,
912 timeout.rewind, &status);
913 check_bot_eot(status); /* update location */
914 } else {
915 result = skip_reverse(segment_id - start_offset, &status);
916 }
917 }
918 if (!location.known) {
919 TRACE(-1, "panic: location not known");
920 result = -EIO;
921 if ((current->signal & _DONT_BLOCK) || ftape_failure) {
922 break;
923 } else {
924 continue;
925 }
926 }
927 TRACEx2(4, "current segment: %d/%d", location.segment, location.sector);
928 /* We're on the right track somewhere before the wanted segment.
929 * Start tape movement if needed and skip to just before or inside
930 * the requested segment. Keep tape running.
931 */
932 result = 0;
933 if (location.segment < segment_id -
934 ((tape_running || location.bot) ? 0 : start_offset)) {
935 if (sector_offset > 0) {
936 result = seek_forward(segment_id);
937 } else {
938 result = seek_forward(segment_id - 1);
939 }
940 }
941 if (result == 0 &&
942 location.segment != segment_id - (sector_offset > 0 ? 0 : 1)) {
943 result = -EIO;
944 }
945 } while (result < 0 && !ftape_failure &&
946 (current->signal & _DONT_BLOCK) == 0 &&
947 ++retry <= 5);
948 if (result < 0) {
949 TRACE(1, "failed to reposition");
950 }
951 TRACE_EXIT;
952 return result;
953 }
![[bottom]](../icons/n_bottom.png){kind=icon}
*/