/*
* Copyright (C) 1993-1995 Bas Laarhoven.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
$Source: /home/bas/distr/ftape-2.03b/RCS/ftape-rw.c,v $
$Author: bas $
*
$Revision: 1.54 $
$Date: 1995/05/27 08:55:27 $
$State: Beta $
*
* This file contains some common code for the segment read and segment
* write routines for the QIC-117 floppy-tape driver for Linux.
*/
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/ftape.h>
#include "tracing.h"
#include "ftape-rw.h"
#include "fdc-io.h"
#include "kernel-interface.h"
#include "qic117.h"
#include "ftape-io.h"
#include "ftape-ctl.h"
#include "ftape-read.h"
#include "ftape-eof.h"
#include "ecc.h"
#include "ftape-bsm.h"
/* Global vars.
*/
volatile enum runner_status_enum runner_status = idle;
byte deblock_buffer[(SECTORS_PER_SEGMENT - 3) * SECTOR_SIZE];
byte scratch_buffer[(SECTORS_PER_SEGMENT - 3) * SECTOR_SIZE];
buffer_struct buffer[NR_BUFFERS];
struct wait_queue *wait_intr = NULL;
volatile int head;
volatile int tail; /* not volatile but need same type as head */
int fdc_setup_error;
ftape_last_segment_struct ftape_last_segment;
int header_segment_1 = -1;
int header_segment_2 = -1;
int used_header_segment = -1;
location_record location =
{-1, 0};
volatile int tape_running = 0;
format_type format_code;
/* Local vars.
*/
static int overrun_count_offset = 0;
static int inhibit_correction = 0;
/* Increment cyclic buffer nr.
*/
buffer_struct *
next_buffer(volatile int *x)
{
if (++*x >= NR_BUFFERS) {
*x = 0;
}
return &buffer[*x];
}
int valid_segment_no(unsigned segment)
{
return (segment >= first_data_segment && segment <= ftape_last_segment.id);
}
/* Count nr of 1's in pattern.
*/
int count_ones(unsigned long mask)
{
int bits;
for (bits = 0; mask != 0; mask >>= 1) {
if (mask & 1) {
++bits;
}
}
return bits;
}
/* Calculate Floppy Disk Controller and DMA parameters for a segment.
* head: selects buffer struct in array.
* offset: number of physical sectors to skip (including bad ones).
* count: number of physical sectors to handle (including bad ones).
*/
static int setup_segment(buffer_struct * buff, unsigned int segment_id,
unsigned int sector_offset, unsigned int sector_count, int retry)
{
TRACE_FUN(8, "setup_segment");
unsigned long offset_mask;
unsigned long mask;
buff->segment_id = segment_id;
buff->sector_offset = sector_offset;
buff->remaining = sector_count;
buff->head = segment_id / segments_per_head;
buff->cyl = (segment_id % segments_per_head) / segments_per_cylinder;
buff->sect = (segment_id % segments_per_cylinder) * SECTORS_PER_SEGMENT + 1;
buff->deleted = 0;
offset_mask = (1 << buff->sector_offset) - 1;
mask = get_bad_sector_entry(segment_id) & offset_mask;
while (mask) {
if (mask & 1) {
offset_mask >>= 1; /* don't count bad sector */
}
mask >>= 1;
}
buff->data_offset = count_ones(offset_mask); /* good sectors to skip */
buff->ptr = buff->address + buff->data_offset * SECTOR_SIZE;
TRACEx1(5, "data offset = %d sectors", buff->data_offset);
if (retry) {
buff->soft_error_map &= offset_mask; /* keep skipped part */
} else {
buff->hard_error_map = buff->soft_error_map = 0;
}
buff->bad_sector_map = get_bad_sector_entry(buff->segment_id);
if (buff->bad_sector_map != 0) {
TRACEx2(4, "segment: %d, bad sector map: %08lx",
buff->segment_id, buff->bad_sector_map);
} else {
TRACEx1(5, "segment: %d", buff->segment_id);
}
if (buff->sector_offset > 0) {
buff->bad_sector_map >>= buff->sector_offset;
}
if (buff->sector_offset != 0 || buff->remaining != SECTORS_PER_SEGMENT) {
TRACEx2(5, "sector offset = %d, count = %d",
buff->sector_offset, buff->remaining);
}
/*
* Segments with 3 or less sectors are not written with
* valid data because there is no space left for the ecc.
* The data written is whatever happens to be in the buffer.
* Reading such a segment will return a zero byte-count.
* To allow us to read/write segments with all bad sectors
* we fake one readable sector in the segment. This prevents
* having to handle these segments in a very special way.
* It is not important if the reading of this bad sector
* fails or not (the data is ignored). It is only read to
* keep the driver running.
* The QIC-40/80 spec. has no information on how to handle
* this case, so this is my interpretation.
*/
if (buff->bad_sector_map == EMPTY_SEGMENT) {
TRACE(5, "empty segment, fake first sector good");
buff->bad_sector_map = FAKE_SEGMENT;
}
fdc_setup_error = 0;
buff->next_segment = segment_id + 1;
TRACE_EXIT;
return 0;
}
/* Calculate Floppy Disk Controller and DMA parameters for a new segment.
*/
int setup_new_segment(buffer_struct * buff, unsigned int segment_id, int skip)
{
TRACE_FUN(5, "setup_new_segment");
int result = 0;
static int old_segment_id = -1;
static int old_ftape_state = idle;
int retry = 0;
unsigned offset = 0;
int count = SECTORS_PER_SEGMENT;
TRACEx3(5, "%s segment %d (old = %d)",
(ftape_state == reading) ? "reading" : "writing",
segment_id, old_segment_id);
if (ftape_state != old_ftape_state) { /* when verifying */
old_segment_id = -1;
old_ftape_state = ftape_state;
}
if (segment_id == old_segment_id) {
++buff->retry;
++history.retries;
TRACEx1(5, "setting up for retry nr %d", buff->retry);
retry = 1;
if (skip && buff->skip > 0) { /* allow skip on retry */
offset = buff->skip;
count -= offset;
TRACEx1(5, "skipping %d sectors", offset);
}
} else {
buff->retry = 0;
buff->skip = 0;
old_segment_id = segment_id;
}
result = setup_segment(buff, segment_id, offset, count, retry);
TRACE_EXIT;
return result;
}
/* Determine size of next cluster of good sectors.
*/
int calc_next_cluster(buffer_struct * buff)
{
/* Skip bad sectors.
*/
while (buff->remaining > 0 && (buff->bad_sector_map & 1) != 0) {
buff->bad_sector_map >>= 1;
++buff->sector_offset;
--buff->remaining;
}
/* Find next cluster of good sectors
*/
if (buff->bad_sector_map == 0) { /* speed up */
buff->sector_count = buff->remaining;
} else {
unsigned long map = buff->bad_sector_map;
buff->sector_count = 0;
while (buff->sector_count < buff->remaining && (map & 1) == 0) {
++buff->sector_count;
map >>= 1;
}
}
return buff->sector_count;
}
int check_bot_eot(int status)
{
TRACE_FUN(5, "check_bot_eot");
if (status & (QIC_STATUS_AT_BOT | QIC_STATUS_AT_EOT)) {
location.bot = ((location.track & 1) == 0 ?
(status & QIC_STATUS_AT_BOT) :
(status & QIC_STATUS_AT_EOT));
location.eot = !location.bot;
location.segment = (location.track +
(location.bot ? 0 : 1)) * segments_per_track - 1;
location.sector = -1;
location.known = 1;
TRACEx1(5, "tape at logical %s", location.bot ? "bot" : "eot");
TRACEx1(5, "segment = %d", location.segment);
} else {
location.known = 0;
}
TRACE_EXIT;
return location.known;
}
/* Read Id of first sector passing tape head.
*/
int ftape_read_id(void)
{
TRACE_FUN(8, "ftape_read_id");
int result;
int status;
byte out[2];
/* Assume tape is running on entry, be able to handle
* situation where it stopped or is stopping.
*/
location.known = 0; /* default is location not known */
out[0] = FDC_READID;
out[1] = FTAPE_UNIT;
result = fdc_command(out, 2);
if (result < 0) {
TRACE(1, "fdc_command failed");
} else {
result = fdc_interrupt_wait(20 * SECOND);
if (result == 0) {
if (fdc_sect == 0) {
result = ftape_report_drive_status(&status);
if (result == 0) {
if (status & QIC_STATUS_READY) {
tape_running = 0;
TRACE(5, "tape has stopped");
check_bot_eot(status);
if (!location.known) {
result = -EIO;
}
} else {
/* If read-id failed because of a hard or soft
* error, return an error. Higher level must retry!
*/
result = -EIO;
}
}
} else {
location.known = 1;
location.segment = (segments_per_head * fdc_head
+ segments_per_cylinder * fdc_cyl
+ (fdc_sect - 1) / SECTORS_PER_SEGMENT);
location.sector = (fdc_sect - 1) % SECTORS_PER_SEGMENT;
location.eot =
location.bot = 0;
}
} else if (result == -ETIME) {
/* Didn't find id on tape, must be near end: Wait until stopped.
*/
result = ftape_ready_wait(FOREVER, &status);
if (result >= 0) {
tape_running = 0;
TRACE(5, "tape has stopped");
check_bot_eot(status);
if (!location.known) {
result = -EIO;
}
}
} else {
/* Interrupted or otherwise failing fdc_interrupt_wait()
*/
TRACE(1, "fdc_interrupt_wait failed :(");
result = -EIO;
}
}
if (!location.known) {
TRACE(5, "no id found");
} else {
if (location.sector == 0) {
TRACEx2(5, "passing segment %d/%d", location.segment, location.sector);
} else {
TRACEx2(6, "passing segment %d/%d", location.segment, location.sector);
}
}
TRACE_EXIT;
return result;
}
static int logical_forward(void)
{
tape_running = 1;
return ftape_command(QIC_LOGICAL_FORWARD);
}
static int stop_tape(int *pstatus)
{
TRACE_FUN(5, "stop_tape");
int retry = 0;
int result;
do {
result = ftape_command_wait(QIC_STOP_TAPE, timeout.stop, pstatus);
if (result == 0) {
if ((*pstatus & QIC_STATUS_READY) == 0) {
result = -EIO;
} else {
tape_running = 0;
}
}
} while (result < 0 && ++retry <= 3);
if (result < 0) {
TRACE(1, "failed ! (fatal)");
}
TRACE_EXIT;
return result;
}
int ftape_dumb_stop(void)
{
TRACE_FUN(5, "ftape_dumb_stop");
int result;
int status;
/* Abort current fdc operation if it's busy (probably read
* or write operation pending) with a reset.
*/
result = fdc_ready_wait(100 /* usec */ );
if (result < 0) {
TRACE(1, "aborting fdc operation");
fdc_reset();
}
/* Reading id's after the last segment on a track may fail
* but eventually the drive will become ready (logical eot).
*/
result = ftape_report_drive_status(&status);
location.known = 0;
do {
if (result == 0 && status & QIC_STATUS_READY) {
/* Tape is not running any more.
*/
TRACE(5, "tape already halted");
check_bot_eot(status);
tape_running = 0;
} else if (tape_running) {
/* Tape is (was) still moving.
*/
#ifdef TESTING
ftape_read_id();
#endif
result = stop_tape(&status);
} else {
/* Tape not yet ready but stopped.
*/
result = ftape_ready_wait(timeout.pause, &status);
}
} while (tape_running);
#ifndef TESTING
location.known = 0;
#endif
TRACE_EXIT;
return result;
}
/* Wait until runner has finished tail buffer.
*/
int wait_segment(buffer_state_enum state)
{
TRACE_FUN(5, "wait_segment");
int result = 0;
while (buffer[tail].status == state) {
/* First buffer still being worked on, wait up to timeout.
*/
result = fdc_interrupt_wait(50 * SECOND);
if (result < 0) {
if (result != -EINTR) {
TRACE(1, "fdc_interrupt_wait failed");
result = -ETIME;
}
break;
}
if (fdc_setup_error) {
TRACE(1, "setup error");
/* recover... */
result = -EIO;
break;
}
}
TRACE_EXIT;
return result;
}
/* forward */ static int seek_forward(int segment_id);
int fast_seek(int count, int reverse)
{
TRACE_FUN(5, "fast_seek");
int result = 0;
int status;
if (count > 0) {
/* If positioned at begin or end of tape, fast seeking needs
* special treatment.
* Starting from logical bot needs a (slow) seek to the first
* segment before the high speed seek. Most drives do this
* automatically but some older don't, so we treat them
* all the same.
* Starting from logical eot is even more difficult because
* we cannot (slow) reverse seek to the last segment.
* TO BE IMPLEMENTED.
*/
inhibit_correction = 0;
if (location.known &&
((location.bot && !reverse) ||
(location.eot && reverse))) {
if (!reverse) {
/* (slow) skip to first segment on a track
*/
seek_forward(location.track * segments_per_track);
--count;
} else {
/* When seeking backwards from end-of-tape the number
* of erased gaps found seems to be higher than expected.
* Therefor the drive must skip some more segments than
* calculated, but we don't know how many.
* Thus we will prevent the re-calculation of offset
* and overshoot when seeking backwards.
*/
inhibit_correction = 1;
count += 3; /* best guess */
}
}
} else {
TRACEx1(5, "warning: zero or negative count: %d", count);
}
if (count > 0) {
int i;
int nibbles = count > 255 ? 3 : 2;
if (count > 4095) {
TRACE(4, "skipping clipped at 4095 segment");
count = 4095;
}
/* Issue this tape command first. */
if (!reverse) {
TRACEx1(4, "skipping %d segment(s)", count);
result = ftape_command(nibbles == 3 ?
QIC_SKIP_EXTENDED_FORWARD : QIC_SKIP_FORWARD);
} else {
TRACEx1(4, "backing up %d segment(s)", count);
result = ftape_command(nibbles == 3 ?
QIC_SKIP_EXTENDED_REVERSE : QIC_SKIP_REVERSE);
}
if (result < 0) {
TRACE(4, "Skip command failed");
} else {
--count; /* 0 means one gap etc. */
for (i = 0; i < nibbles; ++i) {
if (result >= 0) {
result = ftape_parameter(count & 15);
count /= 16;
}
}
result = ftape_ready_wait(timeout.rewind, &status);
if (result >= 0) {
tape_running = 0;
}
}
}
TRACE_EXIT;
return result;
}
static int validate(int id)
{
/* Check to see if position found is off-track as reported once.
* Because all tracks in one direction lie next to each other,
* if off-track the error will be approximately 2 * segments_per_track.
*/
if (location.track == -1) {
return 1; /* unforeseen situation, don't generate error */
} else {
/* Use margin of segments_per_track on both sides because ftape
* needs some margin and the error we're looking for is much larger !
*/
int lo = (location.track - 1) * segments_per_track;
int hi = (location.track + 2) * segments_per_track;
return (id >= lo && id < hi);
}
}
static int seek_forward(int segment_id)
{
TRACE_FUN(5, "seek_forward");
int failures = 0;
int result = 0;
int count;
static int margin = 1; /* fixed: stop this before target */
static int overshoot = 1;
static int min_count = 8;
int expected = -1;
int target = segment_id - margin;
int fast_seeking;
if (!location.known) {
TRACE(1, "fatal: cannot seek from unknown location");
result = -EIO;
} else if (!validate(segment_id)) {
TRACE(1, "fatal: head off track (bad hardware?)");
ftape_sleep(1 * SECOND);
ftape_failure = 1;
result = -EIO;
} else {
int prev_segment = location.segment;
TRACEx4(4, "from %d/%d to %d/0 - %d", location.segment,
location.sector, segment_id, margin);
count = target - location.segment - overshoot;
fast_seeking = (count > min_count + (location.bot ? 1 : 0));
if (fast_seeking) {
TRACEx1(5, "fast skipping %d segments", count);
expected = segment_id - margin;
fast_seek(count, 0);
}
if (!tape_running) {
logical_forward();
}
while (location.segment < segment_id) {
/* This requires at least one sector in a (bad) segment to
* have a valid and readable sector id !
* It looks like this is not guaranteed, so we must try
* to find a way to skip an EMPTY_SEGMENT. !!! FIXME !!!
*/
if (ftape_read_id() < 0 || !location.known) {
location.known = 0;
if (!tape_running || ++failures > SECTORS_PER_SEGMENT ||
(current->signal & _DONT_BLOCK)) {
TRACE(1, "read_id failed completely");
result = -EIO;
break;
} else {
TRACEx1(5, "read_id failed, retry (%d)", failures);
}
} else if (fast_seeking) {
TRACEx4(4, "ended at %d/%d (%d,%d)", location.segment,
location.sector, overshoot, inhibit_correction);
if (!inhibit_correction &&
(location.segment < expected ||
location.segment > expected + margin)) {
int error = location.segment - expected;
TRACEx2(4, "adjusting overshoot from %d to %d",
overshoot, overshoot + error);
overshoot += error;
/* All overshoots have the same direction, so it should
* never become negative, but who knows.
*/
if (overshoot < -5 || overshoot > 10) {
if (overshoot < 0) {
overshoot = -5; /* keep sane value */
} else {
overshoot = 10; /* keep sane value */
}
TRACEx1(4, "clipped overshoot to %d", overshoot);
}
}
fast_seeking = 0;
}
if (location.known) {
if (location.segment > prev_segment + 1) {
TRACEx1(4, "missed segment %d while skipping", prev_segment + 1);
}
prev_segment = location.segment;
}
}
if (location.segment > segment_id) {
TRACEx2(4, "failed: skip ended at segment %d/%d",
location.segment, location.sector);
result = -EIO;
}
}
TRACE_EXIT;
return result;
}
static int skip_reverse(int segment_id, int *pstatus)
{
TRACE_FUN(5, "skip_reverse");
int result = 0;
int failures = 0;
static int overshoot = 1;
static int min_rewind = 2; /* 1 + overshoot */
static const int margin = 1; /* stop this before target */
int expected = 0;
int count;
int short_seek;
int target = segment_id - margin;
if (location.known && !validate(segment_id)) {
TRACE(1, "fatal: head off track (bad hardware?)");
ftape_sleep(1 * SECOND);
ftape_failure = 1;
result = -EIO;
} else
do {
if (!location.known) {
TRACE(-1, "warning: location not known");
}
TRACEx4(4, "from %d/%d to %d/0 - %d",
location.segment, location.sector, segment_id, margin);
/* min_rewind == 1 + overshoot_when_doing_minimum_rewind
* overshoot == overshoot_when_doing_larger_rewind
* Initially min_rewind == 1 + overshoot, optimization
* of both values will be done separately.
* overshoot and min_rewind can be negative as both are
* sums of three components:
* any_overshoot == rewind_overshoot - stop_overshoot - start_overshoot
*/
if (location.segment - target - (min_rewind - 1) < 1) {
short_seek = 1;
} else {
count = location.segment - target - overshoot;
short_seek = (count < 1);
}
if (short_seek) {
count = 1; /* do shortest rewind */
expected = location.segment - min_rewind;
if (expected / segments_per_track != location.track) {
expected = location.track * segments_per_track;
}
} else {
expected = target;
}
fast_seek(count, 1);
logical_forward();
result = ftape_read_id();
if (result == 0 && location.known) {
TRACEx5(4, "ended at %d/%d (%d,%d,%d)", location.segment,
location.sector, min_rewind, overshoot, inhibit_correction);
if (!inhibit_correction &&
(location.segment < expected ||
location.segment > expected + margin)) {
int error = expected - location.segment;
if (short_seek) {
TRACEx2(4, "adjusting min_rewind from %d to %d",
min_rewind, min_rewind + error);
min_rewind += error;
if (min_rewind < -5) { /* is this right ? FIXME ! */
min_rewind = -5; /* keep sane value */
TRACEx1(4, "clipped min_rewind to %d", min_rewind);
}
} else {
TRACEx2(4, "adjusting overshoot from %d to %d",
overshoot, overshoot + error);
overshoot += error;
if (overshoot < -5 || overshoot > 10) {
if (overshoot < 0) {
overshoot = -5; /* keep sane value */
} else {
overshoot = 10; /* keep sane value */
}
TRACEx1(4, "clipped overshoot to %d", overshoot);
}
}
}
} else {
if ((!tape_running && !location.known) ||
++failures > SECTORS_PER_SEGMENT) {
TRACE(1, "read_id failed completely");
result = -EIO;
break;
} else {
TRACEx1(5, "ftape_read_id failed, retry (%d)", failures);
}
result = ftape_report_drive_status(pstatus);
if (result < 0) {
TRACEi(1, "ftape_report_drive_status failed with code", result);
break;
}
}
} while (location.segment > segment_id &&
(current->signal & _DONT_BLOCK) == 0);
if (location.known) {
TRACEx2(4, "current location: %d/%d", location.segment, location.sector);
}
TRACE_EXIT;
return result;
}
static int determine_position(void)
{
TRACE_FUN(5, "determine_position");
int retry = 0;
int fatal = 0;
int status;
int result;
if (!tape_running) {
/* This should only happen if tape is stopped by isr.
*/
TRACE(5, "waiting for tape stop");
result = ftape_ready_wait(timeout.pause, &status);
if (result < 0) {
TRACE(5, "drive still running (fatal)");
tape_running = 1; /* ? */
}
} else {
ftape_report_drive_status(&status);
}
if (status & QIC_STATUS_READY) {
/* Drive must be ready to check error state !
*/
TRACE(5, "drive is ready");
if (status & QIC_STATUS_ERROR) {
int error;
int command;
/* Report and clear error state, try to continue.
*/
TRACE(5, "error status set");
ftape_report_error(&error, &command, 1);
ftape_ready_wait(timeout.reset, &status);
tape_running = 0; /* ? */
}
if (check_bot_eot(status)) {
if (location.bot) {
if ((status & QIC_STATUS_READY) == 0) {
/* tape moving away from bot/eot, let's see if we
* can catch up with the first segment on this track.
*/
} else {
TRACE(5, "start tape from logical bot");
logical_forward(); /* start moving */
}
} else {
if ((status & QIC_STATUS_READY) == 0) {
TRACE(4, "waiting for logical end of track");
result = ftape_ready_wait(timeout.reset, &status);
/* error handling needed ? */
} else {
TRACE(4, "tape at logical end of track");
}
}
} else {
TRACE(5, "start tape");
logical_forward(); /* start moving */
location.known = 0; /* not cleared by logical forward ! */
}
}
if (!location.known) {
/* tape should be moving now, start reading id's
*/
TRACE(5, "location unknown");
do {
result = ftape_read_id();
if (result < 0) {
/* read-id somehow failed, tape may have reached end
* or some other error happened.
*/
TRACE(5, "read-id failed");
ftape_report_drive_status(&status);
if (status & QIC_STATUS_READY) {
tape_running = 0;
TRACEx1(4, "tape stopped for unknown reason ! status = 0x%02x",
status);
if (status & QIC_STATUS_ERROR) {
fatal = 1;
} else {
if (check_bot_eot(status)) {
result = 0;
} else {
fatal = 1; /* oops, tape stopped but not at end ! */
}
}
}
result = -EIO;
}
} while (result < 0 && !fatal && ++retry < SECTORS_PER_SEGMENT);
} else {
result = 0;
}
TRACEx1(5, "tape is positioned at segment %d", location.segment);
TRACE_EXIT;
return result;
}
/* Get the tape running and position it just before the
* requested segment.
* Seek tape-track and reposition as needed.
*/
int ftape_start_tape(int segment_id, int sector_offset)
{
TRACE_FUN(5, "ftape_start_tape");
int track = segment_id / segments_per_track;
int result = -EIO;
int status;
static int last_segment = -1;
static int bad_bus_timing = 0;
/* number of segments passing the head between starting the tape
* and being able to access the first sector.
*/
static int start_offset = 1;
int retry = 0;
/* If sector_offset > 0, seek into wanted segment instead of
* into previous.
* This allows error recovery if a part of the segment is bad
* (erased) causing the tape drive to generate an index pulse
* thus causing a no-data error before the requested sector
* is reached.
*/
tape_running = 0;
TRACEx3(4, "target segment: %d/%d%s", segment_id, sector_offset,
buffer[head].retry > 0 ? " retry" : "");
if (buffer[head].retry > 0) { /* this is a retry */
if (!bad_bus_timing && ftape_data_rate == 1 &&
history.overrun_errors - overrun_count_offset >= 8) {
ftape_set_data_rate(ftape_data_rate + 1);
bad_bus_timing = 1;
TRACE(2, "reduced datarate because of excessive overrun errors");
}
}
last_segment = segment_id;
if (location.track != track || (might_be_off_track &&
buffer[head].retry == 0)) {
/* current track unknown or not equal to destination
*/
ftape_ready_wait(timeout.seek, &status);
ftape_seek_head_to_track(track);
overrun_count_offset = history.overrun_errors;
}
do {
if (!location.known) {
determine_position();
}
/* Check if we are able to catch the requested segment in time.
*/
if (location.known && location.segment >= segment_id -
((tape_running || location.bot) ? 0 : start_offset)) {
/* Too far ahead (in or past target segment).
*/
if (tape_running) {
result = stop_tape(&status);
if (result < 0) {
TRACEi(1, "stop tape failed with code", result);
break;
}
TRACE(5, "tape stopped");
tape_running = 0;
}
TRACE(5, "repositioning");
++history.rewinds;
if (segment_id % segments_per_track < start_offset) {
/* If seeking to first segments on track better do a complete
* rewind to logical begin of track to get a more steady tape
* motion.
*/
result = ftape_command_wait((location.track & 1) ?
QIC_PHYSICAL_FORWARD :
QIC_PHYSICAL_REVERSE,
timeout.rewind, &status);
check_bot_eot(status); /* update location */
} else {
result = skip_reverse(segment_id - start_offset, &status);
}
}
if (!location.known) {
TRACE(-1, "panic: location not known");
result = -EIO;
if ((current->signal & _DONT_BLOCK) || ftape_failure) {
break;
} else {
continue;
}
}
TRACEx2(4, "current segment: %d/%d", location.segment, location.sector);
/* We're on the right track somewhere before the wanted segment.
* Start tape movement if needed and skip to just before or inside
* the requested segment. Keep tape running.
*/
result = 0;
if (location.segment < segment_id -
((tape_running || location.bot) ? 0 : start_offset)) {
if (sector_offset > 0) {
result = seek_forward(segment_id);
} else {
result = seek_forward(segment_id - 1);
}
}
if (result == 0 &&
location.segment != segment_id - (sector_offset > 0 ? 0 : 1)) {
result = -EIO;
}
} while (result < 0 && !ftape_failure &&
(current->signal & _DONT_BLOCK) == 0 &&
++retry <= 5);
if (result < 0) {
TRACE(1, "failed to reposition");
}
TRACE_EXIT;
return result;
}
