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-rw-r--r--drivers/char/ftape/lowlevel/ftape-rw.c1092
1 files changed, 0 insertions, 1092 deletions
diff --git a/drivers/char/ftape/lowlevel/ftape-rw.c b/drivers/char/ftape/lowlevel/ftape-rw.c
deleted file mode 100644
index c0d6dc2cbfd3..000000000000
--- a/drivers/char/ftape/lowlevel/ftape-rw.c
+++ /dev/null
@@ -1,1092 +0,0 @@
-/*
- *      Copyright (C) 1993-1996 Bas Laarhoven,
- *                (C) 1996-1997 Claus-Justus Heine.
-
- 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: /homes/cvs/ftape-stacked/ftape/lowlevel/ftape-rw.c,v $
- * $Revision: 1.7 $
- * $Date: 1997/10/28 14:26:49 $
- *
- *      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 <linux/qic117.h>
-#include "../lowlevel/ftape-tracing.h"
-#include "../lowlevel/ftape-rw.h"
-#include "../lowlevel/fdc-io.h"
-#include "../lowlevel/ftape-init.h"
-#include "../lowlevel/ftape-io.h"
-#include "../lowlevel/ftape-ctl.h"
-#include "../lowlevel/ftape-read.h"
-#include "../lowlevel/ftape-ecc.h"
-#include "../lowlevel/ftape-bsm.h"
-
-/*      Global vars.
- */
-int ft_nr_buffers;
-buffer_struct *ft_buffer[FT_MAX_NR_BUFFERS];
-static volatile int ft_head;
-static volatile int ft_tail;	/* not volatile but need same type as head */
-int fdc_setup_error;
-location_record ft_location = {-1, 0};
-volatile int ftape_tape_running;
-
-/*      Local vars.
- */
-static int overrun_count_offset;
-static int inhibit_correction;
-
-/*  maxmimal allowed overshoot when fast seeking
- */
-#define OVERSHOOT_LIMIT 10
-
-/*      Increment cyclic buffer nr.
- */
-buffer_struct *ftape_next_buffer(ft_buffer_queue_t pos)
-{
-	switch (pos) {
-	case ft_queue_head:
-		if (++ft_head >= ft_nr_buffers) {
-			ft_head = 0;
-		}
-		return ft_buffer[ft_head];
-	case ft_queue_tail:
-		if (++ft_tail >= ft_nr_buffers) {
-			ft_tail = 0;
-		}
-		return ft_buffer[ft_tail];
-	default:
-		return NULL;
-	}
-}
-int ftape_buffer_id(ft_buffer_queue_t pos)
-{
-	switch(pos) {
-	case ft_queue_head: return ft_head;
-	case ft_queue_tail: return ft_tail;
-	default: return -1;
-	}
-}
-buffer_struct *ftape_get_buffer(ft_buffer_queue_t pos)
-{
-	switch(pos) {
-	case ft_queue_head: return ft_buffer[ft_head];
-	case ft_queue_tail: return ft_buffer[ft_tail];
-	default: return NULL;
-	}
-}
-void ftape_reset_buffer(void)
-{
-	ft_head = ft_tail = 0;
-}
-
-buffer_state_enum ftape_set_state(buffer_state_enum new_state)
-{
-	buffer_state_enum old_state = ft_driver_state;
-
-	ft_driver_state = new_state;
-	return old_state;
-}
-/*      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, 
-			 int segment_id,
-			 unsigned int sector_offset, 
-			 unsigned int sector_count, 
-			 int retry)
-{
-	SectorMap offset_mask;
-	SectorMap mask;
-	TRACE_FUN(ft_t_any);
-
-	buff->segment_id = segment_id;
-	buff->sector_offset = sector_offset;
-	buff->remaining = sector_count;
-	buff->head = segment_id / ftape_segments_per_head;
-	buff->cyl = (segment_id % ftape_segments_per_head) / ftape_segments_per_cylinder;
-	buff->sect = (segment_id % ftape_segments_per_cylinder) * FT_SECTORS_PER_SEGMENT + 1;
-	buff->deleted = 0;
-	offset_mask = (1 << buff->sector_offset) - 1;
-	mask = ftape_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 * FT_SECTOR_SIZE;
-	TRACE(ft_t_flow, "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 = ftape_get_bad_sector_entry(buff->segment_id);
-	if (buff->bad_sector_map != 0) {
-		TRACE(ft_t_noise, "segment: %d, bad sector map: %08lx",
-			buff->segment_id, (long)buff->bad_sector_map);
-	} else {
-		TRACE(ft_t_flow, "segment: %d", buff->segment_id);
-	}
-	if (buff->sector_offset > 0) {
-		buff->bad_sector_map >>= buff->sector_offset;
-	}
-	if (buff->sector_offset != 0 || buff->remaining != FT_SECTORS_PER_SEGMENT) {
-		TRACE(ft_t_flow, "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(ft_t_flow, "empty segment %d, fake first sector good",
-		      buff->segment_id);
-		if (buff->ptr != buff->address) {
-			TRACE(ft_t_bug, "This is a bug: %p/%p",
-			      buff->ptr, buff->address);
-		}
-		buff->bad_sector_map = FAKE_SEGMENT;
-	}
-	fdc_setup_error = 0;
-	buff->next_segment = segment_id + 1;
-	TRACE_EXIT 0;
-}
-
-/*      Calculate Floppy Disk Controller and DMA parameters for a new segment.
- */
-int ftape_setup_new_segment(buffer_struct * buff, int segment_id, int skip)
-{
-	int result = 0;
-	static int old_segment_id = -1;
-	static buffer_state_enum old_ft_driver_state = idle;
-	int retry = 0;
-	unsigned offset = 0;
-	int count = FT_SECTORS_PER_SEGMENT;
-	TRACE_FUN(ft_t_flow);
-
-	TRACE(ft_t_flow, "%s segment %d (old = %d)",
-	      (ft_driver_state == reading || ft_driver_state == verifying) 
-	      ? "reading" : "writing",
-	      segment_id, old_segment_id);
-	if (ft_driver_state != old_ft_driver_state) {	/* when verifying */
-		old_segment_id = -1;
-		old_ft_driver_state = ft_driver_state;
-	}
-	if (segment_id == old_segment_id) {
-		++buff->retry;
-		++ft_history.retries;
-		TRACE(ft_t_flow, "setting up for retry nr %d", buff->retry);
-		retry = 1;
-		if (skip && buff->skip > 0) {	/* allow skip on retry */
-			offset = buff->skip;
-			count -= offset;
-			TRACE(ft_t_flow, "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 result;
-}
-
-/*      Determine size of next cluster of good sectors.
- */
-int ftape_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 {
-		SectorMap 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;
-}
-
-/*  if just passed the last segment on a track, wait for BOT
- *  or EOT mark.
- */
-int ftape_handle_logical_eot(void)
-{
-	TRACE_FUN(ft_t_flow);
-
-	if (ft_runner_status == logical_eot) {
-		int status;
-
-		TRACE(ft_t_noise, "tape at logical EOT");
-		TRACE_CATCH(ftape_ready_wait(ftape_timeout.seek, &status),);
-		if ((status & (QIC_STATUS_AT_BOT | QIC_STATUS_AT_EOT)) == 0) {
-			TRACE_ABORT(-EIO, ft_t_err, "eot/bot not reached");
-		}
-		ft_runner_status = end_of_tape;
-	}
-	if (ft_runner_status == end_of_tape) {
-		TRACE(ft_t_noise, "runner stopped because of logical EOT");
-		ft_runner_status = idle;
-	}
-	TRACE_EXIT 0;
-}
-
-static int check_bot_eot(int status)
-{
-	TRACE_FUN(ft_t_flow);
-
-	if (status & (QIC_STATUS_AT_BOT | QIC_STATUS_AT_EOT)) {
-		ft_location.bot = ((ft_location.track & 1) == 0 ?
-				(status & QIC_STATUS_AT_BOT) != 0:
-				(status & QIC_STATUS_AT_EOT) != 0);
-		ft_location.eot = !ft_location.bot;
-		ft_location.segment = (ft_location.track +
-			(ft_location.bot ? 0 : 1)) * ft_segments_per_track - 1;
-		ft_location.sector = -1;
-		ft_location.known  = 1;
-		TRACE(ft_t_flow, "tape at logical %s",
-		      ft_location.bot ? "bot" : "eot");
-		TRACE(ft_t_flow, "segment = %d", ft_location.segment);
-	} else {
-		ft_location.known = 0;
-	}
-	TRACE_EXIT ft_location.known;
-}
-
-/*      Read Id of first sector passing tape head.
- */
-static int ftape_read_id(void)
-{
-	int status;
-	__u8 out[2];
-	TRACE_FUN(ft_t_any);
-
-	/* Assume tape is running on entry, be able to handle
-	 * situation where it stopped or is stopping.
-	 */
-	ft_location.known = 0;	/* default is location not known */
-	out[0] = FDC_READID;
-	out[1] = ft_drive_sel;
-	TRACE_CATCH(fdc_command(out, 2),);
-	switch (fdc_interrupt_wait(20 * FT_SECOND)) {
-	case 0:
-		if (fdc_sect == 0) {
-			if (ftape_report_drive_status(&status) >= 0 &&
-			    (status & QIC_STATUS_READY)) {
-				ftape_tape_running = 0;
-				TRACE(ft_t_flow, "tape has stopped");
-				check_bot_eot(status);
-			}
-		} else {
-			ft_location.known = 1;
-			ft_location.segment = (ftape_segments_per_head
-					       * fdc_head
-					       + ftape_segments_per_cylinder
-					       * fdc_cyl
-					       + (fdc_sect - 1)
-					       / FT_SECTORS_PER_SEGMENT);
-			ft_location.sector = ((fdc_sect - 1)
-					      % FT_SECTORS_PER_SEGMENT);
-			ft_location.eot = ft_location.bot = 0;
-		}
-		break;
-	case -ETIME:
-		/*  Didn't find id on tape, must be near end: Wait
-		 *  until stopped.
-		 */
-		if (ftape_ready_wait(FT_FOREVER, &status) >= 0) {
-			ftape_tape_running = 0;
-			TRACE(ft_t_flow, "tape has stopped");
-			check_bot_eot(status);
-		}
-		break;
-	default:
-		/*  Interrupted or otherwise failing
-		 *  fdc_interrupt_wait() 
-		 */
-		TRACE(ft_t_err, "fdc_interrupt_wait failed");
-		break;
-	}
-	if (!ft_location.known) {
-		TRACE_ABORT(-EIO, ft_t_flow, "no id found");
-	}
-	if (ft_location.sector == 0) {
-		TRACE(ft_t_flow, "passing segment %d/%d",
-		      ft_location.segment, ft_location.sector);
-	} else {
-		TRACE(ft_t_fdc_dma, "passing segment %d/%d",
-		      ft_location.segment, ft_location.sector);
-	}
-	TRACE_EXIT 0;
-}
-
-static int logical_forward(void)
-{
-	ftape_tape_running = 1;
-	return ftape_command(QIC_LOGICAL_FORWARD);
-}
-
-int ftape_stop_tape(int *pstatus)
-{
-	int retry = 0;
-	int result;
-	TRACE_FUN(ft_t_flow);
-
-	do {
-		result = ftape_command_wait(QIC_STOP_TAPE,
-					    ftape_timeout.stop, pstatus);
-		if (result == 0) {
-			if ((*pstatus & QIC_STATUS_READY) == 0) {
-				result = -EIO;
-			} else {
-				ftape_tape_running = 0;
-			}
-		}
-	} while (result < 0 && ++retry <= 3);
-	if (result < 0) {
-		TRACE(ft_t_err, "failed ! (fatal)");
-	}
-	TRACE_EXIT result;
-}
-
-int ftape_dumb_stop(void)
-{
-	int result;
-	int status;
-	TRACE_FUN(ft_t_flow);
-
-	/*  Abort current fdc operation if it's busy (probably read
-	 *  or write operation pending) with a reset.
-	 */
-	if (fdc_ready_wait(100 /* usec */) < 0) {
-		TRACE(ft_t_noise, "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);
-	ft_location.known = 0;
-	do {
-		if (result == 0 && status & QIC_STATUS_READY) {
-			/* Tape is not running any more.
-			 */
-			TRACE(ft_t_noise, "tape already halted");
-			check_bot_eot(status);
-			ftape_tape_running = 0;
-		} else if (ftape_tape_running) {
-			/*  Tape is (was) still moving.
-			 */
-#ifdef TESTING
-			ftape_read_id();
-#endif
-			result = ftape_stop_tape(&status);
-		} else {
-			/*  Tape not yet ready but stopped.
-			 */
-			result = ftape_ready_wait(ftape_timeout.pause,&status);
-		}
-	} while (ftape_tape_running
-		 && !(sigtestsetmask(&current->pending.signal, _NEVER_BLOCK)));
-#ifndef TESTING
-	ft_location.known = 0;
-#endif
-	if (ft_runner_status == aborting || ft_runner_status == do_abort) {
-		ft_runner_status = idle;
-	}
-	TRACE_EXIT result;
-}
-
-/*      Wait until runner has finished tail buffer.
- *
- */
-int ftape_wait_segment(buffer_state_enum state)
-{
-	int status;
-	int result = 0;
-	TRACE_FUN(ft_t_flow);
-
-	while (ft_buffer[ft_tail]->status == state) {
-		TRACE(ft_t_flow, "state: %d", ft_buffer[ft_tail]->status);
-		/*  First buffer still being worked on, wait up to timeout.
-		 *
-		 *  Note: we check two times for being killed. 50
-		 *  seconds are quite long. Note that
-		 *  fdc_interrupt_wait() is not killable by any
-		 *  means. ftape_read_segment() wants us to return
-		 *  -EINTR in case of a signal.  
-		 */
-		FT_SIGNAL_EXIT(_DONT_BLOCK);
-		result = fdc_interrupt_wait(50 * FT_SECOND);
-		FT_SIGNAL_EXIT(_DONT_BLOCK);
-		if (result < 0) {
-			TRACE_ABORT(result,
-				    ft_t_err, "fdc_interrupt_wait failed");
-		}
-		if (fdc_setup_error) {
-			/* recover... FIXME */
-			TRACE_ABORT(-EIO, ft_t_err, "setup error");
-		}
-	}
-	if (ft_buffer[ft_tail]->status != error) {
-		TRACE_EXIT 0;
-	}
-	TRACE_CATCH(ftape_report_drive_status(&status),);
-	TRACE(ft_t_noise, "ftape_report_drive_status: 0x%02x", status);
-	if ((status & QIC_STATUS_READY) && 
-	    (status & QIC_STATUS_ERROR)) {
-		unsigned int error;
-		qic117_cmd_t command;
-		
-		/*  Report and clear error state.
-		 *  In case the drive can't operate at the selected
-		 *  rate, select the next lower data rate.
-		 */
-		ftape_report_error(&error, &command, 1);
-		if (error == 31 && command == QIC_LOGICAL_FORWARD) {
-			/* drive does not accept this data rate */
-			if (ft_data_rate > 250) {
-				TRACE(ft_t_info,
-				      "Probable data rate conflict");
-				TRACE(ft_t_info,
-				      "Lowering data rate to %d Kbps",
-				      ft_data_rate / 2);
-				ftape_half_data_rate();
-				if (ft_buffer[ft_tail]->retry > 0) {
-					/* give it a chance */
-					--ft_buffer[ft_tail]->retry;
-				}
-			} else {
-				/* no rate is accepted... */
-				TRACE(ft_t_err, "We're dead :(");
-			}
-		} else {
-			TRACE(ft_t_err, "Unknown error");
-		}
-		TRACE_EXIT -EIO;   /* g.p. error */
-	}
-	TRACE_EXIT 0;
-}
-
-/* forward */ static int seek_forward(int segment_id, int fast);
-
-static int fast_seek(int count, int reverse)
-{
-	int result = 0;
-	int status;
-	TRACE_FUN(ft_t_flow);
-
-	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 (ft_location.known &&
-		    ((ft_location.bot && !reverse) ||
-		     (ft_location.eot && reverse))) {
-			if (!reverse) {
-				/*  (slow) skip to first segment on a track
-				 */
-				seek_forward(ft_location.track * ft_segments_per_track, 0);
-				--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 {
-		TRACE(ft_t_flow, "warning: zero or negative count: %d", count);
-	}
-	if (count > 0) {
-		int i;
-		int nibbles = count > 255 ? 3 : 2;
-
-		if (count > 4095) {
-			TRACE(ft_t_noise, "skipping clipped at 4095 segment");
-			count = 4095;
-		}
-		/* Issue this tape command first. */
-		if (!reverse) {
-			TRACE(ft_t_noise, "skipping %d segment(s)", count);
-			result = ftape_command(nibbles == 3 ?
-			   QIC_SKIP_EXTENDED_FORWARD : QIC_SKIP_FORWARD);
-		} else {
-			TRACE(ft_t_noise, "backing up %d segment(s)", count);
-			result = ftape_command(nibbles == 3 ?
-			   QIC_SKIP_EXTENDED_REVERSE : QIC_SKIP_REVERSE);
-		}
-		if (result < 0) {
-			TRACE(ft_t_noise, "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(ftape_timeout.rewind, &status);
-			if (result >= 0) {
-				ftape_tape_running = 0;
-			}
-		}
-	}
-	TRACE_EXIT 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 * ft_segments_per_track.
-	 */
-	if (ft_location.track == -1) {
-		return 1; /* unforseen situation, don't generate error */
-	} else {
-		/* Use margin of ft_segments_per_track on both sides
-		 * because ftape needs some margin and the error we're
-		 * looking for is much larger !
-		 */
-		int lo = (ft_location.track - 1) * ft_segments_per_track;
-		int hi = (ft_location.track + 2) * ft_segments_per_track;
-
-		return (id >= lo && id < hi);
-	}
-}
-
-static int seek_forward(int segment_id, int fast)
-{
-	int failures = 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;
-	int prev_segment = ft_location.segment;
-	TRACE_FUN(ft_t_flow);
-
-	if (!ft_location.known) {
-		TRACE_ABORT(-EIO, ft_t_err,
-			    "fatal: cannot seek from unknown location");
-	}
-	if (!validate(segment_id)) {
-		ftape_sleep(1 * FT_SECOND);
-		ft_failure = 1;
-		TRACE_ABORT(-EIO, ft_t_err,
-			    "fatal: head off track (bad hardware?)");
-	}
-	TRACE(ft_t_noise, "from %d/%d to %d/0 - %d",
-	      ft_location.segment, ft_location.sector,segment_id,margin);
-	count = target - ft_location.segment - overshoot;
-	fast_seeking = (fast &&
-			count > (min_count + (ft_location.bot ? 1 : 0)));
-	if (fast_seeking) {
-		TRACE(ft_t_noise, "fast skipping %d segments", count);
-		expected = segment_id - margin;
-		fast_seek(count, 0);
-	}
-	if (!ftape_tape_running) {
-		logical_forward();
-	}
-	while (ft_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 || !ft_location.known ||
-		    sigtestsetmask(&current->pending.signal, _DONT_BLOCK)) {
-			ft_location.known = 0;
-			if (!ftape_tape_running ||
-			    ++failures > FT_SECTORS_PER_SEGMENT) {
-				TRACE_ABORT(-EIO, ft_t_err,
-					    "read_id failed completely");
-			}
-			FT_SIGNAL_EXIT(_DONT_BLOCK);
-			TRACE(ft_t_flow, "read_id failed, retry (%d)",
-			      failures);
-			continue;
-		}
-		if (fast_seeking) {
-			TRACE(ft_t_noise, "ended at %d/%d (%d,%d)",
-			      ft_location.segment, ft_location.sector,
-			      overshoot, inhibit_correction);
-			if (!inhibit_correction &&
-			    (ft_location.segment < expected ||
-			     ft_location.segment > expected + margin)) {
-				int error = ft_location.segment - expected;
-				TRACE(ft_t_noise,
-				      "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 > OVERSHOOT_LIMIT) {
-					if (overshoot < 0) {
-						/* keep sane value */
-						overshoot = -5;
-					} else {
-						/* keep sane value */
-						overshoot = OVERSHOOT_LIMIT;
-					}
-					TRACE(ft_t_noise,
-					      "clipped overshoot to %d",
-					      overshoot);
-				}
-			}
-			fast_seeking = 0;
-		}
-		if (ft_location.known) {
-			if (ft_location.segment > prev_segment + 1) {
-				TRACE(ft_t_noise,
-				      "missed segment %d while skipping",
-				      prev_segment + 1);
-			}
-			prev_segment = ft_location.segment;
-		}
-	}
-	if (ft_location.segment > segment_id) {
-		TRACE_ABORT(-EIO,
-			    ft_t_noise, "failed: skip ended at segment %d/%d",
-			    ft_location.segment, ft_location.sector);
-	}
-	TRACE_EXIT 0;
-}
-
-static int skip_reverse(int segment_id, int *pstatus)
-{
-	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 = 1;
-	int short_seek;
-	int target = segment_id - margin;
-	TRACE_FUN(ft_t_flow);
-
-	if (ft_location.known && !validate(segment_id)) {
-		ftape_sleep(1 * FT_SECOND);
-		ft_failure = 1;
-		TRACE_ABORT(-EIO, ft_t_err,
-			    "fatal: head off track (bad hardware?)");
-	}
-	do {
-		if (!ft_location.known) {
-			TRACE(ft_t_warn, "warning: location not known");
-		}
-		TRACE(ft_t_noise, "from %d/%d to %d/0 - %d",
-		      ft_location.segment, ft_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 (ft_location.segment - target - (min_rewind - 1) < 1) {
-			short_seek = 1;
-		} else {
-			count = ft_location.segment - target - overshoot;
-			short_seek = (count < 1);
-		}
-		if (short_seek) {
-			count = 1;	/* do shortest rewind */
-			expected = ft_location.segment - min_rewind;
-			if (expected/ft_segments_per_track != ft_location.track) {
-				expected = (ft_location.track * 
-					    ft_segments_per_track);
-			}
-		} else {
-			expected = target;
-		}
-		fast_seek(count, 1);
-		logical_forward();
-		if (ftape_read_id() < 0 || !ft_location.known ||
-		    (sigtestsetmask(&current->pending.signal, _DONT_BLOCK))) {
-			if ((!ftape_tape_running && !ft_location.known) ||
-			    ++failures > FT_SECTORS_PER_SEGMENT) {
-				TRACE_ABORT(-EIO, ft_t_err,
-					    "read_id failed completely");
-			}
-			FT_SIGNAL_EXIT(_DONT_BLOCK);
-			TRACE_CATCH(ftape_report_drive_status(pstatus),);
-			TRACE(ft_t_noise, "ftape_read_id failed, retry (%d)",
-			      failures);
-			continue;
-		}
-		TRACE(ft_t_noise, "ended at %d/%d (%d,%d,%d)", 
-		      ft_location.segment, ft_location.sector,
-		      min_rewind, overshoot, inhibit_correction);
-		if (!inhibit_correction &&
-		    (ft_location.segment < expected ||
-		     ft_location.segment > expected + margin)) {
-			int error = expected - ft_location.segment;
-			if (short_seek) {
-				TRACE(ft_t_noise,
-				      "adjusting min_rewind from %d to %d",
-				      min_rewind, min_rewind + error);
-				min_rewind += error;
-				if (min_rewind < -5) {
-					/* is this right ? FIXME ! */
-					/* keep sane value */
-					min_rewind = -5;
-					TRACE(ft_t_noise, 
-					      "clipped min_rewind to %d",
-					      min_rewind);
-				}
-			} else {
-				TRACE(ft_t_noise,
-				      "adjusting overshoot from %d to %d",
-				      overshoot, overshoot + error);
-				overshoot += error;
-				if (overshoot < -5 ||
-				    overshoot > OVERSHOOT_LIMIT) {
-					if (overshoot < 0) {
-						/* keep sane value */
-						overshoot = -5;
-					} else {
-						/* keep sane value */
-						overshoot = OVERSHOOT_LIMIT;
-					}
-					TRACE(ft_t_noise,
-					      "clipped overshoot to %d",
-					      overshoot);
-				}
-			}
-		}
-	} while (ft_location.segment > segment_id);
-	if (ft_location.known) {
-		TRACE(ft_t_noise, "current location: %d/%d",
-		      ft_location.segment, ft_location.sector);
-	}
-	TRACE_EXIT 0;
-}
-
-static int determine_position(void)
-{
-	int retry = 0;
-	int status;
-	int result;
-	TRACE_FUN(ft_t_flow);
-
-	if (!ftape_tape_running) {
-		/*  This should only happen if tape is stopped by isr.
-		 */
-		TRACE(ft_t_flow, "waiting for tape stop");
-		if (ftape_ready_wait(ftape_timeout.pause, &status) < 0) {
-			TRACE(ft_t_flow, "drive still running (fatal)");
-			ftape_tape_running = 1;	/* ? */
-		}
-	} else {
-		ftape_report_drive_status(&status);
-	}
-	if (status & QIC_STATUS_READY) {
-		/*  Drive must be ready to check error state !
-		 */
-		TRACE(ft_t_flow, "drive is ready");
-		if (status & QIC_STATUS_ERROR) {
-			unsigned int error;
-			qic117_cmd_t command;
-
-			/*  Report and clear error state, try to continue.
-			 */
-			TRACE(ft_t_flow, "error status set");
-			ftape_report_error(&error, &command, 1);
-			ftape_ready_wait(ftape_timeout.reset, &status);
-			ftape_tape_running = 0;	/* ? */
-		}
-		if (check_bot_eot(status)) {
-			if (ft_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(ft_t_flow,
-					      "start tape from logical bot");
-					logical_forward();	/* start moving */
-				}
-			} else {
-				if ((status & QIC_STATUS_READY) == 0) {
-					TRACE(ft_t_noise, "waiting for logical end of track");
-					result = ftape_ready_wait(ftape_timeout.reset, &status);
-					/* error handling needed ? */
-				} else {
-					TRACE(ft_t_noise,
-					      "tape at logical end of track");
-				}
-			}
-		} else {
-			TRACE(ft_t_flow, "start tape");
-			logical_forward();	/* start moving */
-			ft_location.known = 0;	/* not cleared by logical forward ! */
-		}
-	}
-	/* tape should be moving now, start reading id's
-	 */
-	while (!ft_location.known &&
-	       retry++ < FT_SECTORS_PER_SEGMENT &&
-	       (result = ftape_read_id()) < 0) {
-
-		TRACE(ft_t_flow, "location unknown");
-
-		/* exit on signal
-		 */
-		FT_SIGNAL_EXIT(_DONT_BLOCK);
-
-		/*  read-id somehow failed, tape may
-		 *  have reached end or some other
-		 *  error happened.
-		 */
-		TRACE(ft_t_flow, "read-id failed");
-		TRACE_CATCH(ftape_report_drive_status(&status),);
-		TRACE(ft_t_err, "ftape_report_drive_status: 0x%02x", status);
-		if (status & QIC_STATUS_READY) {
-			ftape_tape_running = 0;
-			TRACE(ft_t_noise, "tape stopped for unknown reason! "
-			      "status = 0x%02x", status);
-			if (status & QIC_STATUS_ERROR ||
-			    !check_bot_eot(status)) {
-				/* oops, tape stopped but not at end!
-				 */
-				TRACE_EXIT -EIO;
-			}
-		}
-	}
-	TRACE(ft_t_flow,
-	      "tape is positioned at segment %d", ft_location.segment);
-	TRACE_EXIT ft_location.known ? 0 : -EIO;
-}
-
-/*      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)
-{
-	int track = segment_id / ft_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;
-	TRACE_FUN(ft_t_flow);
-
-	/* 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.
-	 */
-	ftape_tape_running = 0;
-	TRACE(ft_t_noise, "target segment: %d/%d%s", segment_id, sector_offset,
-		ft_buffer[ft_head]->retry > 0 ? " retry" : "");
-	if (ft_buffer[ft_head]->retry > 0) {	/* this is a retry */
-		int dist = segment_id - last_segment;
-
-		if ((int)ft_history.overrun_errors < overrun_count_offset) {
-			overrun_count_offset = ft_history.overrun_errors;
-		} else if (dist < 0 || dist > 50) {
-			overrun_count_offset = ft_history.overrun_errors;
-		} else if ((ft_history.overrun_errors -
-			    overrun_count_offset) >= 8) {
-			if (ftape_increase_threshold() >= 0) {
-				--ft_buffer[ft_head]->retry;
-				overrun_count_offset =
-					ft_history.overrun_errors;
-				TRACE(ft_t_warn, "increased threshold because "
-				      "of excessive overrun errors");
-			} else if (!bad_bus_timing && ft_data_rate >= 1000) {
-				ftape_half_data_rate();
-				--ft_buffer[ft_head]->retry;
-				bad_bus_timing = 1;
-				overrun_count_offset =
-					ft_history.overrun_errors;
-				TRACE(ft_t_warn, "reduced datarate because "
-				      "of excessive overrun errors");
-			}
-		}
-	}
-	last_segment = segment_id;
-	if (ft_location.track != track ||
-	    (ftape_might_be_off_track && ft_buffer[ft_head]->retry== 0)) {
-		/* current track unknown or not equal to destination
-		 */
-		ftape_ready_wait(ftape_timeout.seek, &status);
-		ftape_seek_head_to_track(track);
-		/* overrun_count_offset = ft_history.overrun_errors; */
-	}
-	result = -EIO;
-	retry = 0;
-	while (result < 0     &&
-	       retry++ <= 5   &&
-	       !ft_failure &&
-	       !(sigtestsetmask(&current->pending.signal, _DONT_BLOCK))) {
-		
-		if (retry && start_offset < 5) {
-			start_offset ++;
-		}
-		/*  Check if we are able to catch the requested
-		 *  segment in time.
-		 */
-		if ((ft_location.known || (determine_position() == 0)) &&
-		    ft_location.segment >=
-		    (segment_id -
-		     ((ftape_tape_running || ft_location.bot)
-		      ? 0 : start_offset))) {
-			/*  Too far ahead (in or past target segment).
-			 */
-			if (ftape_tape_running) {
-				if ((result = ftape_stop_tape(&status)) < 0) {
-					TRACE(ft_t_err,
-					      "stop tape failed with code %d",
-					      result);
-					break;
-				}
-				TRACE(ft_t_noise, "tape stopped");
-				ftape_tape_running = 0;
-			}
-			TRACE(ft_t_noise, "repositioning");
-			++ft_history.rewinds;
-			if (segment_id % ft_segments_per_track < start_offset){
-				TRACE(ft_t_noise, "end of track condition\n"
-				      KERN_INFO "segment_id        : %d\n"
-				      KERN_INFO "ft_segments_per_track: %d\n"
-				      KERN_INFO "start_offset      : %d",
-				      segment_id, ft_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(
-					(ft_location.track & 1)
-					? QIC_PHYSICAL_FORWARD
-					: QIC_PHYSICAL_REVERSE,
-					ftape_timeout.rewind, &status);
-				check_bot_eot(status);	/* update location */
-			} else {
-				result= skip_reverse(segment_id - start_offset,
-						     &status);
-			}
-		}
-		if (!ft_location.known) {
-			TRACE(ft_t_bug, "panic: location not known");
-			result = -EIO;
-			continue; /* while() will check for failure */
-		}
-		TRACE(ft_t_noise, "current segment: %d/%d",
-		      ft_location.segment, ft_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 (ft_location.segment < 
-		    (segment_id - ((ftape_tape_running || ft_location.bot)
-				   ? 0 : start_offset))) {
-			if (sector_offset > 0) {
-				result = seek_forward(segment_id,
-						      retry <= 3);
-			} else {
-				result = seek_forward(segment_id - 1,
-						      retry <= 3);
-			}
-		}
-		if (result == 0 &&
-		    ft_location.segment !=
-		    (segment_id - (sector_offset > 0 ? 0 : 1))) {
-			result = -EIO;
-		}
-	}
-	if (result < 0) {
-		TRACE(ft_t_err, "failed to reposition");
-	} else {
-		ft_runner_status = running;
-	}
-	TRACE_EXIT result;
-}