ftape-eof.c

arm平台上的uclinux系统全部源代码

/*
 *      Copyright (C) 1994-1995 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: /usr/local/cvsroot/AplioTRIO/linux/drivers/char/ftape/ftape-eof.c,v $
 $Author: vadim $
 *
 $Revision: 1.1.1.1 $
 $Date: 1999/11/15 13:41:57 $
 $State: Exp $
 *
 *      This file contains the eof mark handling code
 *      for the QIC-40/80 floppy-tape driver for Linux.
 */

#include <linux/ftape.h>
#include <linux/string.h>
#include <linux/errno.h>

#include "tracing.h"
#include "ftape-eof.h"
#include "ftape-write.h"
#include "ftape-read.h"
#include "ftape-rw.h"
#include "ftape-ctl.h"
#include "ftape-bsm.h"

/*      Global vars.
 */
int failed_sector_log_changed = 0;
int eof_mark = 0;

/*      Local vars.
 */
static struct failed_sector_entry {
	unsigned short segment;
	unsigned short sector;
} *eof_mark_ptr;

typedef union {
	struct failed_sector_entry mark;
	unsigned long entry;
} eof_mark_union;

/*  a copy of the failed sector log from the header segment.
 */
static eof_mark_union eof_map[(2048 - 256) / 4];

/*  index into eof_map table pointing to last found eof mark.
 */
static int eof_index;

/*  number of eof marks (entries in bad sector log) on tape.
 */
static int nr_of_eof_marks = -1;

static char linux_tape_label[] = "Linux raw format V";
enum {
	min_fmt_version = 1, max_fmt_version = 2
};
static unsigned ftape_fmt_version = 0;


/*  Ftape (mis)uses the bad sector log to record end-of-file marks.
 *  Initially (when the tape is erased) all entries in the bad sector
 *  log are added to the tape's bad sector map. The bad sector log
 *  then is cleared.
 *
 *  The bad sector log normally contains entries of the form:
 *  even 16-bit word: segment number of bad sector
 *   odd 16-bit word: encoded date
 *  There can be a total of 448 entries (1792 bytes).
 *
 *  My guess is that no program is using this bad sector log (the
 *  format seems useless as there is no indication of the bad sector
 *  itself, only the segment)
 *  However, if any program does use the bad sector log, the format
 *  used by ftape will let the program think there are some bad sectors
 *  and no harm is done.
 *  
 *  The eof mark entries that ftape stores in the bad sector log:
 *  even 16-bit word: segment number of eof mark
 *   odd 16-bit word: sector number of eof mark [1..32]
 *  
 *  The eof_map as maintained is a sorted list of eof mark entries.
 *
 *
 *  The tape name field in the header segments is used to store a
 *  linux tape identification string and a version number.
 *  This way the tape can be recognized as a Linux raw format
 *  tape when using tools under other OS's.
 *
 *  'Wide' QIC tapes (format code 4) don't have a failed sector list
 *  anymore. That space is used for the (longer) bad sector map that
 *  now is a variable length list too.
 *  We now store our end-of-file marker list after the bad-sector-map
 *  on tape. The list is delimited by a (long) 0 entry.
 */

int ftape_validate_label(char *label)
{
	TRACE_FUN(8, "ftape_validate_label");
	int result = 0;

	TRACEx1(4, "tape  label = `%s'", label);
	ftape_fmt_version = 0;
	if (memcmp(label, linux_tape_label, strlen(linux_tape_label)) == 0) {
		int pos = strlen(linux_tape_label);
		while (label[pos] >= '0' && label[pos] <= '9') {
			ftape_fmt_version *= 10;
			ftape_fmt_version = label[pos++] - '0';
		}
		result = (ftape_fmt_version >= min_fmt_version &&
			  ftape_fmt_version <= max_fmt_version);
	}
	TRACEx1(4, "format version = %d", ftape_fmt_version);
	TRACE_EXIT;
	return result;
}

static byte *
 find_end_of_eof_list(byte * ptr, byte * limit)
{
	while (ptr + 3 < limit) {
		if (*(unsigned long *) ptr) {
			++(unsigned long *) ptr;
		} else {
			return ptr;
		}
	}
	return NULL;
}

void reset_eof_list(void)
{
	TRACE_FUN(8, "reset_eof_list");

	eof_mark_ptr = &eof_map[0].mark;
	eof_index = 0;
	eof_mark = 0;
	TRACE_EXIT;
}

/*  Test if `segment' has an eof mark set (optimized for sequential access).
 *  return 0 if not eof mark or sector number (> 0) if eof mark set.
 */
int check_for_eof(unsigned segment)
{
	TRACE_FUN(8, "check_for_eof");
	static unsigned last_reference = INT_MAX;
	int result;

	if (segment < last_reference) {
		reset_eof_list();
	}
	last_reference = segment;
	while (eof_index < nr_of_eof_marks && segment > eof_mark_ptr->segment) {
		++eof_mark_ptr;
		++eof_index;
	}
	if (eof_index < nr_of_eof_marks && segment == eof_mark_ptr->segment) {
		TRACEx3(5, "hit mark %d/%d at index %d",
			eof_map[eof_index].mark.segment, eof_map[eof_index].mark.sector,
			eof_index);
		if (eof_mark_ptr->sector >= SECTORS_PER_SEGMENT) {
			TRACEx2(-1, "Bad file mark detected: %d/%d",
			    eof_mark_ptr->segment, eof_mark_ptr->sector);
			result = 0;	/* return bogus (but valid) value */
		} else {
			result = eof_mark_ptr->sector;
		}
	} else {
		result = 0;
	}
	TRACE_EXIT;
	return result;
}

void clear_eof_mark_if_set(unsigned segment, unsigned byte_count)
{
	TRACE_FUN(5, "clear_eof_mark_if_set");
	if (ftape_fmt_version != 0 &&
	    check_for_eof(segment) > 0 &&
	    byte_count >= eof_mark_ptr->sector * SECTOR_SIZE) {
		TRACEx3(5, "clearing mark %d/%d at index %d",
		 eof_mark_ptr->segment, eof_mark_ptr->sector, eof_index);
		memmove(&eof_map[eof_index], &eof_map[eof_index + 1],
			(nr_of_eof_marks - eof_index) * sizeof(*eof_map));
		--nr_of_eof_marks;
		failed_sector_log_changed = 1;
	}
	TRACE_EXIT;
}

void put_file_mark_in_map(unsigned segment, unsigned sector)
{
	TRACE_FUN(8, "put_file_mark_in_map");
	eof_mark_union new;
	int index;
	eof_mark_union *ptr;

	if (ftape_fmt_version != 0) {
		new.mark.segment = segment;
		new.mark.sector = sector;
		for (index = 0, ptr = &eof_map[0];
		  index < nr_of_eof_marks && ptr->mark.segment < segment;
		     ++index, ++ptr) {
		}
		if (index < nr_of_eof_marks) {
			if (ptr->mark.segment == segment) {
				/* overwrite */
				if (ptr->mark.sector == sector) {
					TRACEx2(5, "mark %d/%d already exists",
						new.mark.segment, new.mark.sector);
				} else {
					TRACEx5(5, "overwriting %d/%d at index %d with %d/%d",
						ptr->mark.segment, ptr->mark.sector, index,
						new.mark.segment, new.mark.sector);
					ptr->entry = new.entry;
					failed_sector_log_changed = 1;
				}
			} else {
				/* insert */
				TRACEx5(5, "inserting %d/%d at index %d before %d/%d",
				new.mark.segment, new.mark.sector, index,
				    ptr->mark.segment, ptr->mark.sector);
				memmove(ptr + 1, ptr, (nr_of_eof_marks - index) * sizeof(*eof_map));
				ptr->entry = new.entry;
				++nr_of_eof_marks;
				failed_sector_log_changed = 1;
			}
		} else {
			/* append */
			TRACEx3(5, "appending %d/%d at index %d",
				new.mark.segment, new.mark.sector, index);
			ptr->entry = new.entry;
			++nr_of_eof_marks;
			failed_sector_log_changed = 1;
		}
	}
	TRACE_EXIT;
}

/*  Write count file marks to tape starting at first non-bad
 *  sector following the given segment and sector.
 *  sector = base 1 !
 */
int ftape_weof(unsigned count, unsigned segment, unsigned sector)
{
	TRACE_FUN(5, "ftape_weof");
	int result = 0;
	unsigned long mask = get_bad_sector_entry(segment);
	unsigned sector_nr = 0;

	if (ftape_fmt_version != 0) {
		if (sector < 1 || sector > 29 ||
		    segment + count >= ftape_last_segment.id) {
			TRACEx3(5, "parameter out of range: %d, %d, %d", count, segment, sector);
			result = -EIO;
		} else {
			while (count-- > 0) {
				do {	/* count logical sectors */
					do {	/* skip until good sector */
						while (mask & 1) {	/* skip bad sectors */