ftape-read.c

arm平台上的uclinux系统全部源代码

/*
 *      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: /usr/local/cvsroot/AplioTRIO/linux/drivers/char/ftape/ftape-read.c,v $
 $Author: vadim $
 *
 $Revision: 1.1.1.1 $
 $Date: 1999/11/15 13:41:58 $
 $State: Exp $
 *
 *      This file contains the reading code
 *      for the QIC-117 floppy-tape driver for Linux.
 */

#include <linux/string.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/ftape.h>
#include <asm/segment.h>

#include "tracing.h"
#include "ftape-read.h"
#include "qic117.h"
#include "ftape-io.h"
#include "ftape-ctl.h"
#include "ftape-rw.h"
#include "ftape-write.h"
#include "ftape-eof.h"
#include "ecc.h"
#include "ftape-bsm.h"

/*      Global vars.
 */

/*      Local vars.
 */
int buf_pos_rd = 0;
int buf_len_rd = 0;

void ftape_zap_read_buffers(void)
{
	int i;

	for (i = 0; i < NR_BUFFERS; ++i) {
		/*
		 * changed to "fit" with dynamic allocation of tape_buffer. --khp
		 */
		buffer[i].address = tape_buffer[i];
		buffer[i].status = waiting;
		buffer[i].bytes = 0;
		buffer[i].skip = 0;
		buffer[i].retry = 0;
	}
	buf_len_rd = 0;
	buf_pos_rd = 0;
	eof_mark = 0;
	ftape_state = idle;
}

static unsigned long convert_sector_map(buffer_struct * buff)
{
	TRACE_FUN(8, "convert_sector_map");
	int i = 0;
	unsigned long bad_map = get_bad_sector_entry(buff->segment_id);
	unsigned long src_map = buff->soft_error_map | buff->hard_error_map;
	unsigned long dst_map = 0;

	if (bad_map || src_map) {
		TRACEx1(5, "bad_map = 0x%08lx", bad_map);
		TRACEx1(5, "src_map = 0x%08lx", src_map);
	}
	while (bad_map) {
		while ((bad_map & 1) == 0) {
			if (src_map & 1) {
				dst_map |= (1 << i);
			}
			src_map >>= 1;
			bad_map >>= 1;
			++i;
		}
		/* (bad_map & 1) == 1 */
		src_map >>= 1;
		bad_map >>= 1;
	}
	if (src_map) {
		dst_map |= (src_map << i);
	}
	if (dst_map) {
		TRACEx1(5, "dst_map = 0x%08lx", dst_map);
	}
	TRACE_EXIT;
	return dst_map;
}

int correct_and_copy(unsigned int tail, byte * destination)
{
	TRACE_FUN(8, "correct_and_copy");
	struct memory_segment mseg;
	int result;
	BAD_SECTOR read_bad;

	mseg.read_bad = convert_sector_map(&buffer[tail]);
	mseg.marked_bad = 0;	/* not used... */
	mseg.blocks = buffer[tail].bytes / SECTOR_SIZE;
	mseg.data = buffer[tail].address;
	/*    If there are no data sectors we can skip this segment.
	 */
	if (mseg.blocks <= 3) {
		TRACE(4, "empty segment");
		TRACE_EXIT;
		return 0;
	}
	read_bad = mseg.read_bad;
	history.crc_errors += count_ones(read_bad);
	result = ecc_correct_data(&mseg);
	if (read_bad != 0 || mseg.corrected != 0) {
		TRACElx(4, "crc error map:", read_bad);
		TRACElx(4, "corrected map:", mseg.corrected);
		history.corrected += count_ones(mseg.corrected);
	}
	if (result == ECC_CORRECTED || result == ECC_OK) {
		if (result == ECC_CORRECTED) {
			TRACEi(3, "ecc corrected segment:", buffer[tail].segment_id);
		}
		memcpy(destination, mseg.data, (mseg.blocks - 3) * SECTOR_SIZE);
		if ((read_bad ^ mseg.corrected) & mseg.corrected) {
			/* sectors corrected without crc errors set */
			history.crc_failures++;
		}
		TRACE_EXIT;
		return (mseg.blocks - 3) * SECTOR_SIZE;
	} else {
		TRACEi(1, "ecc failure on segment", buffer[tail].segment_id);
		history.ecc_failures++;
		TRACE_EXIT;
		return -EAGAIN;	/* should retry */
	}
	TRACE_EXIT;
	return 0;
}

/*      Read given segment into buffer at address.
 */
int read_segment(unsigned segment_id, byte * address, int *eof_mark,
		 int read_ahead)
{
	TRACE_FUN(5, "read_segment");
	int read_done = 0;
	int result = 0;
	int bytes_read = 0;
	int retry = 0;

	TRACEi(5, "segment_id =", segment_id);
	if (ftape_state != reading) {
		if (ftape_state == writing) {
			ftape_flush_buffers();	/* flush write buffer */
			TRACE(5, "calling ftape_abort_operation");
			result = ftape_abort_operation();
			if (result < 0) {
				TRACE(1, "ftape_abort_operation failed");
				TRACE_EXIT;
				return -EIO;
			}
		} else {
			/* clear remaining read buffers */
			ftape_zap_read_buffers();
		}
		ftape_state = reading;
	}
	if (segment_id >= segments_per_track * tracks_per_tape) {
		TRACE(5, "reading past end of tape");
		TRACE_EXIT;
		return -ENOSPC;
	}
	for (;;) {
		/*    Search all full buffers for the first matching the wanted segment.
		 *    Clear other buffers on the fly.
		 */
		while (!read_done && buffer[tail].status == done) {
			if (buffer[tail].segment_id == segment_id) {
				unsigned eof_sector;
				unsigned sector_count = 0;
				unsigned long bsm = get_bad_sector_entry(segment_id);
				int i;

				/*        If out buffer is already full, return its contents.
				 */
				if (buffer[tail].deleted) {
					TRACEi(5, "found segment in cache :", segment_id);
					TRACE_EXIT;
					/*  Return a value that read_header_segment understands.
					 *  As this should only occur when searching for the header
					 *  segments it shouldn't be misinterpreted elsewhere.
					 */
					return 0;
				}
				TRACEi(5, "found segment in cache :", segment_id);
				eof_sector = check_for_eof(segment_id);
				if (eof_sector > 0) {
					TRACEi(5, "end of file mark in sector:", eof_sector);
					for (i = 1; i < eof_sector; ++i) {
						if ((bsm & 1) == 0) {
							++sector_count;
						}
						bsm >>= 1;
					}
					*eof_mark = 1;
				}
				if (eof_sector != 1) {	/* not found or gt 1 */
					result = correct_and_copy(tail, address);
					TRACEi(5, "segment contains (bytes) :", result);
					if (result < 0) {
						if (result != -EAGAIN) {
							TRACE_EXIT;
							return result;
						}
						/* keep read_done == 0, will trigger ftape_abort_operation
						 * because reading wrong segment.
						 */
						TRACE(1, "ecc failed, retry");
						++retry;
					} else {
						read_done = 1;
					}
				} else {
					read_done = 1;
				}
				if (eof_sector > 0) {
					bytes_read = sector_count * SECTOR_SIZE;
					TRACEi(5, "partial read count:", bytes_read);
				} else {
					bytes_read = result;
				}
			} else {
				TRACEi(5, "zapping segment in cache :", buffer[tail].segment_id);
			}
			buffer[tail].status = waiting;
			next_buffer(&tail);
		}
		if (!read_done && buffer[tail].status == reading) {
			if (buffer[tail].segment_id == segment_id) {
				int result = wait_segment(reading);
				if (result < 0) {
					if (result == -EINTR) {
						TRACE_EXIT;
						return result;
					}
					TRACE(1, "wait_segment failed while reading");
					ftape_abort_operation();
				}
			} else {
				/*        We're reading the wrong segment, stop runner.
				 */
				ftape_abort_operation();
			}
		}
		/*    if just passed the last segment on a track, wait for BOT or EOT mark.
		 */
		if (runner_status == logical_eot) {
			int status;
			result = ftape_ready_wait(timeout.seek, &status);
			if (result < 0) {
				TRACE(1, "ftape_ready_wait waiting for eot/bot failed");
			}
			if ((status & (QIC_STATUS_AT_BOT | QIC_STATUS_AT_EOT)) == 0) {
				TRACE(1, "eot/bot not reached");
			}
			runner_status = end_of_tape;
		}
		/*    should runner stop ?
		 */
		if (runner_status == aborting || runner_status == buffer_overrun ||
		    runner_status == end_of_tape) {
			if (runner_status != end_of_tape &&
			 !(runner_status == aborting && !tape_running)) {
				ftape_dumb_stop();
			}
			if (runner_status == aborting) {
				if (buffer[head].status == reading || buffer[head].status == error) {
					if (buffer[head].status == error) {
						history.defects += count_ones(buffer[head].hard_error_map);
					}
					buffer[head].status = waiting;
				}
			}
			runner_status = idle;	/* aborted ? */
		}
		/*    If segment to read is empty, do not start runner for it,
		 *    but wait for next read call.
		 */
		if (get_bad_sector_entry(segment_id) == EMPTY_SEGMENT) {
			bytes_read = 0;		/* flag empty segment */
			read_done = 1;
		}
		/*  Allow escape from this loop on signal !
		 */
		if (current->signal & _DONT_BLOCK) {
			TRACE(2, "interrupted by non-blockable signal");
			TRACE_EXIT;
			return -EINTR;
		}
		/*    If we got a segment: quit, or else retry up to limit.
		 */
		if (read_done) {
			break;
		}
		if (retry > RETRIES_ON_ECC_ERROR) {
			history.defects++;
			TRACE(1, "too many retries on ecc failure");
			TRACE_EXIT;
			return -ENODATA;
		}
		/*    Now at least one buffer is empty !
		 *    Restart runner & tape if needed.
		 */
		TRACEx3(8, "head: %d, tail: %d, runner_status: %d",
			head, tail, runner_status);
		TRACEx2(8, "buffer[].status, [head]: %d, [tail]: %d",
			buffer[head].status, buffer[tail].status);
		if (buffer[tail].status == waiting) {
			setup_new_segment(&buffer[head], segment_id, -1);
			if (!read_ahead) {
				buffer[head].next_segment = 0;	/* disable read-ahead */
			}
			calc_next_cluster(&buffer[head]);