patch-1.3.72 linux/drivers/char/ftape/fdc-isr.c

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diff -u --recursive --new-file v1.3.71/linux/drivers/char/ftape/fdc-isr.c linux/drivers/char/ftape/fdc-isr.c
@@ -0,0 +1,814 @@
+/*
+ *      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: /home/bas/distr/ftape-2.03b/RCS/fdc-isr.c,v $
+ $Author: bas $
+ *
+ $Revision: 1.36 $
+ $Date: 1995/05/27 08:54:21 $
+ $State: Beta $
+ *
+ *      This file contains the interrupt service routine and associated
+ *      code for the QIC-40/80 tape streamer device driver.
+ */
+
+#include <linux/module.h>
+#include <linux/ftape.h>
+#include <asm/io.h>
+#include <asm/dma.h>
+
+#define volatile		/* */
+
+#include "tracing.h"
+#include "fdc-isr.h"
+#include "qic117.h"
+#include "fdc-io.h"
+#include "ftape-ctl.h"
+#include "ftape-rw.h"
+#include "ftape-io.h"
+#include "calibr.h"
+#include "ftape-bsm.h"
+
+/*      Global vars.
+ */
+volatile int expected_stray_interrupts = 0;
+volatile int seek_completed = 0;
+volatile int interrupt_seen = 0;
+volatile int expect_stray_interrupt = 0;
+int random_rw = 0;
+
+/*      Local vars.
+ */
+typedef enum {
+	no_error = 0, id_am_error = 0x01, id_crc_error = 0x02,
+	data_am_error = 0x04, data_crc_error = 0x08,
+	no_data_error = 0x10, overrun_error = 0x20,
+} error_cause;
+static int hide_interrupt;
+static int stop_read_ahead = 0;
+
+
+static void print_error_cause(int cause)
+{
+	TRACE_FUN(8, "print_error_cause");
+
+	switch (cause) {
+	case no_data_error:
+		TRACE(4, "no data error");
+		break;
+	case id_am_error:
+		TRACE(4, "id am error");
+		break;
+	case id_crc_error:
+		TRACE(4, "id crc error");
+		break;
+	case data_am_error:
+		TRACE(4, "data am error");
+		break;
+	case data_crc_error:
+		TRACE(4, "data crc error");
+		break;
+	case overrun_error:
+		TRACE(4, "overrun error");
+		break;
+	default:
+	}
+	TRACE_EXIT;
+}
+
+static char *
+get_fdc_mode_text(fdc_mode_enum fdc_mode)
+{
+	switch (fdc_mode) {
+	case fdc_idle:
+		return "fdc_idle";
+	case fdc_reading_data:
+		return "fdc_reading_data";
+	case fdc_seeking:
+		return "fdc_seeking";
+	case fdc_writing_data:
+		return "fdc_writing_data";
+	case fdc_reading_id:
+		return "fdc_reading_id";
+	case fdc_recalibrating:
+		return "fdc_recalibrating";
+	default:
+		return "unknown";
+	}
+}
+
+static void
+decode_irq_cause(fdc_mode_enum fdc_mode, byte st[],
+		 char **fdc_mode_txt, error_cause * cause)
+{
+	TRACE_FUN(8, "decode_irq_cause");
+
+	/*  Valid st[], decode cause of interrupt.
+	 */
+	*fdc_mode_txt = get_fdc_mode_text(fdc_mode);
+	switch (st[0] & ST0_INT_MASK) {
+	case FDC_INT_NORMAL:
+		TRACEx1(fdc_mode == fdc_reading_id ? 6 : 5,
+			"normal completion: %s", *fdc_mode_txt);
+		*cause = no_error;
+		break;
+	case FDC_INT_ABNORMAL:
+		TRACEx1(5, "abnormal completion %s", *fdc_mode_txt);
+		TRACEx3(6, "ST0: 0x%02x, ST1: 0x%02x, ST2: 0x%02x",
+			st[0], st[1], st[2]);
+		TRACEx4(6, "C: 0x%02x, H: 0x%02x, R: 0x%02x, N: 0x%02x",
+			st[3], st[4], st[5], st[6]);
+		if (st[1] & 0x01) {
+			if (st[2] & 0x01) {
+				*cause = data_am_error;
+			} else {
+				*cause = id_am_error;
+			}
+		} else if (st[1] & 0x20) {
+			if (st[2] & 0x20) {
+				*cause = data_crc_error;
+			} else {
+				*cause = id_crc_error;
+			}
+		} else if (st[1] & 0x04) {
+			*cause = no_data_error;
+		} else if (st[1] & 0x10) {
+			*cause = overrun_error;
+		}
+		print_error_cause(*cause);
+		break;
+	case FDC_INT_INVALID:
+		TRACEx1(5, "invalid completion %s", *fdc_mode_txt);
+		*cause = no_error;
+		break;
+	case FDC_INT_READYCH:
+		TRACEx1(5, "ready change %s", *fdc_mode_txt);
+		*cause = no_error;
+		break;
+	default:
+	}
+	TRACE_EXIT;
+}
+
+static void update_history(error_cause cause)
+{
+	switch (cause) {
+	case id_am_error:
+		history.id_am_errors++;
+		break;
+	case id_crc_error:
+		history.id_crc_errors++;
+		break;
+	case data_am_error:
+		history.data_am_errors++;
+		break;
+	case data_crc_error:
+		history.data_crc_errors++;
+		break;
+	case overrun_error:
+		history.overrun_errors++;
+		break;
+	case no_data_error:
+		history.no_data_errors++;
+		break;
+	default:
+	}
+}
+
+static void skip_bad_sector(buffer_struct * buff)
+{
+	TRACE_FUN(8, "skip_bad_sector");
+
+	/* Mark sector as soft error and skip it
+	 */
+	if (buff->remaining > 0) {
+		++buff->sector_offset;
+		++buff->data_offset;
+		--buff->remaining;
+		buff->ptr += SECTOR_SIZE;
+		buff->bad_sector_map >>= 1;
+	} else {
+		++buff->sector_offset;	/* hack for error maps */
+		TRACE(1, "skipping last sector in segment");
+	}
+	TRACE_EXIT;
+}
+
+static void update_error_maps(buffer_struct * buff, unsigned error_offset)
+{
+	TRACE_FUN(8, "update_error_maps");
+	int hard = 0;
+
+	/* error_offset is a sector offset !
+	 */
+	if (buff->retry < SOFT_RETRIES) {
+		buff->soft_error_map |= (1 << error_offset);
+	} else {
+		buff->hard_error_map |= (1 << error_offset);
+		buff->soft_error_map &= ~buff->hard_error_map;
+		buff->retry = -1;	/* will be set to 0 in setup_segment */
+		hard = 1;
+	}
+	TRACEx2(4, "sector %d : %s error", SECTOR(error_offset),
+		hard ? "hard" : "soft");
+	TRACEx2(5, "hard map: 0x%08lx, soft map: 0x%08lx",
+		buff->hard_error_map, buff->soft_error_map);
+	TRACE_EXIT;
+}
+
+/*
+ *  Error cause:   Amount xferred:  Action:
+ *
+ *  id_am_error         0           mark bad and skip
+ *  id_crc_error        0           mark bad and skip
+ *  data_am_error       0           mark bad and skip
+ *  data_crc_error    % 1024        mark bad and skip
+ *  no_data_error       0           retry on write
+ *                                  mark bad and skip on read
+ *  overrun_error  [ 0..all-1 ]     mark bad and skip
+ *  no_error           all          continue
+ */
+static void determine_progress(buffer_struct * buff, error_cause cause, int mode)
+{
+	TRACE_FUN(8, "determine_progress");
+	unsigned nr_not_xferred;
+	unsigned nr_xferred;
+	unsigned dma_residue;
+
+	/*  Using less preferred order of disable_dma and get_dma_residue
+	 *  because this seems to fail on at least one system if reversed!
+	 */
+	dma_residue = get_dma_residue(fdc.dma);
+	disable_dma(fdc.dma);
+	nr_xferred = buff->sector_count * SECTOR_SIZE - dma_residue;
+	if (cause == no_error && dma_residue == 0) {
+		nr_not_xferred = 0;
+	} else {
+		if (cause == no_error) {
+			TRACEx1(4, "unexpected DMA residue: 0x%04x", dma_residue);
+		} else {
+			TRACEx1(6, "DMA residue = 0x%04x", dma_residue);
+		}
+		nr_not_xferred = ((dma_residue + (SECTOR_SIZE - 1)) / SECTOR_SIZE);
+		buff->sector_count -= nr_not_xferred;	/* adjust to actual value */
+	}
+	/*  Update var's influenced by the DMA operation.
+	 */
+	if (buff->sector_count > 0) {
+		buff->sector_offset += buff->sector_count;
+		buff->data_offset += buff->sector_count;
+		buff->ptr += buff->sector_count * SECTOR_SIZE;
+		buff->remaining -= buff->sector_count;
+		buff->bad_sector_map >>= buff->sector_count;
+	}
+	if (cause == no_error) {
+		TRACEx1(5, "%d Sector(s) transferred", buff->sector_count);
+	} else if (cause == no_data_error) {
+		TRACEx1(5, "Sector %d not found", SECTOR(buff->sector_offset));
+	} else if (nr_xferred > 0 || cause == id_crc_error ||
+		   cause == id_am_error || cause == data_am_error) {
+		TRACEx1(5, "Error in sector %d", SECTOR(buff->sector_offset));
+	} else if (cause == overrun_error) {
+		/* got an overrun error on the first byte, must be a hardware problem
+		 */
+		TRACE(-1, "Unexpected error: failing DMA controller ?");
+	} else {
+		TRACEx1(4, "Unexpected error at sector %d", SECTOR(buff->sector_offset));
+	}
+	/*  Sector_offset points to the problem area, except if we got
+	 *  a data_crc_error. In that case it points one past the failing
+	 *  sector.
+	 *  Now adjust sector_offset so it allways points one past he
+	 *  failing sector. I.e. skip the bad sector.
+	 */
+	if (cause != no_error) {
+		if (cause != data_crc_error) {
+			skip_bad_sector(buff);
+		}
+		update_error_maps(buff, buff->sector_offset - 1);
+	}
+	TRACE_EXIT;
+}
+
+static int calc_steps(int cmd)
+{
+	if (current_cylinder > cmd) {
+		return current_cylinder - cmd;
+	} else {
+		return current_cylinder + cmd;
+	}
+}
+
+static void pause_tape(unsigned segment, int retry, int fdc_mode)
+{
+	TRACE_FUN(8, "pause_tape");
+	int result;
+	/*  The 3rd initializer needs to be explicit or else gcc will
+	 *  generate a reference to memset :-(
+	 */
+	byte out[3] =
+	{FDC_SEEK, FTAPE_UNIT, 0};
+
+	/*  We'll use a raw seek command to get the tape to rewind
+	 *  and stop for a retry.
+	 */
+	++history.rewinds;
+	if (qic117_cmds[current_command].non_intr) {
+		TRACE(2, "motion command may be issued too soon");
+	}
+	if (retry && (fdc_mode == fdc_reading_data || fdc_mode == fdc_reading_id)) {
+		current_command = QIC_MICRO_STEP_PAUSE;
+		might_be_off_track = 1;
+	} else {
+		current_command = QIC_PAUSE;
+	}
+	out[2] = calc_steps(current_command);
+	result = fdc_command(out, 3);	/* issue QIC_117 command */
+	if (result < 0) {
+		TRACEx1(4, "qic-pause failed, status = %d", result);
+	} else {
+		location.known = 0;
+		runner_status = idle;
+		hide_interrupt = 1;
+		tape_running = 0;
+	}
+	TRACE_EXIT;
+}
+
+static void stop_tape(unsigned segment)
+{
+	TRACE_FUN(8, "stop_tape");
+	int result;
+	byte out[3] =
+	{FDC_SEEK, FTAPE_UNIT, calc_steps(QIC_STOP_TAPE)};
+
+	if (qic117_cmds[current_command].non_intr) {
+		TRACE(2, "motion command may be issued too soon");
+	}
+	current_command = QIC_STOP_TAPE;
+	/*  We'll use a raw seek command to get the tape to stop
+	 */
+	result = fdc_command(out, 3);	/* issue QIC_117 command */
+	if (result < 0) {
+		TRACEx1(4, "qic-stop failed, status = %d", result);
+	} else {
+		runner_status = idle;
+		hide_interrupt = 1;
+		tape_running = 0;
+	}
+	TRACE_EXIT;
+}
+
+static void continue_xfer(buffer_struct ** p_buff, error_cause cause,
+			  int fdc_mode, unsigned skip)
+{
+	TRACE_FUN(8, "continue_xfer");
+	buffer_struct *buff = *p_buff;
+	int write = (fdc_mode == fdc_writing_data);
+	byte fdc_op = (write) ? FDC_WRITE : FDC_READ;
+
+	if (skip > 0) {
+		/* This part can be removed if it never happens
+		 */
+		if (runner_status != running ||
+		    (buff->status != (write ? writing : reading))) {
+			TRACEx2(1, "unexpected runner/buffer state %d/%d",
+				runner_status, buff->status);
+			buff->status = error;
+			*p_buff = next_buffer(&head);	/* finish this buffer */
+			runner_status = aborting;
+			fdc_mode = fdc_idle;
+		}
+	}
+	if (buff->remaining > 0 && calc_next_cluster(&buffer[head]) > 0) {
+		/* still sectors left in current segment, continue with this segment
+		 */
+		if (setup_fdc_and_dma(&buffer[head], fdc_op) < 0) {
+			/* failed, abort operation
+			 */
+			buff->bytes = buff->ptr - buff->address;
+			buff->status = error;
+			buff = *p_buff = next_buffer(&head);	/* finish this buffer */
+			runner_status = aborting;
+			fdc_mode = fdc_idle;
+		}
+	} else {
+		/* current segment completed
+		 */
+		unsigned last_segment = buff->segment_id;
+		int eot = ((last_segment + 1) % segments_per_track) == 0;
+		int next = buff->next_segment;	/* 0 means stop ! */
+
+		buff->bytes = buff->ptr - buff->address;
+		buff->status = done;
+		buff = *p_buff = next_buffer(&head);
+		if (eot) {
+			/* finished last segment on current track, can't continue
+			 */
+			runner_status = logical_eot;
+			fdc_mode = fdc_idle;
+		} else if (next > 0) {
+			/* continue with next segment
+			 */
+			if (buff->status == waiting) {
+				if (write && next != buff->segment_id) {
+					TRACE(5, "segments out of order, aborting write");
+					runner_status = do_abort;
+					fdc_mode = fdc_idle;
+				} else {
+					setup_new_segment(&buffer[head], next, 0);
+					if (stop_read_ahead) {
+						buff->next_segment = 0;
+						stop_read_ahead = 0;
+					}
+					if (calc_next_cluster(&buffer[head]) == 0 ||
+					    setup_fdc_and_dma(&buffer[head], fdc_op) != 0) {
+						TRACEx1(1, "couldn't start %s-ahead", (write) ? "write" : "read");
+						runner_status = do_abort;
+						fdc_mode = fdc_idle;
+					} else {
+						buff->status = (write) ? writing : reading;	/* keep on going */
+					}
+				}
+			} else {
+				TRACEx1(5, "all input buffers %s, pausing tape",
+					(write) ? "empty" : "full");
+				pause_tape(last_segment, 0, fdc_mode);
+				runner_status = idle;	/* not quite true until next irq */
+			}
+		} else {
+			/* don't continue with next segment
+			 */
+			TRACEx1(5, "no %s allowed, stopping tape",
+				(write) ? "write next" : "read ahead");
+			if (random_rw) {
+				stop_tape(last_segment);
+			} else {
+				pause_tape(last_segment, 0, fdc_mode);
+			}
+			runner_status = idle;	/* not quite true until next irq */
+		}
+	}
+	TRACE_EXIT;
+	return;
+}
+
+static void
+retry_sector(buffer_struct ** p_buff, error_cause cause, int fdc_mode,
+	     unsigned skip)
+{
+	TRACE_FUN(8, "retry_sector");
+	buffer_struct *buff = *p_buff;
+
+	TRACEx1(4, "%s error, will retry",
+		(fdc_mode == fdc_writing_data) ? "write" : "read");
+	pause_tape(buff->segment_id, 1, fdc_mode);
+	runner_status = aborting;
+	buff->status = error;
+	buff->skip = skip;
+	TRACE_EXIT;
+}
+
+static unsigned
+find_resume_point(buffer_struct * buff)
+{
+	TRACE_FUN(8, "find_resume_point");
+	int i = 0;
+	unsigned long mask;
+	unsigned long map;
+
+	/*  This function is to be called after all variables have been
+	 *  updated to point past the failing sector.
+	 *  If there are any soft errors before the failing sector,
+	 *  find the first soft error and return the sector offset.
+	 *  Otherwise find the last hard error.
+	 *  Note: there should allways be at least one hard or soft error !
+	 */
+	if (buff->sector_offset < 1 || buff->sector_offset > 32) {
+		TRACEx1(1, "bug: sector_offset = %d", buff->sector_offset);
+	} else {
+		if (buff->sector_offset >= 32) {	/* C-limitation on shift ! */
+			mask = 0xffffffff;
+		} else {
+			mask = (1 << buff->sector_offset) - 1;
+		}
+		map = buff->soft_error_map & mask;
+		if (map) {
+			while ((map & (1 << i)) == 0) {
+				++i;
+			}
+			TRACEx1(4, "at sector %d", SECTOR(i));
+		} else {
+			map = buff->hard_error_map & mask;
+			i = buff->sector_offset - 1;
+			if (map) {
+				while ((map & (1 << i)) == 0) {
+					--i;
+				}
+				TRACEx1(4, "after sector %d", SECTOR(i));
+				++i;	/* first sector after last hard error */
+			} else {
+				TRACE(1, "bug: no soft or hard errors");
+			}
+		}
+	}
+	TRACE_EXIT;
+	return i;
+}
+
+/*      FDC interrupt service routine.
+ */
+void
+fdc_isr(void)
+{
+	TRACE_FUN(8, "fdc_isr");
+	int result;
+	int status;
+	error_cause cause = no_error;
+	byte in[7];
+	static int isr_active = 0;
+	int t0;
+	buffer_struct *buff = &buffer[head];
+	int skip;
+
+	t0 = timestamp();
+	if (isr_active) {
+		TRACE(-1, "nested interrupt, not good !");
+		*fdc.hook = fdc_isr;	/* hook our handler into the fdc code again */
+		TRACE_EXIT;
+		return;
+	}
+	++isr_active;
+	sti();			/* enables interrupts again */
+	status = inb_p(fdc.msr);
+	if (status & FDC_BUSY) {	/*  Entering Result Phase */
+		hide_interrupt = 0;
+		result = fdc_result(in, 7);	/* better get it fast ! */
+		if (result < 0) {
+			/*  Entered unknown state...
+			 */
+			TRACE(1, "probably fatal error during FDC Result Phase");
+			TRACE(1, "drive may hang until (power) reset :-(");
+			/*  what to do next ????
+			 */
+		} else {
+			int i;
+			char *fdc_mode_txt;
+
+			decode_irq_cause(fdc_mode, in, &fdc_mode_txt, &cause);
+			for (i = 0; i < NR_BUFFERS; ++i) {
+				TRACEx3(8, "buffer[%d] status: %d, segment_id: %d",
+					i, buffer[i].status, buffer[i].segment_id);
+			}
+			switch (fdc_mode) {
+
+			case fdc_reading_data:{
+
+					if (cause == no_error) {
+						TRACEi(5, "reading segment", buff->segment_id);
+					} else {
+						TRACEi(4, "error reading segment", buff->segment_id);
+					}
+					if (runner_status == aborting || runner_status == do_abort) {
+						TRACEx1(4, "aborting %s", fdc_mode_txt);
+						break;
+					}
+					if (buff->retry > 0) {
+						TRACEx1(5, "this is retry nr %d", buff->retry);
+					}
+					if (buff->bad_sector_map == FAKE_SEGMENT) {
+						/* This condition occurs when reading a `fake' sector that's
+						 * not accessible. Doesn't really matter as we would have
+						 * ignored it anyway !
+						 * Chance is that we're past the next segment now, so the
+						 * next operation may fail and result in a retry.
+						 */
+						TRACE(4, "skipping empty segment (read)");
+						buff->remaining = 0;	/* skip failing sector */
+						continue_xfer(&buff, no_error, fdc_mode, 1);	/* fake success */
+					} else {
+						switch (cause) {
+						case no_error:{
+								determine_progress(buff, cause, fdc_reading_data);
+								if (in[2] & 0x40) {
+									/*  Handle deleted data in header segments.
+									 *  Skip segment and force read-ahead.
+									 */
+									TRACEx1(2, "deleted data in sector %d",
+										SECTOR(buff->sector_offset - 1));
+									buff->deleted = 1;
+									buff->remaining = 0;	/* abort transfer */
+									buff->soft_error_map |= (-1L << buff->sector_offset);
+									if (buff->segment_id == 0) {
+										stop_read_ahead = 1;	/* stop on next segment */
+									}
+									buff->next_segment = buff->segment_id + 1;	/* force read-ahead */
+									skip = (SECTORS_PER_SEGMENT - buff->sector_offset);
+								} else {
+									skip = 0;
+								}
+								continue_xfer(&buff, cause, fdc_mode, skip);
+								break;
+							}
+						case no_data_error:
+							/*  Tape started too far ahead of or behind the right sector.
+							 *  This may also happen in the middle of a segment !
+							 *  Handle no-data as soft error. If next sector fails too,
+							 *  a retry (with needed reposition) will follow.
+							 */
+						case id_am_error:
+						case id_crc_error:
+						case data_am_error:
+						case data_crc_error:
+						case overrun_error:{
+								int first_error = (buff->soft_error_map == 0 &&
+										   buff->hard_error_map == 0);
+
+								update_history(cause);
+								determine_progress(buff, cause, fdc_reading_data);
+								if (first_error) {
+									skip = buff->sector_offset;
+								} else {
+									skip = find_resume_point(buff);
+								}
+								/*  Try to resume with next sector on single errors (let ecc
+								 *  correct it), but retry on no_data (we'll be past the
+								 *  target when we get here so we cannot retry) or on multiple
+								 *  errors (reduce chance on ecc failure).
+								 */
+								if (first_error && cause != no_data_error) {
+									continue_xfer(&buff, cause, fdc_mode, skip);
+								} else {
+									retry_sector(&buff, cause, fdc_mode, skip);
+								}
+								break;
+							}
+						default:{
+								/*  Don't know why this could happen but find out.
+								 */
+								TRACE(1, "unexpected error");
+								determine_progress(buff, cause, fdc_reading_data);
+								retry_sector(&buff, cause, fdc_mode, 0);
+								break;
+							}
+						}
+					}
+					break;
+				}
+
+			case fdc_reading_id:{
+
+					if (cause == no_error) {
+						fdc_cyl = in[3];
+						fdc_head = in[4];
+						fdc_sect = in[5];
+						TRACEx3(6, "id read: C: 0x%02x, H: 0x%02x, R: 0x%02x",
+							fdc_cyl, fdc_head, fdc_sect);
+					} else {	/* no valid information, use invalid sector */
+						fdc_cyl =
+						    fdc_head =
+						    fdc_sect = 0;
+						TRACE(5, "Didn't find valid sector Id");
+					}
+					fdc_mode = fdc_idle;
+					break;
+				}
+
+			case fdc_writing_data:{
+
+					if (cause == no_error) {
+						TRACEi(5, "writing segment", buff->segment_id);
+					} else {
+						TRACEi(4, "error writing segment", buff->segment_id);
+					}
+					if (runner_status == aborting || runner_status == do_abort) {
+						TRACEx1(5, "aborting %s", fdc_mode_txt);
+						break;
+					}
+					if (buff->retry > 0) {
+						TRACEx1(5, "this is retry nr %d", buff->retry);
+					}
+					if (buff->bad_sector_map == FAKE_SEGMENT) {
+						/* This condition occurs when trying to write to a `fake'
+						 * sector that's not accessible. Doesn't really matter as
+						 * it isn't used anyway ! Might be located at wrong segment,
+						 * then we'll fail on the next segment.
+						 */
+						TRACE(4, "skipping empty segment (write)");
+						buff->remaining = 0;	/* skip failing sector */
+						continue_xfer(&buff, no_error, fdc_mode, 1);	/* fake success */
+					} else {
+						switch (cause) {
+						case no_error:{
+								determine_progress(buff, cause, fdc_writing_data);
+								continue_xfer(&buff, cause, fdc_mode, 0);
+								break;
+							}
+						case no_data_error:
+						case id_am_error:
+						case id_crc_error:
+						case data_am_error:
+						case overrun_error:{
+								update_history(cause);
+								determine_progress(buff, cause, fdc_writing_data);
+								skip = find_resume_point(buff);
+								retry_sector(&buff, cause, fdc_mode, skip);
+								break;
+							}
+						default:{
+								if (in[1] & 0x02) {
+									TRACE(1, "media not writable");
+								} else {
+									TRACE(-1, "unforseen write error");
+								}
+								fdc_mode = fdc_idle;
+								break;
+							}
+						}
+					}
+					break;
+				}
+			default:
+
+				TRACEx1(1, "Warning: unexpected irq during: %s",
+					fdc_mode_txt);
+				fdc_mode = fdc_idle;
+				break;
+			}
+		}
+		if (runner_status == do_abort) {
+			/*      cease operation, remember tape position
+			 */
+			TRACE(5, "runner aborting");
+			runner_status = aborting;
+			++expected_stray_interrupts;
+		}
+	} else { /* !FDC_BUSY  */
+		/*  clear interrupt, cause should be gotten by issueing
+		 *  a Sense Interrupt Status command.
+		 */
+		if (fdc_mode == fdc_recalibrating || fdc_mode == fdc_seeking) {
+			if (hide_interrupt) {
+				int st0;
+				int pcn;
+
+				result = fdc_sense_interrupt_status(&st0, &pcn);
+				current_cylinder = pcn;
+				TRACE(5, "handled hidden interrupt");
+			}
+			seek_completed = 1;
+			fdc_mode = fdc_idle;
+		} else if (!wait_intr) {
+			if (expected_stray_interrupts == 0) {
+				TRACE(2, "unexpected stray interrupt");
+			} else {
+				TRACE(5, "expected stray interrupt");
+				--expected_stray_interrupts;
+			}
+		} else {
+			if (fdc_mode == fdc_reading_data || fdc_mode == fdc_writing_data ||
+			    fdc_mode == fdc_reading_id) {
+				byte status = inb_p(fdc.msr);
+				if (status & FDC_BUSY) {
+					TRACE(-1, "***** FDC failure, busy too late");
+				} else {
+					TRACE(-1, "***** FDC failure, no busy");
+				}
+			} else {
+				TRACE(6, "awaited stray interrupt");
+			}
+		}
+		hide_interrupt = 0;
+	}
+	/*    Handle sleep code.
+	 */
+	if (!hide_interrupt) {
+		++interrupt_seen;
+		if (wait_intr) {
+			wake_up_interruptible(&wait_intr);
+		}
+	} else {
+		TRACEx1(5, "hiding interrupt while %s", wait_intr ? "waiting" : "active");
+	}
+	t0 = timediff(t0, timestamp());
+	if (t0 >= 1000) {	/* only tell us about long calls */
+		TRACEx1(7, "isr() duration: %5d usec", t0);
+	}
+	*fdc.hook = fdc_isr;	/* hook our handler into the fdc code again */
+	TRACE_EXIT;
+	--isr_active;
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen, slshen@lbl.gov with Sam's (original) version
of this