floppy.c

minix3.1.1源代码

 * If the controller refuses to listen, the FDC chip is given a hard reset.
 */
  clock_t t0, t1;
  int s, status;

  if (need_reset) return;	/* if controller is not listening, return */

  /* It may take several tries to get the FDC to accept a command.  */
  getuptime(&t0);
  do {
  	if ( (s=getuptime(&t1))==OK && (t1-t0) > TIMEOUT_TICKS ) {
  		if (OK!=s) printf("FLOPPY: warning, getuptime failed: %d\n", s); 
		need_reset = TRUE;	/* hit it over the head */
		return;
	}
  	if ((s=sys_inb(FDC_STATUS, &status)) != OK)
  		panic("FLOPPY","Sys_inb in fdc_out() failed", s);
  }
  while ((status & (MASTER | DIRECTION)) != (MASTER | 0)); 
  
  if ((s=sys_outb(FDC_DATA, val)) != OK)
	panic("FLOPPY","Sys_outb in fdc_out() failed", s);
}

/*===========================================================================*
 *				recalibrate				     *
 *===========================================================================*/
PRIVATE int recalibrate()
{
/* The floppy disk controller has no way of determining its absolute arm
 * position (cylinder).  Instead, it steps the arm a cylinder at a time and
 * keeps track of where it thinks it is (in software).  However, after a
 * SEEK, the hardware reads information from the diskette telling where the
 * arm actually is.  If the arm is in the wrong place, a recalibration is done,
 * which forces the arm to cylinder 0.  This way the controller can get back
 * into sync with reality.
 */

  struct floppy *fp = f_fp;
  int r;
  u8_t cmd[2];

  /* Issue the RECALIBRATE command and wait for the interrupt. */
  cmd[0] = FDC_RECALIBRATE;	/* tell drive to recalibrate itself */
  cmd[1] = f_drive;		/* specify drive */
  if (fdc_command(cmd, 2) != OK) return(ERR_SEEK);
  if (f_intr_wait() != OK) return(ERR_TIMEOUT);

  /* Determine if the recalibration succeeded. */
  fdc_out(FDC_SENSE);		/* issue SENSE command to request results */
  r = fdc_results();		/* get results of the FDC_RECALIBRATE command*/
  fp->fl_curcyl = NO_CYL;	/* force a SEEK next time */
  fp->fl_sector = NO_SECTOR;
  if (r != OK ||		/* controller would not respond */
     (f_results[ST0] & ST0_BITS_SEEK) != SEEK_ST0 || f_results[ST_PCN] != 0) {
	/* Recalibration failed.  FDC must be reset. */
	need_reset = TRUE;
	return(ERR_RECALIBRATE);
  } else {
	/* Recalibration succeeded. */
	fp->fl_calibration = CALIBRATED;
	fp->fl_curcyl = f_results[ST_PCN];
	return(OK);
  }
}

/*===========================================================================*
 *				f_reset					     *
 *===========================================================================*/
PRIVATE void f_reset()
{
/* Issue a reset to the controller.  This is done after any catastrophe,
 * like the controller refusing to respond.
 */
  pvb_pair_t byte_out[2];
  int s,i;
  message mess;

  /* Disable interrupts and strobe reset bit low. */
  need_reset = FALSE;

  /* It is not clear why the next lock is needed.  Writing 0 to DOR causes
   * interrupt, while the PC documentation says turning bit 8 off disables
   * interrupts.  Without the lock:
   *   1) the interrupt handler sets the floppy mask bit in the 8259.
   *   2) writing ENABLE_INT to DOR causes the FDC to assert the interrupt
   *      line again, but the mask stops the cpu being interrupted.
   *   3) the sense interrupt clears the interrupt (not clear which one).
   * and for some reason the reset does not work.
   */
  (void) fdc_command((u8_t *) 0, 0);   /* need only the timer */
  motor_status = 0;
  pv_set(byte_out[0], DOR, 0);			/* strobe reset bit low */
  pv_set(byte_out[1], DOR, ENABLE_INT);		/* strobe it high again */
  if ((s=sys_voutb(byte_out, 2)) != OK)
  	panic("FLOPPY", "Sys_voutb in f_reset() failed", s); 

  /* A synchronous alarm timer was set in fdc_command. Expect a HARD_INT
   * message to collect the reset interrupt, but be prepared to handle the 
   * SYN_ALARM message on a timeout.
   */
  do {
  	receive(ANY, &mess); 
  	if (mess.m_type == SYN_ALARM) { 
  		f_expire_tmrs(NULL, NULL);
	} else if(mess.m_type == DEV_PING) {
		notify(mess.m_source);
  	} else {			/* expect HARD_INT */
  		f_busy = BSY_IDLE;
  	}
  } while (f_busy == BSY_IO);

  /* The controller supports 4 drives and returns a result for each of them.
   * Collect all the results now.  The old version only collected the first
   * result.  This happens to work for 2 drives, but it doesn't work for 3
   * or more drives, at least with only drives 0 and 2 actually connected
   * (the controller generates an extra interrupt for the middle drive when
   * drive 2 is accessed and the driver panics).
   *
   * It would be better to keep collecting results until there are no more.
   * For this, fdc_results needs to return the number of results (instead
   * of OK) when it succeeds.
   */
  for (i = 0; i < 4; i++) {
	fdc_out(FDC_SENSE);	/* probe FDC to make it return status */
	(void) fdc_results();	/* flush controller */
  }
  for (i = 0; i < NR_DRIVES; i++)	/* clear each drive */
	floppy[i].fl_calibration = UNCALIBRATED;

  /* The current timing parameters must be specified again. */
  prev_dp = NULL;
}

/*===========================================================================*
 *				f_intr_wait				     *
 *===========================================================================*/
PRIVATE int f_intr_wait()
{
/* Wait for an interrupt, but not forever.  The FDC may have all the time of
 * the world, but we humans do not.
 */
  message mess;

  /* We expect a HARD_INT message from the interrupt handler, but if there is
   * a timeout, a SYN_ALARM notification is received instead. If a timeout 
   * occurs, report an error.
   */
  do {
  	receive(ANY, &mess); 
  	if (mess.m_type == SYN_ALARM) {
  		f_expire_tmrs(NULL, NULL);
	} else if(mess.m_type == DEV_PING) {
		notify(mess.m_source);
  	} else { 
  		f_busy = BSY_IDLE;
  	}
  } while (f_busy == BSY_IO);

  if (f_busy == BSY_WAKEN) {

	/* No interrupt from the FDC, this means that there is probably no
	 * floppy in the drive.  Get the FDC down to earth and return error.
	 */
	need_reset = TRUE;
	return(ERR_TIMEOUT);
  }
  return(OK);
}

/*===========================================================================*
 *				f_timeout				     *
 *===========================================================================*/
PRIVATE void f_timeout(tp)
timer_t *tp;
{
/* This routine is called when a timer expires.  Usually to tell that a
 * motor has spun up, but also to forge an interrupt when it takes too long
 * for the FDC to interrupt (no floppy in the drive).  It sets a flag to tell
 * what has happened.
 */
  if (f_busy == BSY_IO) {
	f_busy = BSY_WAKEN;
  }
}

/*===========================================================================*
 *				read_id					     *
 *===========================================================================*/
PRIVATE int read_id()
{
/* Determine current cylinder and sector. */

  struct floppy *fp = f_fp;
  int result;
  u8_t cmd[2];

  /* Never attempt a read id if the drive is uncalibrated or motor is off. */
  if (fp->fl_calibration == UNCALIBRATED) return(ERR_READ_ID);
  if ((motor_status & (1 << f_drive)) == 0) return(ERR_READ_ID);

  /* The command is issued by outputting 2 bytes to the controller chip. */
  cmd[0] = FDC_READ_ID;		/* issue the read id command */
  cmd[1] = (fp->fl_head << 2) | f_drive;
  if (fdc_command(cmd, 2) != OK) return(ERR_READ_ID);
  if (f_intr_wait() != OK) return(ERR_TIMEOUT);

  /* Get controller status and check for errors. */
  result = fdc_results();
  if (result != OK) return(result);

  if ((f_results[ST0] & ST0_BITS_TRANS) != TRANS_ST0) return(ERR_READ_ID);
  if (f_results[ST1] | f_results[ST2]) return(ERR_READ_ID);

  /* The next sector is next for I/O: */
  fp->fl_sector = f_results[ST_SEC] - BASE_SECTOR + 1;
  return(OK);
}

/*===========================================================================*
 *				f_do_open				     *
 *===========================================================================*/
PRIVATE int f_do_open(dp, m_ptr)
struct driver *dp;
message *m_ptr;			/* pointer to open message */
{
/* Handle an open on a floppy.  Determine diskette type if need be. */

  int dtype;
  struct test_order *top;

  /* Decode the message parameters. */
  if (f_prepare(m_ptr->DEVICE) == NIL_DEV) return(ENXIO);

  dtype = f_device & DEV_TYPE_BITS;	/* get density from minor dev */
  if (dtype >= MINOR_fd0p0) dtype = 0;

  if (dtype != 0) {
	/* All types except 0 indicate a specific drive/medium combination.*/
	dtype = (dtype >> DEV_TYPE_SHIFT) - 1;
	if (dtype >= NT) return(ENXIO);
	f_fp->fl_density = dtype;
	(void) f_prepare(f_device);	/* Recompute parameters. */
	return(OK);
  }
  if (f_device & FORMAT_DEV_BIT) return(EIO);	/* Can't format /dev/fdN */

  /* The device opened is /dev/fdN.  Experimentally determine drive/medium.
   * First check fl_density.  If it is not NO_DENS, the drive has been used
   * before and the value of fl_density tells what was found last time. Try
   * that first.  If the motor is still running then assume nothing changed.
   */
  if (f_fp->fl_density != NO_DENS) {
	if (motor_status & (1 << f_drive)) return(OK);
	if (test_read(f_fp->fl_density) == OK) return(OK);
  }

  /* Either drive type is unknown or a different diskette is now present.
   * Use test_order to try them one by one.
   */
  for (top = &test_order[0]; top < &test_order[NT-1]; top++) {
	dtype = top->t_density;

	/* Skip densities that have been proven to be impossible */
	if (!(f_fp->fl_class & (1 << dtype))) continue;

	if (test_read(dtype) == OK) {
		/* The test succeeded, use this knowledge to limit the
		 * drive class to match the density just read.
		 */
		f_fp->fl_class &= top->t_class;
		return(OK);
	}
	/* Test failed, wrong density or did it time out? */
	if (f_busy == BSY_WAKEN) break;
  }
  f_fp->fl_density = NO_DENS;
  return(EIO);			/* nothing worked */
}

/*===========================================================================*
 *				test_read				     *
 *===========================================================================*/
PRIVATE int test_read(density)
int density;
{
/* Try to read the highest numbered sector on cylinder 2.  Not all floppy
 * types have as many sectors per track, and trying cylinder 2 finds the
 * ones that need double stepping.
 */
  int device;
  off_t position;
  iovec_t iovec1;
  int result;

  f_fp->fl_density = density;
  device = ((density + 1) << DEV_TYPE_SHIFT) + f_drive;

  (void) f_prepare(device);
  position = (off_t) f_dp->test << SECTOR_SHIFT;
  iovec1.iov_addr = (vir_bytes) tmp_buf;
  iovec1.iov_size = SECTOR_SIZE;
  result = f_transfer(SELF, DEV_GATHER, position, &iovec1, 1);

  if (iovec1.iov_size != 0) return(EIO);

  partition(&f_dtab, f_drive, P_FLOPPY, 0);
  return(OK);
}

/*===========================================================================*
 *				f_geometry				     *
 *===========================================================================*/
PRIVATE void f_geometry(entry)
struct partition *entry;
{
  entry->cylinders = f_dp->cyls;
  entry->heads = NR_HEADS;
  entry->sectors = f_sectors;
}