root/drivers/scsi/st_options.h

/* */

INCLUDED FROM

   1 /*
   2    The compile-time configurable defaults for the Linux SCSI tape driver.
   3 
   4    Copyright 1995 Kai Makisara.
   5 
   6    Last modified: Thu Dec 14 21:51:27 1995 by root@kai.makisara.fi
   7 */
   8 
   9 #ifndef _ST_OPTIONS_H
  10 #define _ST_OPTIONS_H
  11 
  12 /* The driver allocates the tape buffers when needed if ST_RUNTIME_BUFFERS
  13    is nonzero. Otherwise a number of buffers are allocated at initialization.
  14    The drawback of runtime allocation is that allocation may fail. In any
  15    case the driver tries to allocate a new tape buffer when none is free. */
  16 #define ST_RUNTIME_BUFFERS 0
  17 
  18 /* The minimum limit for the number of SCSI tape devices is determined by
  19    ST_MAX_TAPES. If the number of tape devices and the "slack" defined by
  20    ST_EXTRA_DEVS exceeds ST_MAX_TAPES, the large number is used. */
  21 #define ST_MAX_TAPES 4
  22 
  23 /* The driver does not wait for some operations to finish before returning
  24    to the user program if ST_NOWAIT is non-zero. This helps if the SCSI
  25    adapter does not support multiple outstanding commands. However, the user
  26    should not give a new tape command before the previous one has finished. */
  27 #define ST_NOWAIT 0
  28 
  29 /* If ST_IN_FILE_POS is nonzero, the driver positions the tape after the
  30    record been read by the user program even if the tape has moved further
  31    because of buffered reads. Should be set to zero to support also drives
  32    that can't space backwards over records. NOTE: The tape will be
  33    spaced backwards over an "accidentally" crossed filemark in any case. */
  34 #define ST_IN_FILE_POS 0
  35 
  36 /* If ST_RECOVERED_WRITE_FATAL is non-zero, recovered errors while writing
  37    are considered "hard errors". */
  38 #define ST_RECOVERED_WRITE_FATAL 0
  39 
  40 /* The "guess" for the block size for devices that don't support MODE
  41    SENSE. */
  42 #define ST_DEFAULT_BLOCK 0
  43 
  44 /* The tape driver buffer size in kilobytes. */
  45 #define ST_BUFFER_BLOCKS 32
  46 
  47 /* The number of kilobytes of data in the buffer that triggers an
  48    asynchronous write in fixed block mode. See also ST_ASYNC_WRITES
  49    below. */
  50 #define ST_WRITE_THRESHOLD_BLOCKS 30
  51 
  52 /* The maximum number of tape buffers the driver allocates. The number
  53    is also constrained by the number of drives detected. Determines the
  54    maximum number of concurrently active tape drives. */
  55 #define ST_MAX_BUFFERS (2 + ST_EXTRA_DEVS)
  56 
  57 
  58 /* The following lines define defaults for properties that can be set
  59    separately for each drive using the MTSTOPTIONS ioctl. */
  60 
  61 /* If ST_TWO_FM is non-zero, the driver writes two filemarks after a
  62    file being written. Some drives can't handle two filemarks at the
  63    end of data. */
  64 #define ST_TWO_FM 0
  65 
  66 /* If ST_BUFFER_WRITES is non-zero, writes in fixed block mode are
  67    buffered until the driver buffer is full or asynchronous write is
  68    triggered. May make detection of End-Of-Medium early enough fail. */
  69 #define ST_BUFFER_WRITES 1
  70 
  71 /* If ST_ASYNC_WRITES is non-zero, the SCSI write command may be started
  72    without waiting for it to finish. May cause problems in multiple
  73    tape backups. */
  74 #define ST_ASYNC_WRITES 1
  75 
  76 /* If ST_READ_AHEAD is non-zero, blocks are read ahead in fixed block
  77    mode. */
  78 #define ST_READ_AHEAD 1
  79 
  80 /* If ST_AUTO_LOCK is non-zero, the drive door is locked at the first
  81    read or write command after the device is opened. The door is opened
  82    when the device is closed. */
  83 #define ST_AUTO_LOCK 0
  84 
  85 /* If ST_FAST_MTEOM is non-zero, the MTEOM ioctl is done using the
  86    direct SCSI command. The file number status is lost but this method
  87    is fast with some drives. Otherwise MTEOM is done by spacing over
  88    files and the file number status is retained. */
  89 #define ST_FAST_MTEOM 0
  90 
  91 #endif

/* */