drivers/scsi/st_options.h

   1 /*
   2    The compile-time configurable defaults for the Linux SCSI tape driver.
   3
   4    Copyright 1995-1999 Kai Makisara.
   5
   6    Last modified: Sat Aug  7 13:42:21 1999 by makisara@kai.makisara.local
   7 */
   8
   9 #ifndef _ST_OPTIONS_H
  10 #define _ST_OPTIONS_H
  11
  12 /* The minimum limit for the number of SCSI tape devices is determined by
  13    ST_MAX_TAPES. If the number of tape devices and the "slack" defined by
  14    ST_EXTRA_DEVS exceeds ST_MAX_TAPES, the large number is used. */
  15 #define ST_MAX_TAPES 4
  16
  17 /* The driver does not wait for some operations to finish before returning
  18    to the user program if ST_NOWAIT is non-zero. This helps if the SCSI
  19    adapter does not support multiple outstanding commands. However, the user
  20    should not give a new tape command before the previous one has finished. */
  21 #define ST_NOWAIT 0
  22
  23 /* If ST_IN_FILE_POS is nonzero, the driver positions the tape after the
  24    record been read by the user program even if the tape has moved further
  25    because of buffered reads. Should be set to zero to support also drives
  26    that can't space backwards over records. NOTE: The tape will be
  27    spaced backwards over an "accidentally" crossed filemark in any case. */
  28 #define ST_IN_FILE_POS 0
  29
  30 /* If ST_RECOVERED_WRITE_FATAL is non-zero, recovered errors while writing
  31    are considered "hard errors". */
  32 #define ST_RECOVERED_WRITE_FATAL 0
  33
  34 /* The "guess" for the block size for devices that don't support MODE
  35    SENSE. */
  36 #define ST_DEFAULT_BLOCK 0
  37
  38 /* The tape driver buffer size in kilobytes. */
  39 #define ST_BUFFER_BLOCKS 32
  40
  41 /* The number of kilobytes of data in the buffer that triggers an
  42    asynchronous write in fixed block mode. See also ST_ASYNC_WRITES
  43    below. */
  44 #define ST_WRITE_THRESHOLD_BLOCKS 30
  45
  46 /* The maximum number of tape buffers the driver tries to allocate at
  47    driver initialisation. The number is also constrained by the number
  48    of drives detected. If more buffers are needed, they are allocated
  49    at run time and freed after use. */
  50 #define ST_MAX_BUFFERS (2 + ST_EXTRA_DEVS)
  51
  52 /* Maximum number of scatter/gather segments */
  53 #define ST_MAX_SG      16
  54
  55 /* The number of scatter/gather segments to allocate at first try (must be
  56    smaller or equal to the maximum). */
  57 #define ST_FIRST_SG    8
  58
  59 /* The size of the first scatter/gather segments (determines the maximum block
  60    size for SCSI adapters not supporting scatter/gather). The default is set
  61    to try to allocate the buffer as one chunk. */
  62 #define ST_FIRST_ORDER  5
  63
  64
  65 /* The following lines define defaults for properties that can be set
  66    separately for each drive using the MTSTOPTIONS ioctl. */
  67
  68 /* If ST_TWO_FM is non-zero, the driver writes two filemarks after a
  69    file being written. Some drives can't handle two filemarks at the
  70    end of data. */
  71 #define ST_TWO_FM 0
  72
  73 /* If ST_BUFFER_WRITES is non-zero, writes in fixed block mode are
  74    buffered until the driver buffer is full or asynchronous write is
  75    triggered. May make detection of End-Of-Medium early enough fail. */
  76 #define ST_BUFFER_WRITES 1
  77
  78 /* If ST_ASYNC_WRITES is non-zero, the SCSI write command may be started
  79    without waiting for it to finish. May cause problems in multiple
  80    tape backups. */
  81 #define ST_ASYNC_WRITES 1
  82
  83 /* If ST_READ_AHEAD is non-zero, blocks are read ahead in fixed block
  84    mode. */
  85 #define ST_READ_AHEAD 1
  86
  87 /* If ST_AUTO_LOCK is non-zero, the drive door is locked at the first
  88    read or write command after the device is opened. The door is opened
  89    when the device is closed. */
  90 #define ST_AUTO_LOCK 0
  91
  92 /* If ST_FAST_MTEOM is non-zero, the MTEOM ioctl is done using the
  93    direct SCSI command. The file number status is lost but this method
  94    is fast with some drives. Otherwise MTEOM is done by spacing over
  95    files and the file number status is retained. */
  96 #define ST_FAST_MTEOM 0
  97
  98 /* If ST_SCSI2LOGICAL is nonzero, the logical block addresses are used for
  99    MTIOCPOS and MTSEEK by default. Vendor addresses are used if ST_SCSI2LOGICAL
 100    is zero. */
 101 #define ST_SCSI2LOGICAL 0
 102
 103 /* If ST_SYSV is non-zero, the tape behaves according to the SYS V semantics.
 104    The default is BSD semantics. */
 105 #define ST_SYSV 0
 106
 107
 108 #endif