scsi-generic.rst 4.3 KB

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  1. .. SPDX-License-Identifier: GPL-2.0
  2. =======================================
  3. Notes on Linux SCSI Generic (sg) driver
  4. =======================================
  5. 20020126
  6. Introduction
  7. ============
  8. The SCSI Generic driver (sg) is one of the four "high level" SCSI device
  9. drivers along with sd, st and sr (disk, tape and CDROM respectively). Sg
  10. is more generalized (but lower level) than its siblings and tends to be
  11. used on SCSI devices that don't fit into the already serviced categories.
  12. Thus sg is used for scanners, CD writers and reading audio CDs digitally
  13. amongst other things.
  14. Rather than document the driver's interface here, version information
  15. is provided plus pointers (i.e. URLs) where to find documentation
  16. and examples.
  17. Major versions of the sg driver
  18. ===============================
  19. There are three major versions of sg found in the linux kernel (lk):
  20. - sg version 1 (original) from 1992 to early 1999 (lk 2.2.5) .
  21. It is based in the sg_header interface structure.
  22. - sg version 2 from lk 2.2.6 in the 2.2 series. It is based on
  23. an extended version of the sg_header interface structure.
  24. - sg version 3 found in the lk 2.4 series (and the lk 2.5 series).
  25. It adds the sg_io_hdr interface structure.
  26. Sg driver documentation
  27. =======================
  28. The most recent documentation of the sg driver is kept at the Linux
  29. Documentation Project's (LDP) site:
  30. - http://www.tldp.org/HOWTO/SCSI-Generic-HOWTO
  31. This describes the sg version 3 driver found in the lk 2.4 series.
  32. The LDP renders documents in single and multiple page HTML, postscript
  33. and pdf. This document can also be found at:
  34. - http://sg.danny.cz/sg/p/sg_v3_ho.html
  35. Documentation for the version 2 sg driver found in the lk 2.2 series can
  36. be found at http://sg.danny.cz/sg/. A larger version
  37. is at: http://sg.danny.cz/sg/p/scsi-generic_long.txt.
  38. The original documentation for the sg driver (prior to lk 2.2.6) can be
  39. found at http://www.torque.net/sg/p/original/SCSI-Programming-HOWTO.txt
  40. and in the LDP archives.
  41. A changelog with brief notes can be found in the
  42. /usr/src/linux/include/scsi/sg.h file. Note that the glibc maintainers copy
  43. and edit this file (removing its changelog for example) before placing it
  44. in /usr/include/scsi/sg.h . Driver debugging information and other notes
  45. can be found at the top of the /usr/src/linux/drivers/scsi/sg.c file.
  46. A more general description of the Linux SCSI subsystem of which sg is a
  47. part can be found at http://www.tldp.org/HOWTO/SCSI-2.4-HOWTO .
  48. Example code and utilities
  49. ==========================
  50. There are two packages of sg utilities:
  51. ========= ==========================================================
  52. sg3_utils for the sg version 3 driver found in lk 2.4
  53. sg_utils for the sg version 2 (and original) driver found in lk 2.2
  54. and earlier
  55. ========= ==========================================================
  56. Both packages will work in the lk 2.4 series however sg3_utils offers more
  57. capabilities. They can be found at: http://sg.danny.cz/sg/sg3_utils.html and
  58. freecode.com
  59. Another approach is to look at the applications that use the sg driver.
  60. These include cdrecord, cdparanoia, SANE and cdrdao.
  61. Mapping of Linux kernel versions to sg driver versions
  62. ======================================================
  63. Here is a list of linux kernels in the 2.4 series that had new version
  64. of the sg driver:
  65. - lk 2.4.0 : sg version 3.1.17
  66. - lk 2.4.7 : sg version 3.1.19
  67. - lk 2.4.10 : sg version 3.1.20 [#]_
  68. - lk 2.4.17 : sg version 3.1.22
  69. .. [#] There were 3 changes to sg version 3.1.20 by third parties in the
  70. next six linux kernel versions.
  71. For reference here is a list of linux kernels in the 2.2 series that had
  72. new version of the sg driver:
  73. - lk 2.2.0 : original sg version [with no version number]
  74. - lk 2.2.6 : sg version 2.1.31
  75. - lk 2.2.8 : sg version 2.1.32
  76. - lk 2.2.10 : sg version 2.1.34 [SG_GET_VERSION_NUM ioctl first appeared]
  77. - lk 2.2.14 : sg version 2.1.36
  78. - lk 2.2.16 : sg version 2.1.38
  79. - lk 2.2.17 : sg version 2.1.39
  80. - lk 2.2.20 : sg version 2.1.40
  81. The lk 2.5 development series has recently commenced and it currently
  82. contains sg version 3.5.23 which is functionally equivalent to sg
  83. version 3.1.22 found in lk 2.4.17.
  84. Douglas Gilbert
  85. 26th January 2002
  86. dgilbert@interlog.com