1.. SPDX-License-Identifier: GPL-2.0 2 3======================================= 4Notes on Linux SCSI Generic (sg) driver 5======================================= 6 7 20020126 8 9Introduction 10============ 11The SCSI Generic driver (sg) is one of the four "high level" SCSI device 12drivers along with sd, st and sr (disk, tape and CDROM respectively). Sg 13is more generalized (but lower level) than its siblings and tends to be 14used on SCSI devices that don't fit into the already serviced categories. 15Thus sg is used for scanners, CD writers and reading audio CDs digitally 16amongst other things. 17 18Rather than document the driver's interface here, version information 19is provided plus pointers (i.e. URLs) where to find documentation 20and examples. 21 22 23Major versions of the sg driver 24=============================== 25There are three major versions of sg found in the linux kernel (lk): 26 - sg version 1 (original) from 1992 to early 1999 (lk 2.2.5) . 27 It is based in the sg_header interface structure. 28 - sg version 2 from lk 2.2.6 in the 2.2 series. It is based on 29 an extended version of the sg_header interface structure. 30 - sg version 3 found in the lk 2.4 series (and the lk 2.5 series). 31 It adds the sg_io_hdr interface structure. 32 33 34Sg driver documentation 35======================= 36The most recent documentation of the sg driver is kept at the Linux 37Documentation Project's (LDP) site: 38 39- http://www.tldp.org/HOWTO/SCSI-Generic-HOWTO 40 41This describes the sg version 3 driver found in the lk 2.4 series. 42 43The LDP renders documents in single and multiple page HTML, postscript 44and pdf. This document can also be found at: 45 46- http://sg.danny.cz/sg/p/sg_v3_ho.html 47 48Documentation for the version 2 sg driver found in the lk 2.2 series can 49be found at http://sg.danny.cz/sg/. A larger version 50is at: http://sg.danny.cz/sg/p/scsi-generic_long.txt. 51 52The original documentation for the sg driver (prior to lk 2.2.6) can be 53found at http://www.torque.net/sg/p/original/SCSI-Programming-HOWTO.txt 54and in the LDP archives. 55 56A changelog with brief notes can be found in the 57/usr/src/linux/include/scsi/sg.h file. Note that the glibc maintainers copy 58and edit this file (removing its changelog for example) before placing it 59in /usr/include/scsi/sg.h . Driver debugging information and other notes 60can be found at the top of the /usr/src/linux/drivers/scsi/sg.c file. 61 62A more general description of the Linux SCSI subsystem of which sg is a 63part can be found at http://www.tldp.org/HOWTO/SCSI-2.4-HOWTO . 64 65 66Example code and utilities 67========================== 68There are two packages of sg utilities: 69 70 ========= ========================================================== 71 sg3_utils for the sg version 3 driver found in lk 2.4 72 sg_utils for the sg version 2 (and original) driver found in lk 2.2 73 and earlier 74 ========= ========================================================== 75 76Both packages will work in the lk 2.4 series however sg3_utils offers more 77capabilities. They can be found at: http://sg.danny.cz/sg/sg3_utils.html and 78freecode.com 79 80Another approach is to look at the applications that use the sg driver. 81These include cdrecord, cdparanoia, SANE and cdrdao. 82 83 84Mapping of Linux kernel versions to sg driver versions 85====================================================== 86Here is a list of linux kernels in the 2.4 series that had new version 87of the sg driver: 88 89 - lk 2.4.0 : sg version 3.1.17 90 - lk 2.4.7 : sg version 3.1.19 91 - lk 2.4.10 : sg version 3.1.20 [#]_ 92 - lk 2.4.17 : sg version 3.1.22 93 94.. [#] There were 3 changes to sg version 3.1.20 by third parties in the 95 next six linux kernel versions. 96 97For reference here is a list of linux kernels in the 2.2 series that had 98new version of the sg driver: 99 100 - lk 2.2.0 : original sg version [with no version number] 101 - lk 2.2.6 : sg version 2.1.31 102 - lk 2.2.8 : sg version 2.1.32 103 - lk 2.2.10 : sg version 2.1.34 [SG_GET_VERSION_NUM ioctl first appeared] 104 - lk 2.2.14 : sg version 2.1.36 105 - lk 2.2.16 : sg version 2.1.38 106 - lk 2.2.17 : sg version 2.1.39 107 - lk 2.2.20 : sg version 2.1.40 108 109The lk 2.5 development series has recently commenced and it currently 110contains sg version 3.5.23 which is functionally equivalent to sg 111version 3.1.22 found in lk 2.4.17. 112 113 114Douglas Gilbert 115 11626th January 2002 117 118dgilbert@interlog.com 119