forked from Minki/linux
102 lines
4.1 KiB
Plaintext
102 lines
4.1 KiB
Plaintext
|
Notes on Linux SCSI Generic (sg) driver
|
||
|
|
---------------------------------------
|
||
|
|
20020126
|
||
|
|
Introduction
|
||
|
|
============
|
||
|
|
The SCSI Generic driver (sg) is one of the four "high level" SCSI device
|
||
|
|
drivers along with sd, st and sr (disk, tape and CDROM respectively). Sg
|
||
|
|
is more generalized (but lower level) than its siblings and tends to be
|
||
|
|
used on SCSI devices that don't fit into the already serviced categories.
|
||
|
|
Thus sg is used for scanners, CD writers and reading audio CDs digitally
|
||
|
|
amongst other things.
|
||
|
|
|
||
|
|
Rather than document the driver's interface here, version information
|
||
|
|
is provided plus pointers (i.e. URLs) where to find documentation
|
||
|
|
and examples.
|
||
|
|
|
||
|
|
|
||
|
|
Major versions of the sg driver
|
||
|
|
===============================
|
||
|
|
There are three major versions of sg found in the linux kernel (lk):
|
||
|
|
- sg version 1 (original) from 1992 to early 1999 (lk 2.2.5) .
|
||
|
|
It is based in the sg_header interface structure.
|
||
|
|
- sg version 2 from lk 2.2.6 in the 2.2 series. It is based on
|
||
|
|
an extended version of the sg_header interface structure.
|
||
|
|
- sg version 3 found in the lk 2.4 series (and the lk 2.5 series).
|
||
|
|
It adds the sg_io_hdr interface structure.
|
||
|
|
|
||
|
|
|
||
|
|
Sg driver documentation
|
||
|
|
=======================
|
||
|
|
The most recent documentation of the sg driver is kept at the Linux
|
||
|
|
Documentation Project's (LDP) site:
|
||
|
|
http://www.tldp.org/HOWTO/SCSI-Generic-HOWTO
|
||
|
|
This describes the sg version 3 driver found in the lk 2.4 series.
|
||
|
|
The LDP renders documents in single and multiple page HTML, postscript
|
||
|
|
and pdf. This document can also be found at:
|
||
|
|
http://www.torque.net/sg/p/sg_v3_ho.html
|
||
|
|
|
||
|
|
Documentation for the version 2 sg driver found in the lk 2.2 series can
|
||
|
|
be found at http://www.torque.net/sg/p/scsi-generic.txt . A larger version
|
||
|
|
is at: http://www.torque.net/sg/p/scsi-generic_long.txt .
|
||
|
|
|
||
|
|
The original documentation for the sg driver (prior to lk 2.2.6) can be
|
||
|
|
found at http://www.torque.net/sg/p/original/SCSI-Programming-HOWTO.txt
|
||
|
|
and in the LDP archives.
|
||
|
|
|
||
|
|
A changelog with brief notes can be found in the
|
||
|
|
/usr/src/linux/include/scsi/sg.h file. Note that the glibc maintainers copy
|
||
|
|
and edit this file (removing its changelog for example) before placing it
|
||
|
|
in /usr/include/scsi/sg.h . Driver debugging information and other notes
|
||
|
|
can be found at the top of the /usr/src/linux/drivers/scsi/sg.c file.
|
||
|
|
|
||
|
|
A more general description of the Linux SCSI subsystem of which sg is a
|
||
|
|
part can be found at http://www.tldp.org/HOWTO/SCSI-2.4-HOWTO .
|
||
|
|
|
||
|
|
|
||
|
|
Example code and utilities
|
||
|
|
==========================
|
||
|
|
There are two packages of sg utilities:
|
||
|
|
- sg3_utils for the sg version 3 driver found in lk 2.4
|
||
|
|
- sg_utils for the sg version 2 (and original) driver found in lk 2.2
|
||
|
|
and earlier
|
||
|
|
Both packages will work in the lk 2.4 series however sg3_utils offers more
|
||
|
|
capabilities. They can be found at: http://www.torque.net/sg and
|
||
|
|
freshmeat.net
|
||
|
|
|
||
|
|
Another approach is to look at the applications that use the sg driver.
|
||
|
|
These include cdrecord, cdparanoia, SANE and cdrdao.
|
||
|
|
|
||
|
|
|
||
|
|
Mapping of Linux kernel versions to sg driver versions
|
||
|
|
======================================================
|
||
|
|
Here is a list of linux kernels in the 2.4 series that had new version
|
||
|
|
of the sg driver:
|
||
|
|
lk 2.4.0 : sg version 3.1.17
|
||
|
|
lk 2.4.7 : sg version 3.1.19
|
||
|
|
lk 2.4.10 : sg version 3.1.20 **
|
||
|
|
lk 2.4.17 : sg version 3.1.22
|
||
|
|
|
||
|
|
** There were 3 changes to sg version 3.1.20 by third parties in the
|
||
|
|
next six linux kernel versions.
|
||
|
|
|
||
|
|
For reference here is a list of linux kernels in the 2.2 series that had
|
||
|
|
new version of the sg driver:
|
||
|
|
lk 2.2.0 : original sg version [with no version number]
|
||
|
|
lk 2.2.6 : sg version 2.1.31
|
||
|
|
lk 2.2.8 : sg version 2.1.32
|
||
|
|
lk 2.2.10 : sg version 2.1.34 [SG_GET_VERSION_NUM ioctl first appeared]
|
||
|
|
lk 2.2.14 : sg version 2.1.36
|
||
|
|
lk 2.2.16 : sg version 2.1.38
|
||
|
|
lk 2.2.17 : sg version 2.1.39
|
||
|
|
lk 2.2.20 : sg version 2.1.40
|
||
|
|
|
||
|
|
The lk 2.5 development series has recently commenced and it currently
|
||
|
|
contains sg version 3.5.23 which is functionally equivalent to sg
|
||
|
|
version 3.1.22 found in lk 2.4.17 .
|
||
|
|
|
||
|
|
|
||
|
|
Douglas Gilbert
|
||
|
|
26th January 2002
|
||
|
|
dgilbert@interlog.com
|