README - platform/external/sg3_utils - Git at Google

                       README for sg3_utils
                       ====================
 Introduction
 ============
 This package contains low level utilities for devices that use a SCSI
 command set. Apart from SCSI parallel interface (SPI) devices, the SCSI
 command set is used by ATAPI devices (CD/DVDs and tapes), USB
 mass storage devices, Fibre Channel disks, IEEE 1394 storage
 devices (that use the "SBP" protocol), SAS and iSCSI.

 This package originally targeted the Linux SCSI subsystem. Since most
 operating systems contain a SCSI command pass-through mechanism, many
 utilities within this package have been ported. This README mainly
 concentrates on Linux: see the README.freebsd file for the FreeBSD port,
 README.solaris for the Solaris port, the README.tru64 file for the Tru64
 (OSF) port and README.win32 for the Windows port.

 Most utilities within the sg3_utils package work at the SCSI command level.
 For example the sg_inq utility issues a SCSI INQUIRY command and decodes the
 response. To view the relationship between a sg3_utils' utility and the
 main SCSI command(s) that it issues see the COVERAGE file. Some utilities
 interface at a slightly higher level, for example: sg_dd, sgm_dd and sgp_dd.
 These are closely related to the Unix dd command and typically issue a
 sequence of SCSI READ and WRITE commands to copy data.

 Description
 ===========
 A web site supporting the sg3_utils package, its predecessor sg_utils, and
 the Linux SCSI generic driver can be found at http://www.torque.net/sg .
 The most recent release version of sg3_utils and the most recent beta are
 available from that page. There is also a page describing the utilities in
 the sg3_utils and sg_utils packages: http://www.torque.net/sg/sg3_utils.html .

 In the Linux 2.4 kernel series these utilities need to use the SCSI generic
 (sg) driver to access SCSI devices. The name of this package (i.e. sg3_utils)
 refers to version 3 of the SCSI generic (sg) driver which was introduced at
 the beginning of the 2.4 linux kernel series. Significantly this added a new
 SCSI command interface structure (i.e. struct sg_io_hdr) that is more
 flexible than the older "sg_header" structure found in the sg driver in the
 2.2 and earlier linux kernel series. The sg_io_hdr structure is also more
 flexible than the awkward (and limiting) interface to the
 SCSI_IOCTL_SEND_COMMAND ioctl supported by the linux SCSI mid level. The
 version 3 sg driver also added the SG_IO ioctl that is synchronous (i.e. it
 issues the requested SCSI command and waits for the response (or a timeout)
 before the ioctl returns to the user space program that invoked it). The
 SG_IO ioctl is now supported in other parts of the linux kernel in the 2.6
 series.

 Utilities that wish to use the asynchronous SCSI command interface (i.e. via
 a write() read() sequence) or issue special "commands" (e.g. bus and device
 resets) still need to use the linux sg driver. Note that various
 drivers (e.g. cdrom/sr) have different open() flag and permissions policies
 that the user may need to take into account.

 If you have problems or questions about them please contact the author.
 Documentation for the linux sg device driver can be found at:
 http://www.torque.net/sg/p/sg_v3_ho.html . This is written in DocBook and the
 original xml can be found in the same directory with the ".xml" extension.
 Postscript and pdf renderings are also in that directory. Older documentation
 for the sg version 3 driver can be found at:
 http://www.torque.net/sg/p/scsi_generic_v3.txt .

 All utilities are either "GPL"-ed or have a FreeBSD license. The author's
 intention is that users may incorporate all or part of the code in their work
 as they please. Attribution is encouraged. Please check the code as other
 contributors (apart from the author) may also have copyright notices. For a
 list of contributors see the CREDITS file.

 The "sg_lib_data.[hc]" files contain ASCII text corresponding to most of the
 SCSI commands, errors and warning conditions. The interface to this data
 plus several related helper functions are found in the sg_lib.[hc] files.
 The "sg_cmds_basic.[hc]" files contains code to invoke common SCSI commands
 and associated response processing. The "sg_cmds_extra.[hc]" files contains
 code to invoke lesser used SCSI commands and associated response processing.
 All are guided by recent drafts at www.t10.org which is the home site of
 SCSI (draft) standards. Linux specific code has been removed from sg_lib.[hc],
 sg_cmds_basic.[hc] and sg_cmds_extra.[hc] . The SCSI command implementations
 in sg_cmds_basic.c and sg_cmds_extra.c access the OS pass through mechanism
 via the function based interface defined in sg_pt.h . The linux specific
 implementation of that pass through is found in the sg_pt_linux.c file. Since
 almost all of the utilities use these files, a shared library called
 "libsgutils.so" is built. Use of this library cuts down the size of the
 binary distributions of sg3_utils significantly. In sg3_utils version 1.25
 then header files mentioned in this paragraph were relocated in the 'include'
 subdirectory while the source code files (i.e. those ending in ".c") were
 reloacted in the 'lib' subdirectory. The build scripts provided in the 'lib'
 subdirectory builds libsgutils.so The rest of the source code files have
 been relocated to the 'src' subdirectory. See the INSTALL file for more
 information.

 All the utilities in the 'src' subdirectory have "man" pages that are now
 placed in the 'doc' subdirectory. There is also a sg3_utils (8) man page that
 summarizes common facilities including exit statuses. Additional
 information (including a version number) can be found towards the top of
 each ".c" file corresponding to each utility.

 The sg driver in Linux can be seen as having 3 distinct versions:

    v1   lk < 2.2.6     sg_header based relatively unchanged since 1992
    v2   lk >= 2.2.6    enhanced sg_header interface structure [1999/4/16]
    v3   lk >= 2.4      additional sg_io_hdr interface structure [2001/1/4]
    v3   lk >= 2.6      same interface as found in lk 2.4 [2.6.0: 2003/12/18]

 This package is targeted at "v3" only. Another package called "sg_utils"
 is targeted at "v2" and to a lesser extent "v1". The "sg_utils" package has
 a subset of the utilities found in this package.

 In linux some sg ioctls (notably SG_IO) are defined for many block devices in
 lk 2.6 . In practice this means all SCSI block devices, ATAPI block
 devices (mainly CD and DVD players) but _not_ ATA disks, depending on which
 kernel configuration options are chosen. SATA disks that use the libata kernel
 library (or some other SCSI to ATA Translation (SAT) Layer (SATL)) accept SCSI
 commands and thus are supported. Support for the SG_IO as been added to the
 scsi tape driver (st) in lk 2.6.6 .

 In linux no utilities in the 'src' subdirectory use the sg driver's
 older "sg_header" interface; instead they use the newer "sg_io_hdr" interface.
 The "sg_io_hdr" interface can be accessed two ways:
   - using the SG_IO ioctl [for synchronous access]
   - using a write()/read() sequence that convey instances of "sg_io_hdr"

 All utilities in the 'src' subdirectory that issue SCSI commands use the
 linux SG_IO ioctl except for sgp_dd. This is due to the asynchronous nature
 of sgp_dd. Note that sgp_dd does _not_ support the "blk_sgio" switch found
 in sg_dd. This is important since block devices often identify themselves
 (programmatically) as sg devices in lk 2.6 and it would cause serious damage
 to do a write() of the sg driver's "sg_io_hdr" meta data (i.e. disk
 corruption).

 Warning
 =======
 Many devices use SCSI command sets over transport protocols not normally
 associated with SCSI (as defined at http://www.t10.org ). Some of these
 devices react poorly (e.g. lock up) when sent SCSI commands that they don't
 support. Even sending a supported SCSI command with a field set to an
 unexpected value can cause problems.

 For example, all "SCSI" devices must support the INQUIRY command which the
 SCSI-2 standard says should request a 36 byte response. However later SCSI
 standards (e.g. SPC-2) have increased that length but some SCSI devices lock
 up when they receive a request for anything other than a 36 byte response.

 Any well implemented "SCSI" device should react sensibly when a utility in
 sg3_utils sends a SCSI command that it doesn't support. Unfortunately this
 cannot be guaranteed.


 Utilities
 =========
 Here is list in alphabetical order of utilities found in the 'src'
 subdirectory of the sg3_utils package:
   - sginfo, sgm_dd, sgp_dd, sg_dd, sg_emc_trespass, sg_get_config,
     sg_format, sg_ident, sg_inq, sg_logs, sg_luns, sg_map, sg_map26,
     sg_modes, sg_opcodes, sg_persist, sg_prevent, sg_raw, sg_rbuf, sg_rdac,
     sg_read, sg_readcap, sg_read_buffer, sg_read_long, sg_reassign,
     sg_request, sg_reset, sg_rmsn, sg_rtpg, sg_safte, sg_sat_identify,
     sg_sat_phy_event, sg_sat_set_features, sg_scan, sg_senddiag, sg_ses,
     sg_start, sg_stpg, sg_sync, sg_test_rwbuff, sg_turs, sg_verify, sg_vpd,
     sg_write_buffer, sg_write_long, sg_wr_mode

 Each of the above utilities depends on header files found in the 'include'
 subdirectory and library code found in the 'lib' subdirectory. Associated
 man pages are found in the 'doc' subdirectory. Additional programs found
 in the 'archive', 'examples' and 'utils' subdirectories in not build by the
 top level build infrastructure. Linux binary distributions of the sg3_utils
 package (e.g. "rpm" and debian packages) typically contain the shared
 library, the utilities found in the 'src' subdirectory, their associated man
 pages and some documentation files (e.g. README, INSTALL, CREDITS, COPYING
 and COVERAGE). See the INSTALL file for instructions about building and
 installing from a source "tarball".

 Man pages can be read (without building and installing the package) by
 going to the 'doc' subdirectory and executing something like this:
  $ man ./sg_dd.8

 To see which SCSI commands (and ATA commands) are used by these utilities
 refer to the COVERAGE file.

 Here is a list in alphabetical order of utilities found in the 'archive'
 subdirectory:
   - isosize, scsi_devfs_scan, sg_debug, sgq_dd
 Some of these utilities have man pages.

 Here is a list in alphabetical order of utilities found in the 'examples'
 subdirectory:
   - sg_excl, scsi_inquiry, sg_iovec_tst, sg_sat_chk_power,
     sg__sat_identify, sg__sat_phy_event, sg__sat_set_features,
     sg_sat_smart_rd_data, sg_simple1, sg_simple2, sg_simple3, sg_simple4,
     sg_simple5 and sg_simple16

 Also in that subdirectory is a script to test sg_persist, an example data
 file for sg_persist (called "transport_ids.txt") and an example data file for
 sg_reassign (called "reassign_addr.txt"). There are several scripts
 for 'sg_senddiag -pf -raw=-' that will put some SAS disk phys into
 a "compliant jitter tolerance pattern" (CJTPAT).

 The 'utils' subdirectory contains source and a Makefile to build "hxascdmp"
 which accepts binary data from stdin (or a file on the command line) and
 outputs an ASCII-HEX and ASCII representation of it. It is similar to the
 Unix od command. There is also code to sg_chk_asc.c which checks a given
 text file (typically a copy of http://www.t10.org/lists/asc-num.txt ) and
 checks it against the asc/ascq text strings held in sg_lib_data.c .

 The 'doc' subdirectory contains a README.doc file containing the urls of
 various related documents.

 The 'scripts' subdirectory contains some bourne (bash) shell scripts that
 rely on utilities in the main directory. One script uses the sdparm utility.
 These scripts are described in the scripts/README file and have usage
 messages.


 Notes for utilities without man pages
 =====================================
 These utils are found in the 'examples' subdirectory.

 The "scsi_inquiry" program shows the use of the SCSI_IOCTL_SEND_COMMAND
 ioctl to send a SCSI INQUIRY command. That ioctl() is supported by the
 SCSI sub system mid level and so is common to all sd, sr, st and sg devices.
 That ioctl is deprecated in the lk 2.6 series. This program has been placed
 in the "examples" subdirectory.

 "sgq_dd" is yet another variant of dd found in the archive directory.
 From the user's point of view it is very similar to sgp_dd but uses a
 non-blocking state machine rather then POSIX threads for parallelism.

 "sg_debug" is effectively defunct now. The user can instead execute:
 'cat /proc/scsi/sg/debug' . This command has been placed in the archive
 directory.

 "sg_simple1" and "sg_simple2" are example programs demonstrating calls
 to the SCSI INQUIRY and TEST UNIT READY commands. They only differ in their
 error processing: sg_simple1 uses sg_lib.[hc] for error processing while
 sg_simple2 does its own more primitive checks.

 "sg_simple3" tests out user space scatter gather added to the version 3
 sg driver.

 "sg_simple4" shows the INQUIRY command using mmap-ed IO to obtain its
 response buffer.

 "sg_simple5" also sends and INQUIRY and TEST UNIT READY commands. It
 uses the generic pass through mechanism based on sg_pt.h . It will
 currently build in linux and FreeBSD (with "make -f Makefile.freebsd").
 It has extensive error checking code.

 "sg_simple16" attempts to send a 16 byte SCSI command, READ_16, to the
 scsi device. This is only supported for lk >= 2.4.15 and for adapter
 drivers that indicate that they have 16 byte CDB capability (otherwise
 DID_ABORT will appear in the host_status).

 "sg_sat_chk_power" attempts to push an ATA CHECK POWER MODE command
 through the SAT-defined ATA PASS_THROUGH (16) SCSI command. That
 ATA command needs to read the "FIS" registers after the command is
 completed which involves using the ATA Status Return (sense data)
 descriptor (as defined in SAT).

 "sg_sat_smart_rd_data" attempts to push an ATA SMART/READ DATA command
 through the SAT-defined ATA PASS_THROUGH (16) SCSI command. If
 successful, the 256 word (512 byte) response is output.


 Command line processing
 =======================
 These utilities can be divided into 3 groups when their handling of command
 line arguments is considered:
   - ad hoc, typically in a short form only, sometimes longer (e.g.
     "sg_logs -pcb /dev/sdc")
   - inspired by the dd Unix command (e.g. sg_dd, sgm_dd, sgp_dd, sg_read)
   - recent utilities use "getopt_long" (see "man getopt_long")
     type command lines. These have short form (starting with "-")
     and corresponding longer form (starting with "--") options.

 The older utilities that use ad hoc options, in alphabetical order:
   - sg_emc_trespass, sginfo(1/2), sg_inq, sg_logs, sg_map, sg_modes,
     sg_opcodes, sg_rbuf, sg_rdac, sg_readcap, sg_reset, sg_scan (linux),
     sg_senddiag, sg_start, sg_test_rwbuf, sg_turs
 In sg3_utils version 1.23 the following utilities from this group were
 converted to have a dual getopt_long/ad_hoc interface, defaulting to
 the getop_long interface:
   - sg_inq, sg_logs, sg_modes, sg_opcodes, sg_rbuf, sg_readcap,
     sg_senddiag, sg_start, sg_turs
 These can be switched back to the older (backward compatible) ad hoc
 interface by defining the SG3_UTILS_OLD_OPTS environment variable
 or using '-O' as the first command line option.

 The more recent utilities that use "getopt_long" only are:
   - sg_format sg_get_config sg_ident sg_luns sg_map26 sg_persist
     sg_prevent sg_raw sg_read_buffer sg_read_long sg_reassign sg_requests
     sg_rmsn sg_rtpg sg_safte sg_sat_identify sg_sat_phy_event
     sg_sat_set_features sg_scan(w) sg_ses sg_stpg sg_sync sg_test_rwbuf
     sg_verify sg_vpd sg_write_buffer sg_write_long sg_wr_mode


 Linux header file problems
 ==========================
 The problems discussed below do not appear in recent Linux distributions.

 Some utilities include 2 important header files:
 #include <scsi/sg.h>
 #include <scsi/scsi.h>
 These files are typically found in the directory /usr/include/scsi which
 is maintained by the GNU glibc team. Unfortunately these GNU supplied
 headers may not be (functionally) the same as those found in the kernel
 source:
 /usr/src/linux/include/scsi/sg.h   and
 /usr/src/linux/include/scsi/scsi.h

 If glibc and the kernel on a machine are of the same vintage then it is
 probably sufficient to use the simple includes listed at the start of this
 section. Another technique that used to work was to rely on
 /usr/include/linux being a symbolic link to /usr/src/linux/include/linux .
 That caused the following:
 #include <linux/../scsi/sg.h>
 #include <linux/../scsi/scsi.h>
 to find the kernel supplied header files. However recent versions of
 glibc have removed this symlink. Hence this technique is no longer
 recommended.

 The include file path issues are now all addressed in one file called
 "sg_linux_inc.h". Please read that file. This fetching of the scsi.h and
 sg.h header files has not been a problem in the latter lk 2.4 and lk 2.6
 series.

 Other SCSI and storage tools
 ============================
 See http://www.torque.net/sg/tools.html


 Doug Gilbert
 22nd January 2008
	README for sg3_utils
	====================
	Introduction
	============
	This package contains low level utilities for devices that use a SCSI
	command set. Apart from SCSI parallel interface (SPI) devices, the SCSI
	command set is used by ATAPI devices (CD/DVDs and tapes), USB
	mass storage devices, Fibre Channel disks, IEEE 1394 storage
	devices (that use the "SBP" protocol), SAS and iSCSI.

	This package originally targeted the Linux SCSI subsystem. Since most
	operating systems contain a SCSI command pass-through mechanism, many
	utilities within this package have been ported. This README mainly
	concentrates on Linux: see the README.freebsd file for the FreeBSD port,
	README.solaris for the Solaris port, the README.tru64 file for the Tru64
	(OSF) port and README.win32 for the Windows port.

	Most utilities within the sg3_utils package work at the SCSI command level.
	For example the sg_inq utility issues a SCSI INQUIRY command and decodes the
	response. To view the relationship between a sg3_utils' utility and the
	main SCSI command(s) that it issues see the COVERAGE file. Some utilities
	interface at a slightly higher level, for example: sg_dd, sgm_dd and sgp_dd.
	These are closely related to the Unix dd command and typically issue a
	sequence of SCSI READ and WRITE commands to copy data.

	Description
	===========
	A web site supporting the sg3_utils package, its predecessor sg_utils, and
	the Linux SCSI generic driver can be found at http://www.torque.net/sg .
	The most recent release version of sg3_utils and the most recent beta are
	available from that page. There is also a page describing the utilities in
	the sg3_utils and sg_utils packages: http://www.torque.net/sg/sg3_utils.html .

	In the Linux 2.4 kernel series these utilities need to use the SCSI generic
	(sg) driver to access SCSI devices. The name of this package (i.e. sg3_utils)
	refers to version 3 of the SCSI generic (sg) driver which was introduced at
	the beginning of the 2.4 linux kernel series. Significantly this added a new
	SCSI command interface structure (i.e. struct sg_io_hdr) that is more
	flexible than the older "sg_header" structure found in the sg driver in the
	2.2 and earlier linux kernel series. The sg_io_hdr structure is also more
	flexible than the awkward (and limiting) interface to the
	SCSI_IOCTL_SEND_COMMAND ioctl supported by the linux SCSI mid level. The
	version 3 sg driver also added the SG_IO ioctl that is synchronous (i.e. it
	issues the requested SCSI command and waits for the response (or a timeout)
	before the ioctl returns to the user space program that invoked it). The
	SG_IO ioctl is now supported in other parts of the linux kernel in the 2.6
	series.

	Utilities that wish to use the asynchronous SCSI command interface (i.e. via
	a write() read() sequence) or issue special "commands" (e.g. bus and device
	resets) still need to use the linux sg driver. Note that various
	drivers (e.g. cdrom/sr) have different open() flag and permissions policies
	that the user may need to take into account.

	If you have problems or questions about them please contact the author.
	Documentation for the linux sg device driver can be found at:
	http://www.torque.net/sg/p/sg_v3_ho.html . This is written in DocBook and the
	original xml can be found in the same directory with the ".xml" extension.
	Postscript and pdf renderings are also in that directory. Older documentation
	for the sg version 3 driver can be found at:
	http://www.torque.net/sg/p/scsi_generic_v3.txt .

	All utilities are either "GPL"-ed or have a FreeBSD license. The author's
	intention is that users may incorporate all or part of the code in their work
	as they please. Attribution is encouraged. Please check the code as other
	contributors (apart from the author) may also have copyright notices. For a
	list of contributors see the CREDITS file.

	The "sg_lib_data.[hc]" files contain ASCII text corresponding to most of the
	SCSI commands, errors and warning conditions. The interface to this data
	plus several related helper functions are found in the sg_lib.[hc] files.
	The "sg_cmds_basic.[hc]" files contains code to invoke common SCSI commands
	and associated response processing. The "sg_cmds_extra.[hc]" files contains
	code to invoke lesser used SCSI commands and associated response processing.
	All are guided by recent drafts at www.t10.org which is the home site of
	SCSI (draft) standards. Linux specific code has been removed from sg_lib.[hc],
	sg_cmds_basic.[hc] and sg_cmds_extra.[hc] . The SCSI command implementations
	in sg_cmds_basic.c and sg_cmds_extra.c access the OS pass through mechanism
	via the function based interface defined in sg_pt.h . The linux specific
	implementation of that pass through is found in the sg_pt_linux.c file. Since
	almost all of the utilities use these files, a shared library called
	"libsgutils.so" is built. Use of this library cuts down the size of the
	binary distributions of sg3_utils significantly. In sg3_utils version 1.25
	then header files mentioned in this paragraph were relocated in the 'include'
	subdirectory while the source code files (i.e. those ending in ".c") were
	reloacted in the 'lib' subdirectory. The build scripts provided in the 'lib'
	subdirectory builds libsgutils.so The rest of the source code files have
	been relocated to the 'src' subdirectory. See the INSTALL file for more
	information.

	All the utilities in the 'src' subdirectory have "man" pages that are now
	placed in the 'doc' subdirectory. There is also a sg3_utils (8) man page that
	summarizes common facilities including exit statuses. Additional
	information (including a version number) can be found towards the top of
	each ".c" file corresponding to each utility.

	The sg driver in Linux can be seen as having 3 distinct versions:

	v1 lk < 2.2.6 sg_header based relatively unchanged since 1992
	v2 lk >= 2.2.6 enhanced sg_header interface structure [1999/4/16]
	v3 lk >= 2.4 additional sg_io_hdr interface structure [2001/1/4]
	v3 lk >= 2.6 same interface as found in lk 2.4 [2.6.0: 2003/12/18]

	This package is targeted at "v3" only. Another package called "sg_utils"
	is targeted at "v2" and to a lesser extent "v1". The "sg_utils" package has
	a subset of the utilities found in this package.

	In linux some sg ioctls (notably SG_IO) are defined for many block devices in
	lk 2.6 . In practice this means all SCSI block devices, ATAPI block
	devices (mainly CD and DVD players) but _not_ ATA disks, depending on which
	kernel configuration options are chosen. SATA disks that use the libata kernel
	library (or some other SCSI to ATA Translation (SAT) Layer (SATL)) accept SCSI
	commands and thus are supported. Support for the SG_IO as been added to the
	scsi tape driver (st) in lk 2.6.6 .

	In linux no utilities in the 'src' subdirectory use the sg driver's
	older "sg_header" interface; instead they use the newer "sg_io_hdr" interface.
	The "sg_io_hdr" interface can be accessed two ways:
	- using the SG_IO ioctl [for synchronous access]
	- using a write()/read() sequence that convey instances of "sg_io_hdr"

	All utilities in the 'src' subdirectory that issue SCSI commands use the
	linux SG_IO ioctl except for sgp_dd. This is due to the asynchronous nature
	of sgp_dd. Note that sgp_dd does _not_ support the "blk_sgio" switch found
	in sg_dd. This is important since block devices often identify themselves
	(programmatically) as sg devices in lk 2.6 and it would cause serious damage
	to do a write() of the sg driver's "sg_io_hdr" meta data (i.e. disk
	corruption).

	Warning
	=======
	Many devices use SCSI command sets over transport protocols not normally
	associated with SCSI (as defined at http://www.t10.org ). Some of these
	devices react poorly (e.g. lock up) when sent SCSI commands that they don't
	support. Even sending a supported SCSI command with a field set to an
	unexpected value can cause problems.

	For example, all "SCSI" devices must support the INQUIRY command which the
	SCSI-2 standard says should request a 36 byte response. However later SCSI
	standards (e.g. SPC-2) have increased that length but some SCSI devices lock
	up when they receive a request for anything other than a 36 byte response.

	Any well implemented "SCSI" device should react sensibly when a utility in
	sg3_utils sends a SCSI command that it doesn't support. Unfortunately this
	cannot be guaranteed.


	Utilities
	=========
	Here is list in alphabetical order of utilities found in the 'src'
	subdirectory of the sg3_utils package:
	- sginfo, sgm_dd, sgp_dd, sg_dd, sg_emc_trespass, sg_get_config,
	sg_format, sg_ident, sg_inq, sg_logs, sg_luns, sg_map, sg_map26,
	sg_modes, sg_opcodes, sg_persist, sg_prevent, sg_raw, sg_rbuf, sg_rdac,
	sg_read, sg_readcap, sg_read_buffer, sg_read_long, sg_reassign,
	sg_request, sg_reset, sg_rmsn, sg_rtpg, sg_safte, sg_sat_identify,
	sg_sat_phy_event, sg_sat_set_features, sg_scan, sg_senddiag, sg_ses,
	sg_start, sg_stpg, sg_sync, sg_test_rwbuff, sg_turs, sg_verify, sg_vpd,
	sg_write_buffer, sg_write_long, sg_wr_mode

	Each of the above utilities depends on header files found in the 'include'
	subdirectory and library code found in the 'lib' subdirectory. Associated
	man pages are found in the 'doc' subdirectory. Additional programs found
	in the 'archive', 'examples' and 'utils' subdirectories in not build by the
	top level build infrastructure. Linux binary distributions of the sg3_utils
	package (e.g. "rpm" and debian packages) typically contain the shared
	library, the utilities found in the 'src' subdirectory, their associated man
	pages and some documentation files (e.g. README, INSTALL, CREDITS, COPYING
	and COVERAGE). See the INSTALL file for instructions about building and
	installing from a source "tarball".

	Man pages can be read (without building and installing the package) by
	going to the 'doc' subdirectory and executing something like this:
	$ man ./sg_dd.8

	To see which SCSI commands (and ATA commands) are used by these utilities
	refer to the COVERAGE file.

	Here is a list in alphabetical order of utilities found in the 'archive'
	subdirectory:
	- isosize, scsi_devfs_scan, sg_debug, sgq_dd
	Some of these utilities have man pages.

	Here is a list in alphabetical order of utilities found in the 'examples'
	subdirectory:
	- sg_excl, scsi_inquiry, sg_iovec_tst, sg_sat_chk_power,
	sg__sat_identify, sg__sat_phy_event, sg__sat_set_features,
	sg_sat_smart_rd_data, sg_simple1, sg_simple2, sg_simple3, sg_simple4,
	sg_simple5 and sg_simple16

	Also in that subdirectory is a script to test sg_persist, an example data
	file for sg_persist (called "transport_ids.txt") and an example data file for
	sg_reassign (called "reassign_addr.txt"). There are several scripts
	for 'sg_senddiag -pf -raw=-' that will put some SAS disk phys into
	a "compliant jitter tolerance pattern" (CJTPAT).

	The 'utils' subdirectory contains source and a Makefile to build "hxascdmp"
	which accepts binary data from stdin (or a file on the command line) and
	outputs an ASCII-HEX and ASCII representation of it. It is similar to the
	Unix od command. There is also code to sg_chk_asc.c which checks a given
	text file (typically a copy of http://www.t10.org/lists/asc-num.txt ) and
	checks it against the asc/ascq text strings held in sg_lib_data.c .

	The 'doc' subdirectory contains a README.doc file containing the urls of
	various related documents.

	The 'scripts' subdirectory contains some bourne (bash) shell scripts that
	rely on utilities in the main directory. One script uses the sdparm utility.
	These scripts are described in the scripts/README file and have usage
	messages.


	Notes for utilities without man pages
	=====================================
	These utils are found in the 'examples' subdirectory.

	The "scsi_inquiry" program shows the use of the SCSI_IOCTL_SEND_COMMAND
	ioctl to send a SCSI INQUIRY command. That ioctl() is supported by the
	SCSI sub system mid level and so is common to all sd, sr, st and sg devices.
	That ioctl is deprecated in the lk 2.6 series. This program has been placed
	in the "examples" subdirectory.

	"sgq_dd" is yet another variant of dd found in the archive directory.
	From the user's point of view it is very similar to sgp_dd but uses a
	non-blocking state machine rather then POSIX threads for parallelism.

	"sg_debug" is effectively defunct now. The user can instead execute:
	'cat /proc/scsi/sg/debug' . This command has been placed in the archive
	directory.

	"sg_simple1" and "sg_simple2" are example programs demonstrating calls
	to the SCSI INQUIRY and TEST UNIT READY commands. They only differ in their
	error processing: sg_simple1 uses sg_lib.[hc] for error processing while
	sg_simple2 does its own more primitive checks.

	"sg_simple3" tests out user space scatter gather added to the version 3
	sg driver.

	"sg_simple4" shows the INQUIRY command using mmap-ed IO to obtain its
	response buffer.

	"sg_simple5" also sends and INQUIRY and TEST UNIT READY commands. It
	uses the generic pass through mechanism based on sg_pt.h . It will
	currently build in linux and FreeBSD (with "make -f Makefile.freebsd").
	It has extensive error checking code.

	"sg_simple16" attempts to send a 16 byte SCSI command, READ_16, to the
	scsi device. This is only supported for lk >= 2.4.15 and for adapter
	drivers that indicate that they have 16 byte CDB capability (otherwise
	DID_ABORT will appear in the host_status).

	"sg_sat_chk_power" attempts to push an ATA CHECK POWER MODE command
	through the SAT-defined ATA PASS_THROUGH (16) SCSI command. That
	ATA command needs to read the "FIS" registers after the command is
	completed which involves using the ATA Status Return (sense data)
	descriptor (as defined in SAT).

	"sg_sat_smart_rd_data" attempts to push an ATA SMART/READ DATA command
	through the SAT-defined ATA PASS_THROUGH (16) SCSI command. If
	successful, the 256 word (512 byte) response is output.


	Command line processing
	=======================
	These utilities can be divided into 3 groups when their handling of command
	line arguments is considered:
	- ad hoc, typically in a short form only, sometimes longer (e.g.
	"sg_logs -pcb /dev/sdc")
	- inspired by the dd Unix command (e.g. sg_dd, sgm_dd, sgp_dd, sg_read)
	- recent utilities use "getopt_long" (see "man getopt_long")
	type command lines. These have short form (starting with "-")
	and corresponding longer form (starting with "--") options.

	The older utilities that use ad hoc options, in alphabetical order:
	- sg_emc_trespass, sginfo(1/2), sg_inq, sg_logs, sg_map, sg_modes,
	sg_opcodes, sg_rbuf, sg_rdac, sg_readcap, sg_reset, sg_scan (linux),
	sg_senddiag, sg_start, sg_test_rwbuf, sg_turs
	In sg3_utils version 1.23 the following utilities from this group were
	converted to have a dual getopt_long/ad_hoc interface, defaulting to
	the getop_long interface:
	- sg_inq, sg_logs, sg_modes, sg_opcodes, sg_rbuf, sg_readcap,
	sg_senddiag, sg_start, sg_turs
	These can be switched back to the older (backward compatible) ad hoc
	interface by defining the SG3_UTILS_OLD_OPTS environment variable
	or using '-O' as the first command line option.

	The more recent utilities that use "getopt_long" only are:
	- sg_format sg_get_config sg_ident sg_luns sg_map26 sg_persist
	sg_prevent sg_raw sg_read_buffer sg_read_long sg_reassign sg_requests
	sg_rmsn sg_rtpg sg_safte sg_sat_identify sg_sat_phy_event
	sg_sat_set_features sg_scan(w) sg_ses sg_stpg sg_sync sg_test_rwbuf
	sg_verify sg_vpd sg_write_buffer sg_write_long sg_wr_mode


	Linux header file problems
	==========================
	The problems discussed below do not appear in recent Linux distributions.

	Some utilities include 2 important header files:
	#include <scsi/sg.h>
	#include <scsi/scsi.h>
	These files are typically found in the directory /usr/include/scsi which
	is maintained by the GNU glibc team. Unfortunately these GNU supplied
	headers may not be (functionally) the same as those found in the kernel
	source:
	/usr/src/linux/include/scsi/sg.h and
	/usr/src/linux/include/scsi/scsi.h

	If glibc and the kernel on a machine are of the same vintage then it is
	probably sufficient to use the simple includes listed at the start of this
	section. Another technique that used to work was to rely on
	/usr/include/linux being a symbolic link to /usr/src/linux/include/linux .
	That caused the following:
	#include <linux/../scsi/sg.h>
	#include <linux/../scsi/scsi.h>
	to find the kernel supplied header files. However recent versions of
	glibc have removed this symlink. Hence this technique is no longer
	recommended.

	The include file path issues are now all addressed in one file called
	"sg_linux_inc.h". Please read that file. This fetching of the scsi.h and
	sg.h header files has not been a problem in the latter lk 2.4 and lk 2.6
	series.

	Other SCSI and storage tools
	============================
	See http://www.torque.net/sg/tools.html


	Doug Gilbert
	22nd January 2008