Ubuntu Manpage: sg_write_buffer - send SCSI WRITE BUFFER commands

Provided by: sg3-utils_1.46-3ubuntu4_amd64

NAME

       sg_write_buffer - send SCSI WRITE BUFFER commands

SYNOPSIS

       sg_write_buffer   [--bpw=CS]   [--dry-run]  [--help]  [--id=ID]  [--in=FILE]  [--length=LEN]  [--mode=MO]
       [--offset=OFF] [--read-stdin] [--skip=SKIP] [--specific=MS] [--timeout=TO] [--verbose] [--version] DEVICE

DESCRIPTION

       Sends one or more SCSI WRITE BUFFER commands to DEVICE, along with data provided by  the  user.  In  some
       cases  no  data  is required, or data can be read from the file given in the --in=FILE option, or data is
       read from stdin when either --read-stdin or --in=- is given.

       Some WRITE BUFFER command variants do not have associated  data  to  send  to  the  device.  For  example
       "activate_mc"  activates  deferred  microcode  that  was sent via prior WRITE BUFFER commands. There is a
       different method used to download microcode to SES devices, see the sg_ses_microcode utility.

OPTIONS

Arguments to long options are mandatory for short options as well. The options are arranged in
alphabetical order based on the long option name.

-b, --bpw=CS
where CS is the chunk size in bytes. This will be the maximum number of bytes sent per WRITE
BUFFER command. So if CS is less than the effective length then multiple WRITE BUFFER commands are
sent, each taking the next chunk from the read data and increasing the buffer offset field in the
WRITE BUFFER command by the appropriate amount. The default is a chunk size of 0 which is
interpreted as a very large number hence only one WRITE BUFFER command will be sent. This option
should only be used with modes that "download microcode, with offsets ..."; namely either mode
0x6, 0x7, 0xd or 0xe.
The number in CS can optionally be followed by ",act" or ",activate". In this case after WRITE
BUFFER commands have been sent until the effective length is exhausted another WRITE BUFFER
command with its mode set to "Activate deferred microcode mode" [mode 0xf] is sent.

-d, --dry-run
Do all the command line processing and sanity checks including reading the input file. However at
the point where a WRITE BUFFER SCSI command(s) would be sent, step over that call and assume it
completed without errors and continue. DEVICE is still opened but can be /dev/null (in Unix). It
is recommended to use --verbose with this option to get an overview of what would have happened.

-h, --help
output the usage message then exit. If used multiple times also prints the mode names and their
acronyms.

-i, --id=ID
this option sets the buffer id field in the cdb. ID is a value between 0 (default) and 255
inclusive.

-I, --in=FILE
read data from file FILE that will be sent with the WRITE BUFFER command. If FILE is '-' then
stdin is read until an EOF is detected (this is the same action as --read-stdin). Data is read
from the beginning of FILE except in the case when it is a regular file and the --skip=SKIP option
is given.

-l, --length=LEN
where LEN is the length, in bytes, of data to be written to the device. If not given (and the
length cannot be deduced from --in=FILE or --read-stdin) then defaults to zero. If the option is
given and the length deduced from --in=FILE or --read-stdin is less (or no data is provided), then
bytes of 0xff are used as fill bytes.

-m, --mode=MO
this option sets the MODE field in the cdb. MO is a value between 0 (default) and 31 inclusive.
Alternatively an abbreviation can be given. See the MODES section below. To list the available
mode abbreviations at run time give an invalid one (e.g. '--mode=xxx') or use the '-hh' option.

-o, --offset=OFF
this option sets the BUFFER OFFSET field in the cdb. OFF is a value between 0 (default) and
2**24-1 . It is a byte offset.

-r, --read-stdin
read data from stdin until an EOF is detected. This data is sent with the WRITE BUFFER command to
DEVICE. The action of this option is the same as using '--in=-'. Previously this option's long
name was --raw and it may still be used for backward compatibility.

-s, --skip=SKIP
this option is only active when --in=FILE is given and FILE is a regular file, rather than stdin.
Data is read starting at byte offset SKIP to the end of file (or the amount given by
--length=LEN). If not given the byte offset defaults to 0 (i.e. the start of the file).

-S, --specific=MS
MS is the MODE SPECIFIC field in the cdb. This is a 3-bit field so the values 0 to 7 are accepted.
This field was introduced in SPC-4 revision 32 and can be used to specify additional events that
activate deferred microcode (when MO is 0xD).

-t, --timeout=TO
TO is the command timeout (in seconds) for each WRITE BUFFER command issued by this utility. Its
default value is 300 seconds (5 minutes) and should only be altered if this is not sufficient.

-v, --verbose
increase the level of verbosity, (i.e. debug output).

-V, --version
print the version string and then exit.

MODES

       Following is a list of WRITE BUFFER command settings for the MODE field.  First is an acronym accepted by
       the MO argument of this utility.  Following the acronym in square brackets are the corresponding  decimal
       and hex values that may also be given for MO. The following are listed in numerical order.

       hd  [0, 0x0]
              Combined header and data (obsolete in SPC-4).

       vendor  [1, 0x1]
              Vendor specific.

       data  [2, 0x2]
              Data (was called "Write Data" in SPC-3).

       dmc  [4, 0x4]
              Download microcode and activate (was called "Download microcode" in SPC-3).

       dmc_save  [5, 0x5]
              Download microcode, save, and activate (was called "Download microcode and save" in SPC-3).

       dmc_offs  [6, 0x6]
              Download  microcode  with  offsets  and  activate (was called "Download microcode with offsets" in
              SPC-3).

       dmc_offs_save  [7, 0x7]
              Download microcode with offsets, save, and activate (was called "Download microcode  with  offsets
              and save" in SPC-3).

       echo  [10, 0xa]
              Write data to echo buffer (was called "Echo buffer" in SPC-3).

       dmc_offs_ev_defer  [13, 0xd]
              Download microcode with offsets, select activation events, save, and defer activate (introduced in
              SPC-4).

       dmc_offs_defer  [14, 0xe]
              Download microcode with offsets, save, and defer activate (introduced in SPC-4).

       activate_mc  [15, 0xf]
              Activate deferred microcode (introduced in SPC-4).

       en_ex  [26, 0x1A]
              Enable expander communications protocol and Echo buffer (obsolete in SPC-4).

       dis_ex  [27, 0x1B]
              Disable expander communications protocol (obsolete in SPC-4).

       deh  [28, 0x1C]
              Download application client error history (was called "Download application log" in SPC-3).

NOTES

If no --length=LEN is given this utility reads up to 8 MiB of data from the given file FILE (or stdin).
If a larger amount of data is required then the --length=LEN option should be given.

The user should be aware that most operating systems have limits on the amount of data that can be sent
with one SCSI command. In Linux this depends on the pass through mechanism used (e.g. block SG_IO or the
sg driver) and various setting in sysfs in the Linux lk 2.6/3 series (e.g.
/sys/block/sda/queue/max_sectors_kb). Devices (i.e. logical units) also typically have limits on the
maximum amount of data they can handle in one command. These two limitations suggest that modes
containing the word "offset" together with the --bpw=CS option are required as firmware files get larger
and larger. And CS can be quite small, for example 4096 bytes, resulting in many WRITE BUFFER commands
being sent.

Attempting to download a microcode/firmware file that is too large may cause an error to occur in the
pass-through layer (i.e. before the SCSI command is issued). In Linux such error reports can be obscure
as in "pass through os error invalid argument". FreeBSD reports such errors well to the machine's console
but returns a cryptic error message to this utility.

Downloading incorrect microcode into a device has the ability to render that device inoperable. One would
hope that the device vendor verifies the data before activating it. If the SCSI WRITE BUFFER command is
given values in its cdb (e.g. LEN) that are inappropriate (e.g. too large) then the device should respond
with a sense key of ILLEGAL REQUEST and an additional sense code of INVALID FIELD in CDB. If a WRITE
BUFFER command (or a sequence of them) fails due to device vendor verification checks then it should
respond with a sense key of ILLEGAL REQUEST and an additional sense code of COMMAND SEQUENCE ERROR.

All numbers given with options are assumed to be decimal. Alternatively numerical values can be given in
hexadecimal preceded by either "0x" or "0X" (or has a trailing "h" or "H").

EXAMPLES

       The following sends new firmware to an enclosure. Sending a 1.5 MB  file  in  one  WRITE  BUFFER  command
       caused  the  enclosure to lock up temporarily and did not update the firmware. Breaking the firmware file
       into 4 KB chunks (an educated guess) was more successful:

         sg_write_buffer -b 4k -m dmc_offs_save -I firmware.bin /dev/sg4

       The firmware update occurred in the following enclosure power cycle. With a modern enclosure the Extended
       Inquiry VPD page gives indications in which situations a firmware upgrade will take place.

EXIT STATUS

       The exit status of sg_write_buffer is 0 when it is successful. Otherwise see the sg3_utils(8) man page.

AUTHORS

       Written by Luben Tuikov and Douglas Gilbert.

REPORTING BUGS

       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

       Copyright © 2006-2018 Luben Tuikov and Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO warranty; not even for  MERCHANTABILITY
       or FITNESS FOR A PARTICULAR PURPOSE.