sg_write_buffer - send SCSI WRITE BUFFER commands
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
SG_WRITE_BUFFER(8) SG3_UTILS SG_WRITE_BUFFER(8)
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 ",acti-
vate". 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 BUF-
FER 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 regu-
lar 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 abbrevia-
tion 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 com-
patibility.
-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 suffi-
cient.
-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 util-
ity. 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 "Down-
load 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 (obso-
lete 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).
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | system/storage/sg3_utils |
+---------------+--------------------------+
|Stability | Pass-through uncommitted |
+---------------+--------------------------+
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. Alterna-
tively numerical values can be given in hexadecimal preceded by either
"0x" or "0X" (or has a trailing "h" or "H").
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from http://sg.danny.cz/sg/p/sg3_utils-1.46.tgz.
Further information about this software can be found on the open source
community website at http://sg.danny.cz/sg/sg3_utils.html.
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. Other-
wise 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 (C) 2006-2018 Luben Tuikov and Douglas Gilbert
This software is distributed under a FreeBSD license. There is NO war-
ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-
POSE.
SEE ALSO
sg_read_buffer, sg_ses_microcode(sg3_utils)
sg3_utils-1.45 November 2018 SG_WRITE_BUFFER(8)