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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  ar-
       ranged 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 num-
              ber 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 de-
              faults 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 (de-
              fault) 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 mecha-
       nism 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 re-
       ports 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 inop-
       erable. 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 BUF-
       FER 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 enclo-
       sure the Extended Inquiry VPD page gives indications in which situations  a  firmware  up-
       grade 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 (C) 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.

SEE ALSO
       sg_read_buffer, sg_ses_microcode(sg3_utils)

sg3_utils-1.45                            November 2018                        SG_WRITE_BUFFER(8)

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