sg_modes - reads SCSI MODE SENSE pages

sg_modes [-a] [-A] [-c=<page_control>] [-d] [-D] [-f] [-h] [-H] [-l] [-L] [-p=<page_code>] [-p=<page_code>,<sub_page_code>] [-r] [-subp=<sub_page_code>] [-v] [-V] [-6] [-?] [<scsi_device>]

This utility sends a MODE SENSE SCSI command (the 10 byte variant by default) to the given device and then outputs the response. There is no facility to change the page or descriptor data with this utility. If no page is given (and '-l' is not selected) then '-a' is assumed.

-a

output all the mode pages supported by the given device.

-A

output all the mode pages and subpages supported by the device.

-c=page_control

up to four different versions of each page are held by the device: the current values [0] (i.e. those active at the moment), the changeable values [1] (bit mask showing which sections could be changed with a MODE SELECT), default values [2] (the manufacturer's settings) and saved values [3] (the values that will be re-instated the next time the device is power cycled). If this option is not given then current values [0] are assumed.

-d

disable block descriptors. By default, block descriptors (usually one or none) are returned in a MODE SENSE response. This option sets the "disable block descriptors" (DBD) bit in the cdb which instructs the device not to return any block descriptors in its response. Older devices may not support this setting and should return an "illegal request" status; alternatively they may ignore it.

-D

disable outputting block descriptors. Irrespective of whether block descriptors are present in the response or not, they are not output.

-f

Be "flexible". Some devices, bridges and/or drivers attempt crude switches between mode sense 6 and 10 byte commands without correcting the response. This will cause the response to be mis-interpreted (usually with an error saying the response is malformed). With this option, the length of the response is checked, and if it looks wrong, the response is then decoded as if the other mode sense (cdb length) was sent.

-h

The default action is to decode known mode page numbers (and subpage numbers) into text. With this option mode page numbers (and subpage numbers) are output in hexadecimal.

-H

same action as the '-h' option.

-l

lists all common page and subpage codes and their names that are found in the command set that matches the peripheral type of the given device. If no device and no page_code is given then the common page and subpage codes and their names for the disk command set are listed. If no device is given and a page_code is given then the common page and subpage codes and their names for the command set whose peripheral device type matches the value given to page_code are listed. For example 'sg_mode -l -p=1' lists the command mode pages and subpages for tape devices. Additionally if a sub_page_code is given then it is interpreted as a transport identifier and command transport specific mode page codes and their names are listed following the main mode page list. Other options are ignored.

-L

set the Long LBA Accepted (LLBAA) bit in the MODE SENSE (10) cdb. This bit is not defined in the MODE SENSE (6) cdb so setting the '-L' and '-6' options is reported as an error. When set the given device may respond with 16 byte block descriptors as indicated by the 'LongLBA' field in the response. In almost all cases setting this option is not needed.

-p=<page_code>

page code to fetch. Should be a hexadecimal number between 0 and 3f inclusive (0 to 63 decimal). The default value is 0.

-p=<page_code>,<sub_page_code>

page code and subpage code values to fetch. The page code should be a hexadecimal number between 0 and 3f inclusive. The subpage code should be a hexadecimal number between 0 and ff inclusive. The default value of both is 0.

-r

output the selected mode page to stdout a byte per line. Each line contains two hexadecimal digits (e.g. "0a"). Useful as input (after editing) to the sg_wr_mode utility.

-subp=<sub_page_code>

sub page code to fetch. Should be a hexadecimal number between 0 and 0xff inclusive. The default value is 0.

-v

verbose: output cdbs in hex before executing them. '-vv' and '-vvv' are also accepted yielding greater verbosity.

-V

print out version string

-6

by default this utility sends out a 10 byte MODE SENSE command. However some SCSI devices only support 6 byte MODE SENSE commands (e.g. SCSI-2 tape drives). This parameter forces the use of 6 byte MODE SENSE commands.

-?

output usage message. Ignore all other parameters.

If the normal sg_modes utility fails with "illegal command operation code" then try the "-6" parameter.

Mode pages cannot be modified with this utility. Mode pages (and subpages) can be modified with the sg_wr_mode and sginfo utilities in the sg3_utils package. See this sdparm utility and those other utilities that are listed in the "SEE ALSO" section below.

This utility performs a SCSI INQUIRY command to determine the peripheral type of the device (e.g. 0 -> Direct Access Device (disk)) prior to sending a MODE SENSE command. This helps in decoding the block descriptor and mode pages.

In the 2.4 series of Linux kernels the given device must be a SCSI generic (sg) device. In the 2.6 series block devices (e.g. disks and SCSI DVDs) can also be specified. For example "sg_modes -a /dev/sda" will work in the 2.6 series kernels.

Written by Doug Gilbert

Report bugs to <dgilbert at interlog dot com>.

Copyright © 2000-2005 Douglas Gilbert

This software is distributed under the GPL version 2. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

sdparm(n), sg_wr_mode(sg3_utils), sginfo(sg3_utils), sgmode(scsirastools), scsiinfo(n), scu(n), seatools(seagate)

All these utilities offer some facility to change mode page (or block descriptor) parameters.