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SG_SAT_READ_GPLOG

Section: SG3_UTILS (8)
Updated: January 2023
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NAME

sg_sat_read_gplog - use ATA READ LOG EXT or SMART READ LOG command via a SCSI to ATA Translation (SAT) layer

SYNOPSIS

sg_sat_read_gplog [--address=LA_L] [--ck_cond] [--count=CO] [--dma] [--help] [--hex] [--len=CMD_LEN] [--log=LA_L] [--page=PN] [--ppt=PPT] [--readonly] [--smart] [--verbose] [--version] DEVICE

DESCRIPTION

This utility sends an ATA READ LOG EXT, an ATA READ LOG DMA EXT, or an ATA SMART READ LOG command to the DEVICE. The default is to send one of the first two commands to read "general purpose log" page(s). Only (S)ATA devices (e.g. disks) but not ATAPI devices (e.g. DVD readers) support the general purpose log pages. Rather than send the READ LOG (DMA) EXT command directly to the device it is sent via a SCSI transport which is assumed to contain a SCSI to ATA Translation (SAT) Layer (SATL). The SATL may be in an operating system driver, in host bus adapter (HBA) firmware or in some external enclosure.

This utility does not currently attempt to decode the response from the ATA disk, rather it outputs the response in ASCII hexadecimal grouped in 8 bit bytes or 16 bit words. Following ATA conventions those words are decoded little endian (note that SCSI commands use a big endian representation). Log address 0, page number 0 is the 'directory' log page and it is decoded if no --hex option is given. In the future this utility may attempt to decode other log pages. Perhaps other ATA utility will be able to decode these log pages given hex output from this utility.

Fetching all log pages seems as simple as reading the directory log page then accessing those log addresses that have more than zero associated page numbers. Unfortunately it is not that simple. Some log addresses (looking specifically at 0xe1 ("SCT Data transfer")) need a SCT command executed prior to fetching the log page at that log address. Other log addresses might be problematic (e.g. it has been suggested that the "Device vendor specific logs" 0xa0:0xdf) so maybe they also should be avoided. That is the reason the --address=LA_L and --log=LA_L options are designed to take a list of ranges.

The SAT-4 standard (SAT ANSI INCITS 491-201r7 prior draft: sat4r06.pdf at www.t10.org) defines three SCSI "ATA PASS-THROUGH" commands: one using a 12 byte "cdb", another using a 16 bytes cdb, and the third a 32 byte cdb. This utility defaults to using the 16 byte cdb variant.

OPTIONS

Arguments to long options are mandatory for short options as well.

-a, --address=LA_L: where LA_L is as single "log address", a range of log addresses, or a list of (ranges of) log addresses. A log address is a number between 0 and 255 (0xff) where log address 0, page number 0, is a directory. A range of log addresses has the form "lo:hi" where log address "hi" must be greater than or equal to "lo". A log address list is a comma separated list of log addresses or log address ranges.
Each log address contain up to 256 (SMART log) or 65536 (General purpose log) page numbers, starting at page number 0. The number of page numbers available for each log address is enumerated in the log directory page.
Summary of LA_L syntax: lo:hi,lo2:hi2,lo3:hi3 ...
-C, --ck_cond: sets the CK_COND bit in the ATA PASS-THROUGH SCSI cdb. The default setting is clear (i.e. 0). When set the SATL should yield a sense buffer containing a ATA Result descriptor irrespective of whether the ATA command succeeded or failed. When clear the SATL should only yield a sense buffer containing an ATA Result descriptor if the ATA command failed.
-c, --count=CO: the number CO is placed in the "count" field in the ATA READ LOG EXT command. This specified the number of 512-byte log pages of data to be read from the specified log address. The given page address starting at the given page number is read. The last page number read will be (PN + CO - 1) if it exists.
The maximum value of CO is 0xffff (65,535) for general purpose log pages and 0xff (255) for SMART log pages.
An error is typically reported if the given --page=PN (default 0) plus CO exceeds the number shown in the log directory (log address 0) for the given log address.
Note that the CO only applies to the current log address; in other words there is no wrap around to the beginning of the next log address.
-d, --dma: use the ATA READ LOG DMA EXT command instead of ATA READ LOG EXT command. Some devices require this to return valid log data.
-h, --help: outputs the usage message summarizing command line options then exits. Ignores DEVICE if given.
-H, --hex: when given once, the response is output in ASCII hexadecimal bytes. When given twice, then the response is grouped into 16 bit words using ATA conventions (i.e. little endian); this is the default output (i.e. when this option is not given). When given thrice (i.e. '-HHH') the output is in hex, grouped in 16 bit words (without a leading offset and trailing ASCII on each line), in a format that is acceptable for 'hdparm --Istdin' to process.

If this option is invoked four times (e.g. '-HHHH') log pages are output as hex bytes, with no leading address at the start of each line. That makes the hex easier for computers to decode (but not humans). If this option is invoked five times then a comment line, starting with a '#' character is output before each 512 byte log page. The comment describes the following log page.

-l, --len=CMD_LEN: where CMD_LEN is the command (cdb) length of the SCSI ATA PASS-THROUGH command that is used to tunnel ATA commands. Three values are permitted: 12, 16 and 32 (bytes long). The 12 byte variant has the most restrictions (e.g. its 'count' field is a single byte) but older systems may not permit 16 or 32 byte commands.
-L, --log=LA_L: see the --address=LA_L option.
-p, --page=PN: the number PN is the page number (within the log address) and is placed in bits 32:16 of the "lba" field of the ATA READ LOG (DMA) EXT command. The default value placed in the "lba" field is 0.
The maximum value of PN is 0xffff (65,535) for general purpose log pages and 0xff (255) for SMART log pages. In the latter case PN must be 0 and CO is 255.

When multiple log addresses are specified (via the LA_L argument) then this option is treated differently. With multiple log addresses and if PN is greater than 0 then it acts as an upper limit of the number of page numbers that will be output for each log address. The actual number of 512 byte log pages output will also depend on the number of page numbers shown in the directory log page for the current log address.

-P, --ppt=PPT: where PPT is the number of pages to transfer from the DEVICE per ATA READ LOG EXT or an ATA READ LOG DMA EX command invocation. The default value is 128 (or 64 kibiBytes) which is chosen because most OSes have an upper limit on the size of transfers to and from a device with a single command. When the number of log pages given with the --count=CO option is large , it can exceed what an OS will allow in a single command invocation. Hence the need for this option.
-l, --len={32|16|12}: this is the length of the SCSI cdb used for the ATA PASS-THROUGH commands. The argument can either be 32, 16 or 12. The default is 16. Some SCSI transports cannot convey SCSI commands longer than 12 bytes.
-r, --readonly: causes the DEVICE to be opened with the read-only flag (O_RDONLY in Unix). The default action is to open DEVICE with the read-write flag (O_RDWR in Unix). In some cases sending power management commands to ATA disks are defeated by OS actions on the close() if the DEVICE was opened with the read-write flag (e.g. the OS might think it needs to flush something to disk).
-s, --smart: in the ATA SMART feature set, "SMART" log pages have been present for a long time and pre-date the later addition of the "general purpose" log pages. So this utility can be easily be extended to read "SMART" log pages instead of the general purpose log pages. That is exactly what this option does.
The ATA SMART READ LOG command has no page number field, all fetches start from page number 0. Also the number of page numbers (in it log address) is limited to a single byte (so 255). The general purpose log directory page and the SMART log directory page have the same format (given the single byte restriction on the number of page numbers in each SMART log address).
-v, --verbose: increases the level or verbosity.
-V, --version: print out version string

NOTES

Prior to Linux kernel 2.6.29 USB mass storage limited sense data to 18 bytes which made the --ck_cond option yield strange (truncated) results.

There are slight differences in handling when a single log address is being fetched, and when multiple log pages are being fetched. In the single log address case the log address, the page number and the count going into the corresponding fields in the ATA READ LOG EXT or ATA SMART READ LOG command. When multiple log addresses are given, the 'directory' log page (log_address=0, page_number=0) is first loaded. Then only log addresses which the directory indicates have more than zero log page numbers, are fetched. The count of log page numbers accessed may be further restricted by the --page=PN option if PN is greater than zero.

EXAMPLES

First here is an example avoiding the problematic log addresses noted in the DESCRIPTION section above.

sg_sat_read_gplog -a 0:0xb,0xd:0x9f,0xe0,0xe2:255 /dev/sdc

The above is using the short form of the --address=LA_L option with a list that avoids log addresses 0xc, 0xa0 to 0xdf and 0xe1 . The output will include all log addresses, apart from those exclusions, that the directory indicates have more than 0 page numbers.
The following invocation uses the SMART READ LOG command instead of the READ LOG EXT command:

sg_sat_read_gplog --smart -a 0:0xb,0xd:0x9f,0xe0,0xe2:255 /dev/sdc

EXIT STATUS

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

AUTHOR

Written by Hannes Reinecke and Douglas Gilbert

REPORTING BUGS

Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

Copyright © 2014-2023 Hannes Reinecke, SUSE Linux GmbH
This software is distributed under a BSD-2-Clause license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

This document was created by man2html, using the manual pages.
Time: 04:00:44 GMT, August 02, 2023