1SG_WR_MODE(8) SG3_UTILS SG_WR_MODE(8)
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6 sg_wr_mode - write (modify) SCSI mode page
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9 sg_wr_mode [--contents=H,H...] [--dbd] [--force] [--help] [--len=10|6]
10 [--mask=M,M...] [--page=PG_H[,SPG_H]] [--rtd] [--save] [--six] [--ver‐
11 bose] [--version] DEVICE
12
14 Writes a modified mode page to DEVICE. Uses the SCSI MODE SENSE (6 or
15 10 byte variant) command to fetch the existing mode data which includes
16 a mode page (or subpage). It then combines that with the contents,
17 potentially masked, and writes the modified mode page with the SCSI
18 MODE SELECT (6 or 10 byte variant) command. This utility does not mod‐
19 ify the block descriptor(s); if any block descriptors are fetched by
20 the MODE SENSE command then the same block descriptors are written back
21 with the following MODE SELECT command.
22 If the --rtd option is given then most other options apart from --save,
24 --len=10|6 and --six are ignored. In this case only a MODE SELECT com‐
25 mand is sent to the DEVICE with the RTD bit (Revert To Defaults) set.
26 This bit was added to this command in SPC-5 revision 11, so older
27 devices may not support it. The Extended Inquiry VPD page has the
28 RTD_SUP bit to indicate whether the DEVICE supports the RTD bit in the
29 MODE SELECT(6 and 10) commands. When the --rtd option is given the rest
30 of this section can be ignored.
31 If a contents argument is not given then the various components (i.e.
33 header, block descriptor(s) and mode page) of the "current" values of
34 the existing mode page are printed out. In this case the mode page is
35 not altered on the device.
36 If the contents are specified, and a mask is not specified, then the
38 contents must match the existing mode page in various aspects unless
39 the --force option is given. These include length, mode page code and
40 subpage code if applicable. If all is well then the contents string is
41 written to DEVICE as the new mode page.
42 If both contents and mask strings are specified then only bit positions
44 in the contents corresponding to set bits in the mask are taken while
45 the existing mode page supplies bit positions corresponding to clear
46 bits. When a mask is given then the mask and/or the contents may be
47 shorter than the existing mode page. If the mask is shorter than the
48 contents then the remaining bytes are taken from the contents. If the
49 contents are shorter than the existing mode page then the remaining
50 bytes are taken from the existing mod page.
51 The force option allows the contents string to be written as the new
53 mode page without any prior checks on the existing mode page. This
54 should only be required for vendor specific mode pages. The existing
55 mode data is ignored apart from the block descriptors which can be sup‐
56 pressed with the --dbd option if need be.
57 Changing individual fields in a mode page is probably more easily done
59 with the sdparm utility. Fields can be identified by acronym or by a
60 numerical descriptor.
61
63 Arguments to long options are mandatory for short options as well.
64 -c, --contents=H,H...
66 where H,H... is a string of comma separated hex numbers each of
67 which should resolve to a byte value (i.e. 0 to ff inclusive). A
68 (single) space separated string of hex numbers is also allowed
69 but the list needs to be in quotes. This is the new contents of
70 the mode page to be written to DEVICE, potentially filtered by
71 the mask string.
72 -c, --contents=-
74 reads contents string from stdin. The hex numbers in the string
75 may be comma, space, tab or linefeed (newline) separated. If a
76 line contains "#" then the remaining characters on that line are
77 ignored. Otherwise each non separator character should resolve
78 to a byte value (i.e. 0 to ff inclusive). This forms the new
79 contents of the mode page to be written to DEVICE, potentially
80 filtered by the mask string.
81 -d, --dbd
83 disable block descriptors (DBD flag in cdb). Some device types
84 include block descriptors in the mode data returned by a MODE
85 SENSE command. If so the same block descriptors are written by
86 the MODE SELECT command. This option instructs the MODE SENSE
87 command not to return any block descriptors. This would be a
88 sensible default for this utility apart from the fact that not
89 all SCSI devices support the DBD bit in the cdb.
90 -f, --force
92 force the contents string to be taken as the new mode page, or
93 at least doesn't do checks on the existing mode page. Note that
94 DEVICE may still reject the new contents for the mode page. Can‐
95 not be given with the --mask=M,M... option.
96 -h, --help
98 output the usage message then exit.
99 -l, --len=10 | 6
101 length of the SCSI commands (cdb) sent to DEVICE. The default is
102 10 so 10 byte MODE SENSE and MODE SELECT commands are issued.
103 Some old devices don't support the 10 byte variants hence this
104 option.
105 -m, --mask=M,M...
107 where M,M... is a string of comma separated hex numbers each of
108 which should resolve to a byte value (i.e. 0 to ff inclusive). A
109 (single) space separated string of hex numbers is also allowed
110 but the list needs to be in quotes. The mask chooses (bit by
111 bit) whether the new mode page comes from the contents (mask bit
112 set) or from the existing mode page (mask bit clear). If the
113 mask string is shorter than the contents string then the remain‐
114 ing bytes are taken from the contents string. If the contents
115 string is shorter than the existing mode page then the remaining
116 bytes are taken from the existing mode page (i.e. they are left
117 unaltered).
118 -p, --page=PG_H
120 where PG_H is the page code value to fetch and modify. The page
121 code is in hex and should be between 0 and 3e inclusive. Notice
122 that page code 3f to fetch all mode pages is disallowed.
123 -p, --page=PG_H,SPG_H
125 where PG_H is the page code value and SPG_H is the subpage code
126 value to fetch and modify. Both values are in hex. The subpage
127 code should be between 0 and fe inclusive. Notice that subpage
128 code ff to fetch all mode subpages (for a given mode page or all
129 mode pages in the case of 3f,ff) is disallowed.
130 -R, --rtd
132 when this option is given most other actions are bypassed and a
133 MODE SELECT(6 or 10) command is sent to the DEVICE with the RTD
134 bit set. This will cause all current values (and saved values
135 if the --save option is also given) of all mode pages to be
136 reverted to their default values.
137 -s, --save
139 changes the "saved" mode page when MODE SELECT is successful. By
140 default (i.e. when --save is not used) only the "current" mode
141 page values are changed when MODE SELECT is successful. In this
142 case the new mode page will stay in effect until the device is
143 reset (e.g. power cycled). When it restarts the "saved" values
144 for the mode page will be re-instated. So to make changes per‐
145 manent use the --save option.
146 When used with the --rtd option then both the current and saved
147 values in each mode page are reverted to their default values.
148 In the absence of --save option only the current values in each
149 mode page are reverted to their default values.
150 -6, --six
152 this option will cause the 6 byte variants of MODE SENSE and
153 MODE SELECT commands to be used. The default is to use the 10
154 byte options. This option is equivalent to using the --len=6
155 option.
156 -v, --verbose
159 increase the level of verbosity, (i.e. debug output).
160 -V, --version
162 print the version string and then exit.
163
165 This utility does not check whether the contents string is trying to
166 modify parts of the mode page which are changeable. The device should
167 do that and if some part is not changeable then it should report:
168 "Invalid field in parameter list".
169 Some mode pages are not saveable. If so an attempt to use the --save
171 option should cause an error to be reported from the device: "Illegal
172 field in cdb".
173 The device is required to do various checks before it accepts a new
175 mode page. If these checks fail then the mode page is not altered and
176 either a "parameter list length error" or an "invalid field in parame‐
177 ter list" error is returned by the device in the sense data.
178 The recommended way to modify a mode page is to read it with a MODE
180 SENSE, modify some part of it then write it back to the device with a
181 MODE SELECT command. For example, reading an existing mode page can be
182 accomplished with 'sg_modes -p=1a -r /dev/sdb > mp_1a.txt' (the power
183 condition mode page). The mp_1a.txt file can be edited and then used as
184 the contents string to this utility (e.g. 'sg_wr_mode -p 1a -s -c -
185 /dev/sdb < mp_1a.txt').
186 Two fields differ between what is read from the device with MODE SENSE
188 and what is written to the device with MODE SELECT: the mode data
189 length is reserved (i.e. zero(es)) in a MODE SELECT command while the
190 PS bit ((sub)page byte 0 bit 7) in each mode (sub)page is reserved
191 (zero) in a MODE SELECT command. The PS bit given in the contents
192 string is zeroed unless the --force option is selected.
193
195 This utility can be used together with the sg_modes utility. To
196 re-instate the default mode page values (i.e. the mode page values cho‐
197 sen by the manufacturer of the device) as both the current and saved
198 mode page values the following sequence could be used:
199 $ sg_modes --control=2 --page=1a -r /dev/sda > t
201 $ sg_wr_mode --page=1a --contents=- --save /dev/sda < t
202 Next is an example of using a mask to modify the "idle condition
204 counter" of the "power condition" mode page (0x1a) from 0x28 to 0x37.
205 Note that the change is not saved so the "idle condition counter" will
206 revert to 0x28 after the next power cycle. The output from sg_modes is
207 abridged.
208 $ sg_modes --page=1a /dev/hdc
210 >> Power condition (mmc), page_control: current
211 00 1a 0a 00 03 00 00 00 28 00 00 01 2c
212 $ sg_wr_mode -p 1a -c 0,0,0,0,0,0,0,37 -m 0,0,0,0,0,0,0,ff /dev/hdc
214 $ sg_modes -p 1a /dev/hdc
216 >> Power condition (mmc), page_control: current
217 00 1a 0a 00 03 00 00 00 37 00 00 01 2c
218
220 The exit status of sg_wr_mode is 0 when it is successful. Otherwise see
221 the sg3_utils(8) man page.
222
224 Written by Douglas Gilbert.
225
227 Report bugs to <dgilbert at interlog dot com>.
228
230 Copyright © 2004-2018 Douglas Gilbert
231 This software is distributed under a FreeBSD license. There is NO war‐
232 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
233 POSE.
234
236 sdparm(sdparm), sg_modes(sg3_utils), sginfo(sg3_utils)
237sg3_utils-1.43 April 2018 SG_WR_MODE(8)