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ACPI: thinkpad-acpi: update CMOS commands documentation

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The CMOS set of commands is often just used to keep the CMOS NVRAM in sync
with whatever the ACPI BIOS has been doing in modern ThinkPads.  In older
ThinkPads, it actually carried out real actions.  Document this.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Henrique de Moraes Holschuh 2007-07-18 23:45:33 -03:00 committed by Len Brown
parent 94b0871318
commit d54b7d7f80
1 changed files with 21 additions and 14 deletions
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35
Documentation/thinkpad-acpi.txt
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@ -464,27 +464,34 @@ CMOS control
procfs: /proc/acpi/ibm/cmos procfs: /proc/acpi/ibm/cmos
sysfs device attribute: cmos_command sysfs device attribute: cmos_command
This feature is used internally by the ACPI firmware to control the This feature is mostly used internally by the ACPI firmware to keep the legacy
ThinkLight on most newer ThinkPad models. It may also control LCD CMOS NVRAM bits in sync with the current machine state, and to record this
brightness, sounds volume and more, but only on some models. state so that the ThinkPad will retain such settings across reboots.
Some of these commands actually perform actions in some ThinkPad models, but
this is expected to disappear more and more in newer models. As an example, in
a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for
real, but commands 0 to 2 don't control the mixer anymore (they have been
phased out) and just update the NVRAM.
The range of valid cmos command numbers is 0 to 21, but not all have an The range of valid cmos command numbers is 0 to 21, but not all have an
effect and the behavior varies from model to model. Here is the behavior effect and the behavior varies from model to model. Here is the behavior
on the X40 (tpb is the ThinkPad Buttons utility): on the X40 (tpb is the ThinkPad Buttons utility):
0 - no effect but tpb reports "Volume down" 0 - Related to "Volume down" key press
1 - no effect but tpb reports "Volume up" 1 - Related to "Volume up" key press
2 - no effect but tpb reports "Mute on" 2 - Related to "Mute on" key press
3 - simulate pressing the "Access IBM" button 3 - Related to "Access IBM" key press
4 - LCD brightness up 4 - Related to "LCD brightness up" key pess
5 - LCD brightness down 5 - Related to "LCD brightness down" key press
11 - toggle screen expansion 11 - Related to "toggle screen expansion" key press/function
12 - ThinkLight on 12 - Related to "ThinkLight on"
13 - ThinkLight off 13 - Related to "ThinkLight off"
14 - no effect but tpb reports ThinkLight status change 14 - Related to "ThinkLight" key press (toggle thinklight)
The cmos command interface is prone to firmware split-brain problems, as The cmos command interface is prone to firmware split-brain problems, as
in newer ThinkPads it is just a compatibility layer. in newer ThinkPads it is just a compatibility layer. Do not use it, it is
exported just as a debug tool.
LED control -- /proc/acpi/ibm/led LED control -- /proc/acpi/ibm/led
--------------------------------- ---------------------------------