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ACPI: thinkpad-acpi: update CMOS commands documentation 

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
sysfs device attribute: cmos_command
This feature is used internally by the ACPI firmware to control the
ThinkLight on most newer ThinkPad models. It may also control LCD
brightness, sounds volume and more, but only on some models.
This feature is mostly used internally by the ACPI firmware to keep the legacy
CMOS NVRAM bits in sync with the current machine state, and to record this
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
effect and the behavior varies from model to model. Here is the behavior
on the X40 (tpb is the ThinkPad Buttons utility):
0 - no effect but tpb reports "Volume down"
1 - no effect but tpb reports "Volume up"
2 - no effect but tpb reports "Mute on"
3 - simulate pressing the "Access IBM" button
4 - LCD brightness up
5 - LCD brightness down
11 - toggle screen expansion
12 - ThinkLight on
13 - ThinkLight off
14 - no effect but tpb reports ThinkLight status change
0 - Related to "Volume down" key press
1 - Related to "Volume up" key press
2 - Related to "Mute on" key press
3 - Related to "Access IBM" key press
4 - Related to "LCD brightness up" key pess
5 - Related to "LCD brightness down" key press
11 - Related to "toggle screen expansion" key press/function
12 - Related to "ThinkLight on"
13 - Related to "ThinkLight off"
14 - Related to "ThinkLight" key press (toggle thinklight)
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
---------------------------------