path: root/Documentation/thinkpad-acpi.txt

		    IBM ThinkPad ACPI Extras Driver

                            Version 0.13
                           31 December 2006

               Borislav Deianov <borislav@users.sf.net>
	     Henrique de Moraes Holschuh <hmh@hmh.eng.br>
		      http://ibm-acpi.sf.net/


This is a Linux ACPI driver for the IBM ThinkPad laptops. It supports
various features of these laptops which are accessible through the
ACPI framework but not otherwise fully supported by the generic Linux
ACPI drivers.


Status
------

The features currently supported are the following (see below for
detailed description):

	- Fn key combinations
	- Bluetooth enable and disable
	- video output switching, expansion control
	- ThinkLight on and off
	- limited docking and undocking
	- UltraBay eject
	- CMOS control
	- LED control
	- ACPI sounds
	- temperature sensors
	- Experimental: embedded controller register dump
	- LCD brightness control
	- Volume control
	- Experimental: fan speed, fan enable/disable
	- Experimental: WAN enable and disable

A compatibility table by model and feature is maintained on the web
site, http://ibm-acpi.sf.net/. I appreciate any success or failure
reports, especially if they add to or correct the compatibility table.
Please include the following information in your report:

	- ThinkPad model name
	- a copy of your DSDT, from /proc/acpi/dsdt
	- which driver features work and which don't
	- the observed behavior of non-working features

Any other comments or patches are also more than welcome.


Installation
------------

If you are compiling this driver as included in the Linux kernel
sources, simply enable the CONFIG_ACPI_IBM option (Power Management /
ACPI / IBM ThinkPad Laptop Extras).

Features
--------

The driver creates the /proc/acpi/ibm directory. There is a file under
that directory for each feature described below. Note that while the
driver is still in the alpha stage, the exact proc file format and
commands supported by the various features is guaranteed to change
frequently.

Driver version -- /proc/acpi/ibm/driver
---------------------------------------

The driver name and version. No commands can be written to this file.

Hot keys -- /proc/acpi/ibm/hotkey
---------------------------------

Without this driver, only the Fn-F4 key (sleep button) generates an
ACPI event. With the driver loaded, the hotkey feature enabled and the
mask set (see below), the various hot keys generate ACPI events in the
following format:

	ibm/hotkey HKEY 00000080 0000xxxx

The last four digits vary depending on the key combination pressed.
All labeled Fn-Fx key combinations generate distinct events. In
addition, the lid microswitch and some docking station buttons may
also generate such events.

The following commands can be written to this file:

	echo enable > /proc/acpi/ibm/hotkey -- enable the hot keys feature
	echo disable > /proc/acpi/ibm/hotkey -- disable the hot keys feature
	echo 0xffff > /proc/acpi/ibm/hotkey -- enable all possible hot keys
	echo 0x0000 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
	... any other 4-hex-digit mask ...
	echo reset > /proc/acpi/ibm/hotkey -- restore the original mask

The bit mask allows some control over which hot keys generate ACPI
events. Not all bits in the mask can be modified. Not all bits that
can be modified do anything. Not all hot keys can be individually
controlled by the mask. Most recent ThinkPad models honor the
following bits (assuming the hot keys feature has been enabled):

	key	bit	behavior when set	behavior when unset

	Fn-F3			always generates ACPI event
	Fn-F4			always generates ACPI event
	Fn-F5	0010	generate ACPI event	enable/disable Bluetooth
	Fn-F7	0040	generate ACPI event	switch LCD and external display
	Fn-F8	0080	generate ACPI event	expand screen or none
	Fn-F9	0100	generate ACPI event	none
	Fn-F12			always generates ACPI event

Some models do not support all of the above. For example, the T30 does
not support Fn-F5 and Fn-F9. Other models do not support the mask at
all. On those models, hot keys cannot be controlled individually.

Note that enabling ACPI events for some keys prevents their default
behavior. For example, if events for Fn-F5 are enabled, that key will
no longer enable/disable Bluetooth by itself. This can still be done
from an acpid handler for the ibm/hotkey event.

Note also that not all Fn key combinations are supported through
ACPI. For example, on the X40, the brightness, volume and "Access IBM"
buttons do not generate ACPI events even with this driver. They *can*
be used through the "ThinkPad Buttons" utility, see
http://www.nongnu.org/tpb/

Bluetooth -- /proc/acpi/ibm/bluetooth
-------------------------------------

This feature shows the presence and current state of a Bluetooth
device. If Bluetooth is installed, the following commands can be used:

	echo enable > /proc/acpi/ibm/bluetooth
	echo disable > /proc/acpi/ibm/bluetooth

Video output control -- /proc/acpi/ibm/video
--------------------------------------------

This feature allows control over the devices used for video output -
LCD, CRT or DVI (if available). The following commands are available:

	echo lcd_enable > /proc/acpi/ibm/video
	echo lcd_disable > /proc/acpi/ibm/video
	echo crt_enable > /proc/acpi/ibm/video
	echo crt_disable > /proc/acpi/ibm/video
	echo dvi_enable > /proc/acpi/ibm/video
	echo dvi_disable > /proc/acpi/ibm/video
	echo auto_enable > /proc/acpi/ibm/video
	echo auto_disable > /proc/acpi/ibm/video
	echo expand_toggle > /proc/acpi/ibm/video
	echo video_switch > /proc/acpi/ibm/video

Each video output device can be enabled or disabled individually.
Reading /proc/acpi/ibm/video shows the status of each device.

Automatic video switching can be enabled or disabled.  When automatic
video switching is enabled, certain events (e.g. opening the lid,
docking or undocking) cause the video output device to change
automatically. While this can be useful, it also causes flickering
and, on the X40, video corruption. By disabling automatic switching,
the flickering or video corruption can be avoided.

The video_switch command cycles through the available video outputs
(it simulates the behavior of Fn-F7).

Video expansion can be toggled through this feature. This controls
whether the display is expanded to fill the entire LCD screen when a
mode with less than full resolution is used. Note that the current
video expansion status cannot be determined through this feature.

Note that on many models (particularly those using Radeon graphics
chips) the X driver configures the video card in a way which prevents
Fn-F7 from working. This also disables the video output switching
features of this driver, as it uses the same ACPI methods as
Fn-F7. Video switching on the console should still work.

UPDATE: There's now a patch for the X.org Radeon driver which
addresses this issue. Some people are reporting success with the patch
while others are still having problems. For more information:

https://bugs.freedesktop.org/show_bug.cgi?id=2000

ThinkLight control -- /proc/acpi/ibm/light
------------------------------------------

The current status of the ThinkLight can be found in this file. A few
models which do not make the status available will show it as
"unknown". The available commands are:

	echo on  > /proc/acpi/ibm/light
	echo off > /proc/acpi/ibm/light

Docking / undocking -- /proc/acpi/ibm/dock
------------------------------------------

Docking and undocking (e.g. with the X4 UltraBase) requires some
actions to be taken by the operating system to safely make or break
the electrical connections with the dock.

The docking feature of this driver generates the following ACPI events:

	ibm/dock GDCK 00000003 00000001 -- eject request
	ibm/dock GDCK 00000003 00000002 -- undocked
	ibm/dock GDCK 00000000 00000003 -- docked

NOTE: These events will only be generated if the laptop was docked
when originally booted. This is due to the current lack of support for
hot plugging of devices in the Linux ACPI framework. If the laptop was
booted while not in the dock, the following message is shown in the
logs:

	Mar 17 01:42:34 aero kernel: ibm_acpi: dock device not present

In this case, no dock-related events are generated but the dock and
undock commands described below still work. They can be executed
manually or triggered by Fn key combinations (see the example acpid
configuration files included in the driver tarball package available
on the web site).

When the eject request button on the dock is pressed, the first event
above is generated. The handler for this event should issue the
following command:

	echo undock > /proc/acpi/ibm/dock

After the LED on the dock goes off, it is safe to eject the laptop.
Note: if you pressed this key by mistake, go ahead and eject the
laptop, then dock it back in. Otherwise, the dock may not function as
expected.

When the laptop is docked, the third event above is generated. The
handler for this event should issue the following command to fully
enable the dock:

	echo dock > /proc/acpi/ibm/dock

The contents of the /proc/acpi/ibm/dock file shows the current status
of the dock, as provided by the ACPI framework.

The docking support in this driver does not take care of enabling or
disabling any other devices you may have attached to the dock. For
example, a CD drive plugged into the UltraBase needs to be disabled or
enabled separately. See the provided example acpid configuration files
for how this can be accomplished.

There is no support yet for PCI devices that may be attached to a
docking station, e.g. in the ThinkPad Dock II. The driver currently
does not recognize, enable or disable such devices. This means that
the only docking stations currently supported are the X-series
UltraBase docks and "dumb" port replicators like the Mini Dock (the
latter don't need any ACPI support, actually).

UltraBay eject -- /proc/acpi/ibm/bay
------------------------------------

Inserting or ejecting an UltraBay device requires some actions to be
taken by the operating system to safely make or break the electrical
connections with the device.

This feature generates the following ACPI events:

	ibm/bay MSTR 00000003 00000000 -- eject request
	ibm/bay MSTR 00000001 00000000 -- eject lever inserted

NOTE: These events will only be generated if the UltraBay was present
when the laptop was originally booted (on the X series, the UltraBay
is in the dock, so it may not be present if the laptop was undocked).
This is due to the current lack of support for hot plugging of devices
in the Linux ACPI framework. If the laptop was booted without the
UltraBay, the following message is shown in the logs:

	Mar 17 01:42:34 aero kernel: ibm_acpi: bay device not present

In this case, no bay-related events are generated but the eject
command described below still works. It can be executed manually or
triggered by a hot key combination.

Sliding the eject lever generates the first event shown above. The
handler for this event should take whatever actions are necessary to
shut down the device in the UltraBay (e.g. call idectl), then issue
the following command:

	echo eject > /proc/acpi/ibm/bay

After the LED on the UltraBay goes off, it is safe to pull out the
device.

When the eject lever is inserted, the second event above is
generated. The handler for this event should take whatever actions are
necessary to enable the UltraBay device (e.g. call idectl).

The contents of the /proc/acpi/ibm/bay file shows the current status
of the UltraBay, as provided by the ACPI framework.

EXPERIMENTAL warm eject support on the 600e/x, A22p and A3x (To use
this feature, you need to supply the experimental=1 parameter when
loading the module):

These models do not have a button near the UltraBay device to request
a hot eject but rather require the laptop to be put to sleep
(suspend-to-ram) before the bay device is ejected or inserted).
The sequence of steps to eject the device is as follows:

	echo eject > /proc/acpi/ibm/bay
	put the ThinkPad to sleep
	remove the drive
	resume from sleep
	cat /proc/acpi/ibm/bay should show that the drive was removed

On the A3x, both the UltraBay 2000 and UltraBay Plus devices are
supported. Use "eject2" instead of "eject" for the second bay.

Note: the UltraBay eject support on the 600e/x, A22p and A3x is
EXPERIMENTAL and may not work as expected. USE WITH CAUTION!

CMOS control -- /proc/acpi/ibm/cmos
-----------------------------------

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.

The commands are non-negative integer numbers:

	echo 0 >/proc/acpi/ibm/cmos
	echo 1 >/proc/acpi/ibm/cmos
	echo 2 >/proc/acpi/ibm/cmos
	...

The range of valid 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

LED control -- /proc/acpi/ibm/led
---------------------------------

Some of the LED indicators can be controlled through this feature. The
available commands are:

	echo '<led number> on' >/proc/acpi/ibm/led
	echo '<led number> off' >/proc/acpi/ibm/led
	echo '<led number> blink' >/proc/acpi/ibm/led

The <led number> range is 0 to 7. The set of LEDs that can be
controlled varies from model to model. Here is the mapping on the X40:

	0 - power
	1 - battery (orange)
	2 - battery (green)
	3 - UltraBase
	4 - UltraBay
	7 - standby

All of the above can be turned on and off and can be made to blink.

ACPI sounds -- /proc/acpi/ibm/beep
----------------------------------

The BEEP method is used internally by the ACPI firmware to provide
audible alerts in various situations. This feature allows the same
sounds to be triggered manually.

The commands are non-negative integer numbers:

	echo <number> >/proc/acpi/ibm/beep

The valid <number> range is 0 to 17. Not all numbers trigger sounds
and the sounds vary from model to model. Here is the behavior on the
X40:

	0 - stop a sound in progress (but use 17 to stop 16)
	2 - two beeps, pause, third beep ("low battery")
	3 - single beep
	4 - high, followed by low-pitched beep ("unable")
	5 - single beep
	6 - very high, followed by high-pitched beep ("AC/DC")
	7 - high-pitched beep
	9 - three short beeps
	10 - very long beep
	12 - low-pitched beep
	15 - three high-pitched beeps repeating constantly, stop with 0
	16 - one medium-pitched beep repeating constantly, stop with 17
	17 - stop 16

Temperature sensors -- /proc/acpi/ibm/thermal
---------------------------------------------

Most ThinkPads include six or more separate temperature sensors but
only expose the CPU temperature through the standard ACPI methods.
This feature shows readings from up to eight different sensors on older
ThinkPads, and it has experimental support for up to sixteen different
sensors on newer ThinkPads.  Readings from sensors that are not available
return -128.

No commands can be written to this file.

EXPERIMENTAL: The 16-sensors feature is marked EXPERIMENTAL because the
implementation directly accesses hardware registers and may not work as
expected. USE WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.  When EXPERIMENTAL
mode is enabled, reading the first 8 sensors on newer ThinkPads will
also use an new experimental thermal sensor access mode.

For example, on the X40, a typical output may be:
temperatures:   42 42 45 41 36 -128 33 -128

EXPERIMENTAL: On the T43/p, a typical output may be:
temperatures:   48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128

The mapping of thermal sensors to physical locations varies depending on
system-board model (and thus, on ThinkPad model).

http://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that
tries to track down these locations for various models.

Most (newer?) models seem to follow this pattern:

1:  CPU
2:  (depends on model)
3:  (depends on model)
4:  GPU
5:  Main battery: main sensor
6:  Bay battery: main sensor
7:  Main battery: secondary sensor
8:  Bay battery: secondary sensor
9-15: (depends on model)

For the R51 (source: Thomas Gruber):
2:  Mini-PCI
3:  Internal HDD

For the T43, T43/p (source: Shmidoax/Thinkwiki.org)
http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p
2:  System board, left side (near PCMCIA slot), reported as HDAPS temp
3:  PCMCIA slot
9:  MCH (northbridge) to DRAM Bus
10: ICH (southbridge), under Mini-PCI card, under touchpad
11: Power regulator, underside of system board, below F2 key

The A31 has a very atypical layout for the thermal sensors
(source: Milos Popovic, http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
1:  CPU
2:  Main Battery: main sensor
3:  Power Converter
4:  Bay Battery: main sensor
5:  MCH (northbridge)
6:  PCMCIA/ambient
7:  Main Battery: secondary sensor
8:  Bay Battery: secondary sensor


EXPERIMENTAL: Embedded controller register dump -- /proc/acpi/ibm/ecdump
------------------------------------------------------------------------

This feature is marked EXPERIMENTAL because the implementation
directly accesses hardware registers and may not work as expected. USE
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.

This feature dumps the values of 256 embedded controller
registers. Values which have changed since the last time the registers
were dumped are marked with a star:

[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
EC 0x30:  01  07  1a  00  30  04  00  00 *85  00  00  10  00  50  00  00
EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03 *bc *02 *bc
EC 0x60: *02 *bc *02  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0x70:  00  00  00  00  00  12  30  40 *24 *26 *2c *27 *20  80 *1f  80
EC 0x80:  00  00  00  06 *37 *0e  03  00  00  00  0e  07  00  00  00  00
EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xa0: *ff  09  ff  09  ff  ff *64  00 *00 *00 *a2  41 *ff *ff *e0  00
EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a

This feature can be used to determine the register holding the fan
speed on some models. To do that, do the following:

	- make sure the battery is fully charged
	- make sure the fan is running
	- run 'cat /proc/acpi/ibm/ecdump' several times, once per second or so

The first step makes sure various charging-related values don't
vary. The second ensures that the fan-related values do vary, since
the fan speed fluctuates a bit. The third will (hopefully) mark the
fan register with a star:

[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
EC 0x30:  01  07  1a  00  30  04  00  00  85  00  00  10  00  50  00  00
EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03  bc  02  bc
EC 0x60:  02  bc  02  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0x70:  00  00  00  00  00  12  30  40  24  27  2c  27  21  80  1f  80
EC 0x80:  00  00  00  06 *be  0d  03  00  00  00  0e  07  00  00  00  00
EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xa0:  ff  09  ff  09  ff  ff  64  00  00  00  a2  41  ff  ff  e0  00
EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a

Another set of values that varies often is the temperature
readings. Since temperatures don't change vary fast, you can take
several quick dumps to eliminate them.

You can use a similar method to figure out the meaning of other
embedded controller registers - e.g. make sure nothing else changes
except the charging or discharging battery to determine which
registers contain the current battery capacity, etc. If you experiment
with this, do send me your results (including some complete dumps with
a description of the conditions when they were taken.)

LCD brightness control -- /proc/acpi/ibm/brightness
---------------------------------------------------

This feature allows software control of the LCD brightness on ThinkPad
models which don't have a hardware brightness slider. The available
commands are:

	echo up   >/proc/acpi/ibm/brightness
	echo down >/proc/acpi/ibm/brightness
	echo 'level <level>' >/proc/acpi/ibm/brightness

The <level> number range is 0 to 7, although not all of them may be
distinct. The current brightness level is shown in the file.

Volume control -- /proc/acpi/ibm/volume
---------------------------------------

This feature allows volume control on ThinkPad models which don't have
a hardware volume knob. The available commands are:

	echo up   >/proc/acpi/ibm/volume
	echo down >/proc/acpi/ibm/volume
	echo mute >/proc/acpi/ibm/volume
	echo 'level <level>' >/proc/acpi/ibm/volume

The <level> number range is 0 to 15 although not all of them may be
distinct. The unmute the volume after the mute command, use either the
up or down command (the level command will not unmute the volume).
The current volume level and mute state is shown in the file.

EXPERIMENTAL: fan speed, fan enable/disable -- /proc/acpi/ibm/fan
-----------------------------------------------------------------

This feature is marked EXPERIMENTAL because the implementation
directly accesses hardware registers and may not work as expected. USE
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.

This feature attempts to show the current fan speed, control mode and
other fan data that might be available.  The speed is read directly
from the hardware registers of the embedded controller.  This is known
to work on later R, T and X series ThinkPads but may show a bogus
value on other models.

Most ThinkPad fans work in "levels".  Level 0 stops the fan.  The higher
the level, the higher the fan speed, although adjacent levels often map
to the same fan speed.  7 is the highest level, where the fan reaches
the maximum recommended speed.  Level "auto" means the EC changes the
fan level according to some internal algorithm, usually based on
readings from the thermal sensors.  Level "disengaged" means the EC
disables the speed-locked closed-loop fan control, and drives the fan as
fast as it can go, which might exceed hardware limits, so use this level
with caution.

The fan usually ramps up or down slowly from one speed to another,
and it is normal for the EC to take several seconds to react to fan
commands.

The fan may be enabled or disabled with the following commands:

	echo enable  >/proc/acpi/ibm/fan
	echo disable >/proc/acpi/ibm/fan

Placing a fan on level 0 is the same as disabling it.  Enabling a fan
will try to place it in a safe level if it is too slow or disabled.

WARNING WARNING WARNING: do not leave the fan disabled unless you are
monitoring all of the temperature sensor readings and you are ready to
enable it if necessary to avoid overheating.

An enabled fan in level "auto" may stop spinning if the EC decides the
ThinkPad is cool enough and doesn't need the extra airflow.  This is
normal, and the EC will spin the fan up if the varios thermal readings
rise too much.

On the X40, this seems to depend on the CPU and HDD temperatures.
Specifically, the fan is turned on when either the CPU temperature
climbs to 56 degrees or the HDD temperature climbs to 46 degrees.  The
fan is turned off when the CPU temperature drops to 49 degrees and the
HDD temperature drops to 41 degrees.  These thresholds cannot
currently be controlled.

The fan level can be controlled with the command:

	echo 'level <level>' > /proc/acpi/ibm/thermal

Where <level> is an integer from 0 to 7, or one of the words "auto"
or "disengaged" (without the quotes).  Not all ThinkPads support the
"auto" and "disengaged" levels.

On the X31 and X40 (and ONLY on those models), the fan speed can be
controlled to a certain degree. Once the fan is running, it can be
forced to run faster or slower with the following command:

	echo 'speed <speed>' > /proc/acpi/ibm/thermal

The sustainable range of fan speeds on the X40 appears to be from
about 3700 to about 7350. Values outside this range either do not have
any effect or the fan speed eventually settles somewhere in that
range. The fan cannot be stopped or started with this command.

The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
certain conditions are met.  It will override any fan programming done
through ibm-acpi.

The ibm-acpi kernel driver can be programmed to revert the fan level
to a safe setting if userspace does not issue one of the fan commands:
"enable", "disable", "level" or "watchdog" within a configurable
ammount of time.  To do this, use the "watchdog" command.

	echo 'watchdog <interval>' > /proc/acpi/ibm/fan

Interval is the ammount of time in seconds to wait for one of the
above mentioned fan commands before reseting the fan level to a safe
one.  If set to zero, the watchdog is disabled (default).  When the
watchdog timer runs out, it does the exact equivalent of the "enable"
fan command.

Note that the watchdog timer stops after it enables the fan.  It will
be rearmed again automatically (using the same interval) when one of
the above mentioned fan commands is received.  The fan watchdog is,
therefore, not suitable to protect against fan mode changes made
through means other than the "enable", "disable", and "level" fan
commands.

EXPERIMENTAL: WAN -- /proc/acpi/ibm/wan
---------------------------------------

This feature is marked EXPERIMENTAL because the implementation
directly accesses hardware registers and may not work as expected. USE
WITH CAUTION! To use this feature, you need to supply the
experimental=1 parameter when loading the module.

This feature shows the presence and current state of a WAN (Sierra
Wireless EV-DO) device. If WAN is installed, the following commands can
be used:

	echo enable > /proc/acpi/ibm/wan
	echo disable > /proc/acpi/ibm/wan

It was tested on a Lenovo Thinkpad X60. It should probably work on other
Thinkpad models which come with this module installed.

Multiple Commands, Module Parameters
------------------------------------

Multiple commands can be written to the proc files in one shot by
separating them with commas, for example:

	echo enable,0xffff > /proc/acpi/ibm/hotkey
	echo lcd_disable,crt_enable > /proc/acpi/ibm/video

Commands can also be specified when loading the ibm_acpi module, for
example:

	modprobe ibm_acpi hotkey=enable,0xffff video=auto_disable