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+                    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
+