[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
diff --git a/src/kernel/linux/v4.14/Documentation/laptops/thinkpad-acpi.txt b/src/kernel/linux/v4.14/Documentation/laptops/thinkpad-acpi.txt
new file mode 100644
index 0000000..00b6dfe
--- /dev/null
+++ b/src/kernel/linux/v4.14/Documentation/laptops/thinkpad-acpi.txt
@@ -0,0 +1,1485 @@
+ ThinkPad ACPI Extras Driver
+
+ Version 0.25
+ October 16th, 2013
+
+ Borislav Deianov <borislav@users.sf.net>
+ Henrique de Moraes Holschuh <hmh@hmh.eng.br>
+ http://ibm-acpi.sf.net/
+
+
+This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It
+supports various features of these laptops which are accessible
+through the ACPI and ACPI EC framework, but not otherwise fully
+supported by the generic Linux ACPI drivers.
+
+This driver used to be named ibm-acpi until kernel 2.6.21 and release
+0.13-20070314. It used to be in the drivers/acpi tree, but it was
+moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel
+2.6.22, and release 0.14. It was moved to drivers/platform/x86 for
+kernel 2.6.29 and release 0.22.
+
+The driver is named "thinkpad-acpi". In some places, like module
+names and log messages, "thinkpad_acpi" is used because of userspace
+issues.
+
+"tpacpi" is used as a shorthand where "thinkpad-acpi" would be too
+long due to length limitations on some Linux kernel versions.
+
+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
+ - CMOS/UCMS control
+ - LED control
+ - ACPI sounds
+ - temperature sensors
+ - Experimental: embedded controller register dump
+ - LCD brightness control
+ - Volume control
+ - Fan control and monitoring: fan speed, fan enable/disable
+ - WAN enable and disable
+ - UWB 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 ACPI tables, using the "acpidump" utility
+ - a copy of the output of dmidecode, with serial numbers
+ and UUIDs masked off
+ - 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, look for the CONFIG_THINKPAD_ACPI Kconfig option.
+It is located on the menu path: "Device Drivers" -> "X86 Platform
+Specific Device Drivers" -> "ThinkPad ACPI Laptop Extras".
+
+
+Features
+--------
+
+The driver exports two different interfaces to userspace, which can be
+used to access the features it provides. One is a legacy procfs-based
+interface, which will be removed at some time in the future. The other
+is a new sysfs-based interface which is not complete yet.
+
+The procfs interface creates the /proc/acpi/ibm directory. There is a
+file under that directory for each feature it supports. The procfs
+interface is mostly frozen, and will change very little if at all: it
+will not be extended to add any new functionality in the driver, instead
+all new functionality will be implemented on the sysfs interface.
+
+The sysfs interface tries to blend in the generic Linux sysfs subsystems
+and classes as much as possible. Since some of these subsystems are not
+yet ready or stabilized, it is expected that this interface will change,
+and any and all userspace programs must deal with it.
+
+
+Notes about the sysfs interface:
+
+Unlike what was done with the procfs interface, correctness when talking
+to the sysfs interfaces will be enforced, as will correctness in the
+thinkpad-acpi's implementation of sysfs interfaces.
+
+Also, any bugs in the thinkpad-acpi sysfs driver code or in the
+thinkpad-acpi's implementation of the sysfs interfaces will be fixed for
+maximum correctness, even if that means changing an interface in
+non-compatible ways. As these interfaces mature both in the kernel and
+in thinkpad-acpi, such changes should become quite rare.
+
+Applications interfacing to the thinkpad-acpi sysfs interfaces must
+follow all sysfs guidelines and correctly process all errors (the sysfs
+interface makes extensive use of errors). File descriptors and open /
+close operations to the sysfs inodes must also be properly implemented.
+
+The version of thinkpad-acpi's sysfs interface is exported by the driver
+as a driver attribute (see below).
+
+Sysfs driver attributes are on the driver's sysfs attribute space,
+for 2.6.23+ this is /sys/bus/platform/drivers/thinkpad_acpi/ and
+/sys/bus/platform/drivers/thinkpad_hwmon/
+
+Sysfs device attributes are on the thinkpad_acpi device sysfs attribute
+space, for 2.6.23+ this is /sys/devices/platform/thinkpad_acpi/.
+
+Sysfs device attributes for the sensors and fan are on the
+thinkpad_hwmon device's sysfs attribute space, but you should locate it
+looking for a hwmon device with the name attribute of "thinkpad", or
+better yet, through libsensors. For 4.14+ sysfs attributes were moved to the
+hwmon device (/sys/bus/platform/devices/thinkpad_hwmon/hwmon/hwmon? or
+/sys/class/hwmon/hwmon?).
+
+Driver version
+--------------
+
+procfs: /proc/acpi/ibm/driver
+sysfs driver attribute: version
+
+The driver name and version. No commands can be written to this file.
+
+
+Sysfs interface version
+-----------------------
+
+sysfs driver attribute: interface_version
+
+Version of the thinkpad-acpi sysfs interface, as an unsigned long
+(output in hex format: 0xAAAABBCC), where:
+ AAAA - major revision
+ BB - minor revision
+ CC - bugfix revision
+
+The sysfs interface version changelog for the driver can be found at the
+end of this document. Changes to the sysfs interface done by the kernel
+subsystems are not documented here, nor are they tracked by this
+attribute.
+
+Changes to the thinkpad-acpi sysfs interface are only considered
+non-experimental when they are submitted to Linux mainline, at which
+point the changes in this interface are documented and interface_version
+may be updated. If you are using any thinkpad-acpi features not yet
+sent to mainline for merging, you do so on your own risk: these features
+may disappear, or be implemented in a different and incompatible way by
+the time they are merged in Linux mainline.
+
+Changes that are backwards-compatible by nature (e.g. the addition of
+attributes that do not change the way the other attributes work) do not
+always warrant an update of interface_version. Therefore, one must
+expect that an attribute might not be there, and deal with it properly
+(an attribute not being there *is* a valid way to make it clear that a
+feature is not available in sysfs).
+
+
+Hot keys
+--------
+
+procfs: /proc/acpi/ibm/hotkey
+sysfs device attribute: hotkey_*
+
+In a ThinkPad, the ACPI HKEY handler is responsible for communicating
+some important events and also keyboard hot key presses to the operating
+system. Enabling the hotkey functionality of thinkpad-acpi signals the
+firmware that such a driver is present, and modifies how the ThinkPad
+firmware will behave in many situations.
+
+The driver enables the HKEY ("hot key") event reporting automatically
+when loaded, and disables it when it is removed.
+
+The driver will report HKEY events in the following format:
+
+ ibm/hotkey HKEY 00000080 0000xxxx
+
+Some of these events refer to hot key presses, but not all of them.
+
+The driver will generate events over the input layer for hot keys and
+radio switches, and over the ACPI netlink layer for other events. The
+input layer support accepts the standard IOCTLs to remap the keycodes
+assigned to each hot key.
+
+The hot key bit mask allows some control over which hot keys generate
+events. If a key is "masked" (bit set to 0 in the mask), the firmware
+will handle it. If it is "unmasked", it signals the firmware that
+thinkpad-acpi would prefer to handle it, if the firmware would be so
+kind to allow it (and it often doesn't!).
+
+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. Some models do not support the mask at all. The behaviour
+of the mask is, therefore, highly dependent on the ThinkPad model.
+
+The driver will filter out any unmasked hotkeys, so even if the firmware
+doesn't allow disabling an specific hotkey, the driver will not report
+events for unmasked hotkeys.
+
+Note that unmasking some keys prevents their default behavior. For
+example, if Fn+F5 is unmasked, that key will no longer enable/disable
+Bluetooth by itself in firmware.
+
+Note also that not all Fn key combinations are supported through ACPI
+depending on the ThinkPad model and firmware version. On those
+ThinkPads, it is still possible to support some extra hotkeys by
+polling the "CMOS NVRAM" at least 10 times per second. The driver
+attempts to enables this functionality automatically when required.
+
+procfs notes:
+
+The following commands can be written to the /proc/acpi/ibm/hotkey file:
+
+ echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
+ echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
+ ... any other 8-hex-digit mask ...
+ echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask
+
+The following commands have been deprecated and will cause the kernel
+to log a warning:
+
+ echo enable > /proc/acpi/ibm/hotkey -- does nothing
+ echo disable > /proc/acpi/ibm/hotkey -- returns an error
+
+The procfs interface does not support NVRAM polling control. So as to
+maintain maximum bug-to-bug compatibility, it does not report any masks,
+nor does it allow one to manipulate the hot key mask when the firmware
+does not support masks at all, even if NVRAM polling is in use.
+
+sysfs notes:
+
+ hotkey_bios_enabled:
+ DEPRECATED, WILL BE REMOVED SOON.
+
+ Returns 0.
+
+ hotkey_bios_mask:
+ DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE.
+
+ Returns the hot keys mask when thinkpad-acpi was loaded.
+ Upon module unload, the hot keys mask will be restored
+ to this value. This is always 0x80c, because those are
+ the hotkeys that were supported by ancient firmware
+ without mask support.
+
+ hotkey_enable:
+ DEPRECATED, WILL BE REMOVED SOON.
+
+ 0: returns -EPERM
+ 1: does nothing
+
+ hotkey_mask:
+ bit mask to enable reporting (and depending on
+ the firmware, ACPI event generation) for each hot key
+ (see above). Returns the current status of the hot keys
+ mask, and allows one to modify it.
+
+ hotkey_all_mask:
+ bit mask that should enable event reporting for all
+ supported hot keys, when echoed to hotkey_mask above.
+ Unless you know which events need to be handled
+ passively (because the firmware *will* handle them
+ anyway), do *not* use hotkey_all_mask. Use
+ hotkey_recommended_mask, instead. You have been warned.
+
+ hotkey_recommended_mask:
+ bit mask that should enable event reporting for all
+ supported hot keys, except those which are always
+ handled by the firmware anyway. Echo it to
+ hotkey_mask above, to use. This is the default mask
+ used by the driver.
+
+ hotkey_source_mask:
+ bit mask that selects which hot keys will the driver
+ poll the NVRAM for. This is auto-detected by the driver
+ based on the capabilities reported by the ACPI firmware,
+ but it can be overridden at runtime.
+
+ Hot keys whose bits are set in hotkey_source_mask are
+ polled for in NVRAM, and reported as hotkey events if
+ enabled in hotkey_mask. Only a few hot keys are
+ available through CMOS NVRAM polling.
+
+ Warning: when in NVRAM mode, the volume up/down/mute
+ keys are synthesized according to changes in the mixer,
+ which uses a single volume up or volume down hotkey
+ press to unmute, as per the ThinkPad volume mixer user
+ interface. When in ACPI event mode, volume up/down/mute
+ events are reported by the firmware and can behave
+ differently (and that behaviour changes with firmware
+ version -- not just with firmware models -- as well as
+ OSI(Linux) state).
+
+ hotkey_poll_freq:
+ frequency in Hz for hot key polling. It must be between
+ 0 and 25 Hz. Polling is only carried out when strictly
+ needed.
+
+ Setting hotkey_poll_freq to zero disables polling, and
+ will cause hot key presses that require NVRAM polling
+ to never be reported.
+
+ Setting hotkey_poll_freq too low may cause repeated
+ pressings of the same hot key to be misreported as a
+ single key press, or to not even be detected at all.
+ The recommended polling frequency is 10Hz.
+
+ hotkey_radio_sw:
+ If the ThinkPad has a hardware radio switch, this
+ attribute will read 0 if the switch is in the "radios
+ disabled" position, and 1 if the switch is in the
+ "radios enabled" position.
+
+ This attribute has poll()/select() support.
+
+ hotkey_tablet_mode:
+ If the ThinkPad has tablet capabilities, this attribute
+ will read 0 if the ThinkPad is in normal mode, and
+ 1 if the ThinkPad is in tablet mode.
+
+ This attribute has poll()/select() support.
+
+ wakeup_reason:
+ Set to 1 if the system is waking up because the user
+ requested a bay ejection. Set to 2 if the system is
+ waking up because the user requested the system to
+ undock. Set to zero for normal wake-ups or wake-ups
+ due to unknown reasons.
+
+ This attribute has poll()/select() support.
+
+ wakeup_hotunplug_complete:
+ Set to 1 if the system was waken up because of an
+ undock or bay ejection request, and that request
+ was successfully completed. At this point, it might
+ be useful to send the system back to sleep, at the
+ user's choice. Refer to HKEY events 0x4003 and
+ 0x3003, below.
+
+ This attribute has poll()/select() support.
+
+input layer notes:
+
+A Hot key is mapped to a single input layer EV_KEY event, possibly
+followed by an EV_MSC MSC_SCAN event that shall contain that key's scan
+code. An EV_SYN event will always be generated to mark the end of the
+event block.
+
+Do not use the EV_MSC MSC_SCAN events to process keys. They are to be
+used as a helper to remap keys, only. They are particularly useful when
+remapping KEY_UNKNOWN keys.
+
+The events are available in an input device, with the following id:
+
+ Bus: BUS_HOST
+ vendor: 0x1014 (PCI_VENDOR_ID_IBM) or
+ 0x17aa (PCI_VENDOR_ID_LENOVO)
+ product: 0x5054 ("TP")
+ version: 0x4101
+
+The version will have its LSB incremented if the keymap changes in a
+backwards-compatible way. The MSB shall always be 0x41 for this input
+device. If the MSB is not 0x41, do not use the device as described in
+this section, as it is either something else (e.g. another input device
+exported by a thinkpad driver, such as HDAPS) or its functionality has
+been changed in a non-backwards compatible way.
+
+Adding other event types for other functionalities shall be considered a
+backwards-compatible change for this input device.
+
+Thinkpad-acpi Hot Key event map (version 0x4101):
+
+ACPI Scan
+event code Key Notes
+
+0x1001 0x00 FN+F1 -
+
+0x1002 0x01 FN+F2 IBM: battery (rare)
+ Lenovo: Screen lock
+
+0x1003 0x02 FN+F3 Many IBM models always report
+ this hot key, even with hot keys
+ disabled or with Fn+F3 masked
+ off
+ IBM: screen lock, often turns
+ off the ThinkLight as side-effect
+ Lenovo: battery
+
+0x1004 0x03 FN+F4 Sleep button (ACPI sleep button
+ semantics, i.e. sleep-to-RAM).
+ It always generates some kind
+ of event, either the hot key
+ event or an ACPI sleep button
+ event. The firmware may
+ refuse to generate further FN+F4
+ key presses until a S3 or S4 ACPI
+ sleep cycle is performed or some
+ time passes.
+
+0x1005 0x04 FN+F5 Radio. Enables/disables
+ the internal Bluetooth hardware
+ and W-WAN card if left in control
+ of the firmware. Does not affect
+ the WLAN card.
+ Should be used to turn on/off all
+ radios (Bluetooth+W-WAN+WLAN),
+ really.
+
+0x1006 0x05 FN+F6 -
+
+0x1007 0x06 FN+F7 Video output cycle.
+ Do you feel lucky today?
+
+0x1008 0x07 FN+F8 IBM: toggle screen expand
+ Lenovo: configure UltraNav,
+ or toggle screen expand
+
+0x1009 0x08 FN+F9 -
+ .. .. ..
+0x100B 0x0A FN+F11 -
+
+0x100C 0x0B FN+F12 Sleep to disk. You are always
+ supposed to handle it yourself,
+ either through the ACPI event,
+ or through a hotkey event.
+ The firmware may refuse to
+ generate further FN+F12 key
+ press events until a S3 or S4
+ ACPI sleep cycle is performed,
+ or some time passes.
+
+0x100D 0x0C FN+BACKSPACE -
+0x100E 0x0D FN+INSERT -
+0x100F 0x0E FN+DELETE -
+
+0x1010 0x0F FN+HOME Brightness up. This key is
+ always handled by the firmware
+ in IBM ThinkPads, even when
+ unmasked. Just leave it alone.
+ For Lenovo ThinkPads with a new
+ BIOS, it has to be handled either
+ by the ACPI OSI, or by userspace.
+ The driver does the right thing,
+ never mess with this.
+0x1011 0x10 FN+END Brightness down. See brightness
+ up for details.
+
+0x1012 0x11 FN+PGUP ThinkLight toggle. This key is
+ always handled by the firmware,
+ even when unmasked.
+
+0x1013 0x12 FN+PGDOWN -
+
+0x1014 0x13 FN+SPACE Zoom key
+
+0x1015 0x14 VOLUME UP Internal mixer volume up. This
+ key is always handled by the
+ firmware, even when unmasked.
+ NOTE: Lenovo seems to be changing
+ this.
+0x1016 0x15 VOLUME DOWN Internal mixer volume up. This
+ key is always handled by the
+ firmware, even when unmasked.
+ NOTE: Lenovo seems to be changing
+ this.
+0x1017 0x16 MUTE Mute internal mixer. This
+ key is always handled by the
+ firmware, even when unmasked.
+
+0x1018 0x17 THINKPAD ThinkPad/Access IBM/Lenovo key
+
+0x1019 0x18 unknown
+.. .. ..
+0x1020 0x1F unknown
+
+The ThinkPad firmware does not allow one to differentiate when most hot
+keys are pressed or released (either that, or we don't know how to, yet).
+For these keys, the driver generates a set of events for a key press and
+immediately issues the same set of events for a key release. It is
+unknown by the driver if the ThinkPad firmware triggered these events on
+hot key press or release, but the firmware will do it for either one, not
+both.
+
+If a key is mapped to KEY_RESERVED, it generates no input events at all.
+If a key is mapped to KEY_UNKNOWN, it generates an input event that
+includes an scan code. If a key is mapped to anything else, it will
+generate input device EV_KEY events.
+
+In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW
+events for switches:
+
+SW_RFKILL_ALL T60 and later hardware rfkill rocker switch
+SW_TABLET_MODE Tablet ThinkPads HKEY events 0x5009 and 0x500A
+
+Non hotkey ACPI HKEY event map:
+-------------------------------
+
+Events that are never propagated by the driver:
+
+0x2304 System is waking up from suspend to undock
+0x2305 System is waking up from suspend to eject bay
+0x2404 System is waking up from hibernation to undock
+0x2405 System is waking up from hibernation to eject bay
+0x5001 Lid closed
+0x5002 Lid opened
+0x5009 Tablet swivel: switched to tablet mode
+0x500A Tablet swivel: switched to normal mode
+0x5010 Brightness level changed/control event
+0x6000 KEYBOARD: Numlock key pressed
+0x6005 KEYBOARD: Fn key pressed (TO BE VERIFIED)
+0x7000 Radio Switch may have changed state
+
+
+Events that are propagated by the driver to userspace:
+
+0x2313 ALARM: System is waking up from suspend because
+ the battery is nearly empty
+0x2413 ALARM: System is waking up from hibernation because
+ the battery is nearly empty
+0x3003 Bay ejection (see 0x2x05) complete, can sleep again
+0x3006 Bay hotplug request (hint to power up SATA link when
+ the optical drive tray is ejected)
+0x4003 Undocked (see 0x2x04), can sleep again
+0x4010 Docked into hotplug port replicator (non-ACPI dock)
+0x4011 Undocked from hotplug port replicator (non-ACPI dock)
+0x500B Tablet pen inserted into its storage bay
+0x500C Tablet pen removed from its storage bay
+0x6011 ALARM: battery is too hot
+0x6012 ALARM: battery is extremely hot
+0x6021 ALARM: a sensor is too hot
+0x6022 ALARM: a sensor is extremely hot
+0x6030 System thermal table changed
+0x6040 Nvidia Optimus/AC adapter related (TO BE VERIFIED)
+0x60C0 X1 Yoga 2016, Tablet mode status changed
+
+Battery nearly empty alarms are a last resort attempt to get the
+operating system to hibernate or shutdown cleanly (0x2313), or shutdown
+cleanly (0x2413) before power is lost. They must be acted upon, as the
+wake up caused by the firmware will have negated most safety nets...
+
+When any of the "too hot" alarms happen, according to Lenovo the user
+should suspend or hibernate the laptop (and in the case of battery
+alarms, unplug the AC adapter) to let it cool down. These alarms do
+signal that something is wrong, they should never happen on normal
+operating conditions.
+
+The "extremely hot" alarms are emergencies. According to Lenovo, the
+operating system is to force either an immediate suspend or hibernate
+cycle, or a system shutdown. Obviously, something is very wrong if this
+happens.
+
+
+Brightness hotkey notes:
+
+Don't mess with the brightness hotkeys in a Thinkpad. If you want
+notifications for OSD, use the sysfs backlight class event support.
+
+The driver will issue KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN events
+automatically for the cases were userspace has to do something to
+implement brightness changes. When you override these events, you will
+either fail to handle properly the ThinkPads that require explicit
+action to change backlight brightness, or the ThinkPads that require
+that no action be taken to work properly.
+
+
+Bluetooth
+---------
+
+procfs: /proc/acpi/ibm/bluetooth
+sysfs device attribute: bluetooth_enable (deprecated)
+sysfs rfkill class: switch "tpacpi_bluetooth_sw"
+
+This feature shows the presence and current state of a ThinkPad
+Bluetooth device in the internal ThinkPad CDC slot.
+
+If the ThinkPad supports it, the Bluetooth state is stored in NVRAM,
+so it is kept across reboots and power-off.
+
+Procfs notes:
+
+If Bluetooth is installed, the following commands can be used:
+
+ echo enable > /proc/acpi/ibm/bluetooth
+ echo disable > /proc/acpi/ibm/bluetooth
+
+Sysfs notes:
+
+ If the Bluetooth CDC card is installed, it can be enabled /
+ disabled through the "bluetooth_enable" thinkpad-acpi device
+ attribute, and its current status can also be queried.
+
+ enable:
+ 0: disables Bluetooth / Bluetooth is disabled
+ 1: enables Bluetooth / Bluetooth is enabled.
+
+ Note: this interface has been superseded by the generic rfkill
+ class. It has been deprecated, and it will be removed in year
+ 2010.
+
+ rfkill controller switch "tpacpi_bluetooth_sw": refer to
+ Documentation/rfkill.txt for details.
+
+
+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
+
+NOTE: Access to this feature is restricted to processes owning the
+CAP_SYS_ADMIN capability for safety reasons, as it can interact badly
+enough with some versions of X.org to crash it.
+
+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: refer to https://bugs.freedesktop.org/show_bug.cgi?id=2000
+
+
+ThinkLight control
+------------------
+
+procfs: /proc/acpi/ibm/light
+sysfs attributes: as per LED class, for the "tpacpi::thinklight" LED
+
+procfs notes:
+
+The ThinkLight status can be read and set through the procfs interface. A
+few models which do not make the status available will show the ThinkLight
+status as "unknown". The available commands are:
+
+ echo on > /proc/acpi/ibm/light
+ echo off > /proc/acpi/ibm/light
+
+sysfs notes:
+
+The ThinkLight sysfs interface is documented by the LED class
+documentation, in Documentation/leds/leds-class.txt. The ThinkLight LED name
+is "tpacpi::thinklight".
+
+Due to limitations in the sysfs LED class, if the status of the ThinkLight
+cannot be read or if it is unknown, thinkpad-acpi will report it as "off".
+It is impossible to know if the status returned through sysfs is valid.
+
+
+CMOS/UCMS control
+-----------------
+
+procfs: /proc/acpi/ibm/cmos
+sysfs device attribute: cmos_command
+
+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 - 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 press
+ 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. Do not use it, it is
+exported just as a debug tool.
+
+
+LED control
+-----------
+
+procfs: /proc/acpi/ibm/led
+sysfs attributes: as per LED class, see below for names
+
+Some of the LED indicators can be controlled through this feature. On
+some older ThinkPad models, it is possible to query the status of the
+LED indicators as well. Newer ThinkPads cannot query the real status
+of the LED indicators.
+
+Because misuse of the LEDs could induce an unaware user to perform
+dangerous actions (like undocking or ejecting a bay device while the
+buses are still active), or mask an important alarm (such as a nearly
+empty battery, or a broken battery), access to most LEDs is
+restricted.
+
+Unrestricted access to all LEDs requires that thinkpad-acpi be
+compiled with the CONFIG_THINKPAD_ACPI_UNSAFE_LEDS option enabled.
+Distributions must never enable this option. Individual users that
+are aware of the consequences are welcome to enabling it.
+
+Audio mute and microphone mute LEDs are supported, but currently not
+visible to userspace. They are used by the snd-hda-intel audio driver.
+
+procfs notes:
+
+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 15. The set of LEDs that can be
+controlled varies from model to model. Here is the common ThinkPad
+mapping:
+
+ 0 - power
+ 1 - battery (orange)
+ 2 - battery (green)
+ 3 - UltraBase/dock
+ 4 - UltraBay
+ 5 - UltraBase battery slot
+ 6 - (unknown)
+ 7 - standby
+ 8 - dock status 1
+ 9 - dock status 2
+ 10, 11 - (unknown)
+ 12 - thinkvantage
+ 13, 14, 15 - (unknown)
+
+All of the above can be turned on and off and can be made to blink.
+
+sysfs notes:
+
+The ThinkPad LED sysfs interface is described in detail by the LED class
+documentation, in Documentation/leds/leds-class.txt.
+
+The LEDs are named (in LED ID order, from 0 to 12):
+"tpacpi::power", "tpacpi:orange:batt", "tpacpi:green:batt",
+"tpacpi::dock_active", "tpacpi::bay_active", "tpacpi::dock_batt",
+"tpacpi::unknown_led", "tpacpi::standby", "tpacpi::dock_status1",
+"tpacpi::dock_status2", "tpacpi::unknown_led2", "tpacpi::unknown_led3",
+"tpacpi::thinkvantage".
+
+Due to limitations in the sysfs LED class, if the status of the LED
+indicators cannot be read due to an error, thinkpad-acpi will report it as
+a brightness of zero (same as LED off).
+
+If the thinkpad firmware doesn't support reading the current status,
+trying to read the current LED brightness will just return whatever
+brightness was last written to that attribute.
+
+These LEDs can blink using hardware acceleration. To request that a
+ThinkPad indicator LED should blink in hardware accelerated mode, use the
+"timer" trigger, and leave the delay_on and delay_off parameters set to
+zero (to request hardware acceleration autodetection).
+
+LEDs that are known not to exist in a given ThinkPad model are not
+made available through the sysfs interface. If you have a dock and you
+notice there are LEDs listed for your ThinkPad that do not exist (and
+are not in the dock), or if you notice that there are missing LEDs,
+a report to ibm-acpi-devel@lists.sourceforge.net is appreciated.
+
+
+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
+-------------------
+
+procfs: /proc/acpi/ibm/thermal
+sysfs device attributes: (hwmon "thinkpad") temp*_input
+
+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 up to sixteen different sensors on newer ThinkPads.
+
+For example, on the X40, a typical output may be:
+temperatures: 42 42 45 41 36 -128 33 -128
+
+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: Clock-generator, mini-pci card and 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
+
+
+Procfs notes:
+ Readings from sensors that are not available return -128.
+ No commands can be written to this file.
+
+Sysfs notes:
+ Sensors that are not available return the ENXIO error. This
+ status may change at runtime, as there are hotplug thermal
+ sensors, like those inside the batteries and docks.
+
+ thinkpad-acpi thermal sensors are reported through the hwmon
+ subsystem, and follow all of the hwmon guidelines at
+ Documentation/hwmon.
+
+EXPERIMENTAL: Embedded controller register dump
+-----------------------------------------------
+
+This feature is not included in the thinkpad driver anymore.
+Instead the EC can be accessed through /sys/kernel/debug/ec with
+a userspace tool which can be found here:
+ftp://ftp.suse.com/pub/people/trenn/sources/ec
+
+Use it 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
+ - use above mentioned tool to read out the EC
+
+Often fan and temperature values vary between
+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
+----------------------
+
+procfs: /proc/acpi/ibm/brightness
+sysfs backlight device "thinkpad_screen"
+
+This feature allows software control of the LCD brightness on ThinkPad
+models which don't have a hardware brightness slider.
+
+It has some limitations: the LCD backlight cannot be actually turned
+on or off by this interface, it just controls the backlight brightness
+level.
+
+On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
+has eight brightness levels, ranging from 0 to 7. Some of the levels
+may not be distinct. Later Lenovo models that implement the ACPI
+display backlight brightness control methods have 16 levels, ranging
+from 0 to 15.
+
+For IBM ThinkPads, there are two interfaces to the firmware for direct
+brightness control, EC and UCMS (or CMOS). To select which one should be
+used, use the brightness_mode module parameter: brightness_mode=1 selects
+EC mode, brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC
+mode with NVRAM backing (so that brightness changes are remembered across
+shutdown/reboot).
+
+The driver tries to select which interface to use from a table of
+defaults for each ThinkPad model. If it makes a wrong choice, please
+report this as a bug, so that we can fix it.
+
+Lenovo ThinkPads only support brightness_mode=2 (UCMS).
+
+When display backlight brightness controls are available through the
+standard ACPI interface, it is best to use it instead of this direct
+ThinkPad-specific interface. The driver will disable its native
+backlight brightness control interface if it detects that the standard
+ACPI interface is available in the ThinkPad.
+
+If you want to use the thinkpad-acpi backlight brightness control
+instead of the generic ACPI video backlight brightness control for some
+reason, you should use the acpi_backlight=vendor kernel parameter.
+
+The brightness_enable module parameter can be used to control whether
+the LCD brightness control feature will be enabled when available.
+brightness_enable=0 forces it to be disabled. brightness_enable=1
+forces it to be enabled when available, even if the standard ACPI
+interface is also available.
+
+Procfs notes:
+
+ The available commands are:
+
+ echo up >/proc/acpi/ibm/brightness
+ echo down >/proc/acpi/ibm/brightness
+ echo 'level <level>' >/proc/acpi/ibm/brightness
+
+Sysfs notes:
+
+The interface is implemented through the backlight sysfs class, which is
+poorly documented at this time.
+
+Locate the thinkpad_screen device under /sys/class/backlight, and inside
+it there will be the following attributes:
+
+ max_brightness:
+ Reads the maximum brightness the hardware can be set to.
+ The minimum is always zero.
+
+ actual_brightness:
+ Reads what brightness the screen is set to at this instant.
+
+ brightness:
+ Writes request the driver to change brightness to the
+ given value. Reads will tell you what brightness the
+ driver is trying to set the display to when "power" is set
+ to zero and the display has not been dimmed by a kernel
+ power management event.
+
+ power:
+ power management mode, where 0 is "display on", and 1 to 3
+ will dim the display backlight to brightness level 0
+ because thinkpad-acpi cannot really turn the backlight
+ off. Kernel power management events can temporarily
+ increase the current power management level, i.e. they can
+ dim the display.
+
+
+WARNING:
+
+ Whatever you do, do NOT ever call thinkpad-acpi backlight-level change
+ interface and the ACPI-based backlight level change interface
+ (available on newer BIOSes, and driven by the Linux ACPI video driver)
+ at the same time. The two will interact in bad ways, do funny things,
+ and maybe reduce the life of the backlight lamps by needlessly kicking
+ its level up and down at every change.
+
+
+Volume control (Console Audio control)
+--------------------------------------
+
+procfs: /proc/acpi/ibm/volume
+ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC"
+
+NOTE: by default, the volume control interface operates in read-only
+mode, as it is supposed to be used for on-screen-display purposes.
+The read/write mode can be enabled through the use of the
+"volume_control=1" module parameter.
+
+NOTE: distros are urged to not enable volume_control by default, this
+should be done by the local admin only. The ThinkPad UI is for the
+console audio control to be done through the volume keys only, and for
+the desktop environment to just provide on-screen-display feedback.
+Software volume control should be done only in the main AC97/HDA
+mixer.
+
+
+About the ThinkPad Console Audio control:
+
+ThinkPads have a built-in amplifier and muting circuit that drives the
+console headphone and speakers. This circuit is after the main AC97
+or HDA mixer in the audio path, and under exclusive control of the
+firmware.
+
+ThinkPads have three special hotkeys to interact with the console
+audio control: volume up, volume down and mute.
+
+It is worth noting that the normal way the mute function works (on
+ThinkPads that do not have a "mute LED") is:
+
+1. Press mute to mute. It will *always* mute, you can press it as
+ many times as you want, and the sound will remain mute.
+
+2. Press either volume key to unmute the ThinkPad (it will _not_
+ change the volume, it will just unmute).
+
+This is a very superior design when compared to the cheap software-only
+mute-toggle solution found on normal consumer laptops: you can be
+absolutely sure the ThinkPad will not make noise if you press the mute
+button, no matter the previous state.
+
+The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain
+amplifiers driving the speakers and headphone output, and the firmware
+also handles volume control for the headphone and speakers on these
+ThinkPads without any help from the operating system (this volume
+control stage exists after the main AC97 or HDA mixer in the audio
+path).
+
+The newer Lenovo models only have firmware mute control, and depend on
+the main HDA mixer to do volume control (which is done by the operating
+system). In this case, the volume keys are filtered out for unmute
+key press (there are some firmware bugs in this area) and delivered as
+normal key presses to the operating system (thinkpad-acpi is not
+involved).
+
+
+The ThinkPad-ACPI volume control:
+
+The preferred way to interact with the Console Audio control is the
+ALSA interface.
+
+The legacy procfs interface allows one to read the current state,
+and if volume control is enabled, accepts the following commands:
+
+ echo up >/proc/acpi/ibm/volume
+ echo down >/proc/acpi/ibm/volume
+ echo mute >/proc/acpi/ibm/volume
+ echo unmute >/proc/acpi/ibm/volume
+ echo 'level <level>' >/proc/acpi/ibm/volume
+
+The <level> number range is 0 to 14 although not all of them may be
+distinct. To unmute the volume after the mute command, use either the
+up or down command (the level command will not unmute the volume), or
+the unmute command.
+
+You can use the volume_capabilities parameter to tell the driver
+whether your thinkpad has volume control or mute-only control:
+volume_capabilities=1 for mixers with mute and volume control,
+volume_capabilities=2 for mixers with only mute control.
+
+If the driver misdetects the capabilities for your ThinkPad model,
+please report this to ibm-acpi-devel@lists.sourceforge.net, so that we
+can update the driver.
+
+There are two strategies for volume control. To select which one
+should be used, use the volume_mode module parameter: volume_mode=1
+selects EC mode, and volume_mode=3 selects EC mode with NVRAM backing
+(so that volume/mute changes are remembered across shutdown/reboot).
+
+The driver will operate in volume_mode=3 by default. If that does not
+work well on your ThinkPad model, please report this to
+ibm-acpi-devel@lists.sourceforge.net.
+
+The driver supports the standard ALSA module parameters. If the ALSA
+mixer is disabled, the driver will disable all volume functionality.
+
+
+Fan control and monitoring: fan speed, fan enable/disable
+---------------------------------------------------------
+
+procfs: /proc/acpi/ibm/fan
+sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
+ pwm1_enable, fan2_input
+sysfs hwmon driver attributes: fan_watchdog
+
+NOTE NOTE NOTE: fan control operations are disabled by default for
+safety reasons. To enable them, the module parameter "fan_control=1"
+must be given to thinkpad-acpi.
+
+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, X and Z series ThinkPads but may show a bogus
+value on other models.
+
+Some Lenovo ThinkPads support a secondary fan. This fan cannot be
+controlled separately, it shares the main fan control.
+
+Fan levels:
+
+Most ThinkPad fans work in "levels" at the firmware interface. 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.
+
+There is also a "full-speed" level, also known as "disengaged" level.
+In this level, 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 full-speed level may take up to two minutes to ramp up to
+maximum speed, and in some ThinkPads, the tachometer readings go stale
+while the EC is transitioning to the full-speed level.
+
+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 various 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 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 thinkpad-acpi.
+
+The thinkpad-acpi kernel driver can be programmed to revert the fan
+level to a safe setting if userspace does not issue one of the procfs
+fan commands: "enable", "disable", "level" or "watchdog", or if there
+are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is
+set to 1, manual mode) within a configurable amount of time of up to
+120 seconds. This functionality is called fan safety watchdog.
+
+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" procfs fan
+commands, or the hwmon fan control sysfs interface.
+
+Procfs notes:
+
+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.
+
+The fan level can be controlled with the command:
+
+ echo 'level <level>' > /proc/acpi/ibm/fan
+
+Where <level> is an integer from 0 to 7, or one of the words "auto" or
+"full-speed" (without the quotes). Not all ThinkPads support the "auto"
+and "full-speed" levels. The driver accepts "disengaged" as an alias for
+"full-speed", and reports it as "disengaged" for backwards
+compatibility.
+
+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/fan
+
+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. This functionality
+is incomplete, and not available through the sysfs interface.
+
+To program the safety watchdog, use the "watchdog" command.
+
+ echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan
+
+If you want to disable the watchdog, use 0 as the interval.
+
+Sysfs notes:
+
+The sysfs interface follows the hwmon subsystem guidelines for the most
+part, and the exception is the fan safety watchdog.
+
+Writes to any of the sysfs attributes may return the EINVAL error if
+that operation is not supported in a given ThinkPad or if the parameter
+is out-of-bounds, and EPERM if it is forbidden. They may also return
+EINTR (interrupted system call), and EIO (I/O error while trying to talk
+to the firmware).
+
+Features not yet implemented by the driver return ENOSYS.
+
+hwmon device attribute pwm1_enable:
+ 0: PWM offline (fan is set to full-speed mode)
+ 1: Manual PWM control (use pwm1 to set fan level)
+ 2: Hardware PWM control (EC "auto" mode)
+ 3: reserved (Software PWM control, not implemented yet)
+
+ Modes 0 and 2 are not supported by all ThinkPads, and the
+ driver is not always able to detect this. If it does know a
+ mode is unsupported, it will return -EINVAL.
+
+hwmon device attribute pwm1:
+ Fan level, scaled from the firmware values of 0-7 to the hwmon
+ scale of 0-255. 0 means fan stopped, 255 means highest normal
+ speed (level 7).
+
+ This attribute only commands the fan if pmw1_enable is set to 1
+ (manual PWM control).
+
+hwmon device attribute fan1_input:
+ Fan tachometer reading, in RPM. May go stale on certain
+ ThinkPads while the EC transitions the PWM to offline mode,
+ which can take up to two minutes. May return rubbish on older
+ ThinkPads.
+
+hwmon device attribute fan2_input:
+ Fan tachometer reading, in RPM, for the secondary fan.
+ Available only on some ThinkPads. If the secondary fan is
+ not installed, will always read 0.
+
+hwmon driver attribute fan_watchdog:
+ Fan safety watchdog timer interval, in seconds. Minimum is
+ 1 second, maximum is 120 seconds. 0 disables the watchdog.
+
+To stop the fan: set pwm1 to zero, and pwm1_enable to 1.
+
+To start the fan in a safe mode: set pwm1_enable to 2. If that fails
+with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255
+would be the safest choice, though).
+
+
+WAN
+---
+
+procfs: /proc/acpi/ibm/wan
+sysfs device attribute: wwan_enable (deprecated)
+sysfs rfkill class: switch "tpacpi_wwan_sw"
+
+This feature shows the presence and current state of the built-in
+Wireless WAN device.
+
+If the ThinkPad supports it, the WWAN state is stored in NVRAM,
+so it is kept across reboots and power-off.
+
+It was tested on a Lenovo ThinkPad X60. It should probably work on other
+ThinkPad models which come with this module installed.
+
+Procfs notes:
+
+If the W-WAN card is installed, the following commands can be used:
+
+ echo enable > /proc/acpi/ibm/wan
+ echo disable > /proc/acpi/ibm/wan
+
+Sysfs notes:
+
+ If the W-WAN card is installed, it can be enabled /
+ disabled through the "wwan_enable" thinkpad-acpi device
+ attribute, and its current status can also be queried.
+
+ enable:
+ 0: disables WWAN card / WWAN card is disabled
+ 1: enables WWAN card / WWAN card is enabled.
+
+ Note: this interface has been superseded by the generic rfkill
+ class. It has been deprecated, and it will be removed in year
+ 2010.
+
+ rfkill controller switch "tpacpi_wwan_sw": refer to
+ Documentation/rfkill.txt for details.
+
+
+EXPERIMENTAL: UWB
+-----------------
+
+This feature is considered EXPERIMENTAL because it has not been extensively
+tested and validated in various ThinkPad models yet. The feature may not
+work as expected. USE WITH CAUTION! To use this feature, you need to supply
+the experimental=1 parameter when loading the module.
+
+sysfs rfkill class: switch "tpacpi_uwb_sw"
+
+This feature exports an rfkill controller for the UWB device, if one is
+present and enabled in the BIOS.
+
+Sysfs notes:
+
+ rfkill controller switch "tpacpi_uwb_sw": refer to
+ Documentation/rfkill.txt for details.
+
+Adaptive keyboard
+-----------------
+
+sysfs device attribute: adaptive_kbd_mode
+
+This sysfs attribute controls the keyboard "face" that will be shown on the
+Lenovo X1 Carbon 2nd gen (2014)'s adaptive keyboard. The value can be read
+and set.
+
+1 = Home mode
+2 = Web-browser mode
+3 = Web-conference mode
+4 = Function mode
+5 = Layflat mode
+
+For more details about which buttons will appear depending on the mode, please
+review the laptop's user guide:
+http://www.lenovo.com/shop/americas/content/user_guides/x1carbon_2_ug_en.pdf
+
+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 thinkpad-acpi module,
+for example:
+
+ modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable
+
+
+Enabling debugging output
+-------------------------
+
+The module takes a debug parameter which can be used to selectively
+enable various classes of debugging output, for example:
+
+ modprobe thinkpad_acpi debug=0xffff
+
+will enable all debugging output classes. It takes a bitmask, so
+to enable more than one output class, just add their values.
+
+ Debug bitmask Description
+ 0x8000 Disclose PID of userspace programs
+ accessing some functions of the driver
+ 0x0001 Initialization and probing
+ 0x0002 Removal
+ 0x0004 RF Transmitter control (RFKILL)
+ (bluetooth, WWAN, UWB...)
+ 0x0008 HKEY event interface, hotkeys
+ 0x0010 Fan control
+ 0x0020 Backlight brightness
+ 0x0040 Audio mixer/volume control
+
+There is also a kernel build option to enable more debugging
+information, which may be necessary to debug driver problems.
+
+The level of debugging information output by the driver can be changed
+at runtime through sysfs, using the driver attribute debug_level. The
+attribute takes the same bitmask as the debug module parameter above.
+
+
+Force loading of module
+-----------------------
+
+If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
+the module parameter force_load=1. Regardless of whether this works or
+not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.
+
+
+Sysfs interface changelog:
+
+0x000100: Initial sysfs support, as a single platform driver and
+ device.
+0x000200: Hot key support for 32 hot keys, and radio slider switch
+ support.
+0x010000: Hot keys are now handled by default over the input
+ layer, the radio switch generates input event EV_RADIO,
+ and the driver enables hot key handling by default in
+ the firmware.
+
+0x020000: ABI fix: added a separate hwmon platform device and
+ driver, which must be located by name (thinkpad)
+ and the hwmon class for libsensors4 (lm-sensors 3)
+ compatibility. Moved all hwmon attributes to this
+ new platform device.
+
+0x020100: Marker for thinkpad-acpi with hot key NVRAM polling
+ support. If you must, use it to know you should not
+ start a userspace NVRAM poller (allows to detect when
+ NVRAM is compiled out by the user because it is
+ unneeded/undesired in the first place).
+0x020101: Marker for thinkpad-acpi with hot key NVRAM polling
+ and proper hotkey_mask semantics (version 8 of the
+ NVRAM polling patch). Some development snapshots of
+ 0.18 had an earlier version that did strange things
+ to hotkey_mask.
+
+0x020200: Add poll()/select() support to the following attributes:
+ hotkey_radio_sw, wakeup_hotunplug_complete, wakeup_reason
+
+0x020300: hotkey enable/disable support removed, attributes
+ hotkey_bios_enabled and hotkey_enable deprecated and
+ marked for removal.
+
+0x020400: Marker for 16 LEDs support. Also, LEDs that are known
+ to not exist in a given model are not registered with
+ the LED sysfs class anymore.
+
+0x020500: Updated hotkey driver, hotkey_mask is always available
+ and it is always able to disable hot keys. Very old
+ thinkpads are properly supported. hotkey_bios_mask
+ is deprecated and marked for removal.
+
+0x020600: Marker for backlight change event support.
+
+0x020700: Support for mute-only mixers.
+ Volume control in read-only mode by default.
+ Marker for ALSA mixer support.
+
+0x030000: Thermal and fan sysfs attributes were moved to the hwmon
+ device instead of being attached to the backing platform
+ device.