Merge tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media

Pull rst conversion of docs from Mauro Carvalho Chehab:
 "As agreed with Jon, I'm sending this big series directly to you, c/c
  him, as this series required a special care, in order to avoid
  conflicts with other trees"

* tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (77 commits)
  docs: kbuild: fix build with pdf and fix some minor issues
  docs: block: fix pdf output
  docs: arm: fix a breakage with pdf output
  docs: don't use nested tables
  docs: gpio: add sysfs interface to the admin-guide
  docs: locking: add it to the main index
  docs: add some directories to the main documentation index
  docs: add SPDX tags to new index files
  docs: add a memory-devices subdir to driver-api
  docs: phy: place documentation under driver-api
  docs: serial: move it to the driver-api
  docs: driver-api: add remaining converted dirs to it
  docs: driver-api: add xilinx driver API documentation
  docs: driver-api: add a series of orphaned documents
  docs: admin-guide: add a series of orphaned documents
  docs: cgroup-v1: add it to the admin-guide book
  docs: aoe: add it to the driver-api book
  docs: add some documentation dirs to the driver-api book
  docs: driver-model: move it to the driver-api book
  docs: lp855x-driver.rst: add it to the driver-api book
  ...

1 files changed, 1562 insertions, 0 deletions

diff --git a/Documentation/admin-guide/laptops/thinkpad-acpi.rst b/Documentation/admin-guide/laptops/thinkpad-acpi.rst
new file mode 100644
index 000000000000..adea0bf2acc5
--- /dev/null
+++ b/Documentation/admin-guide/laptops/thinkpad-acpi.rst
@@ -0,0 +1,1562 @@
+===========================
+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
+0x6032		Thermal Control command set completion  (DYTC, Windows)
+0x6040		Nvidia Optimus/AC adapter related (TO BE VERIFIED)
+0x60C0		X1 Yoga 2016, Tablet mode status changed
+0x60F0		Thermal Transformation changed (GMTS, Windows)
+======		=====================================================
+
+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/driver-api/rfkill.rst 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.rst.  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.rst.
+
+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/driver-api/rfkill.rst 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/driver-api/rfkill.rst 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.
+=========	===============================================================