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thinkpad-acpi.rst (60386B)


      1===========================
      2ThinkPad ACPI Extras Driver
      3===========================
      4
      5Version 0.25
      6
      7October 16th,  2013
      8
      9- Borislav Deianov <borislav@users.sf.net>
     10- Henrique de Moraes Holschuh <hmh@hmh.eng.br>
     11
     12http://ibm-acpi.sf.net/
     13
     14This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It
     15supports various features of these laptops which are accessible
     16through the ACPI and ACPI EC framework, but not otherwise fully
     17supported by the generic Linux ACPI drivers.
     18
     19This driver used to be named ibm-acpi until kernel 2.6.21 and release
     200.13-20070314.  It used to be in the drivers/acpi tree, but it was
     21moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel
     222.6.22, and release 0.14.  It was moved to drivers/platform/x86 for
     23kernel 2.6.29 and release 0.22.
     24
     25The driver is named "thinkpad-acpi".  In some places, like module
     26names and log messages, "thinkpad_acpi" is used because of userspace
     27issues.
     28
     29"tpacpi" is used as a shorthand where "thinkpad-acpi" would be too
     30long due to length limitations on some Linux kernel versions.
     31
     32Status
     33------
     34
     35The features currently supported are the following (see below for
     36detailed description):
     37
     38	- Fn key combinations
     39	- Bluetooth enable and disable
     40	- video output switching, expansion control
     41	- ThinkLight on and off
     42	- CMOS/UCMS control
     43	- LED control
     44	- ACPI sounds
     45	- temperature sensors
     46	- Experimental: embedded controller register dump
     47	- LCD brightness control
     48	- Volume control
     49	- Fan control and monitoring: fan speed, fan enable/disable
     50	- WAN enable and disable
     51	- UWB enable and disable
     52	- LCD Shadow (PrivacyGuard) enable and disable
     53	- Lap mode sensor
     54	- Setting keyboard language
     55	- WWAN Antenna type
     56
     57A compatibility table by model and feature is maintained on the web
     58site, http://ibm-acpi.sf.net/. I appreciate any success or failure
     59reports, especially if they add to or correct the compatibility table.
     60Please include the following information in your report:
     61
     62	- ThinkPad model name
     63	- a copy of your ACPI tables, using the "acpidump" utility
     64	- a copy of the output of dmidecode, with serial numbers
     65	  and UUIDs masked off
     66	- which driver features work and which don't
     67	- the observed behavior of non-working features
     68
     69Any other comments or patches are also more than welcome.
     70
     71
     72Installation
     73------------
     74
     75If you are compiling this driver as included in the Linux kernel
     76sources, look for the CONFIG_THINKPAD_ACPI Kconfig option.
     77It is located on the menu path: "Device Drivers" -> "X86 Platform
     78Specific Device Drivers" -> "ThinkPad ACPI Laptop Extras".
     79
     80
     81Features
     82--------
     83
     84The driver exports two different interfaces to userspace, which can be
     85used to access the features it provides.  One is a legacy procfs-based
     86interface, which will be removed at some time in the future.  The other
     87is a new sysfs-based interface which is not complete yet.
     88
     89The procfs interface creates the /proc/acpi/ibm directory.  There is a
     90file under that directory for each feature it supports.  The procfs
     91interface is mostly frozen, and will change very little if at all: it
     92will not be extended to add any new functionality in the driver, instead
     93all new functionality will be implemented on the sysfs interface.
     94
     95The sysfs interface tries to blend in the generic Linux sysfs subsystems
     96and classes as much as possible.  Since some of these subsystems are not
     97yet ready or stabilized, it is expected that this interface will change,
     98and any and all userspace programs must deal with it.
     99
    100
    101Notes about the sysfs interface
    102^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    103
    104Unlike what was done with the procfs interface, correctness when talking
    105to the sysfs interfaces will be enforced, as will correctness in the
    106thinkpad-acpi's implementation of sysfs interfaces.
    107
    108Also, any bugs in the thinkpad-acpi sysfs driver code or in the
    109thinkpad-acpi's implementation of the sysfs interfaces will be fixed for
    110maximum correctness, even if that means changing an interface in
    111non-compatible ways.  As these interfaces mature both in the kernel and
    112in thinkpad-acpi, such changes should become quite rare.
    113
    114Applications interfacing to the thinkpad-acpi sysfs interfaces must
    115follow all sysfs guidelines and correctly process all errors (the sysfs
    116interface makes extensive use of errors).  File descriptors and open /
    117close operations to the sysfs inodes must also be properly implemented.
    118
    119The version of thinkpad-acpi's sysfs interface is exported by the driver
    120as a driver attribute (see below).
    121
    122Sysfs driver attributes are on the driver's sysfs attribute space,
    123for 2.6.23+ this is /sys/bus/platform/drivers/thinkpad_acpi/ and
    124/sys/bus/platform/drivers/thinkpad_hwmon/
    125
    126Sysfs device attributes are on the thinkpad_acpi device sysfs attribute
    127space, for 2.6.23+ this is /sys/devices/platform/thinkpad_acpi/.
    128
    129Sysfs device attributes for the sensors and fan are on the
    130thinkpad_hwmon device's sysfs attribute space, but you should locate it
    131looking for a hwmon device with the name attribute of "thinkpad", or
    132better yet, through libsensors. For 4.14+ sysfs attributes were moved to the
    133hwmon device (/sys/bus/platform/devices/thinkpad_hwmon/hwmon/hwmon? or
    134/sys/class/hwmon/hwmon?).
    135
    136Driver version
    137--------------
    138
    139procfs: /proc/acpi/ibm/driver
    140
    141sysfs driver attribute: version
    142
    143The driver name and version. No commands can be written to this file.
    144
    145
    146Sysfs interface version
    147-----------------------
    148
    149sysfs driver attribute: interface_version
    150
    151Version of the thinkpad-acpi sysfs interface, as an unsigned long
    152(output in hex format: 0xAAAABBCC), where:
    153
    154	AAAA
    155	  - major revision
    156	BB
    157	  - minor revision
    158	CC
    159	  - bugfix revision
    160
    161The sysfs interface version changelog for the driver can be found at the
    162end of this document.  Changes to the sysfs interface done by the kernel
    163subsystems are not documented here, nor are they tracked by this
    164attribute.
    165
    166Changes to the thinkpad-acpi sysfs interface are only considered
    167non-experimental when they are submitted to Linux mainline, at which
    168point the changes in this interface are documented and interface_version
    169may be updated.  If you are using any thinkpad-acpi features not yet
    170sent to mainline for merging, you do so on your own risk: these features
    171may disappear, or be implemented in a different and incompatible way by
    172the time they are merged in Linux mainline.
    173
    174Changes that are backwards-compatible by nature (e.g. the addition of
    175attributes that do not change the way the other attributes work) do not
    176always warrant an update of interface_version.  Therefore, one must
    177expect that an attribute might not be there, and deal with it properly
    178(an attribute not being there *is* a valid way to make it clear that a
    179feature is not available in sysfs).
    180
    181
    182Hot keys
    183--------
    184
    185procfs: /proc/acpi/ibm/hotkey
    186
    187sysfs device attribute: hotkey_*
    188
    189In a ThinkPad, the ACPI HKEY handler is responsible for communicating
    190some important events and also keyboard hot key presses to the operating
    191system.  Enabling the hotkey functionality of thinkpad-acpi signals the
    192firmware that such a driver is present, and modifies how the ThinkPad
    193firmware will behave in many situations.
    194
    195The driver enables the HKEY ("hot key") event reporting automatically
    196when loaded, and disables it when it is removed.
    197
    198The driver will report HKEY events in the following format::
    199
    200	ibm/hotkey HKEY 00000080 0000xxxx
    201
    202Some of these events refer to hot key presses, but not all of them.
    203
    204The driver will generate events over the input layer for hot keys and
    205radio switches, and over the ACPI netlink layer for other events.  The
    206input layer support accepts the standard IOCTLs to remap the keycodes
    207assigned to each hot key.
    208
    209The hot key bit mask allows some control over which hot keys generate
    210events.  If a key is "masked" (bit set to 0 in the mask), the firmware
    211will handle it.  If it is "unmasked", it signals the firmware that
    212thinkpad-acpi would prefer to handle it, if the firmware would be so
    213kind to allow it (and it often doesn't!).
    214
    215Not all bits in the mask can be modified.  Not all bits that can be
    216modified do anything.  Not all hot keys can be individually controlled
    217by the mask.  Some models do not support the mask at all.  The behaviour
    218of the mask is, therefore, highly dependent on the ThinkPad model.
    219
    220The driver will filter out any unmasked hotkeys, so even if the firmware
    221doesn't allow disabling an specific hotkey, the driver will not report
    222events for unmasked hotkeys.
    223
    224Note that unmasking some keys prevents their default behavior.  For
    225example, if Fn+F5 is unmasked, that key will no longer enable/disable
    226Bluetooth by itself in firmware.
    227
    228Note also that not all Fn key combinations are supported through ACPI
    229depending on the ThinkPad model and firmware version.  On those
    230ThinkPads, it is still possible to support some extra hotkeys by
    231polling the "CMOS NVRAM" at least 10 times per second.  The driver
    232attempts to enables this functionality automatically when required.
    233
    234procfs notes
    235^^^^^^^^^^^^
    236
    237The following commands can be written to the /proc/acpi/ibm/hotkey file::
    238
    239	echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
    240	echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
    241	... any other 8-hex-digit mask ...
    242	echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask
    243
    244The following commands have been deprecated and will cause the kernel
    245to log a warning::
    246
    247	echo enable > /proc/acpi/ibm/hotkey -- does nothing
    248	echo disable > /proc/acpi/ibm/hotkey -- returns an error
    249
    250The procfs interface does not support NVRAM polling control.  So as to
    251maintain maximum bug-to-bug compatibility, it does not report any masks,
    252nor does it allow one to manipulate the hot key mask when the firmware
    253does not support masks at all, even if NVRAM polling is in use.
    254
    255sysfs notes
    256^^^^^^^^^^^
    257
    258	hotkey_bios_enabled:
    259		DEPRECATED, WILL BE REMOVED SOON.
    260
    261		Returns 0.
    262
    263	hotkey_bios_mask:
    264		DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE.
    265
    266		Returns the hot keys mask when thinkpad-acpi was loaded.
    267		Upon module unload, the hot keys mask will be restored
    268		to this value.   This is always 0x80c, because those are
    269		the hotkeys that were supported by ancient firmware
    270		without mask support.
    271
    272	hotkey_enable:
    273		DEPRECATED, WILL BE REMOVED SOON.
    274
    275		0: returns -EPERM
    276		1: does nothing
    277
    278	hotkey_mask:
    279		bit mask to enable reporting (and depending on
    280		the firmware, ACPI event generation) for each hot key
    281		(see above).  Returns the current status of the hot keys
    282		mask, and allows one to modify it.
    283
    284	hotkey_all_mask:
    285		bit mask that should enable event reporting for all
    286		supported hot keys, when echoed to hotkey_mask above.
    287		Unless you know which events need to be handled
    288		passively (because the firmware *will* handle them
    289		anyway), do *not* use hotkey_all_mask.  Use
    290		hotkey_recommended_mask, instead. You have been warned.
    291
    292	hotkey_recommended_mask:
    293		bit mask that should enable event reporting for all
    294		supported hot keys, except those which are always
    295		handled by the firmware anyway.  Echo it to
    296		hotkey_mask above, to use.  This is the default mask
    297		used by the driver.
    298
    299	hotkey_source_mask:
    300		bit mask that selects which hot keys will the driver
    301		poll the NVRAM for.  This is auto-detected by the driver
    302		based on the capabilities reported by the ACPI firmware,
    303		but it can be overridden at runtime.
    304
    305		Hot keys whose bits are set in hotkey_source_mask are
    306		polled for in NVRAM, and reported as hotkey events if
    307		enabled in hotkey_mask.  Only a few hot keys are
    308		available through CMOS NVRAM polling.
    309
    310		Warning: when in NVRAM mode, the volume up/down/mute
    311		keys are synthesized according to changes in the mixer,
    312		which uses a single volume up or volume down hotkey
    313		press to unmute, as per the ThinkPad volume mixer user
    314		interface.  When in ACPI event mode, volume up/down/mute
    315		events are reported by the firmware and can behave
    316		differently (and that behaviour changes with firmware
    317		version -- not just with firmware models -- as well as
    318		OSI(Linux) state).
    319
    320	hotkey_poll_freq:
    321		frequency in Hz for hot key polling. It must be between
    322		0 and 25 Hz.  Polling is only carried out when strictly
    323		needed.
    324
    325		Setting hotkey_poll_freq to zero disables polling, and
    326		will cause hot key presses that require NVRAM polling
    327		to never be reported.
    328
    329		Setting hotkey_poll_freq too low may cause repeated
    330		pressings of the same hot key to be misreported as a
    331		single key press, or to not even be detected at all.
    332		The recommended polling frequency is 10Hz.
    333
    334	hotkey_radio_sw:
    335		If the ThinkPad has a hardware radio switch, this
    336		attribute will read 0 if the switch is in the "radios
    337		disabled" position, and 1 if the switch is in the
    338		"radios enabled" position.
    339
    340		This attribute has poll()/select() support.
    341
    342	hotkey_tablet_mode:
    343		If the ThinkPad has tablet capabilities, this attribute
    344		will read 0 if the ThinkPad is in normal mode, and
    345		1 if the ThinkPad is in tablet mode.
    346
    347		This attribute has poll()/select() support.
    348
    349	wakeup_reason:
    350		Set to 1 if the system is waking up because the user
    351		requested a bay ejection.  Set to 2 if the system is
    352		waking up because the user requested the system to
    353		undock.  Set to zero for normal wake-ups or wake-ups
    354		due to unknown reasons.
    355
    356		This attribute has poll()/select() support.
    357
    358	wakeup_hotunplug_complete:
    359		Set to 1 if the system was waken up because of an
    360		undock or bay ejection request, and that request
    361		was successfully completed.  At this point, it might
    362		be useful to send the system back to sleep, at the
    363		user's choice.  Refer to HKEY events 0x4003 and
    364		0x3003, below.
    365
    366		This attribute has poll()/select() support.
    367
    368input layer notes
    369^^^^^^^^^^^^^^^^^
    370
    371A Hot key is mapped to a single input layer EV_KEY event, possibly
    372followed by an EV_MSC MSC_SCAN event that shall contain that key's scan
    373code.  An EV_SYN event will always be generated to mark the end of the
    374event block.
    375
    376Do not use the EV_MSC MSC_SCAN events to process keys.  They are to be
    377used as a helper to remap keys, only.  They are particularly useful when
    378remapping KEY_UNKNOWN keys.
    379
    380The events are available in an input device, with the following id:
    381
    382	==============  ==============================
    383	Bus		BUS_HOST
    384	vendor		0x1014 (PCI_VENDOR_ID_IBM)  or
    385			0x17aa (PCI_VENDOR_ID_LENOVO)
    386	product		0x5054 ("TP")
    387	version		0x4101
    388	==============  ==============================
    389
    390The version will have its LSB incremented if the keymap changes in a
    391backwards-compatible way.  The MSB shall always be 0x41 for this input
    392device.  If the MSB is not 0x41, do not use the device as described in
    393this section, as it is either something else (e.g. another input device
    394exported by a thinkpad driver, such as HDAPS) or its functionality has
    395been changed in a non-backwards compatible way.
    396
    397Adding other event types for other functionalities shall be considered a
    398backwards-compatible change for this input device.
    399
    400Thinkpad-acpi Hot Key event map (version 0x4101):
    401
    402=======	=======	==============	==============================================
    403ACPI	Scan
    404event	code	Key		Notes
    405=======	=======	==============	==============================================
    4060x1001	0x00	FN+F1		-
    407
    4080x1002	0x01	FN+F2		IBM: battery (rare)
    409				Lenovo: Screen lock
    410
    4110x1003	0x02	FN+F3		Many IBM models always report
    412				this hot key, even with hot keys
    413				disabled or with Fn+F3 masked
    414				off
    415				IBM: screen lock, often turns
    416				off the ThinkLight as side-effect
    417				Lenovo: battery
    418
    4190x1004	0x03	FN+F4		Sleep button (ACPI sleep button
    420				semantics, i.e. sleep-to-RAM).
    421				It always generates some kind
    422				of event, either the hot key
    423				event or an ACPI sleep button
    424				event. The firmware may
    425				refuse to generate further FN+F4
    426				key presses until a S3 or S4 ACPI
    427				sleep cycle is performed or some
    428				time passes.
    429
    4300x1005	0x04	FN+F5		Radio.  Enables/disables
    431				the internal Bluetooth hardware
    432				and W-WAN card if left in control
    433				of the firmware.  Does not affect
    434				the WLAN card.
    435				Should be used to turn on/off all
    436				radios (Bluetooth+W-WAN+WLAN),
    437				really.
    438
    4390x1006	0x05	FN+F6		-
    440
    4410x1007	0x06	FN+F7		Video output cycle.
    442				Do you feel lucky today?
    443
    4440x1008	0x07	FN+F8		IBM: toggle screen expand
    445				Lenovo: configure UltraNav,
    446				or toggle screen expand
    447
    4480x1009	0x08	FN+F9		-
    449
    450...	...	...		...
    451
    4520x100B	0x0A	FN+F11		-
    453
    4540x100C	0x0B	FN+F12		Sleep to disk.  You are always
    455				supposed to handle it yourself,
    456				either through the ACPI event,
    457				or through a hotkey event.
    458				The firmware may refuse to
    459				generate further FN+F12 key
    460				press events until a S3 or S4
    461				ACPI sleep cycle is performed,
    462				or some time passes.
    463
    4640x100D	0x0C	FN+BACKSPACE	-
    4650x100E	0x0D	FN+INSERT	-
    4660x100F	0x0E	FN+DELETE	-
    467
    4680x1010	0x0F	FN+HOME		Brightness up.  This key is
    469				always handled by the firmware
    470				in IBM ThinkPads, even when
    471				unmasked.  Just leave it alone.
    472				For Lenovo ThinkPads with a new
    473				BIOS, it has to be handled either
    474				by the ACPI OSI, or by userspace.
    475				The driver does the right thing,
    476				never mess with this.
    4770x1011	0x10	FN+END		Brightness down.  See brightness
    478				up for details.
    479
    4800x1012	0x11	FN+PGUP		ThinkLight toggle.  This key is
    481				always handled by the firmware,
    482				even when unmasked.
    483
    4840x1013	0x12	FN+PGDOWN	-
    485
    4860x1014	0x13	FN+SPACE	Zoom key
    487
    4880x1015	0x14	VOLUME UP	Internal mixer volume up. This
    489				key is always handled by the
    490				firmware, even when unmasked.
    491				NOTE: Lenovo seems to be changing
    492				this.
    4930x1016	0x15	VOLUME DOWN	Internal mixer volume up. This
    494				key is always handled by the
    495				firmware, even when unmasked.
    496				NOTE: Lenovo seems to be changing
    497				this.
    4980x1017	0x16	MUTE		Mute internal mixer. This
    499				key is always handled by the
    500				firmware, even when unmasked.
    501
    5020x1018	0x17	THINKPAD	ThinkPad/Access IBM/Lenovo key
    503
    5040x1019	0x18	unknown
    505
    506...	...	...
    507
    5080x1020	0x1F	unknown
    509=======	=======	==============	==============================================
    510
    511The ThinkPad firmware does not allow one to differentiate when most hot
    512keys are pressed or released (either that, or we don't know how to, yet).
    513For these keys, the driver generates a set of events for a key press and
    514immediately issues the same set of events for a key release.  It is
    515unknown by the driver if the ThinkPad firmware triggered these events on
    516hot key press or release, but the firmware will do it for either one, not
    517both.
    518
    519If a key is mapped to KEY_RESERVED, it generates no input events at all.
    520If a key is mapped to KEY_UNKNOWN, it generates an input event that
    521includes an scan code.  If a key is mapped to anything else, it will
    522generate input device EV_KEY events.
    523
    524In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW
    525events for switches:
    526
    527==============	==============================================
    528SW_RFKILL_ALL	T60 and later hardware rfkill rocker switch
    529SW_TABLET_MODE	Tablet ThinkPads HKEY events 0x5009 and 0x500A
    530==============	==============================================
    531
    532Non hotkey ACPI HKEY event map
    533------------------------------
    534
    535Events that are never propagated by the driver:
    536
    537======		==================================================
    5380x2304		System is waking up from suspend to undock
    5390x2305		System is waking up from suspend to eject bay
    5400x2404		System is waking up from hibernation to undock
    5410x2405		System is waking up from hibernation to eject bay
    5420x5001		Lid closed
    5430x5002		Lid opened
    5440x5009		Tablet swivel: switched to tablet mode
    5450x500A		Tablet swivel: switched to normal mode
    5460x5010		Brightness level changed/control event
    5470x6000		KEYBOARD: Numlock key pressed
    5480x6005		KEYBOARD: Fn key pressed (TO BE VERIFIED)
    5490x7000		Radio Switch may have changed state
    550======		==================================================
    551
    552
    553Events that are propagated by the driver to userspace:
    554
    555======		=====================================================
    5560x2313		ALARM: System is waking up from suspend because
    557		the battery is nearly empty
    5580x2413		ALARM: System is waking up from hibernation because
    559		the battery is nearly empty
    5600x3003		Bay ejection (see 0x2x05) complete, can sleep again
    5610x3006		Bay hotplug request (hint to power up SATA link when
    562		the optical drive tray is ejected)
    5630x4003		Undocked (see 0x2x04), can sleep again
    5640x4010		Docked into hotplug port replicator (non-ACPI dock)
    5650x4011		Undocked from hotplug port replicator (non-ACPI dock)
    5660x500B		Tablet pen inserted into its storage bay
    5670x500C		Tablet pen removed from its storage bay
    5680x6011		ALARM: battery is too hot
    5690x6012		ALARM: battery is extremely hot
    5700x6021		ALARM: a sensor is too hot
    5710x6022		ALARM: a sensor is extremely hot
    5720x6030		System thermal table changed
    5730x6032		Thermal Control command set completion  (DYTC, Windows)
    5740x6040		Nvidia Optimus/AC adapter related (TO BE VERIFIED)
    5750x60C0		X1 Yoga 2016, Tablet mode status changed
    5760x60F0		Thermal Transformation changed (GMTS, Windows)
    577======		=====================================================
    578
    579Battery nearly empty alarms are a last resort attempt to get the
    580operating system to hibernate or shutdown cleanly (0x2313), or shutdown
    581cleanly (0x2413) before power is lost.  They must be acted upon, as the
    582wake up caused by the firmware will have negated most safety nets...
    583
    584When any of the "too hot" alarms happen, according to Lenovo the user
    585should suspend or hibernate the laptop (and in the case of battery
    586alarms, unplug the AC adapter) to let it cool down.  These alarms do
    587signal that something is wrong, they should never happen on normal
    588operating conditions.
    589
    590The "extremely hot" alarms are emergencies.  According to Lenovo, the
    591operating system is to force either an immediate suspend or hibernate
    592cycle, or a system shutdown.  Obviously, something is very wrong if this
    593happens.
    594
    595
    596Brightness hotkey notes
    597^^^^^^^^^^^^^^^^^^^^^^^
    598
    599Don't mess with the brightness hotkeys in a Thinkpad.  If you want
    600notifications for OSD, use the sysfs backlight class event support.
    601
    602The driver will issue KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN events
    603automatically for the cases were userspace has to do something to
    604implement brightness changes.  When you override these events, you will
    605either fail to handle properly the ThinkPads that require explicit
    606action to change backlight brightness, or the ThinkPads that require
    607that no action be taken to work properly.
    608
    609
    610Bluetooth
    611---------
    612
    613procfs: /proc/acpi/ibm/bluetooth
    614
    615sysfs device attribute: bluetooth_enable (deprecated)
    616
    617sysfs rfkill class: switch "tpacpi_bluetooth_sw"
    618
    619This feature shows the presence and current state of a ThinkPad
    620Bluetooth device in the internal ThinkPad CDC slot.
    621
    622If the ThinkPad supports it, the Bluetooth state is stored in NVRAM,
    623so it is kept across reboots and power-off.
    624
    625Procfs notes
    626^^^^^^^^^^^^
    627
    628If Bluetooth is installed, the following commands can be used::
    629
    630	echo enable > /proc/acpi/ibm/bluetooth
    631	echo disable > /proc/acpi/ibm/bluetooth
    632
    633Sysfs notes
    634^^^^^^^^^^^
    635
    636	If the Bluetooth CDC card is installed, it can be enabled /
    637	disabled through the "bluetooth_enable" thinkpad-acpi device
    638	attribute, and its current status can also be queried.
    639
    640	enable:
    641
    642		- 0: disables Bluetooth / Bluetooth is disabled
    643		- 1: enables Bluetooth / Bluetooth is enabled.
    644
    645	Note: this interface has been superseded by the	generic rfkill
    646	class.  It has been deprecated, and it will be removed in year
    647	2010.
    648
    649	rfkill controller switch "tpacpi_bluetooth_sw": refer to
    650	Documentation/driver-api/rfkill.rst for details.
    651
    652
    653Video output control -- /proc/acpi/ibm/video
    654--------------------------------------------
    655
    656This feature allows control over the devices used for video output -
    657LCD, CRT or DVI (if available). The following commands are available::
    658
    659	echo lcd_enable > /proc/acpi/ibm/video
    660	echo lcd_disable > /proc/acpi/ibm/video
    661	echo crt_enable > /proc/acpi/ibm/video
    662	echo crt_disable > /proc/acpi/ibm/video
    663	echo dvi_enable > /proc/acpi/ibm/video
    664	echo dvi_disable > /proc/acpi/ibm/video
    665	echo auto_enable > /proc/acpi/ibm/video
    666	echo auto_disable > /proc/acpi/ibm/video
    667	echo expand_toggle > /proc/acpi/ibm/video
    668	echo video_switch > /proc/acpi/ibm/video
    669
    670NOTE:
    671  Access to this feature is restricted to processes owning the
    672  CAP_SYS_ADMIN capability for safety reasons, as it can interact badly
    673  enough with some versions of X.org to crash it.
    674
    675Each video output device can be enabled or disabled individually.
    676Reading /proc/acpi/ibm/video shows the status of each device.
    677
    678Automatic video switching can be enabled or disabled.  When automatic
    679video switching is enabled, certain events (e.g. opening the lid,
    680docking or undocking) cause the video output device to change
    681automatically. While this can be useful, it also causes flickering
    682and, on the X40, video corruption. By disabling automatic switching,
    683the flickering or video corruption can be avoided.
    684
    685The video_switch command cycles through the available video outputs
    686(it simulates the behavior of Fn-F7).
    687
    688Video expansion can be toggled through this feature. This controls
    689whether the display is expanded to fill the entire LCD screen when a
    690mode with less than full resolution is used. Note that the current
    691video expansion status cannot be determined through this feature.
    692
    693Note that on many models (particularly those using Radeon graphics
    694chips) the X driver configures the video card in a way which prevents
    695Fn-F7 from working. This also disables the video output switching
    696features of this driver, as it uses the same ACPI methods as
    697Fn-F7. Video switching on the console should still work.
    698
    699UPDATE: refer to https://bugs.freedesktop.org/show_bug.cgi?id=2000
    700
    701
    702ThinkLight control
    703------------------
    704
    705procfs: /proc/acpi/ibm/light
    706
    707sysfs attributes: as per LED class, for the "tpacpi::thinklight" LED
    708
    709procfs notes
    710^^^^^^^^^^^^
    711
    712The ThinkLight status can be read and set through the procfs interface.  A
    713few models which do not make the status available will show the ThinkLight
    714status as "unknown". The available commands are::
    715
    716	echo on  > /proc/acpi/ibm/light
    717	echo off > /proc/acpi/ibm/light
    718
    719sysfs notes
    720^^^^^^^^^^^
    721
    722The ThinkLight sysfs interface is documented by the LED class
    723documentation, in Documentation/leds/leds-class.rst.  The ThinkLight LED name
    724is "tpacpi::thinklight".
    725
    726Due to limitations in the sysfs LED class, if the status of the ThinkLight
    727cannot be read or if it is unknown, thinkpad-acpi will report it as "off".
    728It is impossible to know if the status returned through sysfs is valid.
    729
    730
    731CMOS/UCMS control
    732-----------------
    733
    734procfs: /proc/acpi/ibm/cmos
    735
    736sysfs device attribute: cmos_command
    737
    738This feature is mostly used internally by the ACPI firmware to keep the legacy
    739CMOS NVRAM bits in sync with the current machine state, and to record this
    740state so that the ThinkPad will retain such settings across reboots.
    741
    742Some of these commands actually perform actions in some ThinkPad models, but
    743this is expected to disappear more and more in newer models.  As an example, in
    744a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for
    745real, but commands 0 to 2 don't control the mixer anymore (they have been
    746phased out) and just update the NVRAM.
    747
    748The range of valid cmos command numbers is 0 to 21, but not all have an
    749effect and the behavior varies from model to model.  Here is the behavior
    750on the X40 (tpb is the ThinkPad Buttons utility):
    751
    752	- 0 - Related to "Volume down" key press
    753	- 1 - Related to "Volume up" key press
    754	- 2 - Related to "Mute on" key press
    755	- 3 - Related to "Access IBM" key press
    756	- 4 - Related to "LCD brightness up" key press
    757	- 5 - Related to "LCD brightness down" key press
    758	- 11 - Related to "toggle screen expansion" key press/function
    759	- 12 - Related to "ThinkLight on"
    760	- 13 - Related to "ThinkLight off"
    761	- 14 - Related to "ThinkLight" key press (toggle ThinkLight)
    762
    763The cmos command interface is prone to firmware split-brain problems, as
    764in newer ThinkPads it is just a compatibility layer.  Do not use it, it is
    765exported just as a debug tool.
    766
    767
    768LED control
    769-----------
    770
    771procfs: /proc/acpi/ibm/led
    772sysfs attributes: as per LED class, see below for names
    773
    774Some of the LED indicators can be controlled through this feature.  On
    775some older ThinkPad models, it is possible to query the status of the
    776LED indicators as well.  Newer ThinkPads cannot query the real status
    777of the LED indicators.
    778
    779Because misuse of the LEDs could induce an unaware user to perform
    780dangerous actions (like undocking or ejecting a bay device while the
    781buses are still active), or mask an important alarm (such as a nearly
    782empty battery, or a broken battery), access to most LEDs is
    783restricted.
    784
    785Unrestricted access to all LEDs requires that thinkpad-acpi be
    786compiled with the CONFIG_THINKPAD_ACPI_UNSAFE_LEDS option enabled.
    787Distributions must never enable this option.  Individual users that
    788are aware of the consequences are welcome to enabling it.
    789
    790Audio mute and microphone mute LEDs are supported, but currently not
    791visible to userspace. They are used by the snd-hda-intel audio driver.
    792
    793procfs notes
    794^^^^^^^^^^^^
    795
    796The available commands are::
    797
    798	echo '<LED number> on' >/proc/acpi/ibm/led
    799	echo '<LED number> off' >/proc/acpi/ibm/led
    800	echo '<LED number> blink' >/proc/acpi/ibm/led
    801
    802The <LED number> range is 0 to 15. The set of LEDs that can be
    803controlled varies from model to model. Here is the common ThinkPad
    804mapping:
    805
    806	- 0 - power
    807	- 1 - battery (orange)
    808	- 2 - battery (green)
    809	- 3 - UltraBase/dock
    810	- 4 - UltraBay
    811	- 5 - UltraBase battery slot
    812	- 6 - (unknown)
    813	- 7 - standby
    814	- 8 - dock status 1
    815	- 9 - dock status 2
    816	- 10, 11 - (unknown)
    817	- 12 - thinkvantage
    818	- 13, 14, 15 - (unknown)
    819
    820All of the above can be turned on and off and can be made to blink.
    821
    822sysfs notes
    823^^^^^^^^^^^
    824
    825The ThinkPad LED sysfs interface is described in detail by the LED class
    826documentation, in Documentation/leds/leds-class.rst.
    827
    828The LEDs are named (in LED ID order, from 0 to 12):
    829"tpacpi::power", "tpacpi:orange:batt", "tpacpi:green:batt",
    830"tpacpi::dock_active", "tpacpi::bay_active", "tpacpi::dock_batt",
    831"tpacpi::unknown_led", "tpacpi::standby", "tpacpi::dock_status1",
    832"tpacpi::dock_status2", "tpacpi::unknown_led2", "tpacpi::unknown_led3",
    833"tpacpi::thinkvantage".
    834
    835Due to limitations in the sysfs LED class, if the status of the LED
    836indicators cannot be read due to an error, thinkpad-acpi will report it as
    837a brightness of zero (same as LED off).
    838
    839If the thinkpad firmware doesn't support reading the current status,
    840trying to read the current LED brightness will just return whatever
    841brightness was last written to that attribute.
    842
    843These LEDs can blink using hardware acceleration.  To request that a
    844ThinkPad indicator LED should blink in hardware accelerated mode, use the
    845"timer" trigger, and leave the delay_on and delay_off parameters set to
    846zero (to request hardware acceleration autodetection).
    847
    848LEDs that are known not to exist in a given ThinkPad model are not
    849made available through the sysfs interface.  If you have a dock and you
    850notice there are LEDs listed for your ThinkPad that do not exist (and
    851are not in the dock), or if you notice that there are missing LEDs,
    852a report to ibm-acpi-devel@lists.sourceforge.net is appreciated.
    853
    854
    855ACPI sounds -- /proc/acpi/ibm/beep
    856----------------------------------
    857
    858The BEEP method is used internally by the ACPI firmware to provide
    859audible alerts in various situations. This feature allows the same
    860sounds to be triggered manually.
    861
    862The commands are non-negative integer numbers::
    863
    864	echo <number> >/proc/acpi/ibm/beep
    865
    866The valid <number> range is 0 to 17. Not all numbers trigger sounds
    867and the sounds vary from model to model. Here is the behavior on the
    868X40:
    869
    870	- 0 - stop a sound in progress (but use 17 to stop 16)
    871	- 2 - two beeps, pause, third beep ("low battery")
    872	- 3 - single beep
    873	- 4 - high, followed by low-pitched beep ("unable")
    874	- 5 - single beep
    875	- 6 - very high, followed by high-pitched beep ("AC/DC")
    876	- 7 - high-pitched beep
    877	- 9 - three short beeps
    878	- 10 - very long beep
    879	- 12 - low-pitched beep
    880	- 15 - three high-pitched beeps repeating constantly, stop with 0
    881	- 16 - one medium-pitched beep repeating constantly, stop with 17
    882	- 17 - stop 16
    883
    884
    885Temperature sensors
    886-------------------
    887
    888procfs: /proc/acpi/ibm/thermal
    889
    890sysfs device attributes: (hwmon "thinkpad") temp*_input
    891
    892Most ThinkPads include six or more separate temperature sensors but only
    893expose the CPU temperature through the standard ACPI methods.  This
    894feature shows readings from up to eight different sensors on older
    895ThinkPads, and up to sixteen different sensors on newer ThinkPads.
    896
    897For example, on the X40, a typical output may be:
    898
    899temperatures:
    900	42 42 45 41 36 -128 33 -128
    901
    902On the T43/p, a typical output may be:
    903
    904temperatures:
    905	48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128
    906
    907The mapping of thermal sensors to physical locations varies depending on
    908system-board model (and thus, on ThinkPad model).
    909
    910https://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that
    911tries to track down these locations for various models.
    912
    913Most (newer?) models seem to follow this pattern:
    914
    915- 1:  CPU
    916- 2:  (depends on model)
    917- 3:  (depends on model)
    918- 4:  GPU
    919- 5:  Main battery: main sensor
    920- 6:  Bay battery: main sensor
    921- 7:  Main battery: secondary sensor
    922- 8:  Bay battery: secondary sensor
    923- 9-15: (depends on model)
    924
    925For the R51 (source: Thomas Gruber):
    926
    927- 2:  Mini-PCI
    928- 3:  Internal HDD
    929
    930For the T43, T43/p (source: Shmidoax/Thinkwiki.org)
    931https://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p
    932
    933- 2:  System board, left side (near PCMCIA slot), reported as HDAPS temp
    934- 3:  PCMCIA slot
    935- 9:  MCH (northbridge) to DRAM Bus
    936- 10: Clock-generator, mini-pci card and ICH (southbridge), under Mini-PCI
    937      card, under touchpad
    938- 11: Power regulator, underside of system board, below F2 key
    939
    940The A31 has a very atypical layout for the thermal sensors
    941(source: Milos Popovic, https://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
    942
    943- 1:  CPU
    944- 2:  Main Battery: main sensor
    945- 3:  Power Converter
    946- 4:  Bay Battery: main sensor
    947- 5:  MCH (northbridge)
    948- 6:  PCMCIA/ambient
    949- 7:  Main Battery: secondary sensor
    950- 8:  Bay Battery: secondary sensor
    951
    952
    953Procfs notes
    954^^^^^^^^^^^^
    955
    956	Readings from sensors that are not available return -128.
    957	No commands can be written to this file.
    958
    959Sysfs notes
    960^^^^^^^^^^^
    961
    962	Sensors that are not available return the ENXIO error.  This
    963	status may change at runtime, as there are hotplug thermal
    964	sensors, like those inside the batteries and docks.
    965
    966	thinkpad-acpi thermal sensors are reported through the hwmon
    967	subsystem, and follow all of the hwmon guidelines at
    968	Documentation/hwmon.
    969
    970EXPERIMENTAL: Embedded controller register dump
    971-----------------------------------------------
    972
    973This feature is not included in the thinkpad driver anymore.
    974Instead the EC can be accessed through /sys/kernel/debug/ec with
    975a userspace tool which can be found here:
    976ftp://ftp.suse.com/pub/people/trenn/sources/ec
    977
    978Use it to determine the register holding the fan
    979speed on some models. To do that, do the following:
    980
    981	- make sure the battery is fully charged
    982	- make sure the fan is running
    983	- use above mentioned tool to read out the EC
    984
    985Often fan and temperature values vary between
    986readings. Since temperatures don't change vary fast, you can take
    987several quick dumps to eliminate them.
    988
    989You can use a similar method to figure out the meaning of other
    990embedded controller registers - e.g. make sure nothing else changes
    991except the charging or discharging battery to determine which
    992registers contain the current battery capacity, etc. If you experiment
    993with this, do send me your results (including some complete dumps with
    994a description of the conditions when they were taken.)
    995
    996
    997LCD brightness control
    998----------------------
    999
   1000procfs: /proc/acpi/ibm/brightness
   1001
   1002sysfs backlight device "thinkpad_screen"
   1003
   1004This feature allows software control of the LCD brightness on ThinkPad
   1005models which don't have a hardware brightness slider.
   1006
   1007It has some limitations: the LCD backlight cannot be actually turned
   1008on or off by this interface, it just controls the backlight brightness
   1009level.
   1010
   1011On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
   1012has eight brightness levels, ranging from 0 to 7.  Some of the levels
   1013may not be distinct.  Later Lenovo models that implement the ACPI
   1014display backlight brightness control methods have 16 levels, ranging
   1015from 0 to 15.
   1016
   1017For IBM ThinkPads, there are two interfaces to the firmware for direct
   1018brightness control, EC and UCMS (or CMOS).  To select which one should be
   1019used, use the brightness_mode module parameter: brightness_mode=1 selects
   1020EC mode, brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC
   1021mode with NVRAM backing (so that brightness changes are remembered across
   1022shutdown/reboot).
   1023
   1024The driver tries to select which interface to use from a table of
   1025defaults for each ThinkPad model.  If it makes a wrong choice, please
   1026report this as a bug, so that we can fix it.
   1027
   1028Lenovo ThinkPads only support brightness_mode=2 (UCMS).
   1029
   1030When display backlight brightness controls are available through the
   1031standard ACPI interface, it is best to use it instead of this direct
   1032ThinkPad-specific interface.  The driver will disable its native
   1033backlight brightness control interface if it detects that the standard
   1034ACPI interface is available in the ThinkPad.
   1035
   1036If you want to use the thinkpad-acpi backlight brightness control
   1037instead of the generic ACPI video backlight brightness control for some
   1038reason, you should use the acpi_backlight=vendor kernel parameter.
   1039
   1040The brightness_enable module parameter can be used to control whether
   1041the LCD brightness control feature will be enabled when available.
   1042brightness_enable=0 forces it to be disabled.  brightness_enable=1
   1043forces it to be enabled when available, even if the standard ACPI
   1044interface is also available.
   1045
   1046Procfs notes
   1047^^^^^^^^^^^^
   1048
   1049The available commands are::
   1050
   1051	echo up   >/proc/acpi/ibm/brightness
   1052	echo down >/proc/acpi/ibm/brightness
   1053	echo 'level <level>' >/proc/acpi/ibm/brightness
   1054
   1055Sysfs notes
   1056^^^^^^^^^^^
   1057
   1058The interface is implemented through the backlight sysfs class, which is
   1059poorly documented at this time.
   1060
   1061Locate the thinkpad_screen device under /sys/class/backlight, and inside
   1062it there will be the following attributes:
   1063
   1064	max_brightness:
   1065		Reads the maximum brightness the hardware can be set to.
   1066		The minimum is always zero.
   1067
   1068	actual_brightness:
   1069		Reads what brightness the screen is set to at this instant.
   1070
   1071	brightness:
   1072		Writes request the driver to change brightness to the
   1073		given value.  Reads will tell you what brightness the
   1074		driver is trying to set the display to when "power" is set
   1075		to zero and the display has not been dimmed by a kernel
   1076		power management event.
   1077
   1078	power:
   1079		power management mode, where 0 is "display on", and 1 to 3
   1080		will dim the display backlight to brightness level 0
   1081		because thinkpad-acpi cannot really turn the backlight
   1082		off.  Kernel power management events can temporarily
   1083		increase the current power management level, i.e. they can
   1084		dim the display.
   1085
   1086
   1087WARNING:
   1088
   1089    Whatever you do, do NOT ever call thinkpad-acpi backlight-level change
   1090    interface and the ACPI-based backlight level change interface
   1091    (available on newer BIOSes, and driven by the Linux ACPI video driver)
   1092    at the same time.  The two will interact in bad ways, do funny things,
   1093    and maybe reduce the life of the backlight lamps by needlessly kicking
   1094    its level up and down at every change.
   1095
   1096
   1097Volume control (Console Audio control)
   1098--------------------------------------
   1099
   1100procfs: /proc/acpi/ibm/volume
   1101
   1102ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC"
   1103
   1104NOTE: by default, the volume control interface operates in read-only
   1105mode, as it is supposed to be used for on-screen-display purposes.
   1106The read/write mode can be enabled through the use of the
   1107"volume_control=1" module parameter.
   1108
   1109NOTE: distros are urged to not enable volume_control by default, this
   1110should be done by the local admin only.  The ThinkPad UI is for the
   1111console audio control to be done through the volume keys only, and for
   1112the desktop environment to just provide on-screen-display feedback.
   1113Software volume control should be done only in the main AC97/HDA
   1114mixer.
   1115
   1116
   1117About the ThinkPad Console Audio control
   1118^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   1119
   1120ThinkPads have a built-in amplifier and muting circuit that drives the
   1121console headphone and speakers.  This circuit is after the main AC97
   1122or HDA mixer in the audio path, and under exclusive control of the
   1123firmware.
   1124
   1125ThinkPads have three special hotkeys to interact with the console
   1126audio control: volume up, volume down and mute.
   1127
   1128It is worth noting that the normal way the mute function works (on
   1129ThinkPads that do not have a "mute LED") is:
   1130
   11311. Press mute to mute.  It will *always* mute, you can press it as
   1132   many times as you want, and the sound will remain mute.
   1133
   11342. Press either volume key to unmute the ThinkPad (it will _not_
   1135   change the volume, it will just unmute).
   1136
   1137This is a very superior design when compared to the cheap software-only
   1138mute-toggle solution found on normal consumer laptops:  you can be
   1139absolutely sure the ThinkPad will not make noise if you press the mute
   1140button, no matter the previous state.
   1141
   1142The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain
   1143amplifiers driving the speakers and headphone output, and the firmware
   1144also handles volume control for the headphone and speakers on these
   1145ThinkPads without any help from the operating system (this volume
   1146control stage exists after the main AC97 or HDA mixer in the audio
   1147path).
   1148
   1149The newer Lenovo models only have firmware mute control, and depend on
   1150the main HDA mixer to do volume control (which is done by the operating
   1151system).  In this case, the volume keys are filtered out for unmute
   1152key press (there are some firmware bugs in this area) and delivered as
   1153normal key presses to the operating system (thinkpad-acpi is not
   1154involved).
   1155
   1156
   1157The ThinkPad-ACPI volume control
   1158^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   1159
   1160The preferred way to interact with the Console Audio control is the
   1161ALSA interface.
   1162
   1163The legacy procfs interface allows one to read the current state,
   1164and if volume control is enabled, accepts the following commands::
   1165
   1166	echo up   >/proc/acpi/ibm/volume
   1167	echo down >/proc/acpi/ibm/volume
   1168	echo mute >/proc/acpi/ibm/volume
   1169	echo unmute >/proc/acpi/ibm/volume
   1170	echo 'level <level>' >/proc/acpi/ibm/volume
   1171
   1172The <level> number range is 0 to 14 although not all of them may be
   1173distinct. To unmute the volume after the mute command, use either the
   1174up or down command (the level command will not unmute the volume), or
   1175the unmute command.
   1176
   1177You can use the volume_capabilities parameter to tell the driver
   1178whether your thinkpad has volume control or mute-only control:
   1179volume_capabilities=1 for mixers with mute and volume control,
   1180volume_capabilities=2 for mixers with only mute control.
   1181
   1182If the driver misdetects the capabilities for your ThinkPad model,
   1183please report this to ibm-acpi-devel@lists.sourceforge.net, so that we
   1184can update the driver.
   1185
   1186There are two strategies for volume control.  To select which one
   1187should be used, use the volume_mode module parameter: volume_mode=1
   1188selects EC mode, and volume_mode=3 selects EC mode with NVRAM backing
   1189(so that volume/mute changes are remembered across shutdown/reboot).
   1190
   1191The driver will operate in volume_mode=3 by default. If that does not
   1192work well on your ThinkPad model, please report this to
   1193ibm-acpi-devel@lists.sourceforge.net.
   1194
   1195The driver supports the standard ALSA module parameters.  If the ALSA
   1196mixer is disabled, the driver will disable all volume functionality.
   1197
   1198
   1199Fan control and monitoring: fan speed, fan enable/disable
   1200---------------------------------------------------------
   1201
   1202procfs: /proc/acpi/ibm/fan
   1203
   1204sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1, pwm1_enable, fan2_input
   1205
   1206sysfs hwmon driver attributes: fan_watchdog
   1207
   1208NOTE NOTE NOTE:
   1209   fan control operations are disabled by default for
   1210   safety reasons.  To enable them, the module parameter "fan_control=1"
   1211   must be given to thinkpad-acpi.
   1212
   1213This feature attempts to show the current fan speed, control mode and
   1214other fan data that might be available.  The speed is read directly
   1215from the hardware registers of the embedded controller.  This is known
   1216to work on later R, T, X and Z series ThinkPads but may show a bogus
   1217value on other models.
   1218
   1219Some Lenovo ThinkPads support a secondary fan.  This fan cannot be
   1220controlled separately, it shares the main fan control.
   1221
   1222Fan levels
   1223^^^^^^^^^^
   1224
   1225Most ThinkPad fans work in "levels" at the firmware interface.  Level 0
   1226stops the fan.  The higher the level, the higher the fan speed, although
   1227adjacent levels often map to the same fan speed.  7 is the highest
   1228level, where the fan reaches the maximum recommended speed.
   1229
   1230Level "auto" means the EC changes the fan level according to some
   1231internal algorithm, usually based on readings from the thermal sensors.
   1232
   1233There is also a "full-speed" level, also known as "disengaged" level.
   1234In this level, the EC disables the speed-locked closed-loop fan control,
   1235and drives the fan as fast as it can go, which might exceed hardware
   1236limits, so use this level with caution.
   1237
   1238The fan usually ramps up or down slowly from one speed to another, and
   1239it is normal for the EC to take several seconds to react to fan
   1240commands.  The full-speed level may take up to two minutes to ramp up to
   1241maximum speed, and in some ThinkPads, the tachometer readings go stale
   1242while the EC is transitioning to the full-speed level.
   1243
   1244WARNING WARNING WARNING: do not leave the fan disabled unless you are
   1245monitoring all of the temperature sensor readings and you are ready to
   1246enable it if necessary to avoid overheating.
   1247
   1248An enabled fan in level "auto" may stop spinning if the EC decides the
   1249ThinkPad is cool enough and doesn't need the extra airflow.  This is
   1250normal, and the EC will spin the fan up if the various thermal readings
   1251rise too much.
   1252
   1253On the X40, this seems to depend on the CPU and HDD temperatures.
   1254Specifically, the fan is turned on when either the CPU temperature
   1255climbs to 56 degrees or the HDD temperature climbs to 46 degrees.  The
   1256fan is turned off when the CPU temperature drops to 49 degrees and the
   1257HDD temperature drops to 41 degrees.  These thresholds cannot
   1258currently be controlled.
   1259
   1260The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
   1261certain conditions are met.  It will override any fan programming done
   1262through thinkpad-acpi.
   1263
   1264The thinkpad-acpi kernel driver can be programmed to revert the fan
   1265level to a safe setting if userspace does not issue one of the procfs
   1266fan commands: "enable", "disable", "level" or "watchdog", or if there
   1267are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is
   1268set to 1, manual mode) within a configurable amount of time of up to
   1269120 seconds.  This functionality is called fan safety watchdog.
   1270
   1271Note that the watchdog timer stops after it enables the fan.  It will be
   1272rearmed again automatically (using the same interval) when one of the
   1273above mentioned fan commands is received.  The fan watchdog is,
   1274therefore, not suitable to protect against fan mode changes made through
   1275means other than the "enable", "disable", and "level" procfs fan
   1276commands, or the hwmon fan control sysfs interface.
   1277
   1278Procfs notes
   1279^^^^^^^^^^^^
   1280
   1281The fan may be enabled or disabled with the following commands::
   1282
   1283	echo enable  >/proc/acpi/ibm/fan
   1284	echo disable >/proc/acpi/ibm/fan
   1285
   1286Placing a fan on level 0 is the same as disabling it.  Enabling a fan
   1287will try to place it in a safe level if it is too slow or disabled.
   1288
   1289The fan level can be controlled with the command::
   1290
   1291	echo 'level <level>' > /proc/acpi/ibm/fan
   1292
   1293Where <level> is an integer from 0 to 7, or one of the words "auto" or
   1294"full-speed" (without the quotes).  Not all ThinkPads support the "auto"
   1295and "full-speed" levels.  The driver accepts "disengaged" as an alias for
   1296"full-speed", and reports it as "disengaged" for backwards
   1297compatibility.
   1298
   1299On the X31 and X40 (and ONLY on those models), the fan speed can be
   1300controlled to a certain degree.  Once the fan is running, it can be
   1301forced to run faster or slower with the following command::
   1302
   1303	echo 'speed <speed>' > /proc/acpi/ibm/fan
   1304
   1305The sustainable range of fan speeds on the X40 appears to be from about
   13063700 to about 7350. Values outside this range either do not have any
   1307effect or the fan speed eventually settles somewhere in that range.  The
   1308fan cannot be stopped or started with this command.  This functionality
   1309is incomplete, and not available through the sysfs interface.
   1310
   1311To program the safety watchdog, use the "watchdog" command::
   1312
   1313	echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan
   1314
   1315If you want to disable the watchdog, use 0 as the interval.
   1316
   1317Sysfs notes
   1318^^^^^^^^^^^
   1319
   1320The sysfs interface follows the hwmon subsystem guidelines for the most
   1321part, and the exception is the fan safety watchdog.
   1322
   1323Writes to any of the sysfs attributes may return the EINVAL error if
   1324that operation is not supported in a given ThinkPad or if the parameter
   1325is out-of-bounds, and EPERM if it is forbidden.  They may also return
   1326EINTR (interrupted system call), and EIO (I/O error while trying to talk
   1327to the firmware).
   1328
   1329Features not yet implemented by the driver return ENOSYS.
   1330
   1331hwmon device attribute pwm1_enable:
   1332	- 0: PWM offline (fan is set to full-speed mode)
   1333	- 1: Manual PWM control (use pwm1 to set fan level)
   1334	- 2: Hardware PWM control (EC "auto" mode)
   1335	- 3: reserved (Software PWM control, not implemented yet)
   1336
   1337	Modes 0 and 2 are not supported by all ThinkPads, and the
   1338	driver is not always able to detect this.  If it does know a
   1339	mode is unsupported, it will return -EINVAL.
   1340
   1341hwmon device attribute pwm1:
   1342	Fan level, scaled from the firmware values of 0-7 to the hwmon
   1343	scale of 0-255.  0 means fan stopped, 255 means highest normal
   1344	speed (level 7).
   1345
   1346	This attribute only commands the fan if pmw1_enable is set to 1
   1347	(manual PWM control).
   1348
   1349hwmon device attribute fan1_input:
   1350	Fan tachometer reading, in RPM.  May go stale on certain
   1351	ThinkPads while the EC transitions the PWM to offline mode,
   1352	which can take up to two minutes.  May return rubbish on older
   1353	ThinkPads.
   1354
   1355hwmon device attribute fan2_input:
   1356	Fan tachometer reading, in RPM, for the secondary fan.
   1357	Available only on some ThinkPads.  If the secondary fan is
   1358	not installed, will always read 0.
   1359
   1360hwmon driver attribute fan_watchdog:
   1361	Fan safety watchdog timer interval, in seconds.  Minimum is
   1362	1 second, maximum is 120 seconds.  0 disables the watchdog.
   1363
   1364To stop the fan: set pwm1 to zero, and pwm1_enable to 1.
   1365
   1366To start the fan in a safe mode: set pwm1_enable to 2.  If that fails
   1367with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255
   1368would be the safest choice, though).
   1369
   1370
   1371WAN
   1372---
   1373
   1374procfs: /proc/acpi/ibm/wan
   1375
   1376sysfs device attribute: wwan_enable (deprecated)
   1377
   1378sysfs rfkill class: switch "tpacpi_wwan_sw"
   1379
   1380This feature shows the presence and current state of the built-in
   1381Wireless WAN device.
   1382
   1383If the ThinkPad supports it, the WWAN state is stored in NVRAM,
   1384so it is kept across reboots and power-off.
   1385
   1386It was tested on a Lenovo ThinkPad X60. It should probably work on other
   1387ThinkPad models which come with this module installed.
   1388
   1389Procfs notes
   1390^^^^^^^^^^^^
   1391
   1392If the W-WAN card is installed, the following commands can be used::
   1393
   1394	echo enable > /proc/acpi/ibm/wan
   1395	echo disable > /proc/acpi/ibm/wan
   1396
   1397Sysfs notes
   1398^^^^^^^^^^^
   1399
   1400	If the W-WAN card is installed, it can be enabled /
   1401	disabled through the "wwan_enable" thinkpad-acpi device
   1402	attribute, and its current status can also be queried.
   1403
   1404	enable:
   1405		- 0: disables WWAN card / WWAN card is disabled
   1406		- 1: enables WWAN card / WWAN card is enabled.
   1407
   1408	Note: this interface has been superseded by the	generic rfkill
   1409	class.  It has been deprecated, and it will be removed in year
   1410	2010.
   1411
   1412	rfkill controller switch "tpacpi_wwan_sw": refer to
   1413	Documentation/driver-api/rfkill.rst for details.
   1414
   1415
   1416LCD Shadow control
   1417------------------
   1418
   1419procfs: /proc/acpi/ibm/lcdshadow
   1420
   1421Some newer T480s and T490s ThinkPads provide a feature called
   1422PrivacyGuard. By turning this feature on, the usable vertical and
   1423horizontal viewing angles of the LCD can be limited (as if some privacy
   1424screen was applied manually in front of the display).
   1425
   1426procfs notes
   1427^^^^^^^^^^^^
   1428
   1429The available commands are::
   1430
   1431	echo '0' >/proc/acpi/ibm/lcdshadow
   1432	echo '1' >/proc/acpi/ibm/lcdshadow
   1433
   1434The first command ensures the best viewing angle and the latter one turns
   1435on the feature, restricting the viewing angles.
   1436
   1437
   1438DYTC Lapmode sensor
   1439-------------------
   1440
   1441sysfs: dytc_lapmode
   1442
   1443Newer thinkpads and mobile workstations have the ability to determine if
   1444the device is in deskmode or lapmode. This feature is used by user space
   1445to decide if WWAN transmission can be increased to maximum power and is
   1446also useful for understanding the different thermal modes available as
   1447they differ between desk and lap mode.
   1448
   1449The property is read-only. If the platform doesn't have support the sysfs
   1450class is not created.
   1451
   1452EXPERIMENTAL: UWB
   1453-----------------
   1454
   1455This feature is considered EXPERIMENTAL because it has not been extensively
   1456tested and validated in various ThinkPad models yet.  The feature may not
   1457work as expected. USE WITH CAUTION! To use this feature, you need to supply
   1458the experimental=1 parameter when loading the module.
   1459
   1460sysfs rfkill class: switch "tpacpi_uwb_sw"
   1461
   1462This feature exports an rfkill controller for the UWB device, if one is
   1463present and enabled in the BIOS.
   1464
   1465Sysfs notes
   1466^^^^^^^^^^^
   1467
   1468	rfkill controller switch "tpacpi_uwb_sw": refer to
   1469	Documentation/driver-api/rfkill.rst for details.
   1470
   1471
   1472Setting keyboard language
   1473-------------------------
   1474
   1475sysfs: keyboard_lang
   1476
   1477This feature is used to set keyboard language to ECFW using ASL interface.
   1478Fewer thinkpads models like T580 , T590 , T15 Gen 1 etc.. has "=", "(',
   1479")" numeric keys, which are not displaying correctly, when keyboard language
   1480is other than "english". This is because the default keyboard language in ECFW
   1481is set as "english". Hence using this sysfs, user can set the correct keyboard
   1482language to ECFW and then these key's will work correctly.
   1483
   1484Example of command to set keyboard language is mentioned below::
   1485
   1486        echo jp > /sys/devices/platform/thinkpad_acpi/keyboard_lang
   1487
   1488Text corresponding to keyboard layout to be set in sysfs are: be(Belgian),
   1489cz(Czech), da(Danish), de(German), en(English), es(Spain), et(Estonian),
   1490fr(French), fr-ch(French(Switzerland)), hu(Hungarian), it(Italy), jp (Japan),
   1491nl(Dutch), nn(Norway), pl(Polish), pt(portugese), sl(Slovenian), sv(Sweden),
   1492tr(Turkey)
   1493
   1494WWAN Antenna type
   1495-----------------
   1496
   1497sysfs: wwan_antenna_type
   1498
   1499On some newer Thinkpads we need to set SAR value based on the antenna
   1500type. This interface will be used by userspace to get the antenna type
   1501and set the corresponding SAR value, as is required for FCC certification.
   1502
   1503The available commands are::
   1504
   1505        cat /sys/devices/platform/thinkpad_acpi/wwan_antenna_type
   1506
   1507Currently 2 antenna types are supported as mentioned below:
   1508- type a
   1509- type b
   1510
   1511The property is read-only. If the platform doesn't have support the sysfs
   1512class is not created.
   1513
   1514Adaptive keyboard
   1515-----------------
   1516
   1517sysfs device attribute: adaptive_kbd_mode
   1518
   1519This sysfs attribute controls the keyboard "face" that will be shown on the
   1520Lenovo X1 Carbon 2nd gen (2014)'s adaptive keyboard. The value can be read
   1521and set.
   1522
   1523- 0 = Home mode
   1524- 1 = Web-browser mode
   1525- 2 = Web-conference mode
   1526- 3 = Function mode
   1527- 4 = Layflat mode
   1528
   1529For more details about which buttons will appear depending on the mode, please
   1530review the laptop's user guide:
   1531https://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/x1carbon_2_ug_en.pdf
   1532
   1533Battery charge control
   1534----------------------
   1535
   1536sysfs attributes:
   1537/sys/class/power_supply/BAT*/charge_control_{start,end}_threshold
   1538
   1539These two attributes are created for those batteries that are supported by the
   1540driver. They enable the user to control the battery charge thresholds of the
   1541given battery. Both values may be read and set. `charge_control_start_threshold`
   1542accepts an integer between 0 and 99 (inclusive); this value represents a battery
   1543percentage level, below which charging will begin. `charge_control_end_threshold`
   1544accepts an integer between 1 and 100 (inclusive); this value represents a battery
   1545percentage level, above which charging will stop.
   1546
   1547The exact semantics of the attributes may be found in
   1548Documentation/ABI/testing/sysfs-class-power.
   1549
   1550Multiple Commands, Module Parameters
   1551------------------------------------
   1552
   1553Multiple commands can be written to the proc files in one shot by
   1554separating them with commas, for example::
   1555
   1556	echo enable,0xffff > /proc/acpi/ibm/hotkey
   1557	echo lcd_disable,crt_enable > /proc/acpi/ibm/video
   1558
   1559Commands can also be specified when loading the thinkpad-acpi module,
   1560for example::
   1561
   1562	modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable
   1563
   1564
   1565Enabling debugging output
   1566-------------------------
   1567
   1568The module takes a debug parameter which can be used to selectively
   1569enable various classes of debugging output, for example::
   1570
   1571	 modprobe thinkpad_acpi debug=0xffff
   1572
   1573will enable all debugging output classes.  It takes a bitmask, so
   1574to enable more than one output class, just add their values.
   1575
   1576	=============		======================================
   1577	Debug bitmask		Description
   1578	=============		======================================
   1579	0x8000			Disclose PID of userspace programs
   1580				accessing some functions of the driver
   1581	0x0001			Initialization and probing
   1582	0x0002			Removal
   1583	0x0004			RF Transmitter control (RFKILL)
   1584				(bluetooth, WWAN, UWB...)
   1585	0x0008			HKEY event interface, hotkeys
   1586	0x0010			Fan control
   1587	0x0020			Backlight brightness
   1588	0x0040			Audio mixer/volume control
   1589	=============		======================================
   1590
   1591There is also a kernel build option to enable more debugging
   1592information, which may be necessary to debug driver problems.
   1593
   1594The level of debugging information output by the driver can be changed
   1595at runtime through sysfs, using the driver attribute debug_level.  The
   1596attribute takes the same bitmask as the debug module parameter above.
   1597
   1598
   1599Force loading of module
   1600-----------------------
   1601
   1602If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
   1603the module parameter force_load=1.  Regardless of whether this works or
   1604not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.
   1605
   1606
   1607Sysfs interface changelog
   1608^^^^^^^^^^^^^^^^^^^^^^^^^
   1609
   1610=========	===============================================================
   16110x000100:	Initial sysfs support, as a single platform driver and
   1612		device.
   16130x000200:	Hot key support for 32 hot keys, and radio slider switch
   1614		support.
   16150x010000:	Hot keys are now handled by default over the input
   1616		layer, the radio switch generates input event EV_RADIO,
   1617		and the driver enables hot key handling by default in
   1618		the firmware.
   1619
   16200x020000:	ABI fix: added a separate hwmon platform device and
   1621		driver, which must be located by name (thinkpad)
   1622		and the hwmon class for libsensors4 (lm-sensors 3)
   1623		compatibility.  Moved all hwmon attributes to this
   1624		new platform device.
   1625
   16260x020100:	Marker for thinkpad-acpi with hot key NVRAM polling
   1627		support.  If you must, use it to know you should not
   1628		start a userspace NVRAM poller (allows to detect when
   1629		NVRAM is compiled out by the user because it is
   1630		unneeded/undesired in the first place).
   16310x020101:	Marker for thinkpad-acpi with hot key NVRAM polling
   1632		and proper hotkey_mask semantics (version 8 of the
   1633		NVRAM polling patch).  Some development snapshots of
   1634		0.18 had an earlier version that did strange things
   1635		to hotkey_mask.
   1636
   16370x020200:	Add poll()/select() support to the following attributes:
   1638		hotkey_radio_sw, wakeup_hotunplug_complete, wakeup_reason
   1639
   16400x020300:	hotkey enable/disable support removed, attributes
   1641		hotkey_bios_enabled and hotkey_enable deprecated and
   1642		marked for removal.
   1643
   16440x020400:	Marker for 16 LEDs support.  Also, LEDs that are known
   1645		to not exist in a given model are not registered with
   1646		the LED sysfs class anymore.
   1647
   16480x020500:	Updated hotkey driver, hotkey_mask is always available
   1649		and it is always able to disable hot keys.  Very old
   1650		thinkpads are properly supported.  hotkey_bios_mask
   1651		is deprecated and marked for removal.
   1652
   16530x020600:	Marker for backlight change event support.
   1654
   16550x020700:	Support for mute-only mixers.
   1656		Volume control in read-only mode by default.
   1657		Marker for ALSA mixer support.
   1658
   16590x030000:	Thermal and fan sysfs attributes were moved to the hwmon
   1660		device instead of being attached to the backing platform
   1661		device.
   1662=========	===============================================================