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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 EST.

1			     ThinkPad ACPI Extras Driver
2	
3	                            Version 0.25
4	                        October 16th,  2013
5	
6	               Borislav Deianov <borislav@users.sf.net>
7	             Henrique de Moraes Holschuh <hmh@hmh.eng.br>
8	                      http://ibm-acpi.sf.net/
9	
10	
11	This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It
12	supports various features of these laptops which are accessible
13	through the ACPI and ACPI EC framework, but not otherwise fully
14	supported by the generic Linux ACPI drivers.
15	
16	This driver used to be named ibm-acpi until kernel 2.6.21 and release
17	0.13-20070314.  It used to be in the drivers/acpi tree, but it was
18	moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel
19	2.6.22, and release 0.14.  It was moved to drivers/platform/x86 for
20	kernel 2.6.29 and release 0.22.
21	
22	The driver is named "thinkpad-acpi".  In some places, like module
23	names and log messages, "thinkpad_acpi" is used because of userspace
24	issues.
25	
26	"tpacpi" is used as a shorthand where "thinkpad-acpi" would be too
27	long due to length limitations on some Linux kernel versions.
28	
29	Status
30	------
31	
32	The features currently supported are the following (see below for
33	detailed description):
34	
35		- Fn key combinations
36		- Bluetooth enable and disable
37		- video output switching, expansion control
38		- ThinkLight on and off
39		- CMOS/UCMS control
40		- LED control
41		- ACPI sounds
42		- temperature sensors
43		- Experimental: embedded controller register dump
44		- LCD brightness control
45		- Volume control
46		- Fan control and monitoring: fan speed, fan enable/disable
47		- WAN enable and disable
48		- UWB enable and disable
49	
50	A compatibility table by model and feature is maintained on the web
51	site, http://ibm-acpi.sf.net/. I appreciate any success or failure
52	reports, especially if they add to or correct the compatibility table.
53	Please include the following information in your report:
54	
55		- ThinkPad model name
56		- a copy of your ACPI tables, using the "acpidump" utility
57		- a copy of the output of dmidecode, with serial numbers
58		  and UUIDs masked off
59		- which driver features work and which don't
60		- the observed behavior of non-working features
61	
62	Any other comments or patches are also more than welcome.
63	
64	
65	Installation
66	------------
67	
68	If you are compiling this driver as included in the Linux kernel
69	sources, look for the CONFIG_THINKPAD_ACPI Kconfig option.
70	It is located on the menu path: "Device Drivers" -> "X86 Platform
71	Specific Device Drivers" -> "ThinkPad ACPI Laptop Extras".
72	
73	
74	Features
75	--------
76	
77	The driver exports two different interfaces to userspace, which can be
78	used to access the features it provides.  One is a legacy procfs-based
79	interface, which will be removed at some time in the future.  The other
80	is a new sysfs-based interface which is not complete yet.
81	
82	The procfs interface creates the /proc/acpi/ibm directory.  There is a
83	file under that directory for each feature it supports.  The procfs
84	interface is mostly frozen, and will change very little if at all: it
85	will not be extended to add any new functionality in the driver, instead
86	all new functionality will be implemented on the sysfs interface.
87	
88	The sysfs interface tries to blend in the generic Linux sysfs subsystems
89	and classes as much as possible.  Since some of these subsystems are not
90	yet ready or stabilized, it is expected that this interface will change,
91	and any and all userspace programs must deal with it.
92	
93	
94	Notes about the sysfs interface:
95	
96	Unlike what was done with the procfs interface, correctness when talking
97	to the sysfs interfaces will be enforced, as will correctness in the
98	thinkpad-acpi's implementation of sysfs interfaces.
99	
100	Also, any bugs in the thinkpad-acpi sysfs driver code or in the
101	thinkpad-acpi's implementation of the sysfs interfaces will be fixed for
102	maximum correctness, even if that means changing an interface in
103	non-compatible ways.  As these interfaces mature both in the kernel and
104	in thinkpad-acpi, such changes should become quite rare.
105	
106	Applications interfacing to the thinkpad-acpi sysfs interfaces must
107	follow all sysfs guidelines and correctly process all errors (the sysfs
108	interface makes extensive use of errors).  File descriptors and open /
109	close operations to the sysfs inodes must also be properly implemented.
110	
111	The version of thinkpad-acpi's sysfs interface is exported by the driver
112	as a driver attribute (see below).
113	
114	Sysfs driver attributes are on the driver's sysfs attribute space,
115	for 2.6.23+ this is /sys/bus/platform/drivers/thinkpad_acpi/ and
116	/sys/bus/platform/drivers/thinkpad_hwmon/
117	
118	Sysfs device attributes are on the thinkpad_acpi device sysfs attribute
119	space, for 2.6.23+ this is /sys/devices/platform/thinkpad_acpi/.
120	
121	Sysfs device attributes for the sensors and fan are on the
122	thinkpad_hwmon device's sysfs attribute space, but you should locate it
123	looking for a hwmon device with the name attribute of "thinkpad", or
124	better yet, through libsensors.
125	
126	
127	Driver version
128	--------------
129	
130	procfs: /proc/acpi/ibm/driver
131	sysfs driver attribute: version
132	
133	The driver name and version. No commands can be written to this file.
134	
135	
136	Sysfs interface version
137	-----------------------
138	
139	sysfs driver attribute: interface_version
140	
141	Version of the thinkpad-acpi sysfs interface, as an unsigned long
142	(output in hex format: 0xAAAABBCC), where:
143		AAAA - major revision
144		BB - minor revision
145		CC - bugfix revision
146	
147	The sysfs interface version changelog for the driver can be found at the
148	end of this document.  Changes to the sysfs interface done by the kernel
149	subsystems are not documented here, nor are they tracked by this
150	attribute.
151	
152	Changes to the thinkpad-acpi sysfs interface are only considered
153	non-experimental when they are submitted to Linux mainline, at which
154	point the changes in this interface are documented and interface_version
155	may be updated.  If you are using any thinkpad-acpi features not yet
156	sent to mainline for merging, you do so on your own risk: these features
157	may disappear, or be implemented in a different and incompatible way by
158	the time they are merged in Linux mainline.
159	
160	Changes that are backwards-compatible by nature (e.g. the addition of
161	attributes that do not change the way the other attributes work) do not
162	always warrant an update of interface_version.  Therefore, one must
163	expect that an attribute might not be there, and deal with it properly
164	(an attribute not being there *is* a valid way to make it clear that a
165	feature is not available in sysfs).
166	
167	
168	Hot keys
169	--------
170	
171	procfs: /proc/acpi/ibm/hotkey
172	sysfs device attribute: hotkey_*
173	
174	In a ThinkPad, the ACPI HKEY handler is responsible for communicating
175	some important events and also keyboard hot key presses to the operating
176	system.  Enabling the hotkey functionality of thinkpad-acpi signals the
177	firmware that such a driver is present, and modifies how the ThinkPad
178	firmware will behave in many situations.
179	
180	The driver enables the HKEY ("hot key") event reporting automatically
181	when loaded, and disables it when it is removed.
182	
183	The driver will report HKEY events in the following format:
184	
185		ibm/hotkey HKEY 00000080 0000xxxx
186	
187	Some of these events refer to hot key presses, but not all of them.
188	
189	The driver will generate events over the input layer for hot keys and
190	radio switches, and over the ACPI netlink layer for other events.  The
191	input layer support accepts the standard IOCTLs to remap the keycodes
192	assigned to each hot key.
193	
194	The hot key bit mask allows some control over which hot keys generate
195	events.  If a key is "masked" (bit set to 0 in the mask), the firmware
196	will handle it.  If it is "unmasked", it signals the firmware that
197	thinkpad-acpi would prefer to handle it, if the firmware would be so
198	kind to allow it (and it often doesn't!).
199	
200	Not all bits in the mask can be modified.  Not all bits that can be
201	modified do anything.  Not all hot keys can be individually controlled
202	by the mask.  Some models do not support the mask at all.  The behaviour
203	of the mask is, therefore, highly dependent on the ThinkPad model.
204	
205	The driver will filter out any unmasked hotkeys, so even if the firmware
206	doesn't allow disabling an specific hotkey, the driver will not report
207	events for unmasked hotkeys.
208	
209	Note that unmasking some keys prevents their default behavior.  For
210	example, if Fn+F5 is unmasked, that key will no longer enable/disable
211	Bluetooth by itself in firmware.
212	
213	Note also that not all Fn key combinations are supported through ACPI
214	depending on the ThinkPad model and firmware version.  On those
215	ThinkPads, it is still possible to support some extra hotkeys by
216	polling the "CMOS NVRAM" at least 10 times per second.  The driver
217	attempts to enables this functionality automatically when required.
218	
219	procfs notes:
220	
221	The following commands can be written to the /proc/acpi/ibm/hotkey file:
222	
223		echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
224		echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
225		... any other 8-hex-digit mask ...
226		echo reset > /proc/acpi/ibm/hotkey -- restore the recommended mask
227	
228	The following commands have been deprecated and will cause the kernel
229	to log a warning:
230	
231		echo enable > /proc/acpi/ibm/hotkey -- does nothing
232		echo disable > /proc/acpi/ibm/hotkey -- returns an error
233	
234	The procfs interface does not support NVRAM polling control.  So as to
235	maintain maximum bug-to-bug compatibility, it does not report any masks,
236	nor does it allow one to manipulate the hot key mask when the firmware
237	does not support masks at all, even if NVRAM polling is in use.
238	
239	sysfs notes:
240	
241		hotkey_bios_enabled:
242			DEPRECATED, WILL BE REMOVED SOON.
243	
244			Returns 0.
245	
246		hotkey_bios_mask:
247			DEPRECATED, DON'T USE, WILL BE REMOVED IN THE FUTURE.
248	
249			Returns the hot keys mask when thinkpad-acpi was loaded.
250			Upon module unload, the hot keys mask will be restored
251			to this value.   This is always 0x80c, because those are
252			the hotkeys that were supported by ancient firmware
253			without mask support.
254	
255		hotkey_enable:
256			DEPRECATED, WILL BE REMOVED SOON.
257	
258			0: returns -EPERM
259			1: does nothing
260	
261		hotkey_mask:
262			bit mask to enable reporting (and depending on
263			the firmware, ACPI event generation) for each hot key
264			(see above).  Returns the current status of the hot keys
265			mask, and allows one to modify it.
266	
267		hotkey_all_mask:
268			bit mask that should enable event reporting for all
269			supported hot keys, when echoed to hotkey_mask above.
270			Unless you know which events need to be handled
271			passively (because the firmware *will* handle them
272			anyway), do *not* use hotkey_all_mask.  Use
273			hotkey_recommended_mask, instead. You have been warned.
274	
275		hotkey_recommended_mask:
276			bit mask that should enable event reporting for all
277			supported hot keys, except those which are always
278			handled by the firmware anyway.  Echo it to
279			hotkey_mask above, to use.  This is the default mask
280			used by the driver.
281	
282		hotkey_source_mask:
283			bit mask that selects which hot keys will the driver
284			poll the NVRAM for.  This is auto-detected by the driver
285			based on the capabilities reported by the ACPI firmware,
286			but it can be overridden at runtime.
287	
288			Hot keys whose bits are set in hotkey_source_mask are
289			polled for in NVRAM, and reported as hotkey events if
290			enabled in hotkey_mask.  Only a few hot keys are
291			available through CMOS NVRAM polling.
292	
293			Warning: when in NVRAM mode, the volume up/down/mute
294			keys are synthesized according to changes in the mixer,
295			which uses a single volume up or volume down hotkey
296			press to unmute, as per the ThinkPad volume mixer user
297			interface.  When in ACPI event mode, volume up/down/mute
298			events are reported by the firmware and can behave
299			differently (and that behaviour changes with firmware
300			version -- not just with firmware models -- as well as
301			OSI(Linux) state).
302	
303		hotkey_poll_freq:
304			frequency in Hz for hot key polling. It must be between
305			0 and 25 Hz.  Polling is only carried out when strictly
306			needed.
307	
308			Setting hotkey_poll_freq to zero disables polling, and
309			will cause hot key presses that require NVRAM polling
310			to never be reported.
311	
312			Setting hotkey_poll_freq too low may cause repeated
313			pressings of the same hot key to be misreported as a
314			single key press, or to not even be detected at all.
315			The recommended polling frequency is 10Hz.
316	
317		hotkey_radio_sw:
318			If the ThinkPad has a hardware radio switch, this
319			attribute will read 0 if the switch is in the "radios
320			disabled" position, and 1 if the switch is in the
321			"radios enabled" position.
322	
323			This attribute has poll()/select() support.
324	
325		hotkey_tablet_mode:
326			If the ThinkPad has tablet capabilities, this attribute
327			will read 0 if the ThinkPad is in normal mode, and
328			1 if the ThinkPad is in tablet mode.
329	
330			This attribute has poll()/select() support.
331	
332		wakeup_reason:
333			Set to 1 if the system is waking up because the user
334			requested a bay ejection.  Set to 2 if the system is
335			waking up because the user requested the system to
336			undock.  Set to zero for normal wake-ups or wake-ups
337			due to unknown reasons.
338	
339			This attribute has poll()/select() support.
340	
341		wakeup_hotunplug_complete:
342			Set to 1 if the system was waken up because of an
343			undock or bay ejection request, and that request
344			was successfully completed.  At this point, it might
345			be useful to send the system back to sleep, at the
346			user's choice.  Refer to HKEY events 0x4003 and
347			0x3003, below.
348	
349			This attribute has poll()/select() support.
350	
351	input layer notes:
352	
353	A Hot key is mapped to a single input layer EV_KEY event, possibly
354	followed by an EV_MSC MSC_SCAN event that shall contain that key's scan
355	code.  An EV_SYN event will always be generated to mark the end of the
356	event block.
357	
358	Do not use the EV_MSC MSC_SCAN events to process keys.  They are to be
359	used as a helper to remap keys, only.  They are particularly useful when
360	remapping KEY_UNKNOWN keys.
361	
362	The events are available in an input device, with the following id:
363	
364		Bus:		BUS_HOST
365		vendor:		0x1014 (PCI_VENDOR_ID_IBM)  or
366				0x17aa (PCI_VENDOR_ID_LENOVO)
367		product:	0x5054 ("TP")
368		version:	0x4101
369	
370	The version will have its LSB incremented if the keymap changes in a
371	backwards-compatible way.  The MSB shall always be 0x41 for this input
372	device.  If the MSB is not 0x41, do not use the device as described in
373	this section, as it is either something else (e.g. another input device
374	exported by a thinkpad driver, such as HDAPS) or its functionality has
375	been changed in a non-backwards compatible way.
376	
377	Adding other event types for other functionalities shall be considered a
378	backwards-compatible change for this input device.
379	
380	Thinkpad-acpi Hot Key event map (version 0x4101):
381	
382	ACPI	Scan
383	event	code	Key		Notes
384	
385	0x1001	0x00	FN+F1		-
386	
387	0x1002	0x01	FN+F2		IBM: battery (rare)
388					Lenovo: Screen lock
389	
390	0x1003	0x02	FN+F3		Many IBM models always report
391					this hot key, even with hot keys
392					disabled or with Fn+F3 masked
393					off
394					IBM: screen lock, often turns
395					off the ThinkLight as side-effect
396					Lenovo: battery
397	
398	0x1004	0x03	FN+F4		Sleep button (ACPI sleep button
399					semantics, i.e. sleep-to-RAM).
400					It always generates some kind
401					of event, either the hot key
402					event or an ACPI sleep button
403					event. The firmware may
404					refuse to generate further FN+F4
405					key presses until a S3 or S4 ACPI
406					sleep cycle is performed or some
407					time passes.
408	
409	0x1005	0x04	FN+F5		Radio.  Enables/disables
410					the internal Bluetooth hardware
411					and W-WAN card if left in control
412					of the firmware.  Does not affect
413					the WLAN card.
414					Should be used to turn on/off all
415					radios (Bluetooth+W-WAN+WLAN),
416					really.
417	
418	0x1006	0x05	FN+F6		-
419	
420	0x1007	0x06	FN+F7		Video output cycle.
421					Do you feel lucky today?
422	
423	0x1008	0x07	FN+F8		IBM: toggle screen expand
424					Lenovo: configure UltraNav,
425					or toggle screen expand
426	
427	0x1009	0x08	FN+F9		-
428		..	..		..
429	0x100B	0x0A	FN+F11		-
430	
431	0x100C	0x0B	FN+F12		Sleep to disk.  You are always
432					supposed to handle it yourself,
433					either through the ACPI event,
434					or through a hotkey event.
435					The firmware may refuse to
436					generate further FN+F12 key
437					press events until a S3 or S4
438					ACPI sleep cycle is performed,
439					or some time passes.
440	
441	0x100D	0x0C	FN+BACKSPACE	-
442	0x100E	0x0D	FN+INSERT	-
443	0x100F	0x0E	FN+DELETE	-
444	
445	0x1010	0x0F	FN+HOME		Brightness up.  This key is
446					always handled by the firmware
447					in IBM ThinkPads, even when
448					unmasked.  Just leave it alone.
449					For Lenovo ThinkPads with a new
450					BIOS, it has to be handled either
451					by the ACPI OSI, or by userspace.
452					The driver does the right thing,
453					never mess with this.
454	0x1011	0x10	FN+END		Brightness down.  See brightness
455					up for details.
456	
457	0x1012	0x11	FN+PGUP		ThinkLight toggle.  This key is
458					always handled by the firmware,
459					even when unmasked.
460	
461	0x1013	0x12	FN+PGDOWN	-
462	
463	0x1014	0x13	FN+SPACE	Zoom key
464	
465	0x1015	0x14	VOLUME UP	Internal mixer volume up. This
466					key is always handled by the
467					firmware, even when unmasked.
468					NOTE: Lenovo seems to be changing
469					this.
470	0x1016	0x15	VOLUME DOWN	Internal mixer volume up. This
471					key is always handled by the
472					firmware, even when unmasked.
473					NOTE: Lenovo seems to be changing
474					this.
475	0x1017	0x16	MUTE		Mute internal mixer. This
476					key is always handled by the
477					firmware, even when unmasked.
478	
479	0x1018	0x17	THINKPAD	ThinkPad/Access IBM/Lenovo key
480	
481	0x1019	0x18	unknown
482	..	..	..
483	0x1020	0x1F	unknown
484	
485	The ThinkPad firmware does not allow one to differentiate when most hot
486	keys are pressed or released (either that, or we don't know how to, yet).
487	For these keys, the driver generates a set of events for a key press and
488	immediately issues the same set of events for a key release.  It is
489	unknown by the driver if the ThinkPad firmware triggered these events on
490	hot key press or release, but the firmware will do it for either one, not
491	both.
492	
493	If a key is mapped to KEY_RESERVED, it generates no input events at all.
494	If a key is mapped to KEY_UNKNOWN, it generates an input event that
495	includes an scan code.  If a key is mapped to anything else, it will
496	generate input device EV_KEY events.
497	
498	In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW
499	events for switches:
500	
501	SW_RFKILL_ALL	T60 and later hardware rfkill rocker switch
502	SW_TABLET_MODE	Tablet ThinkPads HKEY events 0x5009 and 0x500A
503	
504	Non hotkey ACPI HKEY event map:
505	-------------------------------
506	
507	Events that are never propagated by the driver:
508	
509	0x2304		System is waking up from suspend to undock
510	0x2305		System is waking up from suspend to eject bay
511	0x2404		System is waking up from hibernation to undock
512	0x2405		System is waking up from hibernation to eject bay
513	0x5001		Lid closed
514	0x5002		Lid opened
515	0x5009		Tablet swivel: switched to tablet mode
516	0x500A		Tablet swivel: switched to normal mode
517	0x5010		Brightness level changed/control event
518	0x6000		KEYBOARD: Numlock key pressed
519	0x6005		KEYBOARD: Fn key pressed (TO BE VERIFIED)
520	0x7000		Radio Switch may have changed state
521	
522	
523	Events that are propagated by the driver to userspace:
524	
525	0x2313		ALARM: System is waking up from suspend because
526			the battery is nearly empty
527	0x2413		ALARM: System is waking up from hibernation because
528			the battery is nearly empty
529	0x3003		Bay ejection (see 0x2x05) complete, can sleep again
530	0x3006		Bay hotplug request (hint to power up SATA link when
531			the optical drive tray is ejected)
532	0x4003		Undocked (see 0x2x04), can sleep again
533	0x4010		Docked into hotplug port replicator (non-ACPI dock)
534	0x4011		Undocked from hotplug port replicator (non-ACPI dock)
535	0x500B		Tablet pen inserted into its storage bay
536	0x500C		Tablet pen removed from its storage bay
537	0x6011		ALARM: battery is too hot
538	0x6012		ALARM: battery is extremely hot
539	0x6021		ALARM: a sensor is too hot
540	0x6022		ALARM: a sensor is extremely hot
541	0x6030		System thermal table changed
542	0x6040		Nvidia Optimus/AC adapter related (TO BE VERIFIED)
543	0x60C0		X1 Yoga 2016, Tablet mode status changed
544	
545	Battery nearly empty alarms are a last resort attempt to get the
546	operating system to hibernate or shutdown cleanly (0x2313), or shutdown
547	cleanly (0x2413) before power is lost.  They must be acted upon, as the
548	wake up caused by the firmware will have negated most safety nets...
549	
550	When any of the "too hot" alarms happen, according to Lenovo the user
551	should suspend or hibernate the laptop (and in the case of battery
552	alarms, unplug the AC adapter) to let it cool down.  These alarms do
553	signal that something is wrong, they should never happen on normal
554	operating conditions.
555	
556	The "extremely hot" alarms are emergencies.  According to Lenovo, the
557	operating system is to force either an immediate suspend or hibernate
558	cycle, or a system shutdown.  Obviously, something is very wrong if this
559	happens.
560	
561	
562	Brightness hotkey notes:
563	
564	Don't mess with the brightness hotkeys in a Thinkpad.  If you want
565	notifications for OSD, use the sysfs backlight class event support.
566	
567	The driver will issue KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN events
568	automatically for the cases were userspace has to do something to
569	implement brightness changes.  When you override these events, you will
570	either fail to handle properly the ThinkPads that require explicit
571	action to change backlight brightness, or the ThinkPads that require
572	that no action be taken to work properly.
573	
574	
575	Bluetooth
576	---------
577	
578	procfs: /proc/acpi/ibm/bluetooth
579	sysfs device attribute: bluetooth_enable (deprecated)
580	sysfs rfkill class: switch "tpacpi_bluetooth_sw"
581	
582	This feature shows the presence and current state of a ThinkPad
583	Bluetooth device in the internal ThinkPad CDC slot.
584	
585	If the ThinkPad supports it, the Bluetooth state is stored in NVRAM,
586	so it is kept across reboots and power-off.
587	
588	Procfs notes:
589	
590	If Bluetooth is installed, the following commands can be used:
591	
592		echo enable > /proc/acpi/ibm/bluetooth
593		echo disable > /proc/acpi/ibm/bluetooth
594	
595	Sysfs notes:
596	
597		If the Bluetooth CDC card is installed, it can be enabled /
598		disabled through the "bluetooth_enable" thinkpad-acpi device
599		attribute, and its current status can also be queried.
600	
601		enable:
602			0: disables Bluetooth / Bluetooth is disabled
603			1: enables Bluetooth / Bluetooth is enabled.
604	
605		Note: this interface has been superseded by the	generic rfkill
606		class.  It has been deprecated, and it will be removed in year
607		2010.
608	
609		rfkill controller switch "tpacpi_bluetooth_sw": refer to
610		Documentation/rfkill.txt for details.
611	
612	
613	Video output control -- /proc/acpi/ibm/video
614	--------------------------------------------
615	
616	This feature allows control over the devices used for video output -
617	LCD, CRT or DVI (if available). The following commands are available:
618	
619		echo lcd_enable > /proc/acpi/ibm/video
620		echo lcd_disable > /proc/acpi/ibm/video
621		echo crt_enable > /proc/acpi/ibm/video
622		echo crt_disable > /proc/acpi/ibm/video
623		echo dvi_enable > /proc/acpi/ibm/video
624		echo dvi_disable > /proc/acpi/ibm/video
625		echo auto_enable > /proc/acpi/ibm/video
626		echo auto_disable > /proc/acpi/ibm/video
627		echo expand_toggle > /proc/acpi/ibm/video
628		echo video_switch > /proc/acpi/ibm/video
629	
630	NOTE: Access to this feature is restricted to processes owning the
631	CAP_SYS_ADMIN capability for safety reasons, as it can interact badly
632	enough with some versions of X.org to crash it.
633	
634	Each video output device can be enabled or disabled individually.
635	Reading /proc/acpi/ibm/video shows the status of each device.
636	
637	Automatic video switching can be enabled or disabled.  When automatic
638	video switching is enabled, certain events (e.g. opening the lid,
639	docking or undocking) cause the video output device to change
640	automatically. While this can be useful, it also causes flickering
641	and, on the X40, video corruption. By disabling automatic switching,
642	the flickering or video corruption can be avoided.
643	
644	The video_switch command cycles through the available video outputs
645	(it simulates the behavior of Fn-F7).
646	
647	Video expansion can be toggled through this feature. This controls
648	whether the display is expanded to fill the entire LCD screen when a
649	mode with less than full resolution is used. Note that the current
650	video expansion status cannot be determined through this feature.
651	
652	Note that on many models (particularly those using Radeon graphics
653	chips) the X driver configures the video card in a way which prevents
654	Fn-F7 from working. This also disables the video output switching
655	features of this driver, as it uses the same ACPI methods as
656	Fn-F7. Video switching on the console should still work.
657	
658	UPDATE: refer to https://bugs.freedesktop.org/show_bug.cgi?id=2000
659	
660	
661	ThinkLight control
662	------------------
663	
664	procfs: /proc/acpi/ibm/light
665	sysfs attributes: as per LED class, for the "tpacpi::thinklight" LED
666	
667	procfs notes:
668	
669	The ThinkLight status can be read and set through the procfs interface.  A
670	few models which do not make the status available will show the ThinkLight
671	status as "unknown". The available commands are:
672	
673		echo on  > /proc/acpi/ibm/light
674		echo off > /proc/acpi/ibm/light
675	
676	sysfs notes:
677	
678	The ThinkLight sysfs interface is documented by the LED class
679	documentation, in Documentation/leds/leds-class.txt.  The ThinkLight LED name
680	is "tpacpi::thinklight".
681	
682	Due to limitations in the sysfs LED class, if the status of the ThinkLight
683	cannot be read or if it is unknown, thinkpad-acpi will report it as "off".
684	It is impossible to know if the status returned through sysfs is valid.
685	
686	
687	CMOS/UCMS control
688	-----------------
689	
690	procfs: /proc/acpi/ibm/cmos
691	sysfs device attribute: cmos_command
692	
693	This feature is mostly used internally by the ACPI firmware to keep the legacy
694	CMOS NVRAM bits in sync with the current machine state, and to record this
695	state so that the ThinkPad will retain such settings across reboots.
696	
697	Some of these commands actually perform actions in some ThinkPad models, but
698	this is expected to disappear more and more in newer models.  As an example, in
699	a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for
700	real, but commands 0 to 2 don't control the mixer anymore (they have been
701	phased out) and just update the NVRAM.
702	
703	The range of valid cmos command numbers is 0 to 21, but not all have an
704	effect and the behavior varies from model to model.  Here is the behavior
705	on the X40 (tpb is the ThinkPad Buttons utility):
706	
707		0 - Related to "Volume down" key press
708		1 - Related to "Volume up" key press
709		2 - Related to "Mute on" key press
710		3 - Related to "Access IBM" key press
711		4 - Related to "LCD brightness up" key press
712		5 - Related to "LCD brightness down" key press
713		11 - Related to "toggle screen expansion" key press/function
714		12 - Related to "ThinkLight on"
715		13 - Related to "ThinkLight off"
716		14 - Related to "ThinkLight" key press (toggle ThinkLight)
717	
718	The cmos command interface is prone to firmware split-brain problems, as
719	in newer ThinkPads it is just a compatibility layer.  Do not use it, it is
720	exported just as a debug tool.
721	
722	
723	LED control
724	-----------
725	
726	procfs: /proc/acpi/ibm/led
727	sysfs attributes: as per LED class, see below for names
728	
729	Some of the LED indicators can be controlled through this feature.  On
730	some older ThinkPad models, it is possible to query the status of the
731	LED indicators as well.  Newer ThinkPads cannot query the real status
732	of the LED indicators.
733	
734	Because misuse of the LEDs could induce an unaware user to perform
735	dangerous actions (like undocking or ejecting a bay device while the
736	buses are still active), or mask an important alarm (such as a nearly
737	empty battery, or a broken battery), access to most LEDs is
738	restricted.
739	
740	Unrestricted access to all LEDs requires that thinkpad-acpi be
741	compiled with the CONFIG_THINKPAD_ACPI_UNSAFE_LEDS option enabled.
742	Distributions must never enable this option.  Individual users that
743	are aware of the consequences are welcome to enabling it.
744	
745	Audio mute and microphone mute LEDs are supported, but currently not
746	visible to userspace. They are used by the snd-hda-intel audio driver.
747	
748	procfs notes:
749	
750	The available commands are:
751	
752		echo '<LED number> on' >/proc/acpi/ibm/led
753		echo '<LED number> off' >/proc/acpi/ibm/led
754		echo '<LED number> blink' >/proc/acpi/ibm/led
755	
756	The <LED number> range is 0 to 15. The set of LEDs that can be
757	controlled varies from model to model. Here is the common ThinkPad
758	mapping:
759	
760		0 - power
761		1 - battery (orange)
762		2 - battery (green)
763		3 - UltraBase/dock
764		4 - UltraBay
765		5 - UltraBase battery slot
766		6 - (unknown)
767		7 - standby
768		8 - dock status 1
769		9 - dock status 2
770		10, 11 - (unknown)
771		12 - thinkvantage
772		13, 14, 15 - (unknown)
773	
774	All of the above can be turned on and off and can be made to blink.
775	
776	sysfs notes:
777	
778	The ThinkPad LED sysfs interface is described in detail by the LED class
779	documentation, in Documentation/leds/leds-class.txt.
780	
781	The LEDs are named (in LED ID order, from 0 to 12):
782	"tpacpi::power", "tpacpi:orange:batt", "tpacpi:green:batt",
783	"tpacpi::dock_active", "tpacpi::bay_active", "tpacpi::dock_batt",
784	"tpacpi::unknown_led", "tpacpi::standby", "tpacpi::dock_status1",
785	"tpacpi::dock_status2", "tpacpi::unknown_led2", "tpacpi::unknown_led3",
786	"tpacpi::thinkvantage".
787	
788	Due to limitations in the sysfs LED class, if the status of the LED
789	indicators cannot be read due to an error, thinkpad-acpi will report it as
790	a brightness of zero (same as LED off).
791	
792	If the thinkpad firmware doesn't support reading the current status,
793	trying to read the current LED brightness will just return whatever
794	brightness was last written to that attribute.
795	
796	These LEDs can blink using hardware acceleration.  To request that a
797	ThinkPad indicator LED should blink in hardware accelerated mode, use the
798	"timer" trigger, and leave the delay_on and delay_off parameters set to
799	zero (to request hardware acceleration autodetection).
800	
801	LEDs that are known not to exist in a given ThinkPad model are not
802	made available through the sysfs interface.  If you have a dock and you
803	notice there are LEDs listed for your ThinkPad that do not exist (and
804	are not in the dock), or if you notice that there are missing LEDs,
805	a report to ibm-acpi-devel@lists.sourceforge.net is appreciated.
806	
807	
808	ACPI sounds -- /proc/acpi/ibm/beep
809	----------------------------------
810	
811	The BEEP method is used internally by the ACPI firmware to provide
812	audible alerts in various situations. This feature allows the same
813	sounds to be triggered manually.
814	
815	The commands are non-negative integer numbers:
816	
817		echo <number> >/proc/acpi/ibm/beep
818	
819	The valid <number> range is 0 to 17. Not all numbers trigger sounds
820	and the sounds vary from model to model. Here is the behavior on the
821	X40:
822	
823		0 - stop a sound in progress (but use 17 to stop 16)
824		2 - two beeps, pause, third beep ("low battery")
825		3 - single beep
826		4 - high, followed by low-pitched beep ("unable")
827		5 - single beep
828		6 - very high, followed by high-pitched beep ("AC/DC")
829		7 - high-pitched beep
830		9 - three short beeps
831		10 - very long beep
832		12 - low-pitched beep
833		15 - three high-pitched beeps repeating constantly, stop with 0
834		16 - one medium-pitched beep repeating constantly, stop with 17
835		17 - stop 16
836	
837	
838	Temperature sensors
839	-------------------
840	
841	procfs: /proc/acpi/ibm/thermal
842	sysfs device attributes: (hwmon "thinkpad") temp*_input
843	
844	Most ThinkPads include six or more separate temperature sensors but only
845	expose the CPU temperature through the standard ACPI methods.  This
846	feature shows readings from up to eight different sensors on older
847	ThinkPads, and up to sixteen different sensors on newer ThinkPads.
848	
849	For example, on the X40, a typical output may be:
850	temperatures:   42 42 45 41 36 -128 33 -128
851	
852	On the T43/p, a typical output may be:
853	temperatures:   48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128
854	
855	The mapping of thermal sensors to physical locations varies depending on
856	system-board model (and thus, on ThinkPad model).
857	
858	http://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that
859	tries to track down these locations for various models.
860	
861	Most (newer?) models seem to follow this pattern:
862	
863	1:  CPU
864	2:  (depends on model)
865	3:  (depends on model)
866	4:  GPU
867	5:  Main battery: main sensor
868	6:  Bay battery: main sensor
869	7:  Main battery: secondary sensor
870	8:  Bay battery: secondary sensor
871	9-15: (depends on model)
872	
873	For the R51 (source: Thomas Gruber):
874	2:  Mini-PCI
875	3:  Internal HDD
876	
877	For the T43, T43/p (source: Shmidoax/Thinkwiki.org)
878	http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p
879	2:  System board, left side (near PCMCIA slot), reported as HDAPS temp
880	3:  PCMCIA slot
881	9:  MCH (northbridge) to DRAM Bus
882	10: Clock-generator, mini-pci card and ICH (southbridge), under Mini-PCI
883	    card, under touchpad
884	11: Power regulator, underside of system board, below F2 key
885	
886	The A31 has a very atypical layout for the thermal sensors
887	(source: Milos Popovic, http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
888	1:  CPU
889	2:  Main Battery: main sensor
890	3:  Power Converter
891	4:  Bay Battery: main sensor
892	5:  MCH (northbridge)
893	6:  PCMCIA/ambient
894	7:  Main Battery: secondary sensor
895	8:  Bay Battery: secondary sensor
896	
897	
898	Procfs notes:
899		Readings from sensors that are not available return -128.
900		No commands can be written to this file.
901	
902	Sysfs notes:
903		Sensors that are not available return the ENXIO error.  This
904		status may change at runtime, as there are hotplug thermal
905		sensors, like those inside the batteries and docks.
906	
907		thinkpad-acpi thermal sensors are reported through the hwmon
908		subsystem, and follow all of the hwmon guidelines at
909		Documentation/hwmon.
910	
911	EXPERIMENTAL: Embedded controller register dump
912	-----------------------------------------------
913	
914	This feature is not included in the thinkpad driver anymore.
915	Instead the EC can be accessed through /sys/kernel/debug/ec with
916	a userspace tool which can be found here:
917	ftp://ftp.suse.com/pub/people/trenn/sources/ec
918	
919	Use it to determine the register holding the fan
920	speed on some models. To do that, do the following:
921		- make sure the battery is fully charged
922		- make sure the fan is running
923		- use above mentioned tool to read out the EC
924	
925	Often fan and temperature values vary between
926	readings. Since temperatures don't change vary fast, you can take
927	several quick dumps to eliminate them.
928	
929	You can use a similar method to figure out the meaning of other
930	embedded controller registers - e.g. make sure nothing else changes
931	except the charging or discharging battery to determine which
932	registers contain the current battery capacity, etc. If you experiment
933	with this, do send me your results (including some complete dumps with
934	a description of the conditions when they were taken.)
935	
936	
937	LCD brightness control
938	----------------------
939	
940	procfs: /proc/acpi/ibm/brightness
941	sysfs backlight device "thinkpad_screen"
942	
943	This feature allows software control of the LCD brightness on ThinkPad
944	models which don't have a hardware brightness slider.
945	
946	It has some limitations: the LCD backlight cannot be actually turned
947	on or off by this interface, it just controls the backlight brightness
948	level.
949	
950	On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
951	has eight brightness levels, ranging from 0 to 7.  Some of the levels
952	may not be distinct.  Later Lenovo models that implement the ACPI
953	display backlight brightness control methods have 16 levels, ranging
954	from 0 to 15.
955	
956	For IBM ThinkPads, there are two interfaces to the firmware for direct
957	brightness control, EC and UCMS (or CMOS).  To select which one should be
958	used, use the brightness_mode module parameter: brightness_mode=1 selects
959	EC mode, brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC
960	mode with NVRAM backing (so that brightness changes are remembered across
961	shutdown/reboot).
962	
963	The driver tries to select which interface to use from a table of
964	defaults for each ThinkPad model.  If it makes a wrong choice, please
965	report this as a bug, so that we can fix it.
966	
967	Lenovo ThinkPads only support brightness_mode=2 (UCMS).
968	
969	When display backlight brightness controls are available through the
970	standard ACPI interface, it is best to use it instead of this direct
971	ThinkPad-specific interface.  The driver will disable its native
972	backlight brightness control interface if it detects that the standard
973	ACPI interface is available in the ThinkPad.
974	
975	If you want to use the thinkpad-acpi backlight brightness control
976	instead of the generic ACPI video backlight brightness control for some
977	reason, you should use the acpi_backlight=vendor kernel parameter.
978	
979	The brightness_enable module parameter can be used to control whether
980	the LCD brightness control feature will be enabled when available.
981	brightness_enable=0 forces it to be disabled.  brightness_enable=1
982	forces it to be enabled when available, even if the standard ACPI
983	interface is also available.
984	
985	Procfs notes:
986	
987		The available commands are:
988	
989		echo up   >/proc/acpi/ibm/brightness
990		echo down >/proc/acpi/ibm/brightness
991		echo 'level <level>' >/proc/acpi/ibm/brightness
992	
993	Sysfs notes:
994	
995	The interface is implemented through the backlight sysfs class, which is
996	poorly documented at this time.
997	
998	Locate the thinkpad_screen device under /sys/class/backlight, and inside
999	it there will be the following attributes:
1000	
1001		max_brightness:
1002			Reads the maximum brightness the hardware can be set to.
1003			The minimum is always zero.
1004	
1005		actual_brightness:
1006			Reads what brightness the screen is set to at this instant.
1007	
1008		brightness:
1009			Writes request the driver to change brightness to the
1010			given value.  Reads will tell you what brightness the
1011			driver is trying to set the display to when "power" is set
1012			to zero and the display has not been dimmed by a kernel
1013			power management event.
1014	
1015		power:
1016			power management mode, where 0 is "display on", and 1 to 3
1017			will dim the display backlight to brightness level 0
1018			because thinkpad-acpi cannot really turn the backlight
1019			off.  Kernel power management events can temporarily
1020			increase the current power management level, i.e. they can
1021			dim the display.
1022	
1023	
1024	WARNING:
1025	
1026	    Whatever you do, do NOT ever call thinkpad-acpi backlight-level change
1027	    interface and the ACPI-based backlight level change interface
1028	    (available on newer BIOSes, and driven by the Linux ACPI video driver)
1029	    at the same time.  The two will interact in bad ways, do funny things,
1030	    and maybe reduce the life of the backlight lamps by needlessly kicking
1031	    its level up and down at every change.
1032	
1033	
1034	Volume control (Console Audio control)
1035	--------------------------------------
1036	
1037	procfs: /proc/acpi/ibm/volume
1038	ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC"
1039	
1040	NOTE: by default, the volume control interface operates in read-only
1041	mode, as it is supposed to be used for on-screen-display purposes.
1042	The read/write mode can be enabled through the use of the
1043	"volume_control=1" module parameter.
1044	
1045	NOTE: distros are urged to not enable volume_control by default, this
1046	should be done by the local admin only.  The ThinkPad UI is for the
1047	console audio control to be done through the volume keys only, and for
1048	the desktop environment to just provide on-screen-display feedback.
1049	Software volume control should be done only in the main AC97/HDA
1050	mixer.
1051	
1052	
1053	About the ThinkPad Console Audio control:
1054	
1055	ThinkPads have a built-in amplifier and muting circuit that drives the
1056	console headphone and speakers.  This circuit is after the main AC97
1057	or HDA mixer in the audio path, and under exclusive control of the
1058	firmware.
1059	
1060	ThinkPads have three special hotkeys to interact with the console
1061	audio control: volume up, volume down and mute.
1062	
1063	It is worth noting that the normal way the mute function works (on
1064	ThinkPads that do not have a "mute LED") is:
1065	
1066	1. Press mute to mute.  It will *always* mute, you can press it as
1067	   many times as you want, and the sound will remain mute.
1068	
1069	2. Press either volume key to unmute the ThinkPad (it will _not_
1070	   change the volume, it will just unmute).
1071	
1072	This is a very superior design when compared to the cheap software-only
1073	mute-toggle solution found on normal consumer laptops:  you can be
1074	absolutely sure the ThinkPad will not make noise if you press the mute
1075	button, no matter the previous state.
1076	
1077	The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain
1078	amplifiers driving the speakers and headphone output, and the firmware
1079	also handles volume control for the headphone and speakers on these
1080	ThinkPads without any help from the operating system (this volume
1081	control stage exists after the main AC97 or HDA mixer in the audio
1082	path).
1083	
1084	The newer Lenovo models only have firmware mute control, and depend on
1085	the main HDA mixer to do volume control (which is done by the operating
1086	system).  In this case, the volume keys are filtered out for unmute
1087	key press (there are some firmware bugs in this area) and delivered as
1088	normal key presses to the operating system (thinkpad-acpi is not
1089	involved).
1090	
1091	
1092	The ThinkPad-ACPI volume control:
1093	
1094	The preferred way to interact with the Console Audio control is the
1095	ALSA interface.
1096	
1097	The legacy procfs interface allows one to read the current state,
1098	and if volume control is enabled, accepts the following commands:
1099	
1100		echo up   >/proc/acpi/ibm/volume
1101		echo down >/proc/acpi/ibm/volume
1102		echo mute >/proc/acpi/ibm/volume
1103		echo unmute >/proc/acpi/ibm/volume
1104		echo 'level <level>' >/proc/acpi/ibm/volume
1105	
1106	The <level> number range is 0 to 14 although not all of them may be
1107	distinct. To unmute the volume after the mute command, use either the
1108	up or down command (the level command will not unmute the volume), or
1109	the unmute command.
1110	
1111	You can use the volume_capabilities parameter to tell the driver
1112	whether your thinkpad has volume control or mute-only control:
1113	volume_capabilities=1 for mixers with mute and volume control,
1114	volume_capabilities=2 for mixers with only mute control.
1115	
1116	If the driver misdetects the capabilities for your ThinkPad model,
1117	please report this to ibm-acpi-devel@lists.sourceforge.net, so that we
1118	can update the driver.
1119	
1120	There are two strategies for volume control.  To select which one
1121	should be used, use the volume_mode module parameter: volume_mode=1
1122	selects EC mode, and volume_mode=3 selects EC mode with NVRAM backing
1123	(so that volume/mute changes are remembered across shutdown/reboot).
1124	
1125	The driver will operate in volume_mode=3 by default. If that does not
1126	work well on your ThinkPad model, please report this to
1127	ibm-acpi-devel@lists.sourceforge.net.
1128	
1129	The driver supports the standard ALSA module parameters.  If the ALSA
1130	mixer is disabled, the driver will disable all volume functionality.
1131	
1132	
1133	Fan control and monitoring: fan speed, fan enable/disable
1134	---------------------------------------------------------
1135	
1136	procfs: /proc/acpi/ibm/fan
1137	sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
1138				  pwm1_enable, fan2_input
1139	sysfs hwmon driver attributes: fan_watchdog
1140	
1141	NOTE NOTE NOTE: fan control operations are disabled by default for
1142	safety reasons.  To enable them, the module parameter "fan_control=1"
1143	must be given to thinkpad-acpi.
1144	
1145	This feature attempts to show the current fan speed, control mode and
1146	other fan data that might be available.  The speed is read directly
1147	from the hardware registers of the embedded controller.  This is known
1148	to work on later R, T, X and Z series ThinkPads but may show a bogus
1149	value on other models.
1150	
1151	Some Lenovo ThinkPads support a secondary fan.  This fan cannot be
1152	controlled separately, it shares the main fan control.
1153	
1154	Fan levels:
1155	
1156	Most ThinkPad fans work in "levels" at the firmware interface.  Level 0
1157	stops the fan.  The higher the level, the higher the fan speed, although
1158	adjacent levels often map to the same fan speed.  7 is the highest
1159	level, where the fan reaches the maximum recommended speed.
1160	
1161	Level "auto" means the EC changes the fan level according to some
1162	internal algorithm, usually based on readings from the thermal sensors.
1163	
1164	There is also a "full-speed" level, also known as "disengaged" level.
1165	In this level, the EC disables the speed-locked closed-loop fan control,
1166	and drives the fan as fast as it can go, which might exceed hardware
1167	limits, so use this level with caution.
1168	
1169	The fan usually ramps up or down slowly from one speed to another, and
1170	it is normal for the EC to take several seconds to react to fan
1171	commands.  The full-speed level may take up to two minutes to ramp up to
1172	maximum speed, and in some ThinkPads, the tachometer readings go stale
1173	while the EC is transitioning to the full-speed level.
1174	
1175	WARNING WARNING WARNING: do not leave the fan disabled unless you are
1176	monitoring all of the temperature sensor readings and you are ready to
1177	enable it if necessary to avoid overheating.
1178	
1179	An enabled fan in level "auto" may stop spinning if the EC decides the
1180	ThinkPad is cool enough and doesn't need the extra airflow.  This is
1181	normal, and the EC will spin the fan up if the various thermal readings
1182	rise too much.
1183	
1184	On the X40, this seems to depend on the CPU and HDD temperatures.
1185	Specifically, the fan is turned on when either the CPU temperature
1186	climbs to 56 degrees or the HDD temperature climbs to 46 degrees.  The
1187	fan is turned off when the CPU temperature drops to 49 degrees and the
1188	HDD temperature drops to 41 degrees.  These thresholds cannot
1189	currently be controlled.
1190	
1191	The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
1192	certain conditions are met.  It will override any fan programming done
1193	through thinkpad-acpi.
1194	
1195	The thinkpad-acpi kernel driver can be programmed to revert the fan
1196	level to a safe setting if userspace does not issue one of the procfs
1197	fan commands: "enable", "disable", "level" or "watchdog", or if there
1198	are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is
1199	set to 1, manual mode) within a configurable amount of time of up to
1200	120 seconds.  This functionality is called fan safety watchdog.
1201	
1202	Note that the watchdog timer stops after it enables the fan.  It will be
1203	rearmed again automatically (using the same interval) when one of the
1204	above mentioned fan commands is received.  The fan watchdog is,
1205	therefore, not suitable to protect against fan mode changes made through
1206	means other than the "enable", "disable", and "level" procfs fan
1207	commands, or the hwmon fan control sysfs interface.
1208	
1209	Procfs notes:
1210	
1211	The fan may be enabled or disabled with the following commands:
1212	
1213		echo enable  >/proc/acpi/ibm/fan
1214		echo disable >/proc/acpi/ibm/fan
1215	
1216	Placing a fan on level 0 is the same as disabling it.  Enabling a fan
1217	will try to place it in a safe level if it is too slow or disabled.
1218	
1219	The fan level can be controlled with the command:
1220	
1221		echo 'level <level>' > /proc/acpi/ibm/fan
1222	
1223	Where <level> is an integer from 0 to 7, or one of the words "auto" or
1224	"full-speed" (without the quotes).  Not all ThinkPads support the "auto"
1225	and "full-speed" levels.  The driver accepts "disengaged" as an alias for
1226	"full-speed", and reports it as "disengaged" for backwards
1227	compatibility.
1228	
1229	On the X31 and X40 (and ONLY on those models), the fan speed can be
1230	controlled to a certain degree.  Once the fan is running, it can be
1231	forced to run faster or slower with the following command:
1232	
1233		echo 'speed <speed>' > /proc/acpi/ibm/fan
1234	
1235	The sustainable range of fan speeds on the X40 appears to be from about
1236	3700 to about 7350. Values outside this range either do not have any
1237	effect or the fan speed eventually settles somewhere in that range.  The
1238	fan cannot be stopped or started with this command.  This functionality
1239	is incomplete, and not available through the sysfs interface.
1240	
1241	To program the safety watchdog, use the "watchdog" command.
1242	
1243		echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan
1244	
1245	If you want to disable the watchdog, use 0 as the interval.
1246	
1247	Sysfs notes:
1248	
1249	The sysfs interface follows the hwmon subsystem guidelines for the most
1250	part, and the exception is the fan safety watchdog.
1251	
1252	Writes to any of the sysfs attributes may return the EINVAL error if
1253	that operation is not supported in a given ThinkPad or if the parameter
1254	is out-of-bounds, and EPERM if it is forbidden.  They may also return
1255	EINTR (interrupted system call), and EIO (I/O error while trying to talk
1256	to the firmware).
1257	
1258	Features not yet implemented by the driver return ENOSYS.
1259	
1260	hwmon device attribute pwm1_enable:
1261		0: PWM offline (fan is set to full-speed mode)
1262		1: Manual PWM control (use pwm1 to set fan level)
1263		2: Hardware PWM control (EC "auto" mode)
1264		3: reserved (Software PWM control, not implemented yet)
1265	
1266		Modes 0 and 2 are not supported by all ThinkPads, and the
1267		driver is not always able to detect this.  If it does know a
1268		mode is unsupported, it will return -EINVAL.
1269	
1270	hwmon device attribute pwm1:
1271		Fan level, scaled from the firmware values of 0-7 to the hwmon
1272		scale of 0-255.  0 means fan stopped, 255 means highest normal
1273		speed (level 7).
1274	
1275		This attribute only commands the fan if pmw1_enable is set to 1
1276		(manual PWM control).
1277	
1278	hwmon device attribute fan1_input:
1279		Fan tachometer reading, in RPM.  May go stale on certain
1280		ThinkPads while the EC transitions the PWM to offline mode,
1281		which can take up to two minutes.  May return rubbish on older
1282		ThinkPads.
1283	
1284	hwmon device attribute fan2_input:
1285		Fan tachometer reading, in RPM, for the secondary fan.
1286		Available only on some ThinkPads.  If the secondary fan is
1287		not installed, will always read 0.
1288	
1289	hwmon driver attribute fan_watchdog:
1290		Fan safety watchdog timer interval, in seconds.  Minimum is
1291		1 second, maximum is 120 seconds.  0 disables the watchdog.
1292	
1293	To stop the fan: set pwm1 to zero, and pwm1_enable to 1.
1294	
1295	To start the fan in a safe mode: set pwm1_enable to 2.  If that fails
1296	with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255
1297	would be the safest choice, though).
1298	
1299	
1300	WAN
1301	---
1302	
1303	procfs: /proc/acpi/ibm/wan
1304	sysfs device attribute: wwan_enable (deprecated)
1305	sysfs rfkill class: switch "tpacpi_wwan_sw"
1306	
1307	This feature shows the presence and current state of the built-in
1308	Wireless WAN device.
1309	
1310	If the ThinkPad supports it, the WWAN state is stored in NVRAM,
1311	so it is kept across reboots and power-off.
1312	
1313	It was tested on a Lenovo ThinkPad X60. It should probably work on other
1314	ThinkPad models which come with this module installed.
1315	
1316	Procfs notes:
1317	
1318	If the W-WAN card is installed, the following commands can be used:
1319	
1320		echo enable > /proc/acpi/ibm/wan
1321		echo disable > /proc/acpi/ibm/wan
1322	
1323	Sysfs notes:
1324	
1325		If the W-WAN card is installed, it can be enabled /
1326		disabled through the "wwan_enable" thinkpad-acpi device
1327		attribute, and its current status can also be queried.
1328	
1329		enable:
1330			0: disables WWAN card / WWAN card is disabled
1331			1: enables WWAN card / WWAN card is enabled.
1332	
1333		Note: this interface has been superseded by the	generic rfkill
1334		class.  It has been deprecated, and it will be removed in year
1335		2010.
1336	
1337		rfkill controller switch "tpacpi_wwan_sw": refer to
1338		Documentation/rfkill.txt for details.
1339	
1340	
1341	EXPERIMENTAL: UWB
1342	-----------------
1343	
1344	This feature is considered EXPERIMENTAL because it has not been extensively
1345	tested and validated in various ThinkPad models yet.  The feature may not
1346	work as expected. USE WITH CAUTION! To use this feature, you need to supply
1347	the experimental=1 parameter when loading the module.
1348	
1349	sysfs rfkill class: switch "tpacpi_uwb_sw"
1350	
1351	This feature exports an rfkill controller for the UWB device, if one is
1352	present and enabled in the BIOS.
1353	
1354	Sysfs notes:
1355	
1356		rfkill controller switch "tpacpi_uwb_sw": refer to
1357		Documentation/rfkill.txt for details.
1358	
1359	Adaptive keyboard
1360	-----------------
1361	
1362	sysfs device attribute: adaptive_kbd_mode
1363	
1364	This sysfs attribute controls the keyboard "face" that will be shown on the
1365	Lenovo X1 Carbon 2nd gen (2014)'s adaptive keyboard. The value can be read
1366	and set.
1367	
1368	1 = Home mode
1369	2 = Web-browser mode
1370	3 = Web-conference mode
1371	4 = Function mode
1372	5 = Layflat mode
1373	
1374	For more details about which buttons will appear depending on the mode, please
1375	review the laptop's user guide:
1376	http://www.lenovo.com/shop/americas/content/user_guides/x1carbon_2_ug_en.pdf
1377	
1378	Multiple Commands, Module Parameters
1379	------------------------------------
1380	
1381	Multiple commands can be written to the proc files in one shot by
1382	separating them with commas, for example:
1383	
1384		echo enable,0xffff > /proc/acpi/ibm/hotkey
1385		echo lcd_disable,crt_enable > /proc/acpi/ibm/video
1386	
1387	Commands can also be specified when loading the thinkpad-acpi module,
1388	for example:
1389	
1390		modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable
1391	
1392	
1393	Enabling debugging output
1394	-------------------------
1395	
1396	The module takes a debug parameter which can be used to selectively
1397	enable various classes of debugging output, for example:
1398	
1399		 modprobe thinkpad_acpi debug=0xffff
1400	
1401	will enable all debugging output classes.  It takes a bitmask, so
1402	to enable more than one output class, just add their values.
1403	
1404		Debug bitmask		Description
1405		0x8000			Disclose PID of userspace programs
1406					accessing some functions of the driver
1407		0x0001			Initialization and probing
1408		0x0002			Removal
1409		0x0004			RF Transmitter control (RFKILL)
1410					(bluetooth, WWAN, UWB...)
1411		0x0008			HKEY event interface, hotkeys
1412		0x0010			Fan control
1413		0x0020			Backlight brightness
1414		0x0040			Audio mixer/volume control
1415	
1416	There is also a kernel build option to enable more debugging
1417	information, which may be necessary to debug driver problems.
1418	
1419	The level of debugging information output by the driver can be changed
1420	at runtime through sysfs, using the driver attribute debug_level.  The
1421	attribute takes the same bitmask as the debug module parameter above.
1422	
1423	
1424	Force loading of module
1425	-----------------------
1426	
1427	If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
1428	the module parameter force_load=1.  Regardless of whether this works or
1429	not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.
1430	
1431	
1432	Sysfs interface changelog:
1433	
1434	0x000100:	Initial sysfs support, as a single platform driver and
1435			device.
1436	0x000200:	Hot key support for 32 hot keys, and radio slider switch
1437			support.
1438	0x010000:	Hot keys are now handled by default over the input
1439			layer, the radio switch generates input event EV_RADIO,
1440			and the driver enables hot key handling by default in
1441			the firmware.
1442	
1443	0x020000:	ABI fix: added a separate hwmon platform device and
1444			driver, which must be located by name (thinkpad)
1445			and the hwmon class for libsensors4 (lm-sensors 3)
1446			compatibility.  Moved all hwmon attributes to this
1447			new platform device.
1448	
1449	0x020100:	Marker for thinkpad-acpi with hot key NVRAM polling
1450			support.  If you must, use it to know you should not
1451			start a userspace NVRAM poller (allows to detect when
1452			NVRAM is compiled out by the user because it is
1453			unneeded/undesired in the first place).
1454	0x020101:	Marker for thinkpad-acpi with hot key NVRAM polling
1455			and proper hotkey_mask semantics (version 8 of the
1456			NVRAM polling patch).  Some development snapshots of
1457			0.18 had an earlier version that did strange things
1458			to hotkey_mask.
1459	
1460	0x020200:	Add poll()/select() support to the following attributes:
1461			hotkey_radio_sw, wakeup_hotunplug_complete, wakeup_reason
1462	
1463	0x020300:	hotkey enable/disable support removed, attributes
1464			hotkey_bios_enabled and hotkey_enable deprecated and
1465			marked for removal.
1466	
1467	0x020400:	Marker for 16 LEDs support.  Also, LEDs that are known
1468			to not exist in a given model are not registered with
1469			the LED sysfs class anymore.
1470	
1471	0x020500:	Updated hotkey driver, hotkey_mask is always available
1472			and it is always able to disable hot keys.  Very old
1473			thinkpads are properly supported.  hotkey_bios_mask
1474			is deprecated and marked for removal.
1475	
1476	0x020600:	Marker for backlight change event support.
1477	
1478	0x020700:	Support for mute-only mixers.
1479			Volume control in read-only mode by default.
1480			Marker for ALSA mixer support.
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