thinkpad-acpi - Move thinkpad-acpi.txt to Documentation/laptops

Also update references to thinkpad-acpi.txt in Kconfig.

Signed-off-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
CC: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 1367 insertions, 0 deletions

diff --git a/Documentation/laptops/00-INDEX b/Documentation/laptops/00-INDEX
index 2edb5967d35c..e806b084e5b2 100644
--- a/Documentation/laptops/00-INDEX
+++ b/Documentation/laptops/00-INDEX
@@ -1,2 +1,4 @@
 00-INDEX
         - This file
+thinkpad-acpi.txt
+        - information on the (IBM and Lenovo) ThinkPad ACPI Extras driver.
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
new file mode 100644
index 000000000000..6c2477754a2a
--- /dev/null
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -0,0 +1,1365 @@
+                     ThinkPad ACPI Extras Driver
+
+                            Version 0.19
+                         January 06th, 2008
+
+               Borislav Deianov <borislav@users.sf.net>
+             Henrique de Moraes Holschuh <hmh@hmh.eng.br>
+                      http://ibm-acpi.sf.net/
+
+
+This is a Linux driver for the IBM and Lenovo ThinkPad laptops. It
+supports various features of these laptops which are accessible
+through the ACPI and ACPI EC framework, but not otherwise fully
+supported by the generic Linux ACPI drivers.
+
+This driver used to be named ibm-acpi until kernel 2.6.21 and release
+0.13-20070314.  It used to be in the drivers/acpi tree, but it was
+moved to the drivers/misc tree and renamed to thinkpad-acpi for kernel
+2.6.22, and release 0.14.
+
+
+Status
+------
+
+The features currently supported are the following (see below for
+detailed description):
+
+        - Fn key combinations
+        - Bluetooth enable and disable
+        - video output switching, expansion control
+        - ThinkLight on and off
+        - limited docking and undocking
+        - UltraBay eject
+        - CMOS control
+        - LED control
+        - ACPI sounds
+        - temperature sensors
+        - Experimental: embedded controller register dump
+        - LCD brightness control
+        - Volume control
+        - Fan control and monitoring: fan speed, fan enable/disable
+        - Experimental: WAN enable and disable
+
+A compatibility table by model and feature is maintained on the web
+site, http://ibm-acpi.sf.net/. I appreciate any success or failure
+reports, especially if they add to or correct the compatibility table.
+Please include the following information in your report:
+
+        - ThinkPad model name
+        - a copy of your DSDT, from /proc/acpi/dsdt
+        - a copy of the output of dmidecode, with serial numbers
+          and UUIDs masked off
+        - which driver features work and which don't
+        - the observed behavior of non-working features
+
+Any other comments or patches are also more than welcome.
+
+
+Installation
+------------
+
+If you are compiling this driver as included in the Linux kernel
+sources, simply enable the CONFIG_THINKPAD_ACPI option, and optionally
+enable the CONFIG_THINKPAD_ACPI_BAY option if you want the
+thinkpad-specific bay functionality.
+
+Features
+--------
+
+The driver exports two different interfaces to userspace, which can be
+used to access the features it provides.  One is a legacy procfs-based
+interface, which will be removed at some time in the distant future.
+The other is a new sysfs-based interface which is not complete yet.
+
+The procfs interface creates the /proc/acpi/ibm directory.  There is a
+file under that directory for each feature it supports.  The procfs
+interface is mostly frozen, and will change very little if at all: it
+will not be extended to add any new functionality in the driver, instead
+all new functionality will be implemented on the sysfs interface.
+
+The sysfs interface tries to blend in the generic Linux sysfs subsystems
+and classes as much as possible.  Since some of these subsystems are not
+yet ready or stabilized, it is expected that this interface will change,
+and any and all userspace programs must deal with it.
+
+
+Notes about the sysfs interface:
+
+Unlike what was done with the procfs interface, correctness when talking
+to the sysfs interfaces will be enforced, as will correctness in the
+thinkpad-acpi's implementation of sysfs interfaces.
+
+Also, any bugs in the thinkpad-acpi sysfs driver code or in the
+thinkpad-acpi's implementation of the sysfs interfaces will be fixed for
+maximum correctness, even if that means changing an interface in
+non-compatible ways.  As these interfaces mature both in the kernel and
+in thinkpad-acpi, such changes should become quite rare.
+
+Applications interfacing to the thinkpad-acpi sysfs interfaces must
+follow all sysfs guidelines and correctly process all errors (the sysfs
+interface makes extensive use of errors).  File descriptors and open /
+close operations to the sysfs inodes must also be properly implemented.
+
+The version of thinkpad-acpi's sysfs interface is exported by the driver
+as a driver attribute (see below).
+
+Sysfs driver attributes are on the driver's sysfs attribute space,
+for 2.6.23 this is /sys/bus/platform/drivers/thinkpad_acpi/ and
+/sys/bus/platform/drivers/thinkpad_hwmon/
+
+Sysfs device attributes are on the thinkpad_acpi device sysfs attribute
+space, for 2.6.23 this is /sys/devices/platform/thinkpad_acpi/.
+
+Sysfs device attributes for the sensors and fan are on the
+thinkpad_hwmon device's sysfs attribute space, but you should locate it
+looking for a hwmon device with the name attribute of "thinkpad".
+
+Driver version
+--------------
+
+procfs: /proc/acpi/ibm/driver
+sysfs driver attribute: version
+
+The driver name and version. No commands can be written to this file.
+
+Sysfs interface version
+-----------------------
+
+sysfs driver attribute: interface_version
+
+Version of the thinkpad-acpi sysfs interface, as an unsigned long
+(output in hex format: 0xAAAABBCC), where:
+        AAAA - major revision
+        BB - minor revision
+        CC - bugfix revision
+
+The sysfs interface version changelog for the driver can be found at the
+end of this document.  Changes to the sysfs interface done by the kernel
+subsystems are not documented here, nor are they tracked by this
+attribute.
+
+Changes to the thinkpad-acpi sysfs interface are only considered
+non-experimental when they are submitted to Linux mainline, at which
+point the changes in this interface are documented and interface_version
+may be updated.  If you are using any thinkpad-acpi features not yet
+sent to mainline for merging, you do so on your own risk: these features
+may disappear, or be implemented in a different and incompatible way by
+the time they are merged in Linux mainline.
+
+Changes that are backwards-compatible by nature (e.g. the addition of
+attributes that do not change the way the other attributes work) do not
+always warrant an update of interface_version.  Therefore, one must
+expect that an attribute might not be there, and deal with it properly
+(an attribute not being there *is* a valid way to make it clear that a
+feature is not available in sysfs).
+
+Hot keys
+--------
+
+procfs: /proc/acpi/ibm/hotkey
+sysfs device attribute: hotkey_*
+
+In a ThinkPad, the ACPI HKEY handler is responsible for comunicating
+some important events and also keyboard hot key presses to the operating
+system.  Enabling the hotkey functionality of thinkpad-acpi signals the
+firmware that such a driver is present, and modifies how the ThinkPad
+firmware will behave in many situations.
+
+The driver enables the hot key feature automatically when loaded.  The
+feature can later be disabled and enabled back at runtime.  The driver
+will also restore the hot key feature to its previous state and mask
+when it is unloaded.
+
+When the hotkey feature is enabled and the hot key mask is set (see
+below), the driver will report HKEY events in the following format:
+
+        ibm/hotkey HKEY 00000080 0000xxxx
+
+Some of these events refer to hot key presses, but not all.
+
+The driver will generate events over the input layer for hot keys and
+radio switches, and over the ACPI netlink layer for other events.  The
+input layer support accepts the standard IOCTLs to remap the keycodes
+assigned to each hot key.
+
+The hot key bit mask allows some control over which hot keys generate
+events.  If a key is "masked" (bit set to 0 in the mask), the firmware
+will handle it.  If it is "unmasked", it signals the firmware that
+thinkpad-acpi would prefer to handle it, if the firmware would be so
+kind to allow it (and it often doesn't!).
+
+Not all bits in the mask can be modified.  Not all bits that can be
+modified do anything.  Not all hot keys can be individually controlled
+by the mask.  Some models do not support the mask at all, and in those
+models, hot keys cannot be controlled individually.  The behaviour of
+the mask is, therefore, higly dependent on the ThinkPad model.
+
+Note that unmasking some keys prevents their default behavior.  For
+example, if Fn+F5 is unmasked, that key will no longer enable/disable
+Bluetooth by itself.
+
+Note also that not all Fn key combinations are supported through ACPI.
+For example, on the X40, the brightness, volume and "Access IBM" buttons
+do not generate ACPI events even with this driver.  They *can* be used
+through the "ThinkPad Buttons" utility, see http://www.nongnu.org/tpb/
+
+procfs notes:
+
+The following commands can be written to the /proc/acpi/ibm/hotkey file:
+
+        echo enable > /proc/acpi/ibm/hotkey -- enable the hot keys feature
+        echo disable > /proc/acpi/ibm/hotkey -- disable the hot keys feature
+        echo 0xffffffff > /proc/acpi/ibm/hotkey -- enable all hot keys
+        echo 0 > /proc/acpi/ibm/hotkey -- disable all possible hot keys
+        ... any other 8-hex-digit mask ...
+        echo reset > /proc/acpi/ibm/hotkey -- restore the original mask
+
+The procfs interface does not support NVRAM polling control.  So as to
+maintain maximum bug-to-bug compatibility, it does not report any masks,
+nor does it allow one to manipulate the hot key mask when the firmware
+does not support masks at all, even if NVRAM polling is in use.
+
+sysfs notes:
+
+        hotkey_bios_enabled:
+                Returns the status of the hot keys feature when
+                thinkpad-acpi was loaded.  Upon module unload, the hot
+                key feature status will be restored to this value.
+
+                0: hot keys were disabled
+                1: hot keys were enabled (unusual)
+
+        hotkey_bios_mask:
+                Returns the hot keys mask when thinkpad-acpi was loaded.
+                Upon module unload, the hot keys mask will be restored
+                to this value.
+
+        hotkey_enable:
+                Enables/disables the hot keys feature in the ACPI
+                firmware, and reports current status of the hot keys
+                feature.  Has no effect on the NVRAM hot key polling
+                functionality.
+
+                0: disables the hot keys feature / feature disabled
+                1: enables the hot keys feature / feature enabled
+
+        hotkey_mask:
+                bit mask to enable driver-handling (and depending on
+                the firmware, ACPI event generation) for each hot key
+                (see above).  Returns the current status of the hot keys
+                mask, and allows one to modify it.
+
+                Note: when NVRAM polling is active, the firmware mask
+                will be different from the value returned by
+                hotkey_mask.  The driver will retain enabled bits for
+                hotkeys that are under NVRAM polling even if the
+                firmware refuses them, and will not set these bits on
+                the firmware hot key mask.
+
+        hotkey_all_mask:
+                bit mask that should enable event reporting for all
+                supported hot keys, when echoed to hotkey_mask above.
+                Unless you know which events need to be handled
+                passively (because the firmware *will* handle them
+                anyway), do *not* use hotkey_all_mask.  Use
+                hotkey_recommended_mask, instead. You have been warned.
+
+        hotkey_recommended_mask:
+                bit mask that should enable event reporting for all
+                supported hot keys, except those which are always
+                handled by the firmware anyway.  Echo it to
+                hotkey_mask above, to use.
+
+        hotkey_source_mask:
+                bit mask that selects which hot keys will the driver
+                poll the NVRAM for.  This is auto-detected by the driver
+                based on the capabilities reported by the ACPI firmware,
+                but it can be overridden at runtime.
+
+                Hot keys whose bits are set in both hotkey_source_mask
+                and also on hotkey_mask are polled for in NVRAM.  Only a
+                few hot keys are available through CMOS NVRAM polling.
+
+                Warning: when in NVRAM mode, the volume up/down/mute
+                keys are synthesized according to changes in the mixer,
+                so you have to use volume up or volume down to unmute,
+                as per the ThinkPad volume mixer user interface.  When
+                in ACPI event mode, volume up/down/mute are reported as
+                separate events, but this behaviour may be corrected in
+                future releases of this driver, in which case the
+                ThinkPad volume mixer user interface semanthics will be
+                enforced.
+
+        hotkey_poll_freq:
+                frequency in Hz for hot key polling. It must be between
+                0 and 25 Hz.  Polling is only carried out when strictly
+                needed.
+
+                Setting hotkey_poll_freq to zero disables polling, and
+                will cause hot key presses that require NVRAM polling
+                to never be reported.
+
+                Setting hotkey_poll_freq too low will cause repeated
+                pressings of the same hot key to be misreported as a
+                single key press, or to not even be detected at all.
+                The recommended polling frequency is 10Hz.
+
+        hotkey_radio_sw:
+                if the ThinkPad has a hardware radio switch, this
+                attribute will read 0 if the switch is in the "radios
+                disabled" postition, and 1 if the switch is in the
+                "radios enabled" position.
+
+                This attribute has poll()/select() support.
+
+        hotkey_report_mode:
+                Returns the state of the procfs ACPI event report mode
+                filter for hot keys.  If it is set to 1 (the default),
+                all hot key presses are reported both through the input
+                layer and also as ACPI events through procfs (but not
+                through netlink).  If it is set to 2, hot key presses
+                are reported only through the input layer.
+
+                This attribute is read-only in kernels 2.6.23 or later,
+                and read-write on earlier kernels.
+
+                May return -EPERM (write access locked out by module
+                parameter) or -EACCES (read-only).
+
+        wakeup_reason:
+                Set to 1 if the system is waking up because the user
+                requested a bay ejection.  Set to 2 if the system is
+                waking up because the user requested the system to
+                undock.  Set to zero for normal wake-ups or wake-ups
+                due to unknown reasons.
+
+                This attribute has poll()/select() support.
+
+        wakeup_hotunplug_complete:
+                Set to 1 if the system was waken up because of an
+                undock or bay ejection request, and that request
+                was sucessfully completed.  At this point, it might
+                be useful to send the system back to sleep, at the
+                user's choice.  Refer to HKEY events 0x4003 and
+                0x3003, below.
+
+                This attribute has poll()/select() support.
+
+input layer notes:
+
+A Hot key is mapped to a single input layer EV_KEY event, possibly
+followed by an EV_MSC MSC_SCAN event that shall contain that key's scan
+code.  An EV_SYN event will always be generated to mark the end of the
+event block.
+
+Do not use the EV_MSC MSC_SCAN events to process keys.  They are to be
+used as a helper to remap keys, only.  They are particularly useful when
+remapping KEY_UNKNOWN keys.
+
+The events are available in an input device, with the following id:
+
+        Bus:            BUS_HOST
+        vendor:         0x1014 (PCI_VENDOR_ID_IBM)  or
+                        0x17aa (PCI_VENDOR_ID_LENOVO)
+        product:        0x5054 ("TP")
+        version:        0x4101
+
+The version will have its LSB incremented if the keymap changes in a
+backwards-compatible way.  The MSB shall always be 0x41 for this input
+device.  If the MSB is not 0x41, do not use the device as described in
+this section, as it is either something else (e.g. another input device
+exported by a thinkpad driver, such as HDAPS) or its functionality has
+been changed in a non-backwards compatible way.
+
+Adding other event types for other functionalities shall be considered a
+backwards-compatible change for this input device.
+
+Thinkpad-acpi Hot Key event map (version 0x4101):
+
+ACPI    Scan
+event   code    Key             Notes
+
+0x1001  0x00    FN+F1           -
+0x1002  0x01    FN+F2           IBM: battery (rare)
+                                Lenovo: Screen lock
+
+0x1003  0x02    FN+F3           Many IBM models always report
+                                this hot key, even with hot keys
+                                disabled or with Fn+F3 masked
+                                off
+                                IBM: screen lock
+                                Lenovo: battery
+
+0x1004  0x03    FN+F4           Sleep button (ACPI sleep button
+                                semanthics, i.e. sleep-to-RAM).
+                                It is always generate some kind
+                                of event, either the hot key
+                                event or a ACPI sleep button
+                                event. The firmware may
+                                refuse to generate further FN+F4
+                                key presses until a S3 or S4 ACPI
+                                sleep cycle is performed or some
+                                time passes.
+
+0x1005  0x04    FN+F5           Radio.  Enables/disables
+                                the internal BlueTooth hardware
+                                and W-WAN card if left in control
+                                of the firmware.  Does not affect
+                                the WLAN card.
+                                Should be used to turn on/off all
+                                radios (bluetooth+W-WAN+WLAN),
+                                really.
+
+0x1006  0x05    FN+F6           -
+
+0x1007  0x06    FN+F7           Video output cycle.
+                                Do you feel lucky today?
+
+0x1008  0x07    FN+F8           IBM: toggle screen expand
+                                Lenovo: configure ultranav
+
+0x1009  0x08    FN+F9           -
+        ..      ..              ..
+0x100B  0x0A    FN+F11          -
+
+0x100C  0x0B    FN+F12          Sleep to disk.  You are always
+                                supposed to handle it yourself,
+                                either through the ACPI event,
+                                or through a hotkey event.
+                                The firmware may refuse to
+                                generate further FN+F4 key
+                                press events until a S3 or S4
+                                ACPI sleep cycle is performed,
+                                or some time passes.
+
+0x100D  0x0C    FN+BACKSPACE    -
+0x100E  0x0D    FN+INSERT       -
+0x100F  0x0E    FN+DELETE       -
+
+0x1010  0x0F    FN+HOME         Brightness up.  This key is
+                                always handled by the firmware
+                                in IBM ThinkPads, even when
+                                unmasked.  Just leave it alone.
+                                For Lenovo ThinkPads with a new
+                                BIOS, it has to be handled either
+                                by the ACPI OSI, or by userspace.
+0x1011  0x10    FN+END          Brightness down.  See brightness
+                                up for details.
+
+0x1012  0x11    FN+PGUP         Thinklight toggle.  This key is
+                                always handled by the firmware,
+                                even when unmasked.
+
+0x1013  0x12    FN+PGDOWN       -
+
+0x1014  0x13    FN+SPACE        Zoom key
+
+0x1015  0x14    VOLUME UP       Internal mixer volume up. This
+                                key is always handled by the
+                                firmware, even when unmasked.
+                                NOTE: Lenovo seems to be changing
+                                this.
+0x1016  0x15    VOLUME DOWN     Internal mixer volume up. This
+                                key is always handled by the
+                                firmware, even when unmasked.
+                                NOTE: Lenovo seems to be changing
+                                this.
+0x1017  0x16    MUTE            Mute internal mixer. This
+                                key is always handled by the
+                                firmware, even when unmasked.
+
+0x1018  0x17    THINKPAD        Thinkpad/Access IBM/Lenovo key
+
+0x1019  0x18    unknown
+..      ..      ..
+0x1020  0x1F    unknown
+
+The ThinkPad firmware does not allow one to differentiate when most hot
+keys are pressed or released (either that, or we don't know how to, yet).
+For these keys, the driver generates a set of events for a key press and
+immediately issues the same set of events for a key release.  It is
+unknown by the driver if the ThinkPad firmware triggered these events on
+hot key press or release, but the firmware will do it for either one, not
+both.
+
+If a key is mapped to KEY_RESERVED, it generates no input events at all.
+If a key is mapped to KEY_UNKNOWN, it generates an input event that
+includes an scan code.  If a key is mapped to anything else, it will
+generate input device EV_KEY events.
+
+Non hot-key ACPI HKEY event map:
+0x5001          Lid closed
+0x5002          Lid opened
+0x7000          Radio Switch may have changed state
+
+The above events are not propagated by the driver, except for legacy
+compatibility purposes when hotkey_report_mode is set to 1.
+
+0x2304          System is waking up from suspend to undock
+0x2305          System is waking up from suspend to eject bay
+0x2404          System is waking up from hibernation to undock
+0x2405          System is waking up from hibernation to eject bay
+
+The above events are never propagated by the driver.
+
+0x3003          Bay ejection (see 0x2x05) complete, can sleep again
+0x4003          Undocked (see 0x2x04), can sleep again
+0x5009          Tablet swivel: switched to tablet mode
+0x500A          Tablet swivel: switched to normal mode
+0x500B          Tablet pen insterted into its storage bay
+0x500C          Tablet pen removed from its storage bay
+0x5010          Brightness level changed (newer Lenovo BIOSes)
+
+The above events are propagated by the driver.
+
+Compatibility notes:
+
+ibm-acpi and thinkpad-acpi 0.15 (mainline kernels before 2.6.23) never
+supported the input layer, and sent events over the procfs ACPI event
+interface.
+
+To avoid sending duplicate events over the input layer and the ACPI
+event interface, thinkpad-acpi 0.16 implements a module parameter
+(hotkey_report_mode), and also a sysfs device attribute with the same
+name.
+
+Make no mistake here: userspace is expected to switch to using the input
+layer interface of thinkpad-acpi, together with the ACPI netlink event
+interface in kernels 2.6.23 and later, or with the ACPI procfs event
+interface in kernels 2.6.22 and earlier.
+
+If no hotkey_report_mode module parameter is specified (or it is set to
+zero), the driver defaults to mode 1 (see below), and on kernels 2.6.22
+and earlier, also allows one to change the hotkey_report_mode through
+sysfs.  In kernels 2.6.23 and later, where the netlink ACPI event
+interface is available, hotkey_report_mode cannot be changed through
+sysfs (it is read-only).
+
+If the hotkey_report_mode module parameter is set to 1 or 2, it cannot
+be changed later through sysfs (any writes will return -EPERM to signal
+that hotkey_report_mode was locked.  On 2.6.23 and later, where
+hotkey_report_mode cannot be changed at all, writes will return -EACES).
+
+hotkey_report_mode set to 1 makes the driver export through the procfs
+ACPI event interface all hot key presses (which are *also* sent to the
+input layer).  This is a legacy compatibility behaviour, and it is also
+the default mode of operation for the driver.
+
+hotkey_report_mode set to 2 makes the driver filter out the hot key
+presses from the procfs ACPI event interface, so these events will only
+be sent through the input layer.  Userspace that has been updated to use
+the thinkpad-acpi input layer interface should set hotkey_report_mode to
+2.
+
+Hot key press events are never sent to the ACPI netlink event interface.
+Really up-to-date userspace under kernel 2.6.23 and later is to use the
+netlink interface and the input layer interface, and don't bother at all
+with hotkey_report_mode.
+
+
+Bluetooth
+---------
+
+procfs: /proc/acpi/ibm/bluetooth
+sysfs device attribute: bluetooth_enable
+
+This feature shows the presence and current state of a ThinkPad
+Bluetooth device in the internal ThinkPad CDC slot.
+
+Procfs notes:
+
+If Bluetooth is installed, the following commands can be used:
+
+        echo enable > /proc/acpi/ibm/bluetooth
+        echo disable > /proc/acpi/ibm/bluetooth
+
+Sysfs notes:
+
+        If the Bluetooth CDC card is installed, it can be enabled /
+        disabled through the "bluetooth_enable" thinkpad-acpi device
+        attribute, and its current status can also be queried.
+
+        enable:
+                0: disables Bluetooth / Bluetooth is disabled
+                1: enables Bluetooth / Bluetooth is enabled.
+
+        Note: this interface will be probably be superseeded by the
+        generic rfkill class, so it is NOT to be considered stable yet.
+
+Video output control -- /proc/acpi/ibm/video
+--------------------------------------------
+
+This feature allows control over the devices used for video output -
+LCD, CRT or DVI (if available). The following commands are available:
+
+        echo lcd_enable > /proc/acpi/ibm/video
+        echo lcd_disable > /proc/acpi/ibm/video
+        echo crt_enable > /proc/acpi/ibm/video
+        echo crt_disable > /proc/acpi/ibm/video
+        echo dvi_enable > /proc/acpi/ibm/video
+        echo dvi_disable > /proc/acpi/ibm/video
+        echo auto_enable > /proc/acpi/ibm/video
+        echo auto_disable > /proc/acpi/ibm/video
+        echo expand_toggle > /proc/acpi/ibm/video
+        echo video_switch > /proc/acpi/ibm/video
+
+Each video output device can be enabled or disabled individually.
+Reading /proc/acpi/ibm/video shows the status of each device.
+
+Automatic video switching can be enabled or disabled.  When automatic
+video switching is enabled, certain events (e.g. opening the lid,
+docking or undocking) cause the video output device to change
+automatically. While this can be useful, it also causes flickering
+and, on the X40, video corruption. By disabling automatic switching,
+the flickering or video corruption can be avoided.
+
+The video_switch command cycles through the available video outputs
+(it simulates the behavior of Fn-F7).
+
+Video expansion can be toggled through this feature. This controls
+whether the display is expanded to fill the entire LCD screen when a
+mode with less than full resolution is used. Note that the current
+video expansion status cannot be determined through this feature.
+
+Note that on many models (particularly those using Radeon graphics
+chips) the X driver configures the video card in a way which prevents
+Fn-F7 from working. This also disables the video output switching
+features of this driver, as it uses the same ACPI methods as
+Fn-F7. Video switching on the console should still work.
+
+UPDATE: There's now a patch for the X.org Radeon driver which
+addresses this issue. Some people are reporting success with the patch
+while others are still having problems. For more information:
+
+https://bugs.freedesktop.org/show_bug.cgi?id=2000
+
+ThinkLight control -- /proc/acpi/ibm/light
+------------------------------------------
+
+The current status of the ThinkLight can be found in this file. A few
+models which do not make the status available will show it as
+"unknown". The available commands are:
+
+        echo on  > /proc/acpi/ibm/light
+        echo off > /proc/acpi/ibm/light
+
+Docking / undocking -- /proc/acpi/ibm/dock
+------------------------------------------
+
+Docking and undocking (e.g. with the X4 UltraBase) requires some
+actions to be taken by the operating system to safely make or break
+the electrical connections with the dock.
+
+The docking feature of this driver generates the following ACPI events:
+
+        ibm/dock GDCK 00000003 00000001 -- eject request
+        ibm/dock GDCK 00000003 00000002 -- undocked
+        ibm/dock GDCK 00000000 00000003 -- docked
+
+NOTE: These events will only be generated if the laptop was docked
+when originally booted. This is due to the current lack of support for
+hot plugging of devices in the Linux ACPI framework. If the laptop was
+booted while not in the dock, the following message is shown in the
+logs:
+
+        Mar 17 01:42:34 aero kernel: thinkpad_acpi: dock device not present
+
+In this case, no dock-related events are generated but the dock and
+undock commands described below still work. They can be executed
+manually or triggered by Fn key combinations (see the example acpid
+configuration files included in the driver tarball package available
+on the web site).
+
+When the eject request button on the dock is pressed, the first event
+above is generated. The handler for this event should issue the
+following command:
+
+        echo undock > /proc/acpi/ibm/dock
+
+After the LED on the dock goes off, it is safe to eject the laptop.
+Note: if you pressed this key by mistake, go ahead and eject the
+laptop, then dock it back in. Otherwise, the dock may not function as
+expected.
+
+When the laptop is docked, the third event above is generated. The
+handler for this event should issue the following command to fully
+enable the dock:
+
+        echo dock > /proc/acpi/ibm/dock
+
+The contents of the /proc/acpi/ibm/dock file shows the current status
+of the dock, as provided by the ACPI framework.
+
+The docking support in this driver does not take care of enabling or
+disabling any other devices you may have attached to the dock. For
+example, a CD drive plugged into the UltraBase needs to be disabled or
+enabled separately. See the provided example acpid configuration files
+for how this can be accomplished.
+
+There is no support yet for PCI devices that may be attached to a
+docking station, e.g. in the ThinkPad Dock II. The driver currently
+does not recognize, enable or disable such devices. This means that
+the only docking stations currently supported are the X-series
+UltraBase docks and "dumb" port replicators like the Mini Dock (the
+latter don't need any ACPI support, actually).
+
+UltraBay eject -- /proc/acpi/ibm/bay
+------------------------------------
+
+Inserting or ejecting an UltraBay device requires some actions to be
+taken by the operating system to safely make or break the electrical
+connections with the device.
+
+This feature generates the following ACPI events:
+
+        ibm/bay MSTR 00000003 00000000 -- eject request
+        ibm/bay MSTR 00000001 00000000 -- eject lever inserted
+
+NOTE: These events will only be generated if the UltraBay was present
+when the laptop was originally booted (on the X series, the UltraBay
+is in the dock, so it may not be present if the laptop was undocked).
+This is due to the current lack of support for hot plugging of devices
+in the Linux ACPI framework. If the laptop was booted without the
+UltraBay, the following message is shown in the logs:
+
+        Mar 17 01:42:34 aero kernel: thinkpad_acpi: bay device not present
+
+In this case, no bay-related events are generated but the eject
+command described below still works. It can be executed manually or
+triggered by a hot key combination.
+
+Sliding the eject lever generates the first event shown above. The
+handler for this event should take whatever actions are necessary to
+shut down the device in the UltraBay (e.g. call idectl), then issue
+the following command:
+
+        echo eject > /proc/acpi/ibm/bay
+
+After the LED on the UltraBay goes off, it is safe to pull out the
+device.
+
+When the eject lever is inserted, the second event above is
+generated. The handler for this event should take whatever actions are
+necessary to enable the UltraBay device (e.g. call idectl).
+
+The contents of the /proc/acpi/ibm/bay file shows the current status
+of the UltraBay, as provided by the ACPI framework.
+
+EXPERIMENTAL warm eject support on the 600e/x, A22p and A3x (To use
+this feature, you need to supply the experimental=1 parameter when
+loading the module):
+
+These models do not have a button near the UltraBay device to request
+a hot eject but rather require the laptop to be put to sleep
+(suspend-to-ram) before the bay device is ejected or inserted).
+The sequence of steps to eject the device is as follows:
+
+        echo eject > /proc/acpi/ibm/bay
+        put the ThinkPad to sleep
+        remove the drive
+        resume from sleep
+        cat /proc/acpi/ibm/bay should show that the drive was removed
+
+On the A3x, both the UltraBay 2000 and UltraBay Plus devices are
+supported. Use "eject2" instead of "eject" for the second bay.
+
+Note: the UltraBay eject support on the 600e/x, A22p and A3x is
+EXPERIMENTAL and may not work as expected. USE WITH CAUTION!
+
+CMOS control
+------------
+
+procfs: /proc/acpi/ibm/cmos
+sysfs device attribute: cmos_command
+
+This feature is mostly used internally by the ACPI firmware to keep the legacy
+CMOS NVRAM bits in sync with the current machine state, and to record this
+state so that the ThinkPad will retain such settings across reboots.
+
+Some of these commands actually perform actions in some ThinkPad models, but
+this is expected to disappear more and more in newer models.  As an example, in
+a T43 and in a X40, commands 12 and 13 still control the ThinkLight state for
+real, but commands 0 to 2 don't control the mixer anymore (they have been
+phased out) and just update the NVRAM.
+
+The range of valid cmos command numbers is 0 to 21, but not all have an
+effect and the behavior varies from model to model.  Here is the behavior
+on the X40 (tpb is the ThinkPad Buttons utility):
+
+        0 - Related to "Volume down" key press
+        1 - Related to "Volume up" key press
+        2 - Related to "Mute on" key press
+        3 - Related to "Access IBM" key press
+        4 - Related to "LCD brightness up" key pess
+        5 - Related to "LCD brightness down" key press
+        11 - Related to "toggle screen expansion" key press/function
+        12 - Related to "ThinkLight on"
+        13 - Related to "ThinkLight off"
+        14 - Related to "ThinkLight" key press (toggle thinklight)
+
+The cmos command interface is prone to firmware split-brain problems, as
+in newer ThinkPads it is just a compatibility layer.  Do not use it, it is
+exported just as a debug tool.
+
+LED control -- /proc/acpi/ibm/led
+---------------------------------
+
+Some of the LED indicators can be controlled through this feature. The
+available commands are:
+
+        echo '<led number> on' >/proc/acpi/ibm/led
+        echo '<led number> off' >/proc/acpi/ibm/led
+        echo '<led number> blink' >/proc/acpi/ibm/led
+
+The <led number> range is 0 to 7. The set of LEDs that can be
+controlled varies from model to model. Here is the mapping on the X40:
+
+        0 - power
+        1 - battery (orange)
+        2 - battery (green)
+        3 - UltraBase
+        4 - UltraBay
+        7 - standby
+
+All of the above can be turned on and off and can be made to blink.
+
+ACPI sounds -- /proc/acpi/ibm/beep
+----------------------------------
+
+The BEEP method is used internally by the ACPI firmware to provide
+audible alerts in various situations. This feature allows the same
+sounds to be triggered manually.
+
+The commands are non-negative integer numbers:
+
+        echo <number> >/proc/acpi/ibm/beep
+
+The valid <number> range is 0 to 17. Not all numbers trigger sounds
+and the sounds vary from model to model. Here is the behavior on the
+X40:
+
+        0 - stop a sound in progress (but use 17 to stop 16)
+        2 - two beeps, pause, third beep ("low battery")
+        3 - single beep
+        4 - high, followed by low-pitched beep ("unable")
+        5 - single beep
+        6 - very high, followed by high-pitched beep ("AC/DC")
+        7 - high-pitched beep
+        9 - three short beeps
+        10 - very long beep
+        12 - low-pitched beep
+        15 - three high-pitched beeps repeating constantly, stop with 0
+        16 - one medium-pitched beep repeating constantly, stop with 17
+        17 - stop 16
+
+Temperature sensors
+-------------------
+
+procfs: /proc/acpi/ibm/thermal
+sysfs device attributes: (hwmon "thinkpad") temp*_input
+
+Most ThinkPads include six or more separate temperature sensors but only
+expose the CPU temperature through the standard ACPI methods.  This
+feature shows readings from up to eight different sensors on older
+ThinkPads, and up to sixteen different sensors on newer ThinkPads.
+
+For example, on the X40, a typical output may be:
+temperatures:   42 42 45 41 36 -128 33 -128
+
+On the T43/p, a typical output may be:
+temperatures:   48 48 36 52 38 -128 31 -128 48 52 48 -128 -128 -128 -128 -128
+
+The mapping of thermal sensors to physical locations varies depending on
+system-board model (and thus, on ThinkPad model).
+
+http://thinkwiki.org/wiki/Thermal_Sensors is a public wiki page that
+tries to track down these locations for various models.
+
+Most (newer?) models seem to follow this pattern:
+
+1:  CPU
+2:  (depends on model)
+3:  (depends on model)
+4:  GPU
+5:  Main battery: main sensor
+6:  Bay battery: main sensor
+7:  Main battery: secondary sensor
+8:  Bay battery: secondary sensor
+9-15: (depends on model)
+
+For the R51 (source: Thomas Gruber):
+2:  Mini-PCI
+3:  Internal HDD
+
+For the T43, T43/p (source: Shmidoax/Thinkwiki.org)
+http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_T43.2C_T43p
+2:  System board, left side (near PCMCIA slot), reported as HDAPS temp
+3:  PCMCIA slot
+9:  MCH (northbridge) to DRAM Bus
+10: Clock-generator, mini-pci card and ICH (southbridge), under Mini-PCI
+    card, under touchpad
+11: Power regulator, underside of system board, below F2 key
+
+The A31 has a very atypical layout for the thermal sensors
+(source: Milos Popovic, http://thinkwiki.org/wiki/Thermal_Sensors#ThinkPad_A31)
+1:  CPU
+2:  Main Battery: main sensor
+3:  Power Converter
+4:  Bay Battery: main sensor
+5:  MCH (northbridge)
+6:  PCMCIA/ambient
+7:  Main Battery: secondary sensor
+8:  Bay Battery: secondary sensor
+
+
+Procfs notes:
+        Readings from sensors that are not available return -128.
+        No commands can be written to this file.
+
+Sysfs notes:
+        Sensors that are not available return the ENXIO error.  This
+        status may change at runtime, as there are hotplug thermal
+        sensors, like those inside the batteries and docks.
+
+        thinkpad-acpi thermal sensors are reported through the hwmon
+        subsystem, and follow all of the hwmon guidelines at
+        Documentation/hwmon.
+
+
+EXPERIMENTAL: Embedded controller register dump -- /proc/acpi/ibm/ecdump
+------------------------------------------------------------------------
+
+This feature is marked EXPERIMENTAL because the implementation
+directly accesses hardware registers and may not work as expected. USE
+WITH CAUTION! To use this feature, you need to supply the
+experimental=1 parameter when loading the module.
+
+This feature dumps the values of 256 embedded controller
+registers. Values which have changed since the last time the registers
+were dumped are marked with a star:
+
+[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
+EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
+EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
+EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
+EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
+EC 0x30:  01  07  1a  00  30  04  00  00 *85  00  00  10  00  50  00  00
+EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
+EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03 *bc *02 *bc
+EC 0x60: *02 *bc *02  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0x70:  00  00  00  00  00  12  30  40 *24 *26 *2c *27 *20  80 *1f  80
+EC 0x80:  00  00  00  06 *37 *0e  03  00  00  00  0e  07  00  00  00  00
+EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xa0: *ff  09  ff  09  ff  ff *64  00 *00 *00 *a2  41 *ff *ff *e0  00
+EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
+EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a
+
+This feature can be used to determine the register holding the fan
+speed on some models. To do that, do the following:
+
+        - make sure the battery is fully charged
+        - make sure the fan is running
+        - run 'cat /proc/acpi/ibm/ecdump' several times, once per second or so
+
+The first step makes sure various charging-related values don't
+vary. The second ensures that the fan-related values do vary, since
+the fan speed fluctuates a bit. The third will (hopefully) mark the
+fan register with a star:
+
+[root@x40 ibm-acpi]# cat /proc/acpi/ibm/ecdump
+EC       +00 +01 +02 +03 +04 +05 +06 +07 +08 +09 +0a +0b +0c +0d +0e +0f
+EC 0x00:  a7  47  87  01  fe  96  00  08  01  00  cb  00  00  00  40  00
+EC 0x10:  00  00  ff  ff  f4  3c  87  09  01  ff  42  01  ff  ff  0d  00
+EC 0x20:  00  00  00  00  00  00  00  00  00  00  00  03  43  00  00  80
+EC 0x30:  01  07  1a  00  30  04  00  00  85  00  00  10  00  50  00  00
+EC 0x40:  00  00  00  00  00  00  14  01  00  04  00  00  00  00  00  00
+EC 0x50:  00  c0  02  0d  00  01  01  02  02  03  03  03  03  bc  02  bc
+EC 0x60:  02  bc  02  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0x70:  00  00  00  00  00  12  30  40  24  27  2c  27  21  80  1f  80
+EC 0x80:  00  00  00  06 *be  0d  03  00  00  00  0e  07  00  00  00  00
+EC 0x90:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xa0:  ff  09  ff  09  ff  ff  64  00  00  00  a2  41  ff  ff  e0  00
+EC 0xb0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xc0:  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xd0:  03  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
+EC 0xe0:  00  00  00  00  00  00  00  00  11  20  49  04  24  06  55  03
+EC 0xf0:  31  55  48  54  35  38  57  57  08  2f  45  73  07  65  6c  1a
+
+Another set of values that varies often is the temperature
+readings. Since temperatures don't change vary fast, you can take
+several quick dumps to eliminate them.
+
+You can use a similar method to figure out the meaning of other
+embedded controller registers - e.g. make sure nothing else changes
+except the charging or discharging battery to determine which
+registers contain the current battery capacity, etc. If you experiment
+with this, do send me your results (including some complete dumps with
+a description of the conditions when they were taken.)
+
+LCD brightness control
+----------------------
+
+procfs: /proc/acpi/ibm/brightness
+sysfs backlight device "thinkpad_screen"
+
+This feature allows software control of the LCD brightness on ThinkPad
+models which don't have a hardware brightness slider.
+
+It has some limitations: the LCD backlight cannot be actually turned on or
+off by this interface, and in many ThinkPad models, the "dim while on
+battery" functionality will be enabled by the BIOS when this interface is
+used, and cannot be controlled.
+
+On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
+has eight brightness levels, ranging from 0 to 7.  Some of the levels
+may not be distinct.  Later Lenovo models that implement the ACPI
+display backlight brightness control methods have 16 levels, ranging
+from 0 to 15.
+
+There are two interfaces to the firmware for direct brightness control,
+EC and CMOS.  To select which one should be used, use the
+brightness_mode module parameter: brightness_mode=1 selects EC mode,
+brightness_mode=2 selects CMOS mode, brightness_mode=3 selects both EC
+and CMOS.  The driver tries to autodetect which interface to use.
+
+When display backlight brightness controls are available through the
+standard ACPI interface, it is best to use it instead of this direct
+ThinkPad-specific interface.  The driver will disable its native
+backlight brightness control interface if it detects that the standard
+ACPI interface is available in the ThinkPad.
+
+The brightness_enable module parameter can be used to control whether
+the LCD brightness control feature will be enabled when available.
+brightness_enable=0 forces it to be disabled.  brightness_enable=1
+forces it to be enabled when available, even if the standard ACPI
+interface is also available.
+
+Procfs notes:
+
+        The available commands are:
+
+        echo up   >/proc/acpi/ibm/brightness
+        echo down >/proc/acpi/ibm/brightness
+        echo 'level <level>' >/proc/acpi/ibm/brightness
+
+Sysfs notes:
+
+The interface is implemented through the backlight sysfs class, which is
+poorly documented at this time.
+
+Locate the thinkpad_screen device under /sys/class/backlight, and inside
+it there will be the following attributes:
+
+        max_brightness:
+                Reads the maximum brightness the hardware can be set to.
+                The minimum is always zero.
+
+        actual_brightness:
+                Reads what brightness the screen is set to at this instant.
+
+        brightness:
+                Writes request the driver to change brightness to the
+                given value.  Reads will tell you what brightness the
+                driver is trying to set the display to when "power" is set
+                to zero and the display has not been dimmed by a kernel
+                power management event.
+
+        power:
+                power management mode, where 0 is "display on", and 1 to 3
+                will dim the display backlight to brightness level 0
+                because thinkpad-acpi cannot really turn the backlight
+                off.  Kernel power management events can temporarily
+                increase the current power management level, i.e. they can
+                dim the display.
+
+
+Volume control -- /proc/acpi/ibm/volume
+---------------------------------------
+
+This feature allows volume control on ThinkPad models which don't have
+a hardware volume knob. The available commands are:
+
+        echo up   >/proc/acpi/ibm/volume
+        echo down >/proc/acpi/ibm/volume
+        echo mute >/proc/acpi/ibm/volume
+        echo 'level <level>' >/proc/acpi/ibm/volume
+
+The <level> number range is 0 to 15 although not all of them may be
+distinct. The unmute the volume after the mute command, use either the
+up or down command (the level command will not unmute the volume).
+The current volume level and mute state is shown in the file.
+
+Fan control and monitoring: fan speed, fan enable/disable
+---------------------------------------------------------
+
+procfs: /proc/acpi/ibm/fan
+sysfs device attributes: (hwmon "thinkpad") fan1_input, pwm1,
+                          pwm1_enable
+sysfs hwmon driver attributes: fan_watchdog
+
+NOTE NOTE NOTE: fan control operations are disabled by default for
+safety reasons.  To enable them, the module parameter "fan_control=1"
+must be given to thinkpad-acpi.
+
+This feature attempts to show the current fan speed, control mode and
+other fan data that might be available.  The speed is read directly
+from the hardware registers of the embedded controller.  This is known
+to work on later R, T, X and Z series ThinkPads but may show a bogus
+value on other models.
+
+Fan levels:
+
+Most ThinkPad fans work in "levels" at the firmware interface.  Level 0
+stops the fan.  The higher the level, the higher the fan speed, although
+adjacent levels often map to the same fan speed.  7 is the highest
+level, where the fan reaches the maximum recommended speed.
+
+Level "auto" means the EC changes the fan level according to some
+internal algorithm, usually based on readings from the thermal sensors.
+
+There is also a "full-speed" level, also known as "disengaged" level.
+In this level, the EC disables the speed-locked closed-loop fan control,
+and drives the fan as fast as it can go, which might exceed hardware
+limits, so use this level with caution.
+
+The fan usually ramps up or down slowly from one speed to another, and
+it is normal for the EC to take several seconds to react to fan
+commands.  The full-speed level may take up to two minutes to ramp up to
+maximum speed, and in some ThinkPads, the tachometer readings go stale
+while the EC is transitioning to the full-speed level.
+
+WARNING WARNING WARNING: do not leave the fan disabled unless you are
+monitoring all of the temperature sensor readings and you are ready to
+enable it if necessary to avoid overheating.
+
+An enabled fan in level "auto" may stop spinning if the EC decides the
+ThinkPad is cool enough and doesn't need the extra airflow.  This is
+normal, and the EC will spin the fan up if the various thermal readings
+rise too much.
+
+On the X40, this seems to depend on the CPU and HDD temperatures.
+Specifically, the fan is turned on when either the CPU temperature
+climbs to 56 degrees or the HDD temperature climbs to 46 degrees.  The
+fan is turned off when the CPU temperature drops to 49 degrees and the
+HDD temperature drops to 41 degrees.  These thresholds cannot
+currently be controlled.
+
+The ThinkPad's ACPI DSDT code will reprogram the fan on its own when
+certain conditions are met.  It will override any fan programming done
+through thinkpad-acpi.
+
+The thinkpad-acpi kernel driver can be programmed to revert the fan
+level to a safe setting if userspace does not issue one of the procfs
+fan commands: "enable", "disable", "level" or "watchdog", or if there
+are no writes to pwm1_enable (or to pwm1 *if and only if* pwm1_enable is
+set to 1, manual mode) within a configurable amount of time of up to
+120 seconds.  This functionality is called fan safety watchdog.
+
+Note that the watchdog timer stops after it enables the fan.  It will be
+rearmed again automatically (using the same interval) when one of the
+above mentioned fan commands is received.  The fan watchdog is,
+therefore, not suitable to protect against fan mode changes made through
+means other than the "enable", "disable", and "level" procfs fan
+commands, or the hwmon fan control sysfs interface.
+
+Procfs notes:
+
+The fan may be enabled or disabled with the following commands:
+
+        echo enable  >/proc/acpi/ibm/fan
+        echo disable >/proc/acpi/ibm/fan
+
+Placing a fan on level 0 is the same as disabling it.  Enabling a fan
+will try to place it in a safe level if it is too slow or disabled.
+
+The fan level can be controlled with the command:
+
+        echo 'level <level>' > /proc/acpi/ibm/fan
+
+Where <level> is an integer from 0 to 7, or one of the words "auto" or
+"full-speed" (without the quotes).  Not all ThinkPads support the "auto"
+and "full-speed" levels.  The driver accepts "disengaged" as an alias for
+"full-speed", and reports it as "disengaged" for backwards
+compatibility.
+
+On the X31 and X40 (and ONLY on those models), the fan speed can be
+controlled to a certain degree.  Once the fan is running, it can be
+forced to run faster or slower with the following command:
+
+        echo 'speed <speed>' > /proc/acpi/ibm/fan
+
+The sustainable range of fan speeds on the X40 appears to be from about
+3700 to about 7350. Values outside this range either do not have any
+effect or the fan speed eventually settles somewhere in that range.  The
+fan cannot be stopped or started with this command.  This functionality
+is incomplete, and not available through the sysfs interface.
+
+To program the safety watchdog, use the "watchdog" command.
+
+        echo 'watchdog <interval in seconds>' > /proc/acpi/ibm/fan
+
+If you want to disable the watchdog, use 0 as the interval.
+
+Sysfs notes:
+
+The sysfs interface follows the hwmon subsystem guidelines for the most
+part, and the exception is the fan safety watchdog.
+
+Writes to any of the sysfs attributes may return the EINVAL error if
+that operation is not supported in a given ThinkPad or if the parameter
+is out-of-bounds, and EPERM if it is forbidden.  They may also return
+EINTR (interrupted system call), and EIO (I/O error while trying to talk
+to the firmware).
+
+Features not yet implemented by the driver return ENOSYS.
+
+hwmon device attribute pwm1_enable:
+        0: PWM offline (fan is set to full-speed mode)
+        1: Manual PWM control (use pwm1 to set fan level)
+        2: Hardware PWM control (EC "auto" mode)
+        3: reserved (Software PWM control, not implemented yet)
+
+        Modes 0 and 2 are not supported by all ThinkPads, and the
+        driver is not always able to detect this.  If it does know a
+        mode is unsupported, it will return -EINVAL.
+
+hwmon device attribute pwm1:
+        Fan level, scaled from the firmware values of 0-7 to the hwmon
+        scale of 0-255.  0 means fan stopped, 255 means highest normal
+        speed (level 7).
+
+        This attribute only commands the fan if pmw1_enable is set to 1
+        (manual PWM control).
+
+hwmon device attribute fan1_input:
+        Fan tachometer reading, in RPM.  May go stale on certain
+        ThinkPads while the EC transitions the PWM to offline mode,
+        which can take up to two minutes.  May return rubbish on older
+        ThinkPads.
+
+hwmon driver attribute fan_watchdog:
+        Fan safety watchdog timer interval, in seconds.  Minimum is
+        1 second, maximum is 120 seconds.  0 disables the watchdog.
+
+To stop the fan: set pwm1 to zero, and pwm1_enable to 1.
+
+To start the fan in a safe mode: set pwm1_enable to 2.  If that fails
+with EINVAL, try to set pwm1_enable to 1 and pwm1 to at least 128 (255
+would be the safest choice, though).
+
+
+EXPERIMENTAL: WAN
+-----------------
+
+procfs: /proc/acpi/ibm/wan
+sysfs device attribute: wwan_enable
+
+This feature is marked EXPERIMENTAL because the implementation
+directly accesses hardware registers and may not work as expected. USE
+WITH CAUTION! To use this feature, you need to supply the
+experimental=1 parameter when loading the module.
+
+This feature shows the presence and current state of a W-WAN (Sierra
+Wireless EV-DO) device.
+
+It was tested on a Lenovo Thinkpad X60. It should probably work on other
+Thinkpad models which come with this module installed.
+
+Procfs notes:
+
+If the W-WAN card is installed, the following commands can be used:
+
+        echo enable > /proc/acpi/ibm/wan
+        echo disable > /proc/acpi/ibm/wan
+
+Sysfs notes:
+
+        If the W-WAN card is installed, it can be enabled /
+        disabled through the "wwan_enable" thinkpad-acpi device
+        attribute, and its current status can also be queried.
+
+        enable:
+                0: disables WWAN card / WWAN card is disabled
+                1: enables WWAN card / WWAN card is enabled.
+
+        Note: this interface will be probably be superseeded by the
+        generic rfkill class, so it is NOT to be considered stable yet.
+
+Multiple Commands, Module Parameters
+------------------------------------
+
+Multiple commands can be written to the proc files in one shot by
+separating them with commas, for example:
+
+        echo enable,0xffff > /proc/acpi/ibm/hotkey
+        echo lcd_disable,crt_enable > /proc/acpi/ibm/video
+
+Commands can also be specified when loading the thinkpad-acpi module,
+for example:
+
+        modprobe thinkpad_acpi hotkey=enable,0xffff video=auto_disable
+
+Enabling debugging output
+-------------------------
+
+The module takes a debug parameter which can be used to selectively
+enable various classes of debugging output, for example:
+
+         modprobe ibm_acpi debug=0xffff
+
+will enable all debugging output classes.  It takes a bitmask, so
+to enable more than one output class, just add their values.
+
+        Debug bitmask           Description
+        0x0001                  Initialization and probing
+        0x0002                  Removal
+
+There is also a kernel build option to enable more debugging
+information, which may be necessary to debug driver problems.
+
+The level of debugging information output by the driver can be changed
+at runtime through sysfs, using the driver attribute debug_level.  The
+attribute takes the same bitmask as the debug module parameter above.
+
+Force loading of module
+-----------------------
+
+If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
+the module parameter force_load=1.  Regardless of whether this works or
+not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.
+
+
+Sysfs interface changelog:
+
+0x000100:       Initial sysfs support, as a single platform driver and
+                device.
+0x000200:       Hot key support for 32 hot keys, and radio slider switch
+                support.
+0x010000:       Hot keys are now handled by default over the input
+                layer, the radio switch generates input event EV_RADIO,
+                and the driver enables hot key handling by default in
+                the firmware.
+
+0x020000:       ABI fix: added a separate hwmon platform device and
+                driver, which must be located by name (thinkpad)
+                and the hwmon class for libsensors4 (lm-sensors 3)
+                compatibility.  Moved all hwmon attributes to this
+                new platform device.
+
+0x020100:       Marker for thinkpad-acpi with hot key NVRAM polling
+                support.  If you must, use it to know you should not
+                start an userspace NVRAM poller (allows to detect when
+                NVRAM is compiled out by the user because it is
+                unneeded/undesired in the first place).
+0x020101:       Marker for thinkpad-acpi with hot key NVRAM polling
+                and proper hotkey_mask semanthics (version 8 of the
+                NVRAM polling patch).  Some development snapshots of
+                0.18 had an earlier version that did strange things
+                to hotkey_mask.
+
+0x020200:       Add poll()/select() support to the following attributes:
+                hotkey_radio_sw, wakeup_hotunplug_complete, wakeup_reason