FreeBSD/Linux Kernel Cross Reference
sys/Documentation/thinkpad-acpi.txt

                          ThinkPad ACPI Extras Driver
     
                                 Version 0.17
                              October 04th, 2007
     
                    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
   
   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, and reports
                   current status of the hot keys feature.
   
                   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 ACPI event
                   generation for each hot key (see above).  Returns the
                   current status of the hot keys mask, and allows one to
                   modify it.
   
           hotkey_all_mask:
                   bit mask that should enable event reporting for all
                   supported hot keys, when echoed to hotkey_mask above.
                   Unless you know which events need to be handled
                   passively (because the firmware *will* handle them
                   anyway), do *not* use hotkey_all_mask.  Use
                   hotkey_recommended_mask, instead. You have been warned.
   
           hotkey_recommended_mask:
                   bit mask that should enable event reporting for all
                   supported hot keys, except those which are always
                   handled by the firmware anyway.  Echo it to
                   hotkey_mask above, to use.
   
           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.
   
           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).
   
   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.
   
   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.

Cache object: 8ba4d29e953504713da219bb1fc309f5