+ 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 -- /proc/acpi/ibm/thermal
+---------------------------------------------
+
+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. Some
+readings may not be valid, e.g. may show large negative values. For
+example, on the X40, a typical output may be:
+
+temperatures: 42 42 45 41 36 -128 33 -128
+
+Thomas Gruber took his R51 apart and traced all six active sensors in
+his laptop (the location of sensors may vary on other models):
+
+1: CPU
+2: Mini PCI Module
+3: HDD
+4: GPU
+5: Battery
+6: N/A
+7: Battery
+8: N/A
+
+No commands can be written to this file.
+
+EXPERIMENTAL: Embedded controller reigster 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.)
+
+EXPERIMENTAL: LCD brightness control -- /proc/acpi/ibm/brightness
+-----------------------------------------------------------------
+
+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 allows software control of the LCD brightness on ThinkPad
+models which don't have a hardware brightness slider. The available
+commands are:
+
+ echo up >/proc/acpi/ibm/brightness
+ echo down >/proc/acpi/ibm/brightness
+ echo 'level <level>' >/proc/acpi/ibm/brightness
+
+The <level> number range is 0 to 7, although not all of them may be
+distinct. The current brightness level is shown in the file.
+
+EXPERIMENTAL: Volume control -- /proc/acpi/ibm/volume
+-----------------------------------------------------
+
+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 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.
+
+EXPERIMENTAL: fan speed, fan enable/disable -- /proc/acpi/ibm/fan
+-----------------------------------------------------------------
+
+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 attempts to show the current fan speed. The speed is read
+directly from the hardware registers of the embedded controller. This
+is known to work on later R, T and X series ThinkPads but may show a
+bogus value on other models.
+
+The fan may be enabled or disabled with the following commands:
+
+ echo enable >/proc/acpi/ibm/fan
+ echo disable >/proc/acpi/ibm/fan
+
+WARNING WARNING WARNING: do not leave the fan disabled unless you are
+monitoring the temperature sensor readings and you are ready to enable
+it if necessary to avoid overheating.
+
+The fan only runs if it's enabled *and* the various temperature
+sensors which control it read high enough. 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.
+
+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/thermal
+
+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.
+
+On the 570, temperature readings are not available through this
+feature and the fan control works a little differently. The fan speed
+is reported in levels from 0 (off) to 7 (max) and can be controlled
+with the following command: