ThinkPad ACPI Extras Driver
- Version 0.23
- April 10th, 2009
+ Version 0.24
+ December 11th, 2009
Borislav Deianov <borislav@users.sf.net>
Henrique de Moraes Holschuh <hmh@hmh.eng.br>
echo expand_toggle > /proc/acpi/ibm/video
echo video_switch > /proc/acpi/ibm/video
+NOTE: Access to this feature is restricted to processes owning the
+CAP_SYS_ADMIN capability for safety reasons, as it can interact badly
+enough with some versions of X.org to crash it.
+
Each video output device can be enabled or disabled individually.
Reading /proc/acpi/ibm/video shows the status of each device.
its level up and down at every change.
-Volume control
---------------
+Volume control (Console Audio control)
+--------------------------------------
procfs: /proc/acpi/ibm/volume
+ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC"
+
+NOTE: by default, the volume control interface operates in read-only
+mode, as it is supposed to be used for on-screen-display purposes.
+The read/write mode can be enabled through the use of the
+"volume_control=1" module parameter.
+
+NOTE: distros are urged to not enable volume_control by default, this
+should be done by the local admin only. The ThinkPad UI is for the
+console audio control to be done through the volume keys only, and for
+the desktop environment to just provide on-screen-display feedback.
+Software volume control should be done only in the main AC97/HDA
+mixer.
+
+
+About the ThinkPad Console Audio control:
+
+ThinkPads have a built-in amplifier and muting circuit that drives the
+console headphone and speakers. This circuit is after the main AC97
+or HDA mixer in the audio path, and under exclusive control of the
+firmware.
+
+ThinkPads have three special hotkeys to interact with the console
+audio control: volume up, volume down and mute.
+
+It is worth noting that the normal way the mute function works (on
+ThinkPads that do not have a "mute LED") is:
-This feature allows volume control on ThinkPad models with a digital
-volume knob (when available, not all models have it), as well as
-mute/unmute control. The available commands are:
+1. Press mute to mute. It will *always* mute, you can press it as
+ many times as you want, and the sound will remain mute.
+
+2. Press either volume key to unmute the ThinkPad (it will _not_
+ change the volume, it will just unmute).
+
+This is a very superior design when compared to the cheap software-only
+mute-toggle solution found on normal consumer laptops: you can be
+absolutely sure the ThinkPad will not make noise if you press the mute
+button, no matter the previous state.
+
+The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain
+amplifiers driving the speakers and headphone output, and the firmware
+also handles volume control for the headphone and speakers on these
+ThinkPads without any help from the operating system (this volume
+control stage exists after the main AC97 or HDA mixer in the audio
+path).
+
+The newer Lenovo models only have firmware mute control, and depend on
+the main HDA mixer to do volume control (which is done by the operating
+system). In this case, the volume keys are filtered out for unmute
+key press (there are some firmware bugs in this area) and delivered as
+normal key presses to the operating system (thinkpad-acpi is not
+involved).
+
+
+The ThinkPad-ACPI volume control:
+
+The preferred way to interact with the Console Audio control is the
+ALSA interface.
+
+The legacy procfs interface allows one to read the current state,
+and if volume control is enabled, accepts the following commands:
echo up >/proc/acpi/ibm/volume
echo down >/proc/acpi/ibm/volume
echo 'level <level>' >/proc/acpi/ibm/volume
The <level> number range is 0 to 14 although not all of them may be
-distinct. The unmute the volume after the mute command, use either the
+distinct. To unmute the volume after the mute command, use either the
up or down command (the level command will not unmute the volume), or
the unmute command.
-The current volume level and mute state is shown in the file.
-
You can use the volume_capabilities parameter to tell the driver
whether your thinkpad has volume control or mute-only control:
volume_capabilities=1 for mixers with mute and volume control,
work well on your ThinkPad model, please report this to
ibm-acpi-devel@lists.sourceforge.net.
-The ALSA mixer interface to this feature is still missing, but patches
-to add it exist. That problem should be addressed in the not so
-distant future.
+The driver supports the standard ALSA module parameters. If the ALSA
+mixer is disabled, the driver will disable all volume functionality.
Fan control and monitoring: fan speed, fan enable/disable
0x020600: Marker for backlight change event support.
0x020700: Support for mute-only mixers.
+ Volume control in read-only mode by default.
+ Marker for ALSA mixer support.