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thinkpad-acpi: disable volume control

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Disable volume control by default.  It can be enabled at module load
time by a module parameter (volume_control=1).

The audio control mixer that thinkpad-acpi interacts with is fully
functional without any drivers, and operated by hotkeys.

The idea behind the console audio control is that the human operator
is the only one that can interact with it.  The ThinkVantage suite in
Windows does not allow any software-based overrides, and only does OSD
(on-screen-display) functions.

The Linux driver will, with the addition of the ALSA interface, try to
follow and enforce the ThinkVantage UI design:

The user is supposed to use the keyboard hotkeys to interact with the
console audio control.  The kernel and the desktop environment is
supposed to cooperate to provide proper user feedback through
on-screen-display functions.

Distros are urged to not to enable volume control by default.
Enabling this must be a local admin's decision.  This is the reason
why there is no Kconfig option.

Keep in mind that all ThinkPads have a normal, main mixer (AC97 or
HDA) for regular software-based audio control.  We are not talking
about that mixer here.

Advanced users are, of course, free to enable volume control and do as
they please.

Signed-off-by: Henrique de Moraes Holschuh <[email protected]>
Cc: Lorne Applebaum <[email protected]>
Cc: Matthew Garrett <[email protected]>
Signed-off-by: Len Brown <[email protected]>
This commit is contained in:
Henrique de Moraes Holschuh 2009-12-15 21:51:10 -02:00 • committed by Len Brown
commit c7ac6291ea
2 changed files with 55 additions and 5 deletions
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13
Documentation/laptops/thinkpad-acpi.txt
View file

@ -1097,6 +1097,18 @@ Volume control
procfs: /proc/acpi/ibm/volume
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.
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:
@ -1465,3 +1477,4 @@ Sysfs interface changelog:
0x020600: Marker for backlight change event support.
0x020700: Support for mute-only mixers.
Volume control in read-only mode by default.