[ltp] x41 volume, mute buttons, and acpi

[Marius Gedminas]

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On Wed, Jun 27, 2007 at 03:28:27PM -0400, Paul Fox wrote:
> i'm running ubuntu feisty on my X41.

Likewise, but on a T42.

> i don't do audio or video very often, so it was only recently
> that i realized that the special volume and mute keys (they're
> separate physical keys) aren't "hooked up" to anything via acpi.

That appears to be true.  Strangely, I notice that Fn-Home (increase
brightness) reports an event to acpid (ibm/hotkey HKEY 00000080
00001010), but Fn-End (decrease brightness) doesn't.

> they do have a very real effect on output volume, but no effect
> on the alsa mixer levels.

They have an effect on alsa mixer levels on my laptop.  Actually, they
have a double effect:

  * the BIOS changes the hardware mixer volume level (you can observe it
    via /proc/acpi/ibm/volume)

  * they send keyboard events (I think thinkpad-keys from the
    hotkey-setup package is responsible for this), which are mapped to
    GNOME's global key bindings that change the volume (of the ALSA
    'master' mixer).

I don't remember if these GNOME keybindings are part of the default
settings, or if I tweaked them myself.

> is there a reason for this?  looking through the archives, it
> seems that these keys might be handled by the bios directly --
> is that really true?

I think so.

The ThinkLight key (Fn-PgUp) is also controlled by the BIOS.  I know
this because when my Ubuntu crashes dead dead dead after a resume, I can
still toggle the ThinkLight, but I cannot even use magic SysRq.

(The crashes-on-resume seem to have stopped after I disabled VBE state
saving and POSTing the video hardware in /etc/default/acpi-support.)

Marius Gedminas
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