[alsa-devel] PC Beep or PC Speaker or just Beep? and HDA Beep code...

Jaroslav Kysela perex at perex.cz
Tue Nov 3 12:01:57 CET 2009

On Fri, 30 Oct 2009, Takashi Iwai wrote:

> At Thu, 22 Oct 2009 17:50:10 +0200 (CEST),
> Jaroslav Kysela wrote:
>> Hi,
>>  	I'm changing the behaviour of Beep / PC Beep controls for HDA
>> drivers (comments?):
>> http://git.alsa-project.org/?p=alsa-kernel.git;a=commitdiff;h=d605dbeed1b102136513e09e95217e8dc19c800d
> Well, IMHO, the fundamental problem is that there is no logic to
> select the beep device in the input layer.  A few line of code to
> drivers/char/keyboard.c would do that.

Yes, it would be good to have possibility to configure which input device 
will receive beep events.

> Regarding your change: I'm afraid that too frequent attach/detach
> calls aren't good.

What's too frequent? The attach/detach is called only when Beep mute 
control is toggled. I don't think that user will toggle this control as 
more as once in a normal system setup. The default value is "muted" 
(no registration) anyway.

I would really like to have the HDA Beep registration to input layer 
configurable at runtime. The control layer seems good for this job.
I can eventually add one more control with name like "Beep Register 
Switch", but the "Beep Playback Switch" does this job well.

>  Also, note that there are hardwares that still
> beep even when the beep volume is set to zero.  So, you may get a
> situation that you can't disable beep tone.

??? If you don't set HDA codec frequency registers, then the HDA 
digital beep cannot be generated.

>>  	I would like to introduce uniform naming for these controls
>> to not confuse users.
>> HDA driver: Beep, PC Beep
>> AC97: PC Speaker, Beep, PC Beep
>> etc..
>>  	I think that the original purpose of PC Speaker is a beep
>> generator. Also, many SoC platforms use AC97 codecs, so removing
>> abbreviation PC might make sense. It would be probably best to change all
>> control names in drivers to 'Beep'. Comments?
> Yes, I agree to rename all to Beep.  The word "PC Speaker" has been
> always confusing.

I'll do this change.


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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