alsa driver and udev.

alsa driver and udev.

[James Courtier-Dutton]

Hi,

How much work would it be to get alsa driver to work nicely with udev, 
so that a specific udev config could be used to decide which sound card 
is card 0 etc.
How about a global config interface whereby userland processes could 
modify the sound card order and possibly provide other general sound 
card related services to userspace. In this way, even if a sound card 
booted up as card 0, we could swap it with card 1 without having to 
unload it.
This might require the device naming in /dev/snd to change so that the 
card number was not included in the device name. Maybe use an extra 
subdirectory for each card, much like the /proc filesystem uses.

James

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Re: alsa driver and udev.

[Jaroslav Kysela]

On Thu, 7 Dec 2006, James Courtier-Dutton wrote:

> Hi,
> 
> How much work would it be to get alsa driver to work nicely with udev, 
> so that a specific udev config could be used to decide which sound card 
> is card 0 etc.
> How about a global config interface whereby userland processes could 
> modify the sound card order and possibly provide other general sound 
> card related services to userspace. In this way, even if a sound card 
> booted up as card 0, we could swap it with card 1 without having to 
> unload it.
> This might require the device naming in /dev/snd to change so that the 
> card number was not included in the device name. Maybe use an extra 
> subdirectory for each card, much like the /proc filesystem uses.

Hi,

	my idea was a bit different. We have card id (aka text alias) 
already. They are fully supported in alsa-lib. So, only missing thing is 
to change these aliases and to use these aliases in application 
configurations rather than card numbers.
	I had already a discussion with Greg on LKML and in mm tree (I 
think) are patches to create a soundcard class. We can put card id (alias) 
to this class with read/write priviledges. So udev can freely change it 
like network device names. I think it could be in 2.6.20.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs

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