[alsa-devel] my udev rules are breaking my dmixer setup why?

Jaroslav Kysela perex at perex.cz
Tue Nov 11 12:01:22 CET 2008

On Tue, 11 Nov 2008, Takashi Iwai wrote:

> > Almost all devices can be managed with udev rules, that is where the
> > system is designed for, there are also alsa rules in there, if they
> > don't work what is wrong then? is it an alsa issue, or udev, what are
> > the dependencies when alsa uses hardware. How are the /dev/snd/* devices
> > used and what is the /proc/asound/* for ?
> The card index mechanism in ALSA was introduced much before udev
> was born.  It's just a legacy mechanism, but it's hard to kill without
> breaking the running system, unfortunately.

Note that you can identify your card via the text identification (check 
/proc/asound/cards to get it in []). You can set this identification in 
the module insert time and use for example 'hw:Intel' in your apps without 
bothering with indexes.

The missing part is the modification of this text identification using
sysfs at runtime for udev. Some time ago, I was trying to add this setup 
to /sys/class/sound, but the sysfs core code was not prepared for this 
change. I'll try to check the situation again.

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

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