[Pkg-alsa-devel] Bug#627351: libasound2: no approved way to order multiple cards with the same driver

Ian Zimmerman itz at buug.org
Thu May 19 19:36:36 UTC 2011


Package: libasound2
Version: 1.0.23-2.1
Severity: normal


The order which ALSA imposes on installed soundcards (which one is hw:0
and hence the default, which is hw:1, etc.) seems to be tied to the
naming of devices under /dev/snd; I assume it is the
/dev/snd/controlC[0-9] device that matters but I may be wrong.  As a
consequence this order is the same as the order udev sets up the
devices, which is not deterministic unless udev's hand is forced in one
way or another.  When the cards are driven by different kernel modules
this can be done with the slots= option to the snd module.

But the situation when the driver is the same is problematic.  It used
to be the case that one could at least directly write udev rules using
conditions on e.g. ATTRS{vendor} and ATTRS{device}, forcing udev to
renumber the devices if needed.  But latest versions of udev deprecate
this functionality, recommending that symlinks be used when a known fixed
name is needed.  (It still seems to work but probably not much longer.)

I think the userspace part of ALSA should not use /dev/snd/* directly,
but instead a symlink farm populated by udev rules of the kind described
above.  Then one could always force the order even in the case of the
same driver module.

-- System Information:
Debian Release: 6.0.1
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.38.6git (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages libasound2 depends on:
ii  libc6                         2.11.2-10  Embedded GNU C Library: Shared lib

libasound2 recommends no packages.

Versions of packages libasound2 suggests:
ii  libasound2-plugins           1.0.23-1+b1 ALSA library additional plugins

-- no debconf information





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