[LAU] Many identical cards - how to keep them straight

[Mark Knecht]

On Sun, Mar 9, 2008 at 7:00 PM, David <dplist at free.fr> wrote:
> On Sun, 9 Mar 2008 15:57:16 -0700
>  "Mark Knecht" <markknecht at gmail.com> wrote:
>
>  > On Sun, Mar 9, 2008 at 3:52 PM, drew Roberts <zotz at 100jamz.com> wrote:
>  > >
>  > > On Sunday 09 March 2008 18:44:21 Mark Knecht wrote:
>  > >  > Hi,
>  > >  >    I'm aware of and use standard Alsa methods to keep different
>  > >  > sound cards in the same system straight as far as Alsa is
>  > >  > concerned. I'm wondering what the proper process would be to
>  > >  > keep 3 HDSP9652's which are physically in the same system, or
>  > >  > multiple USB sound devices external to the system, straight as
>  > >  > far as Alsa is concerned. I'd like to know that a certain card
>  > >  > always will be always be card 0, card 1 or card 2. I do not want
>  > >  > Alsa or Linux to make this decision for me and I certainly don't
>  > >  > want Alsa to change them from boot cycle to boot cycle.
>  > >  >
>  > >  >    What's the process to determine which identical card is
>  > >  > which? Do you need to determine some sort of card specific
>  > >  > hardware ID and then write udev rules or is there some way to do
>  > >  > this within Alsa?
>  > >
>  > >  I needed to solve this problem a while back. The best help I got
>  > > was telling me it was not possible.
>  >
>  > Humm, that's a pretty glaring disappointment, assuming it's true, and
>  > I have no reason to believe it isn't.
>  > >
>  > >  I would be very interested to learn that there is a way. I got a
>  > > lot of info that would help with non-identical cards though.
>
>  I have not tried this but maybe well crafted udev rules could help ?
>  The page http://reactivated.net/writing_udev_rules.html#sysfsmatch
>  gives hints about matching device names to data read from sysfs.
>
>  Reading this doc, it looks like you might find info that uniquely
>  identify each of your cards using the command
>  "udevinfo -a -p $(udevinfo -q path -n /dev/snd/<yourdevice>)" and craft
>  you local rules from there.
>
>  This might be a question worth asking on alsa-users too.
>
>  HTH
>
>  --
>  David
>

Yeah, as I said in the original post I suspected that if Alsa couldn't
do it then udev might be the way to go. Unfortunately that might mean
that every time I set up a new system I'd have to craft a file
specifically for that system. I was hoping that maybe there was some
way for Alsa to look at the card's ID and then automatically assign
the cards in ID order, etc. That would be good until one card crapped
out or you added another card at a later date.

Thanks for the input. I may play with that a bit.

Cheers,
Mark
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