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

Paul Davis paul at linuxaudiosystems.com
Mon Mar 10 08:06:11 EDT 2008


On Mon, 2008-03-10 at 11:22 +0100, Arnold Krille wrote:
> Am Sonntag, 9. März 2008 schrieb Mark Knecht:
> > 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.
> > >  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.
> 
> Probably the one giving that answer was me. It is not entirely impossible. The 
> solution is roughly:

I don't think that this is what Mark was asking for.

The problem he is facing is that if you have, say, 3 RME HDSP's, the
information used to identify them to ALSA (at least) is identical in
every case. It is therefore tricky to ensure that what you consider to
be the "first" card is always hw:0 and so forth. The usual ALSA
mechanism relies on PCI id and other stuff that, IIRC, is not going to
distinguish between 3 identical cards.

He does *not* want to run the 3 cards as one, and if he does, he knows
he has to keep them in sync.

I don't know of a solution to this. I guess that the PCI registers for
the cards contain some kind of serial number, but how you can get ALSA
to based its snd_index assignments on that, I don't know.

--p





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