Re: pcm_multi poll timeout error

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On Tue, Aug 01, 2006 at 12:43:44PM +0200, Takashi Iwai wrote:
> At Mon, 31 Jul 2006 22:04:26 -0400,
> Lee Revell wrote:
> > 
> > On Mon, 2005-12-12 at 12:31 +0100, Takashi Iwai wrote:
> > > At Fri, 9 Dec 2005 20:15:02 +0000,
> > > John Rigg wrote:
> > > > 
> > > > On Fri, Dec 09, 2005 at 12:55:27PM -0500, Jeremy Hall wrote:
> > > > > In the new year, John Rigg wrote:
> > > > > > On Fri, Dec 09, 2005 at 12:40:05PM +0100, Takashi Iwai wrote:
> > > > > > > The link_fd returns the file descriptor for linking multiple PCM
> > > > > > > streams.  If you comment it out, it means that no link is possible.
> > > > > > > It means that snd_pcm_link() didn't do anything in fact after your
> > > > > > > patch.
> > > > > > 
> > > > > > I can't understand why this works after my patch broke snd_pcm_link .
> > > > >
> > > > > It probably works because the rme cards are synced by an external means 
> > > > > such as word clock or the entity they are connected to has master sync
> > > > 
> > > > Makes sense. So, the situation appears to be:
> > > > 1 - The link code is unnecessary for duplex operation of multiple
> > > > clock-synchronised sound cards with jackd.
> > > > 2 - It breaks the above when present.
> > > 
> > > Hm, the question is what the cable-sync really does.  Basically the
> > > linked PCM streams in ALSA are just for trigger actions,
> > > i.e. start/stop streams.  The others are not really related.
> > > 
> > > However, the recent changes of multi pcm tries to use only one pollfd
> > > as a master, and this seems broken in your case.  Or, it's really the
> > > matter of linked streams.
> > > 
> > > Will come back to this issue later...
> > > 
> > 
> > Takashi-san,
> > 
> > I'm not sure I fully understand - are you saying JACK is broken or that
> > it's an ALSA bug?
> 
> It's an "undefined behavior".
> I suppose that software-linked PCM streams do right thing, but we need
> to investigate the detail.
> 
> John, could you check whether the problem still appears with the
> latest ALSA HG version, especially with alsa-lib?  I remember that
> some fixes have been done on multi plugin.

The problem still appears with alsa-lib-1.0.12rc2 version. There are
no changes in pcm_multi since 1.0.11.

Is there an easy way to view changes in the hg repository, ie. an
equivalent to the old cvs viewer on Sourceforge?
I'm testing this on my production system, which is a little disruptive,
so it would be convenient to be able to check for changes in the code before
trying it.

John

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