Re: pcm_multi poll timeout error

[Takashi Iwai <tiwai@suse.de>]

At Sun, 6 Aug 2006 16:03:49 +0100,
John Rigg wrote:
> 
> 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.

The change was not in pcm_multi.c but in pcm_hw.c.
But anyway this seems irrelevant.

> 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.

Try access to http://hg-mirror.alsa-project.org from your browser.


Takashi

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