[alsa-devel] [PATCH] ALSA: snd-usb: properly initialize the sync endpoint

[Eldad Zack]

On Wed, 28 Nov 2012, Eldad Zack wrote:
> On Thu, 22 Nov 2012, Takashi Iwai wrote:
> > At Thu, 22 Nov 2012 20:27:59 +0100,
> > Daniel Mack wrote:
> > > 
> > > Jeffrey Barish reported an obvious bug in the pcm part of the usb-audio
> > > driver which causes the code to not initialize the sync endpoint from
> > > configure_endpoint().
> > > 
> > > Reported-by: Jeffrey Barish <jeff_barish at earthlink.net>
> > > Signed-off-by: Daniel Mack <zonque at gmail.com>
> > > Cc: stable at kernel.org [3.5+]
> > 
> > Thanks, applied.
> 
> This breaks the pcm init for the FT C400 - the reason is once 
> again the mismatch between sync and data in terms of channels and period
> bytes.
> I didn't notice it, since I was always opening capture and playback at 
> the same time.
> 
> After reverting it works as expected (for capture + playback) - however, 
> the revert is not a fix:
> If I open only the playback stream from userspace (using jack with -P),
> it will error out and then it will refuse to open pcm even for capture.
> But if I first open the device for capture (using jackd with -C), stop 
> it, then open just the playback, it works. Not surprising, since the sync
> ep was already set up.
> 
> Any suggestions on how to initialize the sync ep with its specific
> channel and period bytes paramaters?

Update: I found a solution for this - I'll post it with the C400 v4 
(today or tomorrow).

Cheers,
Eldad