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

[Eldad Zack]

Hi Daniel, Takashi,

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?

Cheers,
Eldad