[alsa-devel] Driver code with mpc5200 pointer problem.

Takashi Iwai tiwai at suse.de
Tue Apr 28 08:08:06 CEST 2009

At Mon, 27 Apr 2009 16:15:12 +0100,
Mark Brown wrote:
> On Mon, Apr 27, 2009 at 05:09:27PM +0200, Jaroslav Kysela wrote:
> > Appearently, FIFO is too big. I'm working on some changes to take account 
> > fifo_size to the jiffies based check. Please, set fifo_size correctly in 
> > your driver. USB drivers with big "URB FIFOs" should be changed as well, 
> > too.
> Could you expand a bit on what qualifies as "too big" here?  I've not
> been following the thread here or the changes that caused problems.

It's bigger than the pre-defined tolerance of jiffies check in PCM
core code.

The new PCM core checks the returned hw_ptr together with jiffies
delta whether it's a sane value.  When FIFO is used with the ring
buffer, the hardware tends to report back earlier before the expected


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