[alsa-devel] Debugging custom driver: BUG: pcmC0D0c:0 error

[Takashi Iwai]

At Thu, 19 May 2011 16:34:59 -0400,
Mike Crowe wrote:
> 
> Hi folks,
> 
> I'm digging into a custom, embedded ALSA driver for some hardware we are
> developing.  The basic functionality (interfacing with an soc/wm8990 codec)
> is working fine.
> 
> We have a new library that we are adding which interfaces with the system
> via OSS.  In preparation, I built the vrec/vplay functions, which also use
> OSS, and they work fine with the OSS Emulation layer of ALSA.
> 
> I have enabled verbose printk and debug messages, and am seeing the
> following entries in the log file.  Since I did not have these enabled
> before I started integrating, I'm not sure if this is new, or if they have
> been there for a while.
> 
> Are these a problem, or can I ignore these?
> 
> ALSA sound/core/pcm_lib.c:318: BUG: pcmC0D0c:0, pos = 230989824, buffer size
> = 12304, period size = 769

This one looks broken.  A negative position?

> [ 2018.944000] ALSA sound/core/pcm_lib.c:318: BUG: pcmC0D0c:0, pos = 65536,
> buffer size = 65536, period size = 4096
> [ 2020.304000] ALSA sound/core/pcm_lib.c:318: BUG: pcmC0D0c:0, pos = 65536,
> buffer size = 65536, period size = 4096
> [ 2021.660000] ALSA sound/core/pcm_lib.c:318: BUG: pcmC0D0c:0, pos = 65536,
> buffer size = 65536, period size = 4096

These are just at buffer boundary.  The position must be between 0 and
(buffer_size-1).  If it's on buffer boundary, return zero from pointer
callback.


Takashi