[alsa-devel] [PATCH IO plug API 1/1] ioplug: Use boundary for wrap around

[Takashi Iwai]

On Fri, 23 Feb 2018 11:40:01 +0100,
Takashi Iwai wrote:
> 
> On Fri, 23 Feb 2018 10:28:51 +0100,
> <twischer at de.adit-jv.com> wrote:
> > 
> > From: Timo Wischer <twischer at de.adit-jv.com>
> > 
> > if requested by the IO plugin
> > 
> > Without this changes an IO plugin is not able to report
> > that buffer_size frames were read from the buffer.
> > When the buffer was full this is a valid action and
> > has not to be handled as an under run.
> > 
> > For example when the hw_ptr will be updated with
> > hw_ptr += buffer_size
> > and it is using the buffer_size as wrap around
> > hw_ptr %= buffer_size
> > would result in the same value as before the add operation.
> > 
> > Signed-off-by: Timo Wischer <twischer at de.adit-jv.com>
> > ---
> > Hello Takashi,
> > 
> > > If you need to improve such a situation, you'd have to fix in the
> > > ioplug implementation itself, not the jack plugin.
> > 
> > A have attached a patch which improves the IO plug API.
> > If you are happy with this solution I would also adapt the pending
> > JACK plugin patch and set the SND_PCM_IOPLUG_FLAG_BOUNDARY_WA flag.
> 
> Yep, this looks better now.
> 
> A slightly complex procedure when extending an API is that you need
> to check the existence of SND_PCM_IOPLUG_FLAG_BOUNDARY_WA in jack
> plugin side at the compilation time.  Or make AM_PATH_ALSA() in
> alsa-utils/configure.ac aligned with this change, but it won't work
> until the release of alsa-lib itself.

That said, I'd happily merge the patch once when seeing the
corresponding change in jack plugin side.


thanks,

Takashi