Some io plug-ins might want to adjust the reported delay value and not
strictly follow the current buffer usage (that's why we have two calls
after all).
Allow them to specify a delay() callback and use the previous behaviour
if they don't.
Signed-off-by: Pierre Ossman <ossman@cendio.se>
- Added protocl version check. The caller of snd_pcm_{io|ext}plug_create()
must fill version field with SND_PCM_{IO|EXT}PLUG_VERSION beforehand.
- Added poll_descriptors and poll_descriptors_count callbacks for ioplug.
