SND_COMPR_TRIGGER_DRAIN
retval = stream->ops->trigger(stream, SND_COMPR_TRIGGER_DRAIN);
case SND_COMPR_TRIGGER_DRAIN:
case SND_COMPR_TRIGGER_DRAIN:
case SND_COMPR_TRIGGER_DRAIN:
cmd == SND_COMPR_TRIGGER_DRAIN)
case SND_COMPR_TRIGGER_DRAIN: