On Wed, 07 Jun 2017 02:38:05 +0200, Takashi Sakamoto wrote: > > In recent commit for ALSA PCM core, some arrangement is done for > 'struct snd_pcm_ops.ack' callback. This is called when appl_ptr is > explicitly moved in intermediate buffer for PCM frames, except for > some cases described later. > > For drivers in ALSA firewire stack, usage of this callback has a merit to > reduce latency between time of PCM frame queueing and handling actual > packets in recent isochronous cycle, because no need to wait for software > IRQ context from isochronous context of OHCI 1394. > > If this works well in a case that mapped page frame is used for the > intermediate buffer, user process should execute some commands for ioctl(2) > to tell the number of handled PCM frames in the intermediate buffer just > after handling them. This is one thing that was raised in the discussion with Intel people, and my suggestion was to add a new flag to suppress the status/control mmap like pcm_file->no_compat_mmap. Then alsa-lib falls back to the sync_ptr ioctl, and the driver can catch each appl_ptr update. In anyway, I applied the patch now as is. Thanks. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
