[alsa-devel] [PATCH 0/2] ALSA: pcm: implement the anonymous dup v3

[Phil Burk]

Thanks for the clarification. I was thinking the anon_inode:snd-pcm FD
replaced the /dev/snd/pcm FD.

> fd1 - /dev/snd/pcm (HAL) - standard sound device inode (no restrictions)
> fd2 - anon_inode:snd-pcm-buffer (for the EXCLUSIVE access)

That sounds right.

Thanks again for this work. ALSA is very important for Android Audio.

Phil Burk


On Fri, Feb 1, 2019 at 8:28 AM Jaroslav Kysela <perex at perex.cz> wrote:

> Dne 1.2.2019 v 16:31 Phil Burk napsal(a):
> > Thank you all for sorting this out. It seems like we are moving in a
> > really good direction.
> >
> >> I agree. We can have just two modes for the beginning:
> >> a) full one (useful for testing)
> >> b) buffer only (allow just sound data mmap)
> >
> > The full one is would also be used by the HAL for querying the DSP
> position.
> >
> >>  if we should use different names (like anon_inode:snd-pcm and
> > anon_inode:snd-pcm-buffer)
> >
> > That would be helpful.
> >
> > I have attached a revised requirements doc. The original doc was more of
> > a HowTo for OEMs to create the "anon_inode:dmabuf" FD.. This clarifies
> > the requirements and allows for the use of "anon_inode:snd-pcm*". It
> > should match what we have arrived at by discussion. Let me know if it
> > makes sense.
>
> It looks fine, but the HAL will use probably the standard sound device
> open (/dev/snd/), doesn't? So:
>
> fd1 - /dev/snd/pcm (HAL) - standard sound device inode (no restrictions)
> fd2 - anon_inode:snd-pcm-buffer (for the EXCLUSIVE access)
>
> With modes, I talked about the anonymous dup ioctl parameter. If there's
> another resource manager above HAL, the situation might be:
>
> fd1 - /dev/snd/pcm (resource manager) - standard sound device inode
> fd2 - anon_inode:snd-pcm (access to the full pcm sound API using the
> anonymous inode)
> fd3 - anon_inode:snd-pcm-buffer (for the EXCLUSIVE access)
>
> Perhaps you have different layers in Android.
>
>                         Thanks,
>                                 Jaroslav
>
>
> --
> Jaroslav Kysela <perex at perex.cz>
> Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
>