[alsa-devel] [PATCH] ALSA: hda - Update chmap tlv to report sink's capability

[Takashi Iwai]

On Fri, 01 Apr 2016 11:44:36 +0200,
Subhransu S. Prusty wrote:
> 
> On Fri, Apr 01, 2016 at 11:17:03AM +0200, Takashi Iwai wrote:
> > On Fri, 01 Apr 2016 10:48:37 +0200,
> > Subhransu S. Prusty wrote:
> > > 
> > > Currently channel map controls don't reflect the sink's
> > > capability to userspace. It reports the complete hdmi spec
> > > channel allocation table to the userspace which is of little use
> > > to the userspace applications.
> > > 
> > > With this patch, tlv callback is modified to read the speaker
> > > allocation block from sink, and a mapping alsa channel map is
> > > presented to the userspace.
> > 
> > Well, it's not clear what this patch really achieves.  Could you give
> > more concrete example?
> 
> Sure. The existing TLV callback implementation copies all of the
> cea_channel_speaker_allocation map table to the TLV container irrespective
> of what is reported by sink. With this patch it parses the spk_alloc block
> as queried from the ELD, and copies only the corresponding channel map from
> the cea channel speaker allocation table. Thus the user can parse the TLV
> container to identify sink's capability and set the channel map accordingly.

I see.  I thought the chmap was reported from ELD spk alloc bits from
the beginning, but I was wrong.  The TLV exposed all maps indeed.

> Please let me know if this explains properly, will add to the commit
> message.

Yes, this is more understandable.

> > Also, did you test this with AMD chips?
> 
> No, I dont have access to AMD chips. I believe this wouldn't break behavior
> in AMD chipsets as it makes use of already parsed spk alloc block.

Fair enough.  But then please put this in the changelog, too.


thanks,

Takashi