[alsa-devel] [PATCH 11/11] ALSA: x86: Register multiple PCM devices for the LPE audio card

[Takashi Iwai]

On Wed, 26 Apr 2017 09:04:46 +0200,
Takashi Iwai wrote:
> 
> On Wed, 26 Apr 2017 03:58:57 +0200,
> Pierre-Louis Bossart wrote:
> > 
> > On 04/25/2017 03:27 PM, ville.syrjala at linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > >
> > > Now that everything is in place let's register a PCM device for
> > > each pipe of the display engine. This will make it possible to
> > > actually output audio to multiple displays at the same time. And
> > > it avoids modesets on unrelated displays from clobbering up the
> > > ELD and whatnot for the display currently doing the playback.
> > >
> > > The alternative would be to have a PCM device per port, but per-pipe
> > > is easier since the hardware actually works that way.
> > Very nice. I just tested on a CHT Zotac box which has two connectors
> > (1 HDMI and 1 DP), and I get sound concurrently on both, with hdmi
> > being listed as device 2 and DP as device 0.
> > I thought there were hardware restrictions but you proved me wrong. Kudos.
> > 
> > The only point that I find weird is that the jacks are reported as
> > 'on' on the 3 pipes, is there a way to tie them to an actual cable
> > being used?
> 
> The pdata check was changed to check port=-1 as the monitor off in the
> patch 6.  Maybe the initialization is missing?

I guess the problem is that the hotplug wq is called at the
initialization to retrieve the pdata for all pipes.  It's called with
uninitialized port=0, so all flags are on at init.

And it implies the potential problem: the pdata contains the
information only for a single pipe.  Maybe it should keep the
status/ELD for all three pipes.


Takashi