[alsa-devel] DP1.2 MST audio support discussion

[Yang, Libin]

> >>>> From: Raymond Yau [mailto:superquad.vortex2 at gmail.com]
> >>>> Sent: Friday, October 16, 2015 8:33 AM
> >>>> To: Takashi Iwai
> >>>> Cc: airlied at linux.ie; tanuk at iki.fi; David Henningsson; Yang, Libin;
> >> Lin,
> >>>> Mengdong; Girdwood, Liam R; ALSA Development Mailing List
> >>>> Subject: Re: [alsa-devel] DP1.2 MST audio support discussion
> >>>>
> >>>>
> >>>>>>
> >>>>>> Do it mean that only one DP MST port and no HDMI port on
> the
> >>>> same graphic
> >>>>>> card ?
> >>>>>
> >>>>> No.
> >>>> If there is only one HDMI and one Display Port, this mean that
> there
> >>>> are two pin complexes
> >>>> How about the name of jack detection kctl of three Display Port
> >>>> monitors  which are created on the same pin complex but
> different
> >>>> dev_index ?
> >>>
> >>> For the jack name, what do you think if we change to
> >>> "HDMI/DP, pin=n, dev=m" format? Will it impact on pulseaudio?
> >>
> >> Yes, it will impact PulseAudio. It will require changes to files in
> >>
> >>
> http://cgit.freedesktop.org/pulseaudio/pulseaudio/tree/src/modules/
> >> alsa/mixer/paths
> >
> > So does this mean we should not change the name "HDMI/DP,pcm=3
> Jack"
> > to "HDMI/DP,pin=n, dev=m Jack", otherwise the old PA will not work
> with
> > the new driver?
> 
> Yes. And I don't understand why you need to do it, either - if you have
> three display port monitors on one pin, then they will all get different
> PCMs (8, 9 and 10), and they will signal their Jack status through
> "HDMI/DP,pcm=8 Jack", "HDMI/DP,pcm=9 Jack" and
> "HDMI/DP,pcm=10 Jack".

OK, I see. Thanks. I will not change the jack kctl name.
BTW, the PCM number will be the same as converter, which means
it will be 3 on Intel platforms.

> 
> Given that my proposed mapping algorithm will never change pin to
> PCM
> mapping (unless you have two displayport outputs and use MST on
> both), I
> think we can get away with not exposing the actual pin to userspace.
> And should this later become necessary, we can add a separate kctl for
> that.

My current thought is to expose the same jack kctls (same number and
same name) to userspace while we will create hda_jack_tbl for each device
entry. When pcm is bound to the device entry, the corresponding
jack kctl will be bound to the device entry.

Regards,
Libin

> 
> --
> David Henningsson, Canonical Ltd.
> https://launchpad.net/~diwic
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