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

[Takashi Iwai]

On Fri, 16 Oct 2015 02:32:50 +0200,
Raymond Yau wrote:
> 
> > >
> > > 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

Yes, and the mapping doesn't change in this case as before.

> 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 ?

It's one of the models we've considered.  Basically the number of
devices can be up to 64 (or such) per pin.  For Intel case, due to the
limitation of converters, it's up to 3.  For other GPUs that may drive
more simultaneous outputs, the number increases in square.  If a GPU
may handle 16 outputs, it'll be 256 entries.

Although the 256 entries are certainly manageable as kctl, whether
this is the best representation for user-space is a question.

> Will three three display port monitor playback devices always play
> different stream even when the displays are in clone mode ?

The clone mode is another messy part...

> > > If DP MST are dasiy chained, the unplug of the first monitor from
> Display
> > > Port will cause all DP monitor in the dasiy chain disconnect
> >
> > Yes.
> >
> 
> Do the power off of the Display Port in the middle of the dasiy chain also
> affect the last display port mointor in the dasiy chain ?

Possibly.  But it's not what we really care, as this is the thing the
graphics side should handle.


Takashi