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

[Raymond Yau]

> >
> > > I'll try to explain my suggestion (which I believe Takashi's buying
too) one
> > > more time then:
> > >
> > > First, when a monitor is plugged in, we need to dynamically assign
this
> > > monitor to five PCM devices. I believe this scheme will be best:
> > >
> > > For a monitor at pin nid 0x05, dev index 0, it will prefer PCM 3.
> > > For a monitor at pin nid 0x06, dev index 0, it will prefer PCM 7.
> > > For a monitor at pin nid 0x07, dev index 0, it will prefer PCM 8.
> > > For a monitor at dev index 1 (any pin), it will prefer PCM 9.
> > > For a monitor at dev index 2 (any pin), it will prefer PCM 10.
> > >
> > > For monitors at dev indices > 2 (can that happen?), or if the PCM is
already
> > > assigned to something else, try PCMs in this order: 9, 10, 3, 7, 8.
> > > (Subject to discussion perhaps, I don't think the order matters too
much,
> > > because conflicts will be rare in practice.)
> >
> > Hi David,
> >
> > Would you please clarify why PA needs such a fixed binding between PCM
3,7, 8 and pin 0x05,6,7?
>
> It's not PA's requirement.  The only concern here is for people who
> uses ALSA device directly, e.g. via aplay -Dhdmi:2.  The first monitor
> is guaranteed to be mapped to the compatible position for such
> people.
>
> > And how will PA handle PCM 9,10 in a different way?
> > They are not bound to pins, and even not able to dev indexes.
> > In practice, a platform will usually support either a DP port or a HDMI
port from the Intel integrated GPU for cost consideration.
> > But theoretically i915 can use same device index on two different pins
to connect monitors, e.g. pin 0x05, dev index 2 for one monitor and pin
0x06, dev index 2 for the other.
> >
> > On Intel platforms, the max dev indices is 2. Not sure about Nvidia and
AMD.
>
> The whole number should be min(pins * 2 - 1, pins * 64).  It's two for
> Intel, and 7 or more on AMD/Nvidia.
>
> As we've discussed, this "reserved" area is basically optional.  We
> have them for keeping compatibility more easily.  Even if this are is
> exhausted, you can still try to map to any empty slot as the last
> resort.  So, in practice, maybe adding just two extra for this
> reserved area should suffice.  That is, the scheme is:
>
> - Try a static mapping at first
> - If already occupied, try a dynamic mapping in reserved area
> - If a dynamic mapping area is exhausted, try to find any empty slot
>
> The device index number doesn't matter.  If it conflicts, try
> another.
>
>

How do those pcm assigned when the controller have HDMI and two display
ports ?

http://www.intel.com/support/motherboards/desktop/sb/CS-034199.htm

Intel® NUC Kit DC53427HYE and Intel® NUC Board D53427RKE

In this configuration, the two displays that you connect to the mini
DisplayPort ports must be native DisplayPort-capable. Adapters that change
DisplayPort to HDMI or DVI will not work. It is also best that the first
display be HDMI without any adapters.

First display HDMI on Intel NUC connected to HDMI or DVI on monitor/TV
Max resolution: 1920x1200
Second display Mini-DisplayPort 1 on Intel NUC connected to DisplayPort on
monitor/TV
Max resolution: 1920x1200
Third display Mini-DisplayPort 2 on Intel NUC connected to DisplayPort on
monitor/TV
Max resolution: 1920x1200