On Fri, 03 Jul 2015, Raymond Yau <superquad.vortex2@xxxxxxxxx> wrote: > 2015-6-29 下午3:58於 "Jani Nikula" <jani.nikula@xxxxxxxxxxxxxxx>寫道： >> >> On Sat, 27 Jun 2015, Raymond Yau <superquad.vortex2@xxxxxxxxx> wrote: >> >> > > >> >> > > Shall we move or cc this discussion on audio driver side to ALSA > ML? >> >> > >> >> > Oops I thought I had cc'ed these patches to alsa-devel as well when I >> > sent them. >> >> > >> >> > > I think we also need to decide how to manage PCM devices for DP > MST. >> >> > > Now the HD-A driver create a PCM device for each pin, and the >> > substream >> >> > > number is 1 for each PCM. Now with DP MST enabled, each pin can >> > support >> >> > > multiple streams (e.g. 3 on Intel HSW/BDW/SKL). >> >> > > >> >> > > There may be 2 options: >> >> > > -#1: Let an HDMI codec specify number of substreams, same as the >> > number >> >> > > of device entries on a pin. We can specify 3 for HSW/BDW/SKL. Other >> >> > > vendors can also specify a value according to actual HW > capabilities. >> >> > > >> >> > > So for HSW, we have 3x3 subtreams totally. But we only have 3 >> > convertors >> >> > > (for 3 display pipelines), so we can open up to 3 substreams at the >> > same >> >> > > time. When the audio driver finds all 3 convertors are used when >> > opening >> >> > > a new substream, it will fail. >> >> > >> >> > One thing I noticed is the number of devices on a PIN is only updated >> > when >> >> > the MST device is plugged in so normally pins 5,6,7 have 0 devices, > and >> > when >> >> > I plug in MST device, I get the 3 devices on port 6. So it seems > dynamic >> >> > enough at this point, though I guess it'll always be 0 or 3. >> >> > > >> >> > > - #2: Create PCM device dynamically. Only create a PCM devices for > a >> > device >> >> > > entry which connects to monitor with audio support. When the > monitor >> >> > > is removed, the PCM device will be disconnected, closed and > removed, >> >> > > similar to the USB case. >> > >> > Do the driver really need dynamic PCM since display ports are dasiy > chained >> > and the locations within the dasiy chain are fixed ? > > http://www.intel.com/support/motherboards/desktop/sb/CS-034199.htm > > Do the first display always support sound since hdmi can connect to tv > using dvi ? I don't see the relevance. > As Pulseaudio does not support multi streaming ( playing different audio > streams to headphone and rear panel speakers , how can pulseaudion support > displayport MST ? Even if it couldn't support multiple streams at the same time, there has to be a way to choose one of the audio capable sinks in the DP MST topology (which will change dynamically). BR, Jani. -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
