2015-6-29 下午3:58於 "Jani Nikula" <<a href="mailto:jani.nikula@linux.intel.com">jani.nikula@linux.intel.com</a>>寫道： > > On Sat, 27 Jun 2015, Raymond Yau <<a href="mailto:superquad.vortex2@gmail.com">superquad.vortex2@gmail.com</a>> 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 ? <a href="http://www.intel.com/support/motherboards/desktop/sb/CS-034199.htm">http://www.intel.com/support/motherboards/desktop/sb/CS-034199.htm</a> Do the first display always support sound since hdmi can connect to tv using dvi ? As Pulseaudio does not support multi streaming ( playing different audio streams to headphone and rear panel speakers , how can pulseaudion support displayport MST ?