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 ? Please elaborate. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
