[SRU][H/G/OEM-5.10][PATCH 0/1] alsa/hda: the hdmi audio dosn't work on TGL machines

[Hui Wang]

BugLink: https://bugs.launchpad.net/bugs/1917829

[Impact]
On the TGL machines, we plug a dp mst hub to the thunderbolt port,
and plug a hdmi/dp monitor to the dp mst hub, then check the
gnome-sound-setting, could not find the hdmi/dp audio device.

[Fix]
backport a patch from upstream, this patch change to assign
the pcm slot dynamically on TGL macines.

[Test]
On 2 lenovo and dell TGL machines, plug dp mst hub and plug
2 monitors to the hub or to the machine hdmi/dp ports, check
the gnome-sound-setting, there are 2 hdmi/dp audio devices.
and they all could output sound.


[Where problems could occur]
After this change, the hdmi audio device number starts from 0, 1, ...,
while without this change, the hdmi audio device number is fix
mapped, it could be 3 or 5 directly. So if there is some userspace
applications depends on the fix mapped hdmi audio device, these
applicatons could not work on TGL machines.

So far, we don't know if those applications exists or not, but I
could confirm the ubuntu audio stack builds on the alsa-lib and
pulseaudio, this change will not affect the applications based
on the alsa-lib and pulseaudio.

And I already tested audio functions under ubuntu on the TGL machines,
there is no regression.


Hui Wang (1):
  ALSA: hda/hdmi: let new platforms assign the pcm slot dynamically

 sound/pci/hda/patch_hdmi.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

-- 
2.25.1