Public bug reported:
When using HDMI or Displayport audio, the EDID-like Data (ELD) fails to
update properly when hotplugging or hot-unplugging displays. This in
turn prevents tools like the GNOME sound settings control panel from
accurately presenting the system's current audio capabilities.
How reproducible:
Hot plug and hot unplug an audio-capable display and observe the state
of the ELDs, either by directly reading the ELD files in
/proc/asound/card*/eld* or by examining the available audio output
devices in the GNOME sound settings control panel.
Steps to Reproduce:
1. Log into a desktop session with no audio-capable displays plugged in
2. Plug in an audio-capable display
3. Open the GNOME sound settings control panel
Actual results:
The audio-capable display is not selectable as an output device.
Expected results:
The audio-capable display should be selectable as an output device.
Additional info:
This bug has been fixed upstream with commit
37a3a98ef601f89100e3bb657fb0e190b857028c. Applying this change alone to
the bionic 4.18 HWE kernel is sufficient to allow the expected behavior
to occur. It is likely to be sufficient to fix the same bug, assuming it
exists, in Cosmic, but neither the presence of the bug nor the
sufficiency of the patch were tested. The bug is likely not present in
Disco, but this was not tested.
This behavior was observed on a system with an NVIDIA GPU running the
NVIDIA proprietary driver. The particular NVIDIA GPU on the system is
not currently compatible with Nouveau. It is possible and likely that
this problem is also reproducible on other systems which do have GPUs
that are compatible with Nouveau, and even on systems with HDMI or
Displayport connectors being driven by non-NVIDIA GPUs.
When the ELD fails to update in response to a hotplug event, an update
can be forced by accessing the underlying ALSA codec directly. For
example, playing an audio stream directly via ALSA or even just reading
from the /proc/asound/cardX/codec#Y file will cause the ELD to become
updated. This is of course unnecessary if the patch which fixes the
issue is applied, but it does offer a somewhat simple workaround for
affected users until the patch can be backported.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1831945
Title:
HDMI/DP audio: ELD not updated on hotplug event
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