[alsa-devel] ALSA HDMI output not detected

[Takashi Iwai]

At Wed, 22 Oct 2014 19:46:58 +0200,
samuelchemla at orange.fr wrote:
> 
> Hi guys,
> 
> I opened a bug about HDMI sound output not detected on an NVIDIA optimus 
> laptop.
> I don't know if HDMI sound card detection is up to ALSA, the kernel or 
> the video driver.

Actually all of three are involved fairly tightly.

> Could anyone give me a clue so the bug can be routed to its correct 
> destination?
> Link to the bug: 
> https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1377653

You should start checking EDID on the video side and ELD on the audio
side.  ALSA driver shows the connection and ELD status in proc files
and control elements.  If EDID is given, but ELD (or monitor
connection state) isn't, usually it's a video driver problem, e.g. the
audio register bit isn't set properly.


Takashi