In the case of HD-audio, it's passed via the normal IEC958 status bits controls separately. ELD itself is exposed as a byte array in a control element, but it's read-only.
Thanks for the reply. Couple more questions
- Is kcontrol "ELD" being read directly by application or there is
ALSA library API to parse the information.
Nothing so far. It's just a raw data.
- Also, I see you submit this patch [PATCH 3/3] ELD proc interface for
HDMI sinks in 2008. I presume it's just for information purpose. You still expect application to query for HDMI sink capability through "ELD" kcontrol. Am I correct?
It's not prohibited for apps to parse the proc interface but it's not guaranteed to be stable :) So yes, parsing ELD manually would be a safer way.
I wrote some code to parse the ELD kcontrol to enable passthrough if AC3 is supported by the receiver, I believe it's been integrated by Arun in a branch of PulseAudio. It's probably 1 year old now..