[alsa-devel] [PATCH] ALSA: HDA: Add jack detection for HDMI

Takashi Iwai tiwai at suse.de
Tue May 17 18:08:08 CEST 2011

At Tue, 17 May 2011 09:00:51 -0700,
Stephen Warren wrote:
> David Henningsson wrote at Tuesday, May 17, 2011 7:47 AM:
> > Just as for headphones and microphone jacks, this patch adds reporting
> > of HDMI jack status through the input layer.
> Interesting. I was asked to look into this, but you beat me to it; thanks!
> A couple questions though:
> a) Is it possible to report more information alongside the plug events,
> such as ELD/EDID content? Or, is the idea that the kernel sends a plug
> event, and then user-space retrieves that information via some other
> API? I don't think there's an API to retrieve ELD information at present
> though right? Although certainly it'd make sense for that to be a 
> completely separate patch.

A simple approach would be adding a control element containing
byte-array of ELD/EDID.

> b) We might discuss how to tie ALSA jacks/ports/PCMs to X displays in
> some way, so that we can represent to the user which specific active
> monitor is the one that supports audio (e.g. in a 2-head setup with both
> monitors connected over HDMI, yet only 1 monitor supports audio).

Yeah, most tight coupling with display vs audio-port is needed.

> I note that the ELD data contains a port_id field, which might be usable
> for this purpose. Could this contain an xrandr value, or an NV-CTRL
> (NVIDIA's proprietary control protocol) display ID, or something similar?

Hm, rather it's a question to X side, i.e. what information is exposed
via xrandr.


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