From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takashi Iwai <tiwai@suse.de>
Subject: Re: [RFC v2 6/6] ASoC: hdmi-codec: Use HDMI
	notifications to add jack support
Date: Fri, 08 Jan 2016 11:52:40 +0100
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Jean-Francois Moine <moinejf@free.fr>, alsa-devel@alsa-project.org, Lars-Peter Clausen <lars@metafoo.de>, Philipp Zabel <p.zabel@pengutronix.de>, Arnaud Pouliquen <arnaud.pouliquen@st.com>, Koro Chen <koro.chen@mediatek.com>, Jyri Sarha <jsarha@ti.com>, Liam Girdwood <lgirdwood@gmail.com>, Mark Brown <broonie@kernel.org>, linux-mediatek@lists.infradead.org, Daniel Kurtz <djkurtz@chromium.org>, kernel@pengutronix.de, Matthias Brugger <matthias.bgg@gmail.com>, Cawa Cheng <cawa.cheng@mediatek.com>
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On Fri, 08 Jan 2016 11:46:23 +0100,
Russell King - ARM Linux wrote:
> 
> Given that, I'd like to throw in here another detail: iirc, i915's
> HDMI exports the ELD to userspace via a control called "ELD" - see
> eld_bytes_ctl in sound/pci/hda/patch_hdmi.c.  This allows userspace
> to monitor, and read the ELD including which compressed audio formats
> are supported.  I'm not currently aware of anything that makes use of
> this, but as there is this precedent for exporting this information,
> maybe it should become a standard way, so that video playback
> applications can then select an appropriate audio stream depending on
> the current properties of the connected device?

Right, the ELD ctl elements were introduced exactly for such a
purpose.  Though, I'm not sure currently which user-space app is
actually referring to this information, too.  But certainly it's a
good thing to have for other drivers.


Takashi