linux-kernel - Re: [PATCH] ASoC: dt-bindings: qcom,apq8016-sbc-sndcard: move to separate binding

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Message-ID: <d7067720-5524-4f8d-82fa-b2636be79676@sirena.org.uk>
Date: Tue, 30 Jul 2024 11:35:36 +0100
From: Mark Brown <broonie@...nel.org>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
	Stephan Gerhold <stephan@...hold.net>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Banajit Goswami <bgoswami@...cinc.com>,
	Liam Girdwood <lgirdwood@...il.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, alsa-devel@...a-project.org,
	linux-arm-msm@...r.kernel.org, linux-sound@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Adam Skladowski <a39.skl@...il.com>
Subject: Re: [PATCH] ASoC: dt-bindings: qcom,apq8016-sbc-sndcard: move to
 separate binding

On Tue, Jul 30, 2024 at 12:30:38PM +0200, Stephan Gerhold wrote:
> On Sun, Jul 28, 2024 at 12:30:12PM +0200, Krzysztof Kozlowski wrote:

> > This was added to the common driver code but it does not mean it is
> > reasonable binding. I don't understand why for example we even accept
> > here aux-devs, instead of putting them into one of DAI links.

> The auxiliary devices (typically analog audio components) are not
> necessarily related to one particular digital audio interface link. It
> is typically the case (e.g. an analog speaker amplifier connected in
> parallel to the headphone output of one of the codecs), but I don't
> think we can assume that as a general rule. There are often multiple DAI
> links that go to one codec and then it might be tricky to decide which
> of the DAI links the aux-dev belongs to.

Right, aux devices may cover more than one DAI link (eg, if there's a
CODEC that can do mixing and they're connected to an analog output) or
may in rare cases not fit with one at all (there's use cases where you
have a sound card that has no DAIs and is all analog bypass).

> > The pin-switches and widgets could be used, but are they? The only valid
> > argument to keep them is that you added them to common driver code.

> These go hand in hand with the aux-devs property. If you have multiple
> analog audio components connected to a codec output (e.g. an analog
> speaker amplifier connected to the codec headphone output) then the
> pin-switches/widgets describe that the output paths (speaker and
> headphones) should be separately controllable.

Plus the above cases where you don't have a direct mapping with aux devs
and DAIs also apply to pin switches since they're in the analog domain.

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