linux-kernel - Re: [PATCH v1 2/2] ASoC: meson: implement link-name optional property in meson card utils

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Message-ID: <51b39153-d1a4-4e7f-9b30-8c77fc4ee46f@sirena.org.uk>
Date: Mon, 8 Apr 2024 19:45:00 +0100
From: Mark Brown <broonie@...nel.org>
To: Dmitry Rokosov <ddrokosov@...utedevices.com>
Cc: Jerome Brunet <jbrunet@...libre.com>, neil.armstrong@...aro.org,
	lgirdwood@...il.com, conor+dt@...nel.org, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, perex@...ex.cz, tiwai@...e.com,
	khilman@...libre.com, martin.blumenstingl@...glemail.com,
	kernel@...utedevices.com, rockosov@...il.com,
	linux-amlogic@...ts.infradead.org, alsa-devel@...a-project.org,
	linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 2/2] ASoC: meson: implement link-name optional
 property in meson card utils

On Mon, Apr 08, 2024 at 09:40:41PM +0300, Dmitry Rokosov wrote:
> On Mon, Apr 08, 2024 at 08:15:54PM +0200, Jerome Brunet wrote:

> > Userspace pcm, otherwise known as DPCM frontend, are merely that:
> > frontends. What they do is entirely defined by the routing defined by
> > the userspace (amixer and friends)

> > So naming the interface in DT (the FW describing the HW) after what the
> > the userspace SW could possibly set later on is wrong.

> > Bottom line: I have mixed feeling about this change. It could allow all
> > sort of bad names to be set.

> > The only way it could make sense HW wise is if the only allowed names
> > where (fr|to)ddr_[abcd], which could help maps the interface and the
> > kcontrol.

> The link-name is an optional parameter. Yes, you are right, it can be
> routed in a way that it no longer functions as a speaker in most cases.
> However, if you plan to use your board's dt for common purposes, you
> should not change the common names for DAI links. But if you know that
> you have a static setup for speakers, microphones, loopback, or other
> references (you 100% know it, because you are HW developer of this
> board), why not help the user understand the PCM device assignment in
> the easiest way?

I would expect that the place to fix names based on the userspace
configuration is in whatever userspace is using to define it's
configurations, like a UCM config.

> Ultimately, it is the responsibility of the DT board developer to define
> specific DAIs and name them based on their own knowledge about HW and
> understanding of the board's usage purposes.

DT seems like the wrong abstraction layer here.

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