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

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Message-ID: <20240408184744.nfktcppdqewurmgg@CAB-WSD-L081021>
Date: Mon, 8 Apr 2024 21:47:44 +0300
From: Dmitry Rokosov <ddrokosov@...utedevices.com>
To: Mark Brown <broonie@...nel.org>
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 07:45:00PM +0100, Mark Brown wrote:
> 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.
> 

Honestly, I have tried to find a way to rename the PCM device name or
mark it in some way (such as using a metainformation tag or any other
method), but unfortunately, my search has been unsuccessful.

> > 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.

-- 
Thank you,
Dmitry