Message-ID: <20241015112806.GA2712@pendragon.ideasonboard.com>
Date: Tue, 15 Oct 2024 14:28:06 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Martin Kepplinger <martink@...teo.de>,
	Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
	"Paul J. Murphy" <paul.j.murphy@...el.com>,
	Daniele Alessandrelli <daniele.alessandrelli@...el.com>,
	Tommaso Merciai <tomm.merciai@...il.com>,
	Martin Hecht <martin.hecht@...et.eu>,
	Zhi Mao <zhi.mao@...iatek.com>,
	Alain Volmat <alain.volmat@...s.st.com>,
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	Ricardo Ribalda <ribalda@...nel.org>,
	Kieran Bingham <kieran.bingham@...asonboard.com>,
	Umang Jain <umang.jain@...asonboard.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
	Dongchun Zhu <dongchun.zhu@...iatek.com>,
	Quentin Schulz <quentin.schulz@...obroma-systems.com>,
	Todor Tomov <todor.too@...il.com>, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] media: dt-bindings: Use additionalProperties: false
 for endpoint: properties:

Hi Krzysztof,

On Tue, Oct 15, 2024 at 08:11:18AM +0200, Krzysztof Kozlowski wrote:
> On 14/10/2024 22:29, Laurent Pinchart wrote:
> > On Mon, Oct 14, 2024 at 10:47:31AM +0200, Krzysztof Kozlowski wrote:
> >> On 14/10/2024 10:31, Bryan O'Donoghue wrote:
> >>> On 14/10/2024 08:45, Krzysztof Kozlowski wrote:
> >>>> I do not understand the reasoning behind this change at all. I don't
> >>>> think DT maintainers ever suggested it (in fact, rather opposite:
> >>>> suggested using unevaluatedProps) and I think is not a consensus of any
> >>>> talks.
> >>>
> >>> No there is not but then, how do you give consistent feedback except 
> >>> proposing something to be a baseline.
> >>>
> >>> On the one hand you have upstream additionalProperties: false and 
> >>> unevaluatedProperites: false - it'd be better to have a consistent 
> >>> message on which is to be used.
> >>
> >> Well, I am afraid that push towards additionalProps will lead to grow
> >> common schema (video-interface-devices or video-interfaces) into huge
> >> one-fit-all binding. And that's not good.
> >>
> >> If a common binding for a group of devices encourages you to list its
> >> subset, then it is not that common.
> >>
> >> Solution is to fix that, e.g. split it per classes of devices.
> > 
> > I think splitting large schemas per class is a good idea, but the
> > problem will still exist. For instance, if we were to move the
> > CSI-2-specific properties to a separate schema, that schema would define
> > clock-lanes, data-lanes and clock-noncontinuous. The clock-lanes and
> > clock-noncontinuous properties do not apply to every device, how would
> > we then handle that ? I see three options:
> 
> Why is this a problem? Why is this a problem here, but not in other
> subsystems having exactly the same case?

I won't talk for other subsystems, but I can say I see value in
explicitly expressing what properties are valid for a device in DT
bindings both to inform DT authors and to perform validation on DT
sources. That's the whole point of YAML schemas, and I can't see a good
reason not to use the tooling we have developed when it has an easy way
to do the job.

-- 
Regards,

Laurent Pinchart

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