Re: [PATCH 1/2] media: dt-bindings: i2c: Drop redundant endpoint properties

[Rob Herring <robh@kernel.org>]

On Wed, Mar 18, 2026 at 07:12:46PM +0200, Laurent Pinchart wrote:
> Hello Krzysztof,
> 
> On Mon, Mar 16, 2026 at 07:02:41PM +0100, Krzysztof Kozlowski wrote:
> > On 16/03/2026 18:19, Sakari Ailus wrote:
> > > On Mon, Mar 16, 2026 at 03:42:09PM +0100, Krzysztof Kozlowski wrote:
> > >> On 16/03/2026 14:53, Laurent Pinchart wrote:
> > >>> On Mon, Mar 16, 2026 at 02:45:34PM +0100, Krzysztof Kozlowski wrote:
> > >>>> The "endpoint" node references video-interfaces.yaml schema with
> > >>>> "unevaluatedProperties: false" which means that all properties from
> > >>>> referenced schema apply.  Listing some of them with ": true" is simply
> > >>>> redundant and does not make this code easier to read.
> > >>>
> > >>> I think you know my opinion on this topic. I believe we would be better
> > >>> off by turning "unevaluatedProperties: false" into
> > >>> "additionalProperties: false" here, and keeping the list of applicable
> > >>> properties. It brings value to device tree authors by telling which
> > >>> properties are applicable to the device at hand. For instance ... (see
> > >>> below)
> > >>
> > >> (let me trim)
> > >>
> > >>>> diff --git a/Documentation/devicetree/bindings/media/i2c/ovti,ov5647.yaml b/Documentation/devicetree/bindings/media/i2c/ovti,ov5647.yaml
> > >>>> index 2d7937a372a2..7a05a1eda58d 100644
> > >>>> --- a/Documentation/devicetree/bindings/media/i2c/ovti,ov5647.yaml
> > >>>> +++ b/Documentation/devicetree/bindings/media/i2c/ovti,ov5647.yaml
> > >>>> @@ -51,9 +51,6 @@ properties:
> > >>>>          $ref: /schemas/media/video-interfaces.yaml#
> > >>>>          unevaluatedProperties: false
> > >>>>  
> > >>>> -        properties:
> > >>>> -          clock-noncontinuous: true
> > >>>> -
> > >>>
> > >>> ... Without this, an integrator will need to dive into driver code to
> > >>> know if non-continuous clock is usable for the device.
> > >>
> > >> I see. Our usual interpretation of common schema, expressed by @Rob in
> > >> few places, that eventually all properties might be applicable. This
> > >> applies especially for ABI tied to the core Linux specifics, e.g.
> > >> rotation and orientation from video-interface-devices.yaml.
> > >>
> > >> Absolutely every sensor can be mounted rotated, therefore every binding
> > >> referencing video-interface-devices should allow it, even if driver is
> > >> not using it. Because basically that's the ABI we want to define for
> > >> each sensor, thus each binding referencing common schema should have
> > >> "unevaluatedProps: true" without listing them.
> 
> Yes, that's totally fine. I agree that properties defined in
> video-interface-devices.yaml should not be listed in individual
> bindings. They're generic, and all of them are applicable to each image
> sensor device. That part is fine, I think we have no disagreement.
> 
> > >> Similarly touchscreen.yaml.
> > >>
> > >> OTOH, second option, properties which are strictly hardware, e.g. name
> > >> of power supply or whether clock has or has not non-continuous mode,
> > >> should be allowed only when they match the hardware. Such bindings
> > >> should use "additionalProperties: false" so the hardware description is
> > >> constrained/fixed/specific.
> > > 
> > > The patch may be technically correct but I'm afraid it won't improve the
> > > bindings but rather the opposite: it removes information telling whether a
> > > property is relevant for a given device.
> > > 
> > > I bet there are a lot of possibilities to write invalid DTS while the
> > > checker says it's fine (missing data-lanes or link-frequencies, for
> > > instance). That may have been the case before the patch but I'd make
> > > properties a driver needs to function mandatory rather than removing them
> > > from bindings altogether.
> > 
> > That's pretty different problem and I am not removing any mandatory
> > properties. I changed absolutely nothing from functional point of view.
> > 
> > > It'd been on my to-do list to split the current video-interfaces.yaml into
> > > several files: generic camera sensor properties, CSI-2 interface
> > > properties, DVP/Bt.656 interface properties and the rest (full list
> > > probably requires more thought). That way we could only include properties
> > > that are relevant for the device without necessarily listing each one for
> > > all bindings.
> > > 
> > > I'd also continue to list boolean properties relevant for devices as well
> > > as other properties that are relevant for a device but not mandatory.
> > 
> > I don't think there is such goal and particular subsystem does not get
> > exception here. What is relevant for device comes either from the
> > hardware or implemented ABI, as I explained. Bindings arbitrarily
> > choosing "I think this might be relevant" from some big schema with
> > irrelevant pieces is not manageable and not correct.
> 
> But that's not what we're discussing. The properties you're dropping
> here are not "arbitrarily" choosen as being relevant. Whether it is
> possible or not to use a non-continuous clock is a hardware property,
> it's not an arbitrary choice.
> 
> Your patch will not change anything when it comes to validation of DT by
> tools using the schema, but it drops important information relevant to
> DT writers. What I recommend instead is to switch from
> "unevaluatedProperties: false" to "additionalProperties: false". Not
> only will we keep the information, but it will also be enforced properly
> by tools.

I agree with keeping the information. Really, I'm indifferent, so if 
anyone finds it useful then let's leave it. I'm also not going to care 
in reviews either, so it's up to the media maintainers to care and 
ensure consistency.

Also, I don't think we can switch to additionalProperties here because 
then we have to list all the standard graph properties, too. That I do 
care about and don't care to see.

Rob