Re: [PATCH v3 1/7] dt-bindings: input: syna,rmi4: document syna,pdt-fallback-desc

[David Heidelberg]

On 10/03/2025 10:45, Krzysztof Kozlowski wrote:
> On Sat, Mar 08, 2025 at 03:08:37PM +0100, David Heidelberg wrote:
> > From: Caleb Connolly <caleb.connolly@xxxxxxxxxx>
> >
> > This new property allows devices to specify some register values which
> > are missing on units with third party replacement displays. These
> > displays use unofficial touch ICs which only implement a subset of the
> > RMI4 specification.
>
> These are different ICs, so they have their own compatibles. Why this
> cannot be deduced from the compatible?

Yes, but these identify as the originals.

Some of them can be detected at runtime which is what this patchset 
tries to do.

> > Signed-off-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx>
> > Signed-off-by: David Heidelberg <david@xxxxxxx>
> > ---
> >   Documentation/devicetree/bindings/input/syna,rmi4.yaml | 18 ++++++++++++++++++
> >   1 file changed, 18 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/input/syna,rmi4.yaml b/Documentation/devicetree/bindings/input/syna,rmi4.yaml
> > index b522c8d3ce0db719ff379f2fefbdca79e73d027c..a80ec0c052cb1b7278f0832dd18ebd3256bc0874 100644
> > --- a/Documentation/devicetree/bindings/input/syna,rmi4.yaml
> > +++ b/Documentation/devicetree/bindings/input/syna,rmi4.yaml
> > @@ -49,6 +49,24 @@ properties:
> >       description:
> >         Delay to wait after powering on the device.
> >   
> > +  syna,pdt-fallback-desc:
> > +    $ref: /schemas/types.yaml#/definitions/uint8-matrix
> > +    description:
> > +      This property provides fallback values for certain register fields that
> > +      are missing on devices using third-party replacement displays.
> > +      These unofficial displays contain touch controllers that claim RMI4
> > +      compliance but fail to populate the function_number and function_version
> > +      registers of their Page Descriptor Table (PDT) entries.
> > +
> > +      Since the number of required fallback entries depends on the number of
> > +      Page Descriptor Tables supported by a given device, this property
> > +      should be provided on a best-effort basis.
> > +
> > +    items:
>
> min/maxItems here

There is no hardcoded limit how many of these items will be provided, 
should I put there some huge range as 1..1024?

Thank you
David

> > +      items:
> > +        - description: The 5th byte of the PDT entry (function number)
> > +        - description: The 4th byte of the PDT entry (version value)
>
> Best regards,
> Krzysztof

--
David Heidelberg