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

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Message-ID: <20250310-hissing-vagabond-pegasus-cc8aed@krzk-bin>
Date: Mon, 10 Mar 2025 10:45:28 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: David Heidelberg <david@...t.cz>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, "Jason A. Donenfeld" <Jason@...c4.com>, 
	Matthias Schiffer <matthias.schiffer@...tq-group.com>, Vincent Huang <vincent.huang@...synaptics.com>, 
	linux-input@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht, 
	Caleb Connolly <caleb.connolly@...aro.org>
Subject: Re: [PATCH v3 1/7] dt-bindings: input: syna,rmi4: document
 syna,pdt-fallback-desc

On Sat, Mar 08, 2025 at 03:08:37PM +0100, David Heidelberg wrote:
> From: Caleb Connolly <caleb.connolly@...aro.org>
> 
> 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?

> 
> Signed-off-by: Caleb Connolly <caleb.connolly@...aro.org>
> Signed-off-by: David Heidelberg <david@...t.cz>
> ---
>  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

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

Best regards,
Krzysztof