linux-kernel - Re: [PATCH 1/2] dt-bindings: input: goodix,gt9916: Document stylus support

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Message-ID: <20250605085836.424932-1-mitltlatltl@gmail.com>
Date: Thu,  5 Jun 2025 16:58:35 +0800
From: Pengyu Luo <mitltlatltl@...il.com>
To: krzk@...nel.org
Cc: charles.goodix@...il.com,
	conor+dt@...nel.org,
	dan.j.williams@...el.com,
	devicetree@...r.kernel.org,
	dionnaglaze@...gle.com,
	dmitry.torokhov@...il.com,
	ebiggers@...gle.com,
	fdmanana@...e.com,
	hdegoede@...hat.com,
	kees@...nel.org,
	krzk+dt@...nel.org,
	len.brown@...el.com,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mitltlatltl@...il.com,
	neil.armstrong@...aro.org,
	pengdonglin@...omi.com,
	quic_luoj@...cinc.com,
	robh@...nel.org,
	thomas.weissschuh@...utronix.de,
	yury.norov@...il.com
Subject: Re: [PATCH 1/2] dt-bindings: input: goodix,gt9916: Document stylus support

On Thu, Jun 5, 2025 at 1:54 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> On 05/06/2025 07:48, Pengyu Luo wrote:
> > Document stylus support. Optional support for DT properties:
> >   - `goodix,stylus-enable`
> >   - `goodix,stylus-pressure-level`
> >   - `goodix,physical-x`
> >   - `goodix,physical-y`
> >
> > Signed-off-by: Pengyu Luo <mitltlatltl@...il.com>
> > ---
> >  .../input/touchscreen/goodix,gt9916.yaml      | 23 +++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/input/touchscreen/goodix,gt9916.yaml b/Documentation/devicetree/bindings/input/touchscreen/goodix,gt9916.yaml
> > index c40d92b7f..e5476ea36 100644
> > --- a/Documentation/devicetree/bindings/input/touchscreen/goodix,gt9916.yaml
> > +++ b/Documentation/devicetree/bindings/input/touchscreen/goodix,gt9916.yaml
> > @@ -44,6 +44,27 @@ properties:
> >    touchscreen-size-y: true
> >    touchscreen-swapped-x-y: true
> >
> > +  goodix,stylus-enable:
> > +    type: boolean
> > +    description:
> > +      Indicates that stylus (pen) functionality is enabled. If present,
>
> Looks like deducible from the compatible.
>
> > +      the driver will initialize stylus-specific input reporting.
>
> What if my driver does something else? Shall we change the binding? No.
>

Ack, I will drop it in v2.

> > +
> > +  goodix,physical-x:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Physical width of the touchscreen in millimeters.
>
> No, use existing input properties.
>

Ack, I overlooked it.

> > +
> > +  goodix,physical-y:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Physical height of the touchscreen in millimeters.
> > +
> > +  goodix,stylus-pressure-level:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description:
> > +      Number of discrete pressure levels supported by the stylus.
> > +      The reported ABS_PRESSURE range will be 0 to
> > +      (goodix,stylus-pressure-level - 1).
>
> Use existing input properties.
>

With a quick check, I think there is no suitable property for stylus,
"touchscreen-max-pressure" is for touchscreen, not for stylus. AFAIK,
Pressure data is reported by stylus, received by touch IC.

Best wishes,
Pengyu