linux-kernel - Re: [PATCH 1/8] dt-bindings: HID: i2c-hid: elan: Introduce Elan eKTH8D18

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Message-ID: <20250314234248.GA2536020-robh@kernel.org>
Date: Fri, 14 Mar 2025 18:42:48 -0500
From: Rob Herring <robh@...nel.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Chen-Yu Tsai <wenst@...omium.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Benson Leung <bleung@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, chrome-platform@...ts.linux.dev,
	linux-input@...r.kernel.org
Subject: Re: [PATCH 1/8] dt-bindings: HID: i2c-hid: elan: Introduce Elan
 eKTH8D18

On Fri, Mar 14, 2025 at 02:58:36PM -0700, Doug Anderson wrote:
> Hi,
> 
> 
> On Wed, Mar 12, 2025 at 3:43 AM Chen-Yu Tsai <wenst@...omium.org> wrote:
> >
> > The Elan eKTH8D18 touchscreen controller is an I2C HID device with a
> > longer boot-up time. Power sequence timing wise it is compatible with
> > the eKTH6A12NAY, with a power-on delay of at least 5ms, 20ms
> > out-of-reset for I2C ack response, and 150ms out-of-reset for I2C HID
> > enumeration. Enumeration and subsequent operation follows the I2C HID
> > standard. The eKTH6A12NAY requires longer times for both parts.
> 
> Somehow the last sentence above confused me. Can it just be dropped?
> All you care about is that the new trackpad matches the timings for
> "eKTH6A12NAY". Not sure what you mean by "eKTH6A12NAY" needing
> "longer" timings.
> 
> 
> > Add a compatible string for it with the ekth6a12nay one as a fallback.
> >
> > Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> > ---
> >  .../bindings/input/elan,ekth6915.yaml         | 29 ++++++++++++++++---
> >  1 file changed, 25 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/input/elan,ekth6915.yaml b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > index cb3e1801b0d3..81c391952ccc 100644
> > --- a/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > +++ b/Documentation/devicetree/bindings/input/elan,ekth6915.yaml
> > @@ -4,14 +4,14 @@
> >  $id: http://devicetree.org/schemas/input/elan,ekth6915.yaml#
> >  $schema: http://devicetree.org/meta-schemas/core.yaml#
> >
> > -title: Elan eKTH6915 touchscreen controller
> > +title: Elan I2C-HID touchscreen controllers
> >
> >  maintainers:
> >    - Douglas Anderson <dianders@...omium.org>
> >
> >  description:
> > -  Supports the Elan eKTH6915 touchscreen controller.
> > -  This touchscreen controller uses the i2c-hid protocol with a reset GPIO.
> > +  Supports the Elan eKTH6915 and other I2C-HID touchscreen controllers.
> > +  These touchscreen controller use the i2c-hid protocol with a reset GPIO.
> >
> >  allOf:
> >    - $ref: /schemas/input/touchscreen/touchscreen.yaml#
> > @@ -23,12 +23,18 @@ properties:
> >            - enum:
> >                - elan,ekth5015m
> >            - const: elan,ekth6915
> > +      - items:
> > +          - enum:
> > +              - elan,ekth8d18
> > +          - const: elan,ekth6a12nay
> 
> The "enum" above is weird, but it matches what we did for
> "elan,ekth5015m" so I guess it's fine? I'd leave it up to bindings
> maintainers. I guess the assumption is that we might add additional
> touchscreens to the list...

Yes, but up to you all if that's a valid assumption.

> 
> 
> >    reg:
> > -    const: 0x10
> > +    enum:
> > +      - 0x10
> > +      - 0x16
> 
> Again happy to leave it to the bindings maintainers, but _maybe_ just
> drop the "reg" parts here and below. It doesn't really have to be part
> of the bindings.

I tend to agree. Sometimes we list I2C addresses as that is part of the 
device whereas elsewhere it is not. I don't know that it's worth the 
if/then schema in this case. 

Rob