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

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Message-ID: <CAD=FV=X14XEdikE3hP4y53uZec12O_ZPtU+GyJ+Tf8R3DK89AA@mail.gmail.com>
Date: Fri, 14 Mar 2025 14:58:36 -0700
From: Doug Anderson <dianders@...omium.org>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Rob Herring <robh@...nel.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

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...


>    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.