linux-kernel - Re: [PATCH] dt-bindings: input: Convert adc-keys to DT schema

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Message-ID: <eb0ea0d5-0650-53e8-f83c-eb4b82343c7a@gmx.de>
Date:   Tue, 7 Jun 2022 22:45:58 +0200
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-input@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH] dt-bindings: input: Convert adc-keys to DT schema

On 6/7/22 17:03, Rob Herring wrote:
> On Tue, Jun 07, 2022 at 09:48:33AM +0200, Heinrich Schuchardt wrote:
>> On 6/6/22 20:42, Rob Herring wrote:
>>> Convert the adc-keys binding to DT schema format.
>>>
>>> Signed-off-by: Rob Herring <robh@...nel.org>
>>> ---
>>>    .../devicetree/bindings/input/adc-keys.txt    |  67 ------------
>>>    .../devicetree/bindings/input/adc-keys.yaml   | 103 ++++++++++++++++++
>>>    2 files changed, 103 insertions(+), 67 deletions(-)
>>>    delete mode 100644 Documentation/devicetree/bindings/input/adc-keys.txt
>>>    create mode 100644 Documentation/devicetree/bindings/input/adc-keys.yaml
>
>>> -+--------------------------------+------------------------+
>>> diff --git a/Documentation/devicetree/bindings/input/adc-keys.yaml b/Documentation/devicetree/bindings/input/adc-keys.yaml
>>> new file mode 100644
>>> index 000000000000..a3a1af9550bc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/input/adc-keys.yaml
>>> @@ -0,0 +1,103 @@
>>> +# SPDX-License-Identifier: GPL-2.0
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/input/adc-keys.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: ADC attached resistor ladder buttons
>>> +
>>> +maintainers:
>>> +  - Heinrich Schuchardt <xypron.glpk@....de>
>>
>> Thanks for converting to yaml.
>>
>> I only contributed a single patch. I am not a maintainer. Please, remove
>> that line.
>
> Okay.
>
>> scripts/get_maintainer.pl
>> Documentation/devicetree/bindings/input/adc-keys.txt yields
>> Dmitry Torokhov <dmitry.torokhov@...il.com> (maintainer:INPUT (KEYBOARD,
>> MOUSE, JOYSTICK, TOUCHSCREEN)...)
>
> The maintainer here is supposed to be someone that cares about this
> particular binding, not who applies patches. IOW, who would care if the
> binding was deleted.
>
>> It would be preferable to have a single reference point for
>> maintainership: file /MAINTAINERS.
>
> There's 2 main reasons why it is not. MAINTAINERS doesn't work for the
> DT only tree we generate[1]. Second, having an entry in MAINTAINERS
> for bindings is not consistent. With it in the schema, I don't have to
> check, the tools do it for me.
>
>>> +  - Alexandre Belloni <alexandre.belloni@...tlin.com>
>>> +
>>> +allOf:
>>> +  - $ref: /schemas/input/input.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: adc-keys
>>> +
>>> +  io-channels:
>>> +    maxItems: 1
>>
>> Please, add a description to each property.
>
> Common properties don't get descriptions unless there is something
> specific about this binding to say. What would that be?
>
>
>>> +  io-channel-names:
>>> +    const: buttons
>>> +
>>> +  keyup-threshold-microvolt:
>>> +    description:
>>> +      Voltage above or equal to which all the keys are considered up.
>>> +
>>> +patternProperties:
>>> +  '^button-':
>>> +    type: object
>>> +    additionalProperties: false
>>> +    description:
>>> +      Each button (key) is represented as a sub-node.
>>> +
>>> +    properties:
>>> +      label: true
>>
>> Please, add a description.
>
> No, common property.
>
>>> +      linux,code:
>>> +        description: Keycode to emit.
>>> +        $ref: /schemas/types.yaml#/definitions/uint32
>>
>> Unfortunately usable values are only defined in
>> include/uapi/linux/input-event-codes.h up to now. Please, consider
>> adding that link to the description.
>
> linux,code is common for lots of bindings, so really the type,
> description, and any common constraints need to be documented somewhere
> common. I'm not sure if input.yaml makes sense given that includes a
> bunch of other properties.
>
>> It is unclear to me if using values above KEY_MAX (=0x2ff) could make
>> sense of should be forbidden by this yaml file.
>
> Shrug. I have no idea.
>
>> For interoperability of device-trees with other operating systems we
>> should have a yaml file defining an enum with used values and their meaning.
>
> Certainly, but that's an orthogonal issue.

Yes, it is orthogonal.

git grep -ni keycode Documentation/devicetree/bindings/
finds 15+ documents referring to key-codes.

So this will be a worthwhile undertaking.

Best regards

Heinrich

>
>>> +
>>> +      press-threshold-microvolt:
>>> +        description:
>>> +          Voltage above or equal to which this key is considered pressed. No
>>> +          two values of press-threshold-microvolt may be the same. All values
>>> +          of press-threshold-microvolt must be less than
>>> +          keyup-threshold-microvolt.
>>> +
>>> +    required:
>>> +      - label
>>
>> Property label is not used in our the driver code. It only exists for
>> human readability. Why is it marked as required? Stripping the labels
>> would reduce the DT size.
>
>>>From the original:
>
>>> -Required subnode-properties:
>>> -	- label: Descriptive name of the key.
>
> But I'll drop it.
>
> Rob
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git/tree/