Re: [PATCH input-next 2/4] dt-bindings: input: mpr121: Add poll-interval property

[Rob Herring <robh@kernel.org>]

On Tue, Sep 17, 2019 at 9:17 AM Michal Vokáč <michal.vokac@ysoft.com> wrote:
>
> On 03. 09. 19 9:01, Rob Herring wrote:
> > On Mon, Sep 02, 2019 at 01:40:15PM +0200, Michal Vokáč wrote:
> >> Add an option to periodicaly poll the device to get the buttons states
> >> as the interrupt line may not be used on some platforms.
> >>
> >> Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
> >> ---
> >> I am not sure how to propperly handle this.
> >> Either interrupt or linux,poll-interval is required, but not both.
> >
> > Add this at the top level:
> >
> > oneOf:
> >    - required: [ interrupts ]
> >    - required: [ linux,poll-interval ]
> >
>
> Nice, works as expected.
>
> >>
> >>   .../bindings/input/fsl,mpr121-touchkey.yaml          | 20 +++++++++++++++++++-
> >>   1 file changed, 19 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/input/fsl,mpr121-touchkey.yaml b/Documentation/devicetree/bindings/input/fsl,mpr121-touchkey.yaml
> >> index c463c1c81755..2b3073a3c9f4 100644
> >> --- a/Documentation/devicetree/bindings/input/fsl,mpr121-touchkey.yaml
> >> +++ b/Documentation/devicetree/bindings/input/fsl,mpr121-touchkey.yaml
> >> @@ -34,6 +34,10 @@ properties:
> >>       minItems: 1
> >>       maxItems: 12
> >>
> >> +  linux,poll-interval:
> >> +    description: Poll interval time in milliseconds.
> >> +    maxItems: 1
> >
> > We already have 'poll-interval' in several bindings. Use that.
>
> OK, will do.
> linux,poll-intervall was initially suggested by Dmitry but AFAICT he is OK
> with this.
>
> > This should have a type definition and you don't need maxItems:
> >
> > $ref: /schemas/types.yaml#/definitions/uint32
>
> OK.
>
> > Really this should go in a common input schema doc.
>
> I am not sure how to deal with this. Do you suggest to create
>
>   Documentation/devicetree/bindings/input/input.yaml
>
> and put all the common input properties there? Something like:

Yes.

>
> diff --git a/Documentation/devicetree/bindings/input/input.yaml b/Documentation/devicetree/bindings/input/input.yaml
> new file mode 100644
> index 000000000000..5dc10ebdfdf0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/input.yaml
> @@ -0,0 +1,24 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/input/input.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common input schema binding
> +
> +maintainers:
> +  - Dmitry Torokhov <dmitry.torokhov@gmail.com>
> +
> +properties:
> +  linux,keycodes:
> +    description:
> +      Specifies an array of numeric keycode values to be used for reporting
> +      button presses. The array can contain up to 12 entries.
> +    minItems: 1
> +    maxItems: 12
> +    $ref: /schemas/types.yaml#/definitions/uint32-array

When you have additional constraints on a referenced schema, the
reference has to be under an 'allOf':

allOf:
  - $ref: /schemas/types.yaml#/definitions/uint32-array

I still really don't get why and I've researched it...

However, for the common schema, you probably want to drop minItems/maxItems.

But you could define the value ranges?

items:
  minimum: 0
  maximum: 0xff


> +
> +  poll-interval:
> +    description: Poll interval time in milliseconds.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
> ---
>
> Or something else?
> And what is the impact on the fsl,mpr121-touchkey.yaml content/format?
> I could not find any example in any subsystem of such approach.

You only need to define any additional constraints on the common
properties (such as minItems/maxItems) and don't need to repeat things
like the type or description.

In order to get the common schema applied, you do at the top-level of
your binding:

allOf:
  - $ref: input.yaml#

Sometimes we don't have to do this if we have a reliable way of
matching in the common binding such as the node name.

Rob