Re: [PATCH 1/2] dt-bindings: gpio: add binding for the GPIO block for Apple Mac SMC

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Thu, Oct 27, 2022 at 03:53:25PM -0400, Krzysztof Kozlowski wrote:
> On 27/10/2022 13:03, Russell King (Oracle) wrote:
> > Add the DT binding for the Apple Mac System Management Controller GPIOs.
> > 
> > Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> > ---
> >  .../devicetree/bindings/gpio/gpio-macsmc.yaml | 28 +++++++++++++++++++
> >  1 file changed, 28 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-macsmc.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/gpio/gpio-macsmc.yaml b/Documentation/devicetree/bindings/gpio/gpio-macsmc.yaml
> > new file mode 100644
> > index 000000000000..a3883d62292d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/gpio/gpio-macsmc.yaml
> 
> Filename based on compatible, so "apple,smc-gpio.yaml"

Many of the other yaml files in gpio/ are named as such.

> > @@ -0,0 +1,28 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/gpio/gpio-macsmc.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Apple Mac System Management Controller GPIO
> > +
> > +maintainers:
> > +  - Hector Martin <marcan@marcan.st>
> > +
> > +description:
> > +  This describes the binding for the Apple Mac System Management Controller
> 
> Drop "This describes the binding for"
> 
> > +  GPIO block.
> > +
> > +properties:
> > +  compatible:
> > +    allOf:
> 
> That's not proper syntax. Look at other examples (e.g. Apple bindings)
> doing it. Probably you wanted items here.

Really? You're joking. I had sent an email to Rob to ask how this should
be done because my first guess spat out unhelpful error messages from
dt_bindings_check, and this is the best I could come up with based on
other "examples".

I tried "- items:" but that made no difference - dt_bindings_check spat
errors, so that's clearly incorrect. Specifically, I tried:

properties:
  compatible:
    - items:
        - enum:
	    - apple,t8103-smc
	- const: apple,smc-gpio

That doesn't work:

Documentation/devicetree/bindings/gpio/gpio-macsmc.yaml: properties:compatible: [{'items': [{'const': 'apple,t8103-smc'}, {'const': 'apple,smc-gpio'}]}] is not of type 'object', 'boolean'  from schema $id: http://json-schema.org/draft-07/schema#

> > +      - enum:
> > +          - apple,t8103-smc
> > +      - const: apple,smc-gpio
> > +
> > +  gpio-controller: true
> > +
> > +  '#gpio-cells':
> > +    const: 2
> 
> Missing required properties. Start from new bindings or example-schema.

What's missing? All the other bindings that I see follow this pattern.

> > +
> > +additionalProperties: false
> 
> Missing example, it's necessary to validate these.

Documentation states that examples are optional according to the
"writing-schema" documentation.

Honestly, I find this YAML stuff extremely difficult, especially given
the lack of documentation on how to write it and the cryptic error
messages from the tooling. It's impossible to get it right before
submitting it - and I suspect from what I see above, it's impossible
for reviewers to know what is correct either, since some of what you've
said above appears to be wrong!

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