Re: [v9 1/4] dt-bindings: i2c: Add Maxim MAX735x/MAX736x variants

[Krzysztof Kozlowski]

On 09/10/2022 14:03, Serge Semin wrote:
> On Sun, Oct 09, 2022 at 05:25:22PM +0200, Krzysztof Kozlowski wrote:
>> On 08/10/2022 13:50, Serge Semin wrote:
>>> On Fri, Oct 07, 2022 at 09:53:50AM +0200, Patrick Rudolph wrote:
>>>> Update the pca954x bindings to add support for the Maxim MAX735x/MAX736x
>>>> chips. The functionality will be provided by the exisintg pca954x driver.
>>>>
>>>> While on it make the interrupts support conditionally as not all of the
>>>> existing chips have interrupts.
>>>>
>>>> For chips that are powered off by default add an optional regulator
>>>> called vdd-supply.
>>>>
>>>> Signed-off-by: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
>>>> ---
>>>>  .../bindings/i2c/i2c-mux-pca954x.yaml         | 39 ++++++++++++++++---
>>>>  1 file changed, 34 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
>>>> index 9f1726d0356b..efad0a95806f 100644
>>>> --- a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
>>>> +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.yaml
>>>> @@ -4,21 +4,25 @@
>>>>  $id: http://devicetree.org/schemas/i2c/i2c-mux-pca954x.yaml#
>>>>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>  
>>>> -title: NXP PCA954x I2C bus switch
>>>> +title: NXP PCA954x I2C and compatible bus switches
>>>>  
>>>>  maintainers:
>>>>    - Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>>>>  
>>>>  description:
>>>> -  The binding supports NXP PCA954x and PCA984x I2C mux/switch devices.
>>>> -
>>>
>>>> -allOf:
>>>> -  - $ref: /schemas/i2c/i2c-mux.yaml#
>>>
>>> Why do you move the allOf statement to the bottom of the schema?
>>
> 
>> Because it goes with 'ifs' at the bottom of the schema...
> 
> Is there a requirement to move the allOf array to the bottom of the
> schema if it contains the 'if' statement? If only there were some
> kernel doc with all such implicit conventions...

It's just a convention, although quite logical because "ifs" can grow
significantly, so putting it before properties is outside of context.
Reader does not know yet to what this if applies.

> 
>>
>>>
>>>> +  The binding supports NXP PCA954x and PCA984x I2C mux/switch devices,
>>>> +  and the Maxim MAX735x and MAX736x I2C mux/switch devices.
>>>
>>> What about combining the sentence: "The binding supports NXP
>>> PCA954x/PCA984x and Maxim MAX735x/MAX736x I2C mux/switch devices." ?
>>> Currently it does look a bit bulky.
>>
>> Drop "The binding supports". Instead describe the hardware.
>>
>>>
>>>>  
>>>>  properties:
>>>>    compatible:
>>>>      oneOf:
>>>>        - enum:
>>>> +          - maxim,max7356
>>>> +          - maxim,max7357
>>>> +          - maxim,max7358
>>>> +          - maxim,max7367
>>>> +          - maxim,max7368
>>>> +          - maxim,max7369
>>>>            - nxp,pca9540
>>>>            - nxp,pca9542
>>>>            - nxp,pca9543
>>>> @@ -59,10 +63,33 @@ properties:
>>>>      description: if present, overrides i2c-mux-idle-disconnect
>>>>      $ref: /schemas/mux/mux-controller.yaml#/properties/idle-state
>>>>  
>>>> +  vdd-supply:
>>>> +    description: A voltage regulator supplying power to the chip.
>>>> +
>>>>  required:
>>>>    - compatible
>>>>    - reg
>>>>  
>>>> +allOf:
>>>> +  - $ref: /schemas/i2c/i2c-mux.yaml#
>>>> +  - if:
>>>> +      not:
>>>> +        properties:
>>>> +          compatible:
>>>> +            contains:
>>>> +              enum:
>>>> +                - maxim,max7367
>>>> +                - maxim,max7369
>>>> +                - nxp,pca9542
>>>> +                - nxp,pca9543
>>>> +                - nxp,pca9544
>>>> +                - nxp,pca9545
>>>> +    then:
>>>
>>>> +      properties:
>>>> +        interrupts: false
>>>> +        "#interrupt-cells": false
>>>> +        interrupt-controller: false
>>>
>>> I'd suggest to add an opposite definition. Evaluate the properties for
>>> the devices which expect them being evaluated instead of falsing their
>>> existence for the devices which don't support the interrupts.
>>
> 
>> The properties rather should be defined in top-level than in "if", so I
>> am not sure how would you want to achieve opposite way.
> 
> With one more implicit convention like "preferably define the
> properties in the top-level than in if" of course I can't. Otherwise I
> thought something like this would work:
> +allOf:
> +  - ...
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum: [...]
> +    then:
> +      properties:
> +        interrupts: ...
> +        "#interrupt-cells": ...
> +        interrupt-controller: ...
> ...
> -  interrupts:
> -  "#interrupt-cells":
> -  interrupt-controller: ...
> 
> With unevaluatedProperties set to false and evaluation performed for
> the particular compatibles such schema shall work with the same
> semantic.

Yes, this will work, but defining properties inside "if" is usually not
readable.

Best regards,
Krzysztof