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

Krzysztof Kozlowski
2022-10-10T10:28:42Z

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@9elements.com>
>>>> ---
>>>> .../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@ideasonboard.com>
>>>>
>>>> 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