linux-kernel - Re: [PATCH 1/3] dt-bindings: iio: adc: add AD4695 and similar ADCs

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Date: Thu, 13 Jun 2024 08:57:46 -0500
From: David Lechner <dlechner@...libre.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Jonathan Cameron
 <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Jonathan Corbet <corbet@....net>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: iio: adc: add AD4695 and similar ADCs

On 6/13/24 2:11 AM, Krzysztof Kozlowski wrote:
> On 12/06/2024 21:20, David Lechner wrote:
>> Add device tree bindings for AD4695 and similar ADCs.
>>
>> Signed-off-by: David Lechner <dlechner@...libre.com>
>> ---
>>  .../devicetree/bindings/iio/adc/adi,ad4695.yaml    | 297 +++++++++++++++++++++
>>  MAINTAINERS                                        |   9 +
>>  2 files changed, 306 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
>> new file mode 100644
>> index 000000000000..8ff5bbbbef9f
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4695.yaml
>> @@ -0,0 +1,297 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/adi,ad4695.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Analog Devices Easy Drive Multiplexed SAR Analog to Digital Converters
>> +
>> +maintainers:
>> +  - Michael Hennerich <Michael.Hennerich@...log.com>
>> +  - Nuno Sá <nuno.sa@...log.com>
>> +
>> +description: |
>> +  A family of similar multi-channel analog to digital converters with SPI bus.
>> +
>> +  * https://www.analog.com/en/products/ad4695.html
>> +  * https://www.analog.com/en/products/ad4696.html
>> +  * https://www.analog.com/en/products/ad4697.html
>> +  * https://www.analog.com/en/products/ad4698.html
>> +
>> +$ref: /schemas/spi/spi-peripheral-props.yaml#
>> +
>> +properties:
>> +  compatible:
>> +    oneOf:
>> +      - enum:
>> +          - adi,ad4695
>> +          - adi,ad4697
>> +      # same chips in WLCSP package with more pins
>> +      - items:
>> +          - const: adi,ad4695-wlcsp
> 
> Usually we do not add compatibles for such differences. Programming
> model is the same. Same for all other wlcsp. Unless something differs?

OK, I will drop all of the -wlcsp stuff. It made the .dts validation
catch more stuff, but wasn't being used in the driver because there
really isn't a difference other than some of the pins not being there.

> 
>> +          - const: adi,ad4695
>> +      - items:
>> +          - const: adi,ad4697-wlcsp
>> +          - const: adi,ad4697
>> +      # same chips with higher max sample rate

I suppose one could make the argument that the programming model is
the same on these too, but the maximum sampling frequency does seem
like an important bit of information so that you don't try to set
the conversion trigger rate too high.

>> +      - items:
>> +          - const: adi,ad4696
> 
> Anyway, keep all fallbacked variants in one entry, so enum with const
> fallback.
> 
>> +          - const: adi,ad4695
>> +      - items:
>> +          - const: adi,ad4698
>> +          - const: adi,ad4697
>> +      # same chips with higher max sample rate in WLCSP package
>> +      - items:
>> +          - const: adi,ad4696-wlcsp
>> +          - const: adi,ad4696
> 
> That's wrong. ad4696 is compatible with 4695 as stated before. It is not
> compatible with ad4695-wlcsp.
> 
>> +          - const: adi,ad4695-wlcsp
>> +          - const: adi,ad4695
>> +      - items:
>> +          - const: adi,ad4698-wlcsp
>> +          - const: adi,ad4698
>> +          - const: adi,ad4697-wlcsp
>> +          - const: adi,ad4697
>> +