linux-kernel - Re: [PATCH] dt-bindings: iio: adc: ti,adc081c: Document the binding

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Date:   Sun, 27 Nov 2022 22:08:59 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Samuel Holland <samuel@...lland.org>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: iio: adc: ti,adc081c: Document the binding

On 27/11/2022 19:01, Samuel Holland wrote:
> On 11/27/22 11:42, Jonathan Cameron wrote:
>> On Sun, 27 Nov 2022 13:51:19 +0100
>> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
>>
>>> On 25/11/2022 23:09, Samuel Holland wrote:
>>>> Linux has a driver for these ADCs at drivers/iio/adc/ti-adc081c.c, but
>>>> the compatible strings were undocumented. Add a binding for them. The
>>>> hardware has an alert interrupt output, but existing ti,adc081c users
>>>> do not provide the 'interrupts' property, so leave it as optional.
>>>>
>>>> Signed-off-by: Samuel Holland <samuel@...lland.org>
>>>> ---
>>>>
>>>>  .../bindings/iio/adc/ti,adc081c.yaml          | 55 +++++++++++++++++++
>>>>  1 file changed, 55 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml b/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
>>>> new file mode 100644
>>>> index 000000000000..caaad777580c
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
>>>> @@ -0,0 +1,55 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/iio/adc/ti,adc081c.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: TI Single-channel I2C ADCs
>>>> +
>>>> +maintainers:
>>>> +  - Jonathan Cameron <jic23@...nel.org>
>>>> +  - Lars-Peter Clausen <lars@...afoo.de>
>>>> +
>>>> +description: |
>>>> +  Single-channel ADC supporting 8, 10, or 12-bit samples and high/low alerts.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    enum:
>>>> +      - ti,adc081c
>>>> +      - ti,adc101c
>>>> +      - ti,adc121c
>>>> +
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  interrupts:
>>>> +    maxItems: 1
>>>> +
>>>> +  vref-supply:
>>>> +    description:
>>>> +      Regulator for the combined power supply and voltage reference
>>>> +
>>>> +  "#io-channel-cells":
>>>> +    const: 1
>>>> +
>>>> +required:
>>>> +  - compatible
>>>> +  - reg  
>>>
>>> Why not requiring io-channel-cells? If it is an IIO ADC provider, you
>>> need the cells, right?
>>
>> Only if anyone is using it as a provider.  If it's purely being used via
>> IIO then there are no consumers registered.
>>
>> So historically I've left it up to those defining the binding to decide if
>> they think #io-channel-cells should be required or optional.
>>
>> It gets a bit non obvious with some of the more complex special ADCs on whether
>> they will ever be consumed.  This one is generic, so quite likely it will be.
> 
> I kept #io-channel-cells optional because there are already a handful of
> boards using ti,adc081c without it.
> 
> On the board I am adding (Clockwork DevTerm), the ADC is used a
> temperature sensor for a thermal printer. So whether or not the ADC is
> used as an OF provider depends on how the printer driver gets implemented.

Thanks, it's fine.

Best regards,
Krzysztof