linux-kernel - Re: [PATCH 1/4] dt-bindings: iio: adc: adi,ad4000: Add PulSAR

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Message-ID: <d6539dc1-2fef-48c1-9b03-c07fe82c670e@baylibre.com>
Date: Mon, 18 Nov 2024 09:39:05 -0600
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt1@...il.com>
Cc: Marcelo Schmitt <marcelo.schmitt@...log.com>, lars@...afoo.de,
 Michael.Hennerich@...log.com, jic23@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: iio: adc: adi,ad4000: Add PulSAR

On 11/18/24 5:24 AM, Marcelo Schmitt wrote:
> On 11/15, David Lechner wrote:
>> On 11/14/24 5:50 PM, Marcelo Schmitt wrote:
>>> Extend the AD4000 series device tree documentation to also describe
>>> PulSAR devices.
>>>
>>> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
>>> ---

...

>>>  
>>>  $ref: /schemas/spi/spi-peripheral-props.yaml#
>>>  
>>> @@ -63,6 +78,38 @@ properties:
>>>  
>>>        - const: adi,adaq4003
>>>  
>>> +      - const: adi,ad7946
>>> +      - items:
>>> +          - enum:
>>> +              - adi,ad7942
>>> +          - const: adi,ad7946
>>> +
>>> +      - const: adi,ad7983
>>> +      - items:
>>> +          - enum:
>>> +              - adi,ad7980
>>> +              - adi,ad7988-5
>>> +              - adi,ad7686
>>> +              - adi,ad7685
>>> +              - adi,ad7694
>>> +              - adi,ad7988-1
>>> +          - const: adi,ad7983
>>> +
>>> +      - const: adi,ad7688
>>> +      - items:
>>> +          - enum:
>>> +              - adi,ad7693
>>> +              - adi,ad7687
>>> +          - const: adi,ad7688
>>> +
>>> +      - const: adi,ad7984
>>> +      - items:
>>> +          - enum:
>>> +              - adi,ad7982
>>> +              - adi,ad7690
>>> +              - adi,ad7691
>>> +          - const: adi,ad7984
>>> +
>>
>> IMHO, having fallbacks just makes the bindings harder to use and doesn't
>> actually provide any useful benefit.
>>
> Having fallbacks was a suggestion from a dt maintainer to the ad4000 series.
> I assumed they would ask it for PulSAR too. Will wait a comment from a dt
> maintainer to change it.
> 
>> And with this many chips, it can be easy to overlook a small difference
>> in one chips, like ad7694 not having VIO pin, so is it really fallback
>> compatible? Easier to just avoid the question and not have fallbacks.
>>
> The absence of a VIO pin does not change how the driver handles the devices.
> They are compatible from software perspective.
> 
OK. Another difference for consideration that I noticed is that on some chips,
the SDO line can generate a BUSY interrupt while others can't. Not sure if
that matters from the point of view of fallbacks or not.