Re: [RFC PATCH] arm64: dts: qcom: Use labels with generic node names for ADC channels

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 10/12/2022 17:54, Marijn Suijten wrote:
> On 2022-12-10 12:02:03, Krzysztof Kozlowski wrote:
>> On 09/12/2022 22:53, Marijn Suijten wrote:
>>> As discussed in [1] the DT should use labels to describe ADC
>>> channels, with generic node names, since the IIO drivers now
>>> moved to the fwnode API where node names include the `@xx`
>>> address suffix.
>>> 
>>> Especially for the ADC5 driver that uses extend_name - which
>>> cannot be removed for compatibility reasons - this results in
>>> sysfs files with the @xx name that wasn't previously present, and
>>> leads to an unpleasant file-browsing experience.
>>> 
>>> Also remove all the unused channel labels in pm660.dtsi.
>>> 
>>> [1]:
>>> https://lore.kernel.org/linux-arm-msm/20221106193018.270106-1-marijn.suijten@somainline.org/T/#u
>>>
>>>
>>> 
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
>> 
>> The talk was in context of bindings, not about changing all
>> existing users thus affecting DTS.
> 
> And as a consequence, DTS.  The already-merged transition from OF to 
> fwnode resulted in `@xx` to be included in the ADC channel name - and
> in the case of ADC5 even in sysfs filenames - so this seems like a 
> necessary change to make.
> 
> At the very least I would have changed the bindings submitted or 
> co-authored /by myself/ since I initially decided to rely on this
> (now obviously) wrong behaviour, and should have used labels from the
> get go.
> 
>> What's more, to me "skin-temp-thermistor" is quite generic name,
>> maybe "thermistor" would be more and reflects the purpose of the
>> node, so it was more or less fine.
> 
> Are you suggesting to not use "adc-chan", but "thermistor" as node
> name (and still use skin_temp as label)?

No, I am just saying that some of the names were correct, so the
reasoning in commit msg is not entirely accurate.

> Or to keep the fully-written-out "thermistor" word in the label?

No, I don't refer to labels. Labels don't matter, they are being removed
entirely during DTS build.

> 
>> Anyway I am against such changes without expressing it in the
>> bindings.
> 
> As expressed in [1] I suggested and am all for locking this change
> in via bindings, and you are right to expect that to have gone paired
> with this patch.

Yes, I expect such changes to have both binding and DTS change together.

> 
> I'll submit that as the leading patch to this in v2, with the
> wildcard pattern changed to adc-chan (or something else pending the
> discussion above), and should I then also require the label property
> via `label: true`?

I don't think label is required.

Best regards,
Krzysztof