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

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Message-ID: <20221210165434.3hhen5mgtvflghks@SoMainline.org>
Date:   Sat, 10 Dec 2022 17:54:34 +0100
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] arm64: dts: qcom: Use labels with generic node names
 for ADC channels

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@...ainline.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)?  Or to keep the fully-written-out
"thermistor" word in the label?

> 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.

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`?

[1]: https://lore.kernel.org/linux-arm-msm/20221208101232.536i3cmjf4uk2z52@SoMainline.org/

- Marijn