linux-kernel - Re: [PATCH v3 1/2] dt-bindings: thermal: generic-adc: Add optional io-channel-cells property

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Message-ID: <20250305161032.GA2068051-robh@kernel.org>
Date: Wed, 5 Mar 2025 10:10:32 -0600
From: Rob Herring <robh@...nel.org>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org,
	devicetree@...r.kernel.org, Laxman Dewangan <ldewangan@...dia.com>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v3 1/2] dt-bindings: thermal: generic-adc: Add optional
 io-channel-cells property

On Wed, Mar 05, 2025 at 12:03:20PM +0200, Svyatoslav Ryhel wrote:
> ср, 5 бер. 2025 р. о 12:00 Lukasz Luba <lukasz.luba@....com> пише:
> >
> >
> >
> > On 3/3/25 12:21, Svyatoslav Ryhel wrote:
> > > This implements a mechanism to derive temperature values from an existing ADC IIO
> > > channel, effectively creating a temperature IIO channel. This approach avoids adding
> > > a new sensor and its associated conversion table, while providing IIO-based temperature
> > > data for devices that may not utilize hwmon.
> > >
> > > Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> > > ---
> > >   .../devicetree/bindings/thermal/generic-adc-thermal.yaml      | 4 ++++
> > >   1 file changed, 4 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/thermal/generic-adc-thermal.yaml b/Documentation/devicetree/bindings/thermal/generic-adc-thermal.yaml
> > > index 12e6418dc24d..4bc2cff0593c 100644
> > > --- a/Documentation/devicetree/bindings/thermal/generic-adc-thermal.yaml
> > > +++ b/Documentation/devicetree/bindings/thermal/generic-adc-thermal.yaml
> > > @@ -30,6 +30,9 @@ properties:
> > >     io-channel-names:
> > >       const: sensor-channel
> > >
> > > +  '#io-channel-cells':
> > > +    const: 1
> > > +
> > >     temperature-lookup-table:
> > >       description: |
> > >         Lookup table to map the relation between ADC value and temperature.
> > > @@ -60,6 +63,7 @@ examples:
> > >           #thermal-sensor-cells = <0>;
> > >           io-channels = <&ads1015 1>;
> > >           io-channel-names = "sensor-channel";
> > > +        #io-channel-cells = <1>;
> > >           temperature-lookup-table = <
> > >                 (-40000) 2578
> > >                 (-39000) 2577
> >
> > Do we really need this change in the DT?
> > Won't the code in the thermal driver that registers a new iio device
> > would just be enough?
> >
> > I agree with Rob that it looks odd.
> 
> Building tree will complain on missing cells property if you try to
> bind it. It is not in required category anyway.

Sorry, I don't follow nor see why you need the property if there are no 
DT consumers.

Rob