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

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Message-ID: <08f305fa-0dbe-4ed9-bec5-cf8b5bbecfdb@arm.com>
Date: Wed, 5 Mar 2025 10:00:25 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: 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>, Rob Herring <robh@...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 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.