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    SubjectRe: [PATCH v1 7/9] dt-bindings: iio: afe: add binding for temperature-sense-rtd
    On Sat, 29 May 2021 20:59:15 -0400
    Liam Beguin <liambeguin@gmail.com> wrote:

    > From: Liam Beguin <lvb@xiphos.com>
    >
    > An ADC is often used to measure other quantities indirectly. This
    > binding describe one cases, the measurement of a temperature through
    > the voltage across an RTD resistor such as a PT1000.
    >
    > Signed-off-by: Liam Beguin <lvb@xiphos.com>

    Just one nit pick inline.

    Hmm. these devices use some 'special' units for their coefficients.
    Ah well, guess we copy the industry standard.

    > ---
    > .../iio/afe/temperature-sense-rtd.yaml | 65 +++++++++++++++++++
    > MAINTAINERS | 1 +
    > 2 files changed, 66 insertions(+)
    > create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
    >
    > diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
    > new file mode 100644
    > index 000000000000..4798eda6e533
    > --- /dev/null
    > +++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
    > @@ -0,0 +1,65 @@
    > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
    > +%YAML 1.2
    > +---
    > +$id: http://devicetree.org/schemas/iio/afe/temperature-sense-rtd.yaml#
    > +$schema: http://devicetree.org/meta-schemas/core.yaml#
    > +
    > +title: Temperature Sense RTD
    > +
    > +maintainers:
    > + - Liam Beguin <lvb@xiphos.com>
    > +
    > +description: |
    > + When an io-channel measures the output voltage across an RTD such as a
    > + PT1000, the interesting measurement is almost always the corresponding
    > + temperature, not the voltage output. This binding describes such a circuit.
    > +
    > +properties:
    > + compatible:
    > + const: temperature-sense-rtd
    > +
    > + io-channels:
    > + maxItems: 1
    > + description: |
    > + Channel node of a voltage io-channel.
    > +
    > + '#io-channel-cells':
    > + const: 1
    > +
    > + excitation-current-microamp:
    > + description: The current fed through the RTD sensor.
    > +
    > + alpha-micro-ohms-per-ohm-celsius:
    > + description: |
    > + Linear approximation of the resistance versus temperature relationship
    > + between 0 and 100 degrees Celsius.
    > +
    > + Pure platinum has an alpha of 3925. Industry standards such as IEC60751
    > + and ASTM E-1137 specify an alpha of 3850.
    > +
    > + r-naught-ohms:
    > + description: |
    > + Resistance of the sensor at 0 degrees Celsius.
    > + Common values are 100 for PT100 and 1000 for PT1000.
    > +
    > +additionalProperties: false
    > +required:
    > + - compatible
    > + - io-channels
    > + - excitation-current-microamp
    > + - alpha-micro-ohms-per-ohm-celsius
    > + - r-naught-ohms
    > +
    > +examples:
    > + - |
    > + pt1000_1: iio-rescale0 {
    > + compatible = "temperature-sense-rtd";
    > + #io-channel-cells = <1>;
    > + io-channels = <&temp_adc1 0>;
    > +
    > + excitation-current-microamp = <1000>;
    > + alpha-micro-ohms-per-ohm-celsius = <3908>;
    > + r-naught-ohms = <1000>;
    > + };
    > +

    Drop this blank line. Doesn't add anything ;)

    > +...
    > diff --git a/MAINTAINERS b/MAINTAINERS
    > index d3ab0ccc34ab..a7279af85adb 100644
    > --- a/MAINTAINERS
    > +++ b/MAINTAINERS
    > @@ -8721,6 +8721,7 @@ L: linux-iio@vger.kernel.org
    > S: Maintained
    > F: Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml
    > F: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml
    > +F: Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
    > F: Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
    > F: drivers/iio/afe/iio-rescale.c
    >

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