On Mon, 7 Jun 2021 10:47:18 -0400 Liam Beguin <liambeguin@xxxxxxxxx> wrote: > From: Liam Beguin <lvb@xxxxxxxxxx> > > An ADC is often used to measure other quantities indirectly. This > binding describe such a use case, the measurement of a temperature > through an analog front end connected to a voltage channel. > > Signed-off-by: Liam Beguin <lvb@xxxxxxxxxx> > --- > .../iio/afe/temperature-sense-amplifier.yaml | 57 +++++++++++++++++++ > MAINTAINERS | 1 + > 2 files changed, 58 insertions(+) > create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-sense-amplifier.yaml > > diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-sense-amplifier.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-sense-amplifier.yaml > new file mode 100644 > index 000000000000..08f97f052a91 > --- /dev/null > +++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-amplifier.yaml > @@ -0,0 +1,57 @@ > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/iio/afe/temperature-sense-amplifier.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: Temperature Sense Amplifier > + > +maintainers: > + - Liam Beguin <lvb@xxxxxxxxxx> > + > +description: | > + When an io-channel measures the output voltage of a temperature analog front > + end such as an RTD (resistance thermometer) or a temperature to current > + sensor, the interesting measurement is almost always the corresponding > + temperature, not the voltage output. This binding describes such a circuit. Perhaps add something about this only covering the linear cases... > + > +properties: > + compatible: > + const: temperature-sense-amplifier > + > + io-channels: > + maxItems: 1 > + description: | > + Channel node of a voltage io-channel. > + > + '#io-channel-cells': > + const: 1 > + > + sense-gain-mult: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: Amplifier gain multiplier. The default is <1>. > + > + sense-gain-div: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: Amplifier gain divider. The default is <1>. > + > + sense-offset-millicelsius: > + description: Amplifier offset. The default is <0>. Whilst it may seem obvious I'd like to see a statement of how these are used somewhere in here. temp_celcius = voltage * gain-mult / gain-div + offset Mainly because those familiar with the IIO usage of offset would expect (voltage + offset) * gain-mult/gain-div which doesn't make sense for this device but might leave people confused! > + > +additionalProperties: false > +required: > + - compatible > + - io-channels > + > +examples: > + - | > + pt1000_1: temperature-sensor { > + compatible = "temperature-sense-amplifier"; > + #io-channel-cells = <1>; > + io-channels = <&temp_adc 3>; > + > + sense-gain-mult = <1000000>; > + sense-gain-div = <3908>; > + sense-offset-millicelsius = <(-255885)>; > + }; > +... > diff --git a/MAINTAINERS b/MAINTAINERS > index e679d422b472..4f7b4ee9f19b 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -8887,6 +8887,7 @@ L: linux-iio@xxxxxxxxxxxxxxx > 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-amplifier.yaml > F: Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml > F: drivers/iio/afe/iio-rescale.c >
