Hi! Should "amplifier" really be part of the name for this binding when it's now just a generic voltage-to-temperature rescale binding? Or, perhaps a better description is THE generic voltage-to-temperature rescale binding? But that's not a strong opinion, I know next to nothing about these things and it might be that an amplifier is involved in the vast majority of cases? Maybe it's enough to be more explicit in the describing text that the binding is intended for analog front ends lacking an amplifier as well? I just find it a bit confusing since there are actual HW that calls itself "temperature sence amplifiers" that I think this binding targets but then isn't exemplified anywhere. Also, it disturbs my sense of symmetry if volt->temp gets a generic binding like this, when volt->current and volt->volt have bindings for specific front ends. Again, it's not a strong opinion, I'm just pointing it out. For the record, I started out with a generic volt->current binding similar to this volt->temp binding, but got push-back so that we now have two specific volt->current bindings. Again, I'm just pointing this out, and I'm perfectly aware that "rules" and opinions change over time. On 2021-06-07 16:47, Liam Beguin 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> Here, you claim maintainership... > + > +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. Why would you convert from a voltage if you have a "temperature to current sensor"? Such a sensor should give you a current. Yeah yeah, I get it, you bake some resistance into the "gain" and you are done. But I think these things should be explicitly mentioned with examples. I think it would be a lot less terse if you spell out a couple of common ways to connect one of these linear temperature sensors and how that then maps to the gain that the consumer of the binding needs to use. It would also be a good thing to mention sensors by name, so that someone grepping for them finds this binding. It's a djungle out there. > + > +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>. > + > +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 ...and here, you give maintenance to me. I didn't want all afe bindings so I didn't put an asterisk there for a reason :-) This binding is backed by the iio-rescale driver, so it's not totally alien for me to maintain it, but I'd be more happy if you listed yourself as I think you intended to? Cheers, Peter > F: Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml > F: drivers/iio/afe/iio-rescale.c > >
