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[198.48.202.89]) by smtp.gmail.com with ESMTPSA id q184sm4945265qkd.35.2021.07.04.21.31.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 04 Jul 2021 21:31:50 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 05 Jul 2021 00:31:49 -0400 Message-Id: Cc: , , , , , , Subject: Re: [PATCH v3 09/10] dt-bindings: iio: afe: add bindings for temperature-sense-rtd From: "Liam Beguin" To: "Jonathan Cameron" References: <20210701010034.303088-1-liambeguin@gmail.com> <20210701010034.303088-10-liambeguin@gmail.com> <20210704180259.7cba5831@jic23-huawei> In-Reply-To: <20210704180259.7cba5831@jic23-huawei> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun Jul 4, 2021 at 1:02 PM EDT, Jonathan Cameron wrote: > On Wed, 30 Jun 2021 21:00:33 -0400 > Liam Beguin wrote: > > > From: Liam Beguin > >=20 > > An ADC is often used to measure other quantities indirectly. This > > binding describe one case, the measurement of a temperature through the > > voltage across an RTD resistor such as a PT1000. > >=20 > > Signed-off-by: Liam Beguin > > --- > > .../iio/afe/temperature-sense-rtd.yaml | 101 ++++++++++++++++++ > > MAINTAINERS | 7 ++ > > 2 files changed, 108 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/iio/afe/temperatu= re-sense-rtd.yaml > >=20 > > diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-sens= e-rtd.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rt= d.yaml > > new file mode 100644 > > index 000000000000..e23e74e63ec5 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.y= aml > > @@ -0,0 +1,101 @@ > > +# 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 > > + > > +description: | > > + RTDs (Resistance Temperature Detectors) are a kind of temperature se= nsors > > + used to get a linear voltage to temperature reading within a give ra= nge > > + (usually 0 to 100 degrees Celsius). > > + > > + When an io-channel measures the output voltage across an RTD such as= a > > + PT1000, the interesting measurement is almost always the correspondi= ng > > + temperature, not the voltage output. This binding describes such a c= ircuit. > > + > > + The general transfer function here is (using SI units) > > + > > + V =3D R(T) * iexc > > + R(T) =3D r0 * (1 + alpha * T) > > + T =3D 1 / (alpha * r0 * iexc) * (V - r0 * iexc) > > + > > + The following circuit matches what's in the examples section. > > + > > + 5V0 > > + ----- > > + | > > + +---+----+ > > + | R 5k | > > + +---+----+ > > + | > > + V 1mA > > + | > > + +---- Vout > > + | > > + +---+----+ > > + | PT1000 | > > + +---+----+ > > + | > > + ----- > > + GND > > + > > +properties: > > + compatible: > > + const: temperature-sense-rtd > > + > > + io-channels: > > + maxItems: 1 > > + description: | > > + Channel node of a voltage io-channel. > > + > > + '#io-channel-cells': > > + const: 1 > > Only 1 channel, so this should be 0. For consumers of this driver > they only need to identify the device, not the device + channel. > > https://github.com/devicetree-org/dt-schema/blob/master/schemas/iio/iio.y= aml > Thanks for pointing that out. will fix. > > + > > + excitation-current-microamp: > > + description: The current fed through the RTD sensor. > > + > > + alpha-ppm-per-celsius: > > + description: | > > + alpha can also be expressed in micro-ohms per ohm Celsius. It's = a linear > > + approximation of the resistance versus temperature relationship > > + between 0 and 100 degrees Celsius. > > + > > + alpha =3D (R_100 - R_0) / (100 * R_0) > > + > > + Where, R_100 is the resistance of the sensor at 100 degrees Cels= ius, and > > + R_0 (or r-naught-ohms) is the resistance of the sensor at 0 degr= ees > > + Celsius. > > + > > + Pure platinum has an alpha of 3925. Industry standards such as I= EC60751 > > + 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, 500 for PT500, and 1000 for PT1= 000 > > + > > +additionalProperties: false > > +required: > > + - compatible > > + - io-channels > > + - excitation-current-microamp > > + - alpha-ppm-per-celsius > > + - r-naught-ohms > > + > > +examples: > > + - | > > + pt1000_1: temperature-sensor0 { > > + compatible =3D "temperature-sense-rtd"; > > + #io-channel-cells =3D <1>; > > + io-channels =3D <&temp_adc1 0>; > > + > > + excitation-current-microamp =3D <1000>; /* i =3D U/R =3D 5 / 5= 000 */ > > + alpha-ppm-per-celsius =3D <3908>; > > + r-naught-ohms =3D <1000>; > > + }; > > +... > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 9bf553e53f0f..ed80e671a16a 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -8897,6 +8897,13 @@ F: Documentation/devicetree/bindings/iio/afe/cur= rent-sense-shunt.yaml > > F: Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml > > F: drivers/iio/afe/iio-rescale.c > > =20 > > +IIO UNIT CONVERTER (TEMPERATURE) > > +M: Liam Beguin > > +R: Peter Rosin > > +L: linux-iio@vger.kernel.org > > +S: Maintained > > +F: Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yam= l > > I'm not sure we'd normally bother with a MAINTAINERS entry when it is > just the binding doc > (as rest is in the driver). The binding doc itself has it's own local > maintainers entry > which is the more useful one. > You're right, it makes sense to drop the changes to MAINTAINERS as the information is already contained it the bindings. I added this after briefly talking about it with Peter. Thanks again for reviewing these changes, Liam > > + > > IKANOS/ADI EAGLE ADSL USB DRIVER > > M: Matthieu Castet > > M: Stanislaw Gruszka