dt-bindings: iio: afe: add binding for current-sense-shunt

An ADC is often used to measure other quantities indirectly. This
binding describe one cases, a current through a shunt resistor
measured by the voltage over it.

Signed-off-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
new file mode 100644 (file)
index 0000000..8e7b3e4
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
@@ -0,0 +1,41 @@
+Current Sense Shunt
+===================
+
+When an io-channel measures the voltage over a current sense shunt,
+the interesting mesaurement is almost always the current through the
+shunt, not the voltage over it. This binding describes such a current
+sense circuit.
+
+Required properties:
+- compatible : "current-sense-shunt"
+- io-channels : Channel node of a voltage io-channel.
+- shunt-resistor-micro-ohms : The shunt resistance in microohms.
+
+Example:
+The system current is measured by measuring the voltage over a
+3.3 ohms shunt resistor.
+
+sysi {
+       compatible = "current-sense-shunt";
+       io-channels = <&tiadc 0>;
+
+       /* Divide the voltage by 3300000/1000000 (or 3.3) for the current. */
+       shunt-resistor-micro-ohms = <3300000>;
+};
+
+&i2c {
+       tiadc: adc@48 {
+               compatible = "ti,ads1015";
+               reg = <0x48>;
+               #io-channel-cells = <1>;
+
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               channel@0 { /* IN0,IN1 differential */
+                       reg = <0>;
+                       ti,gain = <1>;
+                       ti,datarate = <4>;
+               };
+       };
+};

diff --git a/MAINTAINERS b/MAINTAINERS
index 002cb013b0004b204e7d22aaf55f8d5ae4f039e2..d3052bd4a75290530ec4bdc842a16e935e477723 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6898,6 +6898,12 @@ F:       drivers/staging/iio/
 F:     include/linux/iio/
 F:     tools/iio/
 
+IIO UNIT CONVERTER
+M:     Peter Rosin <peda@axentia.se>
+L:     linux-iio@vger.kernel.org
+S:     Maintained
+F:     Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
+
 IKANOS/ADI EAGLE ADSL USB DRIVER
 M:     Matthieu Castet <castet.matthieu@free.fr>
 M:     Stanislaw Gruszka <stf_xl@wp.pl>