On 2018-04-08 18:50, Jonathan Cameron wrote: > On Tue, 3 Apr 2018 17:36:34 +0200 > Peter Rosin <peda@xxxxxxxxxx> wrote: > > circuit in the patch title is spelled wrong. > >> An ADC is often used to measure other quantities indirectly. These >> bindings describe two cases, a current through a sense resistor, and >> a "big" voltage measured with the help of a voltage divider. >> >> Signed-off-by: Peter Rosin <peda@xxxxxxxxxx> > > Will definitely be wanting wide opinions on this one - Rob in particularly > for the binding side. > > One comment inline. What we have here is nice and generic, but is > it what would be 'expected' for current sense circuit? Should we > also be more specific in the naming. There are lots of options for > current sense circuits and this is just the simplest (current loop > for example). > > One option would be to use current-sense-shunt perhaps? Heh, I'm obviously happy to not use anything "circuit", because I fail to type it correctly most of the time. I don't know how many instances I fixed before sending and there were still a few lingering. Anyway, I have fixed those locally and I have also locally removed the error message on registration failure in patch 2/2 so that will be in v3. But I'm holding off that v3, since I expect more input on the naming. > https://en.wikipedia.org/wiki/Current_sensing_techniques > Gives a few that I didn't think of beyond current loops etc. I'll give it a read. Cheers, Peter >> --- >> .../bindings/iio/afe/current-sense-circuit.txt | 45 ++++++++++++++++++++++ >> .../bindings/iio/afe/voltage-divider.txt | 45 ++++++++++++++++++++++ >> MAINTAINERS | 7 ++++ >> 3 files changed, 97 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt >> create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt >> >> diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt >> new file mode 100644 >> index 000000000000..0bc7d89387c0 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt >> @@ -0,0 +1,45 @@ >> +Current Sense Curcuit >> +===================== >> + >> +When an io-channel measures the voltage over a current sense resistor, >> +the interesting mesaurement is often the current through the resistor, >> +not the voltage over it. This binding describes such a current sense >> +curcuit. >> + >> +Required properties: >> +- compatible : "current-sense-circuit" >> +- io-channels : Channel node of a voltage io-channel. >> + >> +Optional properties: >> +- numerator : The io-channel scale is multiplied by this value (default 1). >> +- denominator : The io-channel scale is divided by this value (default 1). >> + >> +Example: >> +The system current is measured by measuring the voltage over a >> +3.3 ohms sense resistor. > > Hmm. It sort of feels like the binding doesn't really reflect the > hardware as directly as it might. Should we be explicitly having the > resistance in this case? (with some more mapping logic needed in the > driver to figure out the scaling this causes). > >> + >> +sysi { >> + compatible = "current-sense-circuit"; >> + io-channels = <&tiadc 0>; >> + >> + /* Divide the ADC voltage by 33/10 (i.e. 3.3) to get the current. */ >> + numerator = <10>; >> + denominator = <33>; >> +}; >> + >> +&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/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt >> new file mode 100644 >> index 000000000000..fd4a215d9e6d >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt >> @@ -0,0 +1,45 @@ >> +Voltage divider >> +=============== >> + >> +When an io-channel measures the midpoint of a voltage divider, the >> +interesting voltage is often the voltage over the full resistance >> +of the divider. This binding describes the voltage divider in such >> +a curcuit. >> + >> +Required properties: >> +- compatible : "voltage-divider" >> +- io-channels : Channel node of a voltage io-channel. >> + >> +Optional properties: >> +- numerator : The io-channel scale is multiplied by this value (default 1). >> +- denominator : The io-channel scale is divided by this value (default 1). >> + >> +Example: >> +The system voltage is circa 12V, but divided down with a 22/200 >> +voltage divider to adjust it to the ADC range. >> + >> +SYSV ADC GND >> + + + + >> + | .-----. | .----. | >> + '--| 200 |-+-| 22 |--' >> + '-----' '----' >> + >> +sysv { >> + compatible = "voltage-divider"; >> + io-channels = <&maxadc 1>; >> + >> + /* Multiply the ADC voltage by 222/22 to get the system voltage. */ >> + numerator = <222>; /* 200 + 22 */ >> + denominator = <22>; >> +}; >> + >> +&spi { >> + maxadc: adc@0 { >> + compatible = "maxim,max1027"; >> + reg = <0>; >> + #io-channel-cells = <1>; >> + interrupt-parent = <&gpio5>; >> + interrupts = <15 IRQ_TYPE_EDGE_RISING>; >> + spi-max-frequency = <1000000>; >> + }; >> +}; >> diff --git a/MAINTAINERS b/MAINTAINERS >> index 36a28e979e9a..9dbe5019c6bd 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -6889,6 +6889,13 @@ F: drivers/staging/iio/ >> F: include/linux/iio/ >> F: tools/iio/ >> >> +IIO UNIT CONVERTER >> +M: Peter Rosin <peda@xxxxxxxxxx> >> +L: linux-iio@xxxxxxxxxxxxxxx >> +S: Maintained >> +F: Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt >> +F: Documentation/devicetree/bindings/iio/afe/voltage-divider.txt >> + >> IKANOS/ADI EAGLE ADSL USB DRIVER >> M: Matthieu Castet <castet.matthieu@xxxxxxx> >> M: Stanislaw Gruszka <stf_xl@xxxxx> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
