On Mon, Apr 11, 2016 at 10:59:10AM -0500, Andrew F. Davis wrote: > On 04/10/2016 10:16 AM, Guenter Roeck wrote: > > On 04/10/2016 04:57 AM, Jonathan Cameron wrote: > >> On 08/04/16 19:19, Andrew F. Davis wrote: > >>> The INA3221 is a three-channel, high-side current and bus voltage > >>> monitor > >>> with an I2C and SMBUS compatible interface. > >>> > >>> Signed-off-by: Andrew F. Davis <afd@xxxxxx> > >> Hi Andrew, > >> > >> My immediate thought on this one is whether it would be better off in > >> hwmon. > >> I'm not convinced either way from a quick glance at the data sheet, > >> but the > >> question needs to be addressed. > >> > > > > It looks like a typical hardware monitoring device to me. > > > >> It's not exactly a clean fit for the IIO ABI either at the moment though > >> I think some elements of that could be easily sorted out. > >> The key think in my mind is to look at what is actually being measured > >> rather than assume all the external components will be as the datasheet > >> assumes them to be... > >> > >> + where do the alert lines actually go? > >> > > In a typical application they would connect to interrupts or to gpio pins. > > They could also trigger some direct action, such as turning on a fan, > > though that is unlikely nowadays. The 'critical' pin might sometimes > > trigger a system reset. > > > > Some more comments inline. > > > > Guenter > > > >> Jonathan > >>> --- > >>> .../ABI/testing/sysfs-bus-iio-adc-ina3221 | 23 ++ > >>> drivers/iio/adc/Kconfig | 7 + > >>> drivers/iio/adc/Makefile | 1 + > >>> drivers/iio/adc/ina3221.c | 417 > >>> +++++++++++++++++++++ > >>> 4 files changed, 448 insertions(+) > >>> create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ina3221 > >>> create mode 100644 drivers/iio/adc/ina3221.c > >>> > >>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ina3221 > >>> b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina3221 > >>> new file mode 100644 > >>> index 0000000..bbe4f8c > >>> --- /dev/null > >>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ina3221 > >>> @@ -0,0 +1,23 @@ > >>> +What: > >>> /sys/bus/iio/devices/iio:deviceX/in_voltageY_shunt_(raw|scale) > >>> +What: > >>> /sys/bus/iio/devices/iio:deviceX/in_voltageY_bus_(raw|scale) > >>> +Date: April 2016 > >>> +KernelVersion: 4.7 > >>> +Contact: Andrew F. Davis <afd@xxxxxx> > >>> +Description: > >>> + Shunt and Bus voltage for each channel. > >> Units etc need specifying or at least a reference to the main > >> in_voltageY_raw > >> docs etc. These are really completely separate measurements be it > >> differential measurements where the + on one is the - on the other > >> (second is really a > >> unipolar measurement as it's relative to 0). I wonder if we are > >> better off supporting them as such so define this device as having the > >> channels. > >> in_voltage1-voltage0_raw (shunt voltage 1) > >> in_voltage0_raw (bus voltage 1) > >> in_voltage3-voltage2_raw (shunt voltage 2) > >> in_voltage2_raw (bus voltage 2) > >> in_voltage5-voltage4_raw (shunt voltage 3) > >> in_voltage4_raw > >> > >> That I think reflects the actual measuring options, without applying > >> assumptions on what is connected to them. Yes the datasheet says you > >> should > >> put a shunt between the first two connections and the load between the > >> second connection and the 0 volt line, but I can't see anything > >> preventing > >> this being used differently... > > > > Shunt voltage (or voltage difference) has a LSB of 40uV. Using it for > > anything else but current measurement doesn't really make much sense. > > I would report it not as voltage but as current, but that is from > > my filtered hwmon point of view, so maybe it doesn't really apply here. > > > > I would need to know the shunt resistance, I could get this from the > user somehow (DT/sysfs) but I decided to report directly from the ADC > and let the reader do the math so I don't have to make any use assumptions. > That is why one would specify it in devicetree. The board designers (those who hopefully help writing the devicetree description of a board) would know. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
