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SubjectRe: [RFC PATCH] hwmon: (iio_hwmon) Enable power exporting from IIO
On Thu, Aug 22, 2019 at 03:43:39PM +0200, Michal Simek wrote:
> On 20. 08. 19 17:39, Guenter Roeck wrote:
> > On 8/12/19 6:29 AM, Michal Simek wrote:
> >> There is no reason why power channel shouldn't be exported as is done for
> >> voltage, current, temperature and humidity.
> >>
> >> Power channel is available on iio ina226 driver.
> >>
> >> Tested on Xilinx ZCU102 board.
> >>
> >> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> >> ---
> >>
> >> But I don't think values are properly converted. Voltage1 is fine but the
> >> rest is IMHO wrong. But this patch should enable power channel to be
> >> shown
> >> which looks good.
> >>
> >
> > No idea what is going on there. I don't really know what "scaled" units
> > the iio subsystem reports. power is supposed to be reported to user space
> > in micro-Watt. Is that what the scaled value from iio reports ?
>
> I have take a look at it again.
>
> root@zynqmp-debian:~/libiio/examples# sensors ina226_u76-*
> ina226_u76-isa-0000
> Adapter: ISA adapter
> in1: +0.01 V
> in2: +0.85 V
> power1: 1.16 mW
> curr1: +1.60 A
>
> from iio_monitor
> voltage0 0.007 V
> voltage1 0.848 V
> power2 1.150 W
> current3 1.361 A
>
> from iio_info
> IIO context has 18 devices:
> iio:device0: ps_pmbus (buffer capable)
> 9 channels found:
> voltage0: (input, index: 0, format: le:U16/16>>0)
> 3 channel-specific attributes found:
> attr 0: integration_time value: 0.001100
> attr 1: raw value: 3152
> attr 2: scale value: 0.002500000
> voltage1: (input, index: 1, format: le:U16/16>>0)
> 3 channel-specific attributes found:
> attr 0: integration_time value: 0.001100
> attr 1: raw value: 678
> attr 2: scale value: 1.250000000
> power2: (input, index: 2, format: le:U16/16>>0)
> 2 channel-specific attributes found:
> attr 0: raw value: 106
> attr 1: scale value: 12.500000000
> current3: (input, index: 3, format: le:U16/16>>0)
> 2 channel-specific attributes found:
> attr 0: raw value: 3152
> attr 1: scale value: 0.500000000
>
>
> And if you look at power2 (in iio_info) then you see that calculation is
> returning mili-Watts not micro-Watts.
>
> And looking at it back it is also said there.
>
> What: /sys/bus/iio/devices/iio:deviceX/in_powerY_raw
> KernelVersion: 4.5
> Contact: linux-iio@vger.kernel.org
> Description:
> Raw (unscaled no bias removal etc.) power measurement from
> channel Y. The number must always be specified and
> unique to allow association with event codes. Units after
> application of scale and offset are milliwatts.
>
> That means for power channel value needs to be multiply by 1000.
>
> Are you OK with this solution?
>
Yes, looks good.

Thanks,
Guenter

> diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c
> index aedb95fa24e3..7ea105bd195b 100644
> --- a/drivers/hwmon/iio_hwmon.c
> +++ b/drivers/hwmon/iio_hwmon.c
> @@ -44,12 +44,20 @@ static ssize_t iio_hwmon_read_val(struct device *dev,
> int ret;
> struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
> struct iio_hwmon_state *state = dev_get_drvdata(dev);
> + struct iio_channel *chan = &state->channels[sattr->index];
> + enum iio_chan_type type;
>
> - ret = iio_read_channel_processed(&state->channels[sattr->index],
> - &result);
> + ret = iio_read_channel_processed(chan, &result);
> if (ret < 0)
> return ret;
>
> + ret = iio_get_channel_type(chan, &type);
> + if (ret < 0)
> + return ret;
> +
> + if (type == IIO_POWER)
> + result *= 1000;
> +
> return sprintf(buf, "%d\n", result);
> }
>
>
> Thanks,
> Michal

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