linux-kernel - Re: [RFC PATCH] hwmon: (iio_hwmon) Enable power exporting from IIO

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Date:   Tue, 20 Aug 2019 08:39:55 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Michal Simek <michal.simek@...inx.com>,
        linux-kernel@...r.kernel.org, monstr@...str.eu
Cc:     linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>
Subject: Re: [RFC PATCH] hwmon: (iio_hwmon) Enable power exporting from IIO

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@...inx.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 ?

Thanks,
Guenter

> root@...qmp-debian:~# iio_info -a && sensors -u
> Library version: 0.16 (git tag: v0.16)
> Compiled with backends: local xml ip usb serial
> Using auto-detected IIO context at URI "local:"
> IIO context created with local backend.
> Backend version: 0.16 (git tag: v0.16)
> Backend description string: Linux zynqmp-debian 5.3.0-rc4-00004-ga7ca33daed22-dirty #41 SMP PREEMPT Mon Aug 12 15:06:58 CEST 2019 aarch64
> IIO context has 1 attributes:
> 	local,kernel: 5.3.0-rc4-00004-ga7ca33daed22-dirty
> IIO context has 1 devices:
> 	iio:device0: ina226 (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: 70
> 				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: 958
> 				attr  2: scale value: 1.250000000
> 			power2:  (input, index: 2, format: le:U16/16>>0)
> 			2 channel-specific attributes found:
> 				attr  0: raw value: 3
> 				attr  1: scale value: 0.006250000
> 			current3:  (input, index: 3, format: le:U16/16>>0)
> 			2 channel-specific attributes found:
> 				attr  0: raw value: 70
> 				attr  1: scale value: 0.000250000
> 			timestamp:  (input, index: 4, format: le:S64/64>>0)
> 			allow:  (input)
> 			1 channel-specific attributes found:
> 				attr  0: async_readout value: 0
> 			oversampling:  (input)
> 			1 channel-specific attributes found:
> 				attr  0: ratio value: 4
> 			sampling:  (input)
> 			1 channel-specific attributes found:
> 				attr  0: frequency value: 114
> 			shunt:  (input)
> 			1 channel-specific attributes found:
> 				attr  0: resistor value: 10.000000000
> 		2 device-specific attributes found:
> 				attr  0: current_timestamp_clock value: realtime
> 
> 				attr  1: integration_time_available value: 0.000140 0.000204 0.000332 0.000588 0.001100 0.002116 0.004156 0.008244
> 		2 buffer-specific attributes found:
> 				attr  0: data_available value: 0
> 				attr  1: watermark value: 1
> 		1 debug attributes found:
> 				debug attr  0: direct_reg_access value: 0x4327
> ina226_fourth-isa-0000
> Adapter: ISA adapter
> in1:
>    in1_input: 0.000
> in2:
>    in2_input: 1.198
> power1:
>    power1_input: 0.000
> curr1:
>    curr1_input: 0.000
> ---
>   drivers/hwmon/iio_hwmon.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/iio_hwmon.c b/drivers/hwmon/iio_hwmon.c
> index f1c2d5faedf0..aedb95fa24e3 100644
> --- a/drivers/hwmon/iio_hwmon.c
> +++ b/drivers/hwmon/iio_hwmon.c
> @@ -59,7 +59,7 @@ static int iio_hwmon_probe(struct platform_device *pdev)
>   	struct iio_hwmon_state *st;
>   	struct sensor_device_attribute *a;
>   	int ret, i;
> -	int in_i = 1, temp_i = 1, curr_i = 1, humidity_i = 1;
> +	int in_i = 1, temp_i = 1, curr_i = 1, humidity_i = 1, power_i = 1;
>   	enum iio_chan_type type;
>   	struct iio_channel *channels;
>   	struct device *hwmon_dev;
> @@ -114,6 +114,10 @@ static int iio_hwmon_probe(struct platform_device *pdev)
>   			n = curr_i++;
>   			prefix = "curr";
>   			break;
> +		case IIO_POWER:
> +			n = power_i++;
> +			prefix = "power";
> +			break;
>   		case IIO_HUMIDITYRELATIVE:
>   			n = humidity_i++;
>   			prefix = "humidity";
>