linux-kernel - Re: [PATCH] iio: chemical: bme680: Fix pressure and humidity ABI mismatch

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Date:   Sun, 11 Aug 2019 09:32:43 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Himanshu Jha <himanshujha199640@...il.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        dpfrey@...il.com, mike.looijmans@...ic.nl
Subject: Re: [PATCH] iio: chemical: bme680: Fix pressure and humidity ABI
 mismatch

On Thu,  8 Aug 2019 21:13:50 +0530
Himanshu Jha <himanshujha199640@...il.com> wrote:

> Standard ABI for reporting pressure is kilopascal and for
> relative humidity it is millipercent.
> 
> What:           /sys/bus/iio/devices/iio:deviceX/in_pressureY_input
> What:           /sys/bus/iio/devices/iio:deviceX/in_pressure_input
> KernelVersion:  3.8
> Contact:        linux-iio@...r.kernel.org
> Description:
>                 Scaled pressure measurement from channel Y, in kilopascal.
> 
> What:           /sys/bus/iio/devices/iio:deviceX/in_humidityrelative_input
> KernelVersion:  3.14
> Contact:        linux-iio@...r.kernel.org
> Description:
>                 Scaled humidity measurement in milli percent.
> 
> Currently pressure is reported in hectopascal(hPa) and relative humidity
> in percent. Hence fix this ABI mismatch conforming to the standard ABI.
> 
> Fixes: 1b3bd8592780 ("iio: chemical: Add support for Bosch BME680 sensor")
> Signed-off-by: Himanshu Jha <himanshujha199640@...il.com>

Hopefully any users will cope with their scripts getting broken
by this.

I'm going to let this one sit for a little longer to give others time
to take a look.

Give me a poke if it looks like I've lost it down the back of the sofa
in a week or two.

Thanks,

Jonathan


> ---
> 
> While cleaning this mess I wonder about the gas channel and there
> exists no `in_resistance_input` in standard ABI :-(
> 
> We only have:
> 
> What:           /sys/bus/iio/devices/iio:deviceX/in_resistance_raw
> What:           /sys/bus/iio/devices/iio:deviceX/in_resistanceX_raw
> What:           /sys/bus/iio/devices/iio:deviceX/out_resistance_raw
> What:           /sys/bus/iio/devices/iio:deviceX/out_resistanceX_raw
> KernelVersion:  4.3
> Contact:        linux-iio@...r.kernel.org
> Description:
>                 Raw (unscaled no offset etc.) resistance reading that can be processed
>                 into an ohm value.
> 
> The sensor outputs processed value which is reported as is.
> 
> So, does it need a new ABI ?

New documentation as the ABI is clearly already there.   Good for completeness
but that description for _raw makes it obvious what the units will be etc so
hopefully we don't have any disagreement between drivers.


> 
>  drivers/iio/chemical/bme680_core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
> index ccde4c65ff93..28cc96d1e3c8 100644
> --- a/drivers/iio/chemical/bme680_core.c
> +++ b/drivers/iio/chemical/bme680_core.c
> @@ -670,7 +670,7 @@ static int bme680_read_press(struct bme680_data *data,
>  	}
>  
>  	*val = bme680_compensate_press(data, adc_press);
> -	*val2 = 100;
> +	*val2 = 1000;
>  	return IIO_VAL_FRACTIONAL;
>  }
>  
> @@ -704,7 +704,7 @@ static int bme680_read_humid(struct bme680_data *data,
>  	comp_humidity = bme680_compensate_humid(data, adc_humidity);
>  
>  	*val = comp_humidity;
> -	*val2 = 1000;
> +	*val2 = 1000000;
>  	return IIO_VAL_FRACTIONAL;
>  }
>