linux-kernel - Re: [PATCH v8 1/3] iio: pressure: bmp280: Generalize read

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Date: Sun, 23 Jun 2024 17:23:30 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Vasileios Amoiridis <vassilisamir@...il.com>, ak@...klinger.de,
 phil@...pberrypi.com
Cc: lars@...afoo.de, andriy.shevchenko@...ux.intel.com,
 ang.iglesiasg@...il.com, mazziesaccount@...il.com,
 petre.rodan@...dimension.ro, 579lpy@...il.com, linus.walleij@...aro.org,
 semen.protsenko@...aro.org, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, Adam Rizkalla <ajarizzo@...il.com>
Subject: Re: [PATCH v8 1/3] iio: pressure: bmp280: Generalize read_*()
 functions

On Sat, 22 Jun 2024 14:19:18 +0200
Vasileios Amoiridis <vassilisamir@...il.com> wrote:

> On Sat, Jun 22, 2024 at 10:28:26AM +0100, Jonathan Cameron wrote:
> > On Tue, 18 Jun 2024 01:05:38 +0200
> > Vasileios Amoiridis <vassilisamir@...il.com> wrote:
> >   
> > > Add the coefficients for the IIO standard units and the IIO value
> > > inside the chip_info structure.
> > > 
> > > Move the calculations for the IIO unit compatibility from inside the
> > > read_{temp,press,humid}() functions and move them to the general
> > > read_raw() function.
> > > 
> > > In this way, all the data for the calculation of the value are
> > > located in the chip_info structure of the respective sensor.
> > > 
> > > Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>  
> > Does this incorporate the fix?  I'm a little confused looking at
> > what is visible here, so I'd like Adam to take a look.
> > 
> > Btw, you missed cc'ing Adam.
> >   
> 
> Ah, I only used the output of get_maintainer...

always be careful to sanity check that :)

> ...
>   
> > > @@ -518,11 +511,29 @@ static int bmp280_read_raw_impl(struct iio_dev *indio_dev,
> > >  	case IIO_CHAN_INFO_PROCESSED:
> > >  		switch (chan->type) {
> > >  		case IIO_HUMIDITYRELATIVE:
> > > -			return data->chip_info->read_humid(data, val, val2);
> > > +			ret = data->chip_info->read_humid(data, &chan_value);
> > > +			if (ret)
> > > +				return ret;
> > > +
> > > +			*val = data->chip_info->humid_coeffs[0] * chan_value;
> > > +			*val2 = data->chip_info->humid_coeffs[1];
> > > +			return data->chip_info->humid_coeffs_type;
> > >  		case IIO_PRESSURE:
> > > -			return data->chip_info->read_press(data, val, val2);
> > > +			ret = data->chip_info->read_press(data, &chan_value);
> > > +			if (ret)
> > > +				return ret;
> > > +
> > > +			*val = data->chip_info->press_coeffs[0] * chan_value;
> > > +			*val2 = data->chip_info->press_coeffs[1];
> > > +			return data->chip_info->press_coeffs_type;
> > >  		case IIO_TEMP:
> > > -			return data->chip_info->read_temp(data, val, val2);
> > > +			ret = data->chip_info->read_temp(data, &chan_value);
> > > +			if (ret)
> > > +				return ret;
> > > +
> > > +			*val = data->chip_info->temp_coeffs[0] * (s64)chan_value;  
> 
> This is the first difference with the previous version where I incorporated
> the typecasting to (s64).

On a 32 bit platform that will then get pushed into a 32 bit int and overflow
I think.  Back when IIO got started everything was 32 bit so it didn't make sense
to make these 64 bit or indeed to worry about forcing the size.

Jonathan