Re: [PATCH] iio: pressure: bmp280: fix bmp580 temp read

[Vasileios Amoiridis <vassilisamir@gmail.com>]

On Tue, Jun 04, 2024 at 08:01:07PM +0100, Jonathan Cameron wrote:
> On Sun,  2 Jun 2024 15:12:01 -0500
> Adam Rizkalla <ajarizzo@gmail.com> wrote:
> 
> > Fix overflow when storing bmp580 temperature reading and preserve sign.
> > 
> > This patch re-applies the fix in [1] after the merge conflict resolution
> > mentioned in [2].
> > 
> > [1] https://lore.kernel.org/all/Zin2udkXRD0+GrML@adam-asahi.lan/
> > [2] https://lore.kernel.org/linux-kernel/20240531140621.264f0848@canb.auug.org.au/
> > 
> > Signed-off-by: Adam Rizkalla <ajarizzo@gmail.com>
> 
> Thanks! I was just about to email about this fix currently being lost in
> linux-next.
> 
> Rather than dance around this, I'm going to pull the later part of Vasielios'
> series off the togreg tree for now then reapply later once I have the fix
> in my upstream.
> 
> It's a shame that we need to do the maths in driver to keep within range.
> Maybe we can be cheeky and avoid doing the division?
> I believe the IIO core formatting code should be fine with that as it
> already casts up to 64 bits to do the maths.
> 
> (s64)*raw_temp * 250);
> 
> bmp580_temp_coeffs = {1, 18}
> 
> Anyhow, I've dropped (for now) the following patches from my togreg tree
>   iio: pressure: bmp280: Generalize read_{temp,press,humid}() functions
>   iio: pressure: bmp280: Add SCALE, RAW values in channels and refactorize them
>   iio: pressure: bmp280: Add triggered buffer support
> 
> Jonathan
> 

Hi Jonathan, Adam,

I had mentioned it here [1], when I applied v7 of the patches that this would 
happen. No worries though,  I already have the new version of these 3 patches
that include Adam's fix, so when we have it upstream I can resubmit them
(no need to keep a note Jonathan, I have it) and I think we will be fine!

Cheers,
Vasilis

[1]: https://lore.kernel.org/linux-iio/20240512230524.53990-1-vassilisamir@gmail.com/T/#t

> > ---
> >  drivers/iio/pressure/bmp280-core.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> > index 95c88b0e1c49..3a003843c79c 100644
> > --- a/drivers/iio/pressure/bmp280-core.c
> > +++ b/drivers/iio/pressure/bmp280-core.c
> > @@ -1752,6 +1752,8 @@ static int bmp580_read_temp(struct bmp280_data *data, s32 *raw_temp)
> >  		dev_err(data->dev, "reading temperature skipped\n");
> >  		return -EIO;
> >  	}
> > +	*raw_temp = sign_extend32(*raw_temp, 23);
> > +	*raw_temp = ((s64)*raw_temp * 1000) / (1 << 16);
> >  
> >  	return 0;
> >  }
> > @@ -2154,7 +2156,7 @@ static irqreturn_t bmp580_buffer_handler(int irq, void *p)
> >  
> >  static const int bmp580_oversampling_avail[] = { 1, 2, 4, 8, 16, 32, 64, 128 };
> >  static const u8 bmp580_chip_ids[] = { BMP580_CHIP_ID, BMP580_CHIP_ID_ALT };
> > -static const int bmp580_temp_coeffs[] = { 1000, 16 };
> > +static const int bmp580_temp_coeffs[] = { 1, 0 };
> >  static const int bmp580_press_coeffs[] = { 1, 64000};
> >  
> >  const struct bmp280_chip_info bmp580_chip_info = {
> > @@ -2184,7 +2186,7 @@ const struct bmp280_chip_info bmp580_chip_info = {
> >  	.iir_filter_coeff_default = 2,
> >  
> >  	.temp_coeffs = bmp580_temp_coeffs,
> > -	.temp_coeffs_type = IIO_VAL_FRACTIONAL_LOG2,
> > +	.temp_coeffs_type = IIO_VAL_INT,
> >  	.press_coeffs = bmp580_press_coeffs,
> >  	.press_coeffs_type = IIO_VAL_FRACTIONAL,
> >  
>