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

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 4 Jun 2024 21:19:04 +0200
Vasileios Amoiridis <vassilisamir@gmail.com> wrote:

> 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!

Excellent.  The fix is no in the upstream of my togreg branch.

I've only pushed it out as testing for now, but if you send a version based
on my testing branch or 20460472952 (currently char-misc-next head) that would be great.

Thanks,

Jonathan

> 
> 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,
> > >    
> >