Re: [PATCH] iio: humidity: hts221: fix division by zero in calibration data parsing

[Jonathan Cameron]

On Tue, 25 Aug 2026 11:39:58 +0200
Joshua Crofts <joshua.crofts1@xxxxxxxxx> wrote:

> On Tue, 25 Aug 2026 17:21:10 +0800
> Yang Zi <2959243019@xxxxxx> wrote:
> 
> > hts221_parse_temp_caldata() and hts221_parse_rh_caldata() compute the
> > sensor slope as ((cal_y1 - cal_y0) * 8000) / (cal_x1 - cal_x0). If the
> > device reports cal_x1 == cal_x0 the division causes a divide-by-zero
> > error.
> > 
> > Return -EINVAL when cal_x1 == cal_x0 in both functions before performing
> > the division.
> > 
> > Signed-off-by: Yang Zi <2959243019@xxxxxx>
> > ---
> > diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
> > index bfeb0a60d3af..7d1f04951d8b 100644
> > --- a/drivers/iio/humidity/hts221_core.c
> > +++ b/drivers/iio/humidity/hts221_core.c
> > @@ -288,6 +288,9 @@ static int hts221_parse_temp_caldata(struct hts221_hw *hw)
> >          return err;
> >      cal_x1 = le16_to_cpu(val);
> >  
> > +    if (cal_x1 == cal_x0)
> > +        return -EINVAL;
> > +
> >      slope = &hw->sensors[HTS221_SENSOR_T].slope;
> >      b_gen = &hw->sensors[HTS221_SENSOR_T].b_gen;
> >  
> > @@ -327,6 +330,9 @@ static int hts221_parse_rh_caldata(struct hts221_hw *hw)
> >          return err;
> >      cal_x1 = le16_to_cpu(val);
> >  
> > +    if (cal_x1 == cal_x0)
> > +        return -EINVAL;
> > +
> >      slope = &hw->sensors[HTS221_SENSOR_H].slope;
> >      b_gen = &hw->sensors[HTS221_SENSOR_H].b_gen;
> >  
> > 
> >   
> 
> This definitely needs a Fixes: tag, otherwise LGTM.
Looks like hardening to me rather than a fix. Given those algs come
off the datasheet and the div zero case makes no sense, I'd not expect
the hardware to ever return a combination that triggers this.

With that said, the cost in catching it is low.

I was going to pick this up, but seems patch is corrupted.
Looks like we have tabs replaced with white space but I haven't checked closely.

Please fix that up and send a v2.

thanks,

Jonathan


> 
> Feel free to carry my review tag.
> 
> Reviewed-by: Joshua Crofts <joshua.crofts1@xxxxxxxxx>
> 
> PS, a bit of process info: I noticed Sashiko (sashiko.dev) failed to apply your
> patches. To prevent this from happening in the future, please use the `--base` flag
> when running `git format-patch` to specify which commit it should be applied onto.
>