Messages in this thread | | | Subject | Re: [PATCH v4 05/10] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support | From | Peter Rosin <> | Date | Fri, 9 Jul 2021 18:29:15 +0200 |
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On 2021-07-06 18:09, Liam Beguin wrote: > From: Liam Beguin <lvb@xiphos.com> > > Add IIO_VAL_INT_PLUS_{NANO,MICRO} scaling support. > Scale the integer part and the decimal parts individually and keep the > original scaling type. > > Signed-off-by: Liam Beguin <lvb@xiphos.com> > --- > drivers/iio/afe/iio-rescale.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c > index ba3bdcc69b16..1d0e24145d87 100644 > --- a/drivers/iio/afe/iio-rescale.c > +++ b/drivers/iio/afe/iio-rescale.c > @@ -89,7 +89,15 @@ static int rescale_read_raw(struct iio_dev *indio_dev, > do_div(tmp, 1000000000LL); > *val = tmp; > return ret; > + case IIO_VAL_INT_PLUS_NANO: > + case IIO_VAL_INT_PLUS_MICRO: > + tmp = (s64)*val * rescale->numerator; > + *val = div_s64(tmp, rescale->denominator); > + tmp = (s64)*val2 * rescale->numerator; > + *val2 = div_s64(tmp, rescale->denominator);
Hi!
You are losing precision, and you are not mormalising after the calculation. I think it's better to not even attempt this given that the results can be really poor.
Cheers, Peter
> + return ret; > default: > + dev_err(&indio_dev->dev, "unsupported type %d\n", ret); > return -EOPNOTSUPP; > } > default: >
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