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SubjectRe: [PATCH v8 05/14] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support
On Thu, Aug 26, 2021 at 10:11:18AM +0200, Peter Rosin wrote:
> On 2021-08-20 21:17, Liam Beguin wrote:
> > From: Liam Beguin <lvb@xiphos.com>
> >
> > Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
> > Add support for these to allow using the iio-rescaler with them.
> >
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> > drivers/iio/afe/iio-rescale.c | 35 +++++++++++++++++++++++++++++++++++
> > 1 file changed, 35 insertions(+)
> >
> > diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
> > index d0669fd8eac5..8488f1d83527 100644
> > --- a/drivers/iio/afe/iio-rescale.c
> > +++ b/drivers/iio/afe/iio-rescale.c
> > @@ -22,6 +22,9 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
> > int *val, int *val2)
> > {
> > unsigned long long tmp;
> > + s32 rem;
> > + u32 mult;
> > + u32 neg;
> >
> > switch (scale_type) {
> > case IIO_VAL_FRACTIONAL:
> > @@ -40,6 +43,38 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
> > tmp *= rescale->numerator;
> > do_div(tmp, 1000000000LL);
> > *val = tmp;
> > + return scale_type;
> > + case IIO_VAL_INT_PLUS_NANO:
> > + case IIO_VAL_INT_PLUS_MICRO:
> > + if (scale_type == IIO_VAL_INT_PLUS_NANO)
> > + mult = 1000000000LL;
> > + else
> > + mult = 1000000LL;
> > + /*
> > + * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if *val OR
> > + * *val2 is negative the schan scale is negative
>
> The last line doesn't parse for me. It doesn't end with a period either, so
> it looks like you moved on before you finished it?

I meant to warn that IIO_VAL_INT_PLUS_{MICRO,NANO} are a little odd, and
that if either one *val or *val2 is negative, the result will be
negative.

i.e. *val = 1 and *val2 = -0.5 gives -1.5 and not 0.5.

I'll give it another try and will add the period.

Thanks,
Liam

>
> Cheers,
> Peter
>
> > + */
> > + neg = *val < 0 || *val2 < 0;
> > +
> > + tmp = (s64)abs(*val) * abs(rescale->numerator);
> > + *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
> > +
> > + tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
> > + tmp = div_s64(tmp, abs(rescale->denominator));
> > +
> > + *val += div_s64_rem(tmp, mult, val2);
> > +
> > + /*
> > + * If only one of the rescaler elements or the schan scale is
> > + * negative, the combined scale is negative.
> > + */
> > + if (neg ^ ((rescale->numerator < 0) ^ (rescale->denominator < 0))) {
> > + if (*val)
> > + *val = -*val;
> > + else
> > + *val2 = -*val2;
> > + }
> > +
> > return scale_type;
> > default:
> > return -EOPNOTSUPP;
> >

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