[PATCH 4.19 019/338] iio: afe: rescale: use s64 for temporary scale calculations

Greg Kroah-Hartman
2022-04-14T13:15:49Z

From: Liam Beguin <liambeguin@gmail.com>

commit 51593106b608ae4247cc8da928813347da16d025 upstream.

All four scaling coefficients can take signed values.
Make tmp a signed 64-bit integer and switch to div_s64() to preserve
signs during 64-bit divisions.

Fixes: 8b74816b5a9a ("iio: afe: rescale: new driver")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220108205319.2046348-5-liambeguin@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/afe/iio-rescale.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -38,7 +38,7 @@ static int rescale_read_raw(struct iio_d
int *val, int *val2, long mask)
{
struct rescale *rescale = iio_priv(indio_dev);
- unsigned long long tmp;
+ s64 tmp;
int ret;

switch (mask) {
@@ -59,10 +59,10 @@ static int rescale_read_raw(struct iio_d
*val2 = rescale->denominator;
return IIO_VAL_FRACTIONAL;
case IIO_VAL_FRACTIONAL_LOG2:
- tmp = *val * 1000000000LL;
- do_div(tmp, rescale->denominator);
+ tmp = (s64)*val * 1000000000LL;
+ tmp = div_s64(tmp, rescale->denominator);
tmp *= rescale->numerator;
- do_div(tmp, 1000000000LL);
+ tmp = div_s64(tmp, 1000000000LL);
*val = tmp;
return ret;