linux-kernel - [PATCH v9 07/14] iio: afe: rescale: use s64 for temporary scale calculations

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Date:   Sun, 14 Nov 2021 22:43:27 -0500
From:   Liam Beguin <liambeguin@...il.com>
To:     liambeguin@...il.com, peda@...ntia.se, jic23@...nel.org,
        lars@...afoo.de
Cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: [PATCH v9 07/14] iio: afe: rescale: use s64 for temporary scale calculations

From: Liam Beguin <lvb@...hos.com>

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.

Signed-off-by: Liam Beguin <lvb@...hos.com>
---
 drivers/iio/afe/iio-rescale.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index da462e0910ff..394f8b16b29c 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -21,7 +21,7 @@
 int rescale_process_scale(struct rescale *rescale, int scale_type,
 			  int *val, int *val2)
 {
-	unsigned long long tmp;
+	s64 tmp;
 	s32 rem;
 	u32 mult;
 	u32 neg;
@@ -38,10 +38,10 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		*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 scale_type;
 	case IIO_VAL_INT_PLUS_NANO:
-- 
2.32.0.452.g940fe202adcb