linux-kernel - [PATCH 5.4 024/475] iio: afe: rescale: use s64 for temporary scale calculations

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Date:   Thu, 14 Apr 2022 15:06:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Liam Beguin <liambeguin@...il.com>,
        Peter Rosin <peda@...ntia.se>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 5.4 024/475] iio: afe: rescale: use s64 for temporary scale calculations

From: Liam Beguin <liambeguin@...il.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@...il.com>
Reviewed-by: Peter Rosin <peda@...ntia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Link: https://lore.kernel.org/r/20220108205319.2046348-5-liambeguin@gmail.com
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;
 		default: