[PATCH 4.10 014/110] iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

[Greg Kroah-Hartman]

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolaus Schulz <nikolaus.schulz@xxxxxxxxxxxxxxxxx>

commit 7fd6592d1287046f61bfd3cda3c03cd35be490f7 upstream.

Fix formatting of negative values of type IIO_VAL_FRACTIONAL_LOG2 by
switching from do_div(), which can't handle negative numbers, to
div_s64_rem().  Also use shift_right for shifting, which is safe with
negative values.

Signed-off-by: Nikolaus Schulz <nikolaus.schulz@xxxxxxxxxxxxxxxxx>
Reviewed-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Signed-off-by: Jonathan Cameron <jic23@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/iio/industrialio-core.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -608,10 +608,9 @@ static ssize_t __iio_format_value(char *
 		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
 		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_FRACTIONAL_LOG2:
-		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
-		tmp1 = do_div(tmp, 1000000000LL);
-		tmp0 = tmp;
-		return snprintf(buf, len, "%d.%09u", tmp0, tmp1);
+		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
+		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
+		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_INT_MULTIPLE:
 	{
 		int i;