iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

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@avionic-design.de>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index d18ded4..3ff91e0 100644 (file)
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -610,10 +610,9 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
                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;