iio: core: Fix IIO_VAL_FRACTIONAL_LOG2 for negative values

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@avionic-design.de>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index aaca42862389b9e675807437b1231760bfb3a859..d9c15e411e10f255dbb10a464e5cedea89659d6c 100644 (file)
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -608,10 +608,9 @@ 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;