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>
[bwh: Backported to 3.16:
 - Use vals[] instead of tmp{0,1}
 - Keep using sprintf()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index eb62d1629785335f3e788663fe91e0e7db5cb630..c6b0f15033660e4c8d281674d2c66612f1fd8148 100644 (file)
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -406,10 +406,9 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals)
                vals[0] = (int)div_s64_rem(tmp, 1000000000, &vals[1]);
                return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1]));
        case IIO_VAL_FRACTIONAL_LOG2:
-               tmp = (s64)vals[0] * 1000000000LL >> vals[1];
-               vals[1] = do_div(tmp, 1000000000LL);
-               vals[0] = tmp;
-               return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
+               tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
+               vals[0] = (int)div_s64_rem(tmp, 1000000000LL, &vals[1]);
+               return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1]));
        case IIO_VAL_INT_MULTIPLE:
        {
                int i;