Commit 171c0091 authored Sep 02, 2016 by Gregor Boirie Committed by Jonathan Cameron Sep 05, 2016

iio:core: fix IIO_VAL_FRACTIONAL sign handling



7985e7c1 ("iio: Introduce a new fractional value type") introduced a
new IIO_VAL_FRACTIONAL value type meant to represent rational type numbers
expressed by a numerator and denominator combination.

Formating of IIO_VAL_FRACTIONAL values relies upon do_div() usage. This
fails handling negative values properly since parameters are reevaluated
as unsigned values.
Fix this by using div_s64_rem() instead. Computed integer part will carry
properly signed value. Formatted fractional part will always be positive.

Fixes: 7985e7c1 ("iio: Introduce a new fractional value type")
Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

parent 5dba4b14

drivers/iio/industrialio-core.c

+2 −3

Original line number	Original line	Diff line number	Diff line
	@@ -613,9 +613,8 @@ ssize_t iio_format_value(char buf, unsigned int type, int size, int vals)
	return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);		return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
	case IIO_VAL_FRACTIONAL:		case IIO_VAL_FRACTIONAL:
	tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);		tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
	vals[1] = do_div(tmp, 1000000000LL);		vals[0] = (int)div_s64_rem(tmp, 1000000000, &vals[1]);
	vals[0] = tmp;		return sprintf(buf, "%d.%09u\n", vals[0], abs(vals[1]));
	return sprintf(buf, "%d.%09u\n", vals[0], vals[1]);
	case IIO_VAL_FRACTIONAL_LOG2:		case IIO_VAL_FRACTIONAL_LOG2:
	tmp = (s64)vals[0] * 1000000000LL >> vals[1];		tmp = (s64)vals[0] * 1000000000LL >> vals[1];
	vals[1] = do_div(tmp, 1000000000LL);		vals[1] = do_div(tmp, 1000000000LL);