On Fri, 19 Jul 2019 00:14:06 -0400 Sasha Levin sashal@kernel.org wrote:
From: Bastien Nocera hadess@hadess.net
[ Upstream commit 208a68c8393d6041a90862992222f3d7943d44d6 ]
On some machines, iio-sensor-proxy was returning all 0's for IIO sensor values. It turns out that the bits_used for this sensor is 32, which makes the mask calculation:
*mask = (1 << 32) - 1;
If the compiler interprets the 1 literals as 32-bit ints, it generates undefined behavior depending on compiler version and optimization level. On my system, it optimizes out the shift, so the mask value becomes
*mask = (1) - 1;
With a mask value of 0, iio-sensor-proxy will always return 0 for every axis.
Avoid incorrect 0 values caused by compiler optimization.
See original fix by Brett Dutro brett.dutro@gmail.com in iio-sensor-proxy: https://github.com/hadess/iio-sensor-proxy/commit/9615ceac7c134d838660e20972...
Signed-off-by: Bastien Nocera hadess@hadess.net Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org
Good catch, I should have cc'd stable on this one.
Thanks,
Jonathan
tools/iio/iio_utils.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c index 5eb6793f3972..2d0dcd6fc64c 100644 --- a/tools/iio/iio_utils.c +++ b/tools/iio/iio_utils.c @@ -163,9 +163,9 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used, *be = (endianchar == 'b'); *bytes = padint / 8; if (*bits_used == 64)
*mask = ~0;
*mask = ~(0ULL); else
*mask = (1ULL << *bits_used) - 1;
*mask = (1ULL << *bits_used) - 1ULL;*is_signed = (signchar == 's'); if (fclose(sysfsfp)) {