On Fri, 19 Jul 2019 00:14:06 -0400 Sasha Levin <sashal@xxxxxxxxxx> wrote: > From: Bastien Nocera <hadess@xxxxxxxxxx> > > [ 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@xxxxxxxxx> in > iio-sensor-proxy: > https://github.com/hadess/iio-sensor-proxy/commit/9615ceac7c134d838660e209726cd86aa2064fd3 > > Signed-off-by: Bastien Nocera <hadess@xxxxxxxxxx> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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)) {
