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iio: iio-utils: Fix possible incorrect mask calculation

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[ 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:
9615ceac7c

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>
This commit is contained in:
Bastien Nocera 2019-06-27 09:20:45 +02:00 committed by Greg Kroah-Hartman
parent fc9c15c4e3
commit b150423e0d
1 changed files with 2 additions and 2 deletions
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4
tools/iio/iio_utils.c
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@ -159,9 +159,9 @@ 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)) {