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    Subject[PATCH 4.14 248/293] iio: iio-utils: Fix possible incorrect mask calculation
    Date
    [ 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/9615ceac7c134d838660e209726cd86aa2064fd3

    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>
    ---
    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 7a6d61c6c012..55272fef3b50 100644
    --- a/tools/iio/iio_utils.c
    +++ b/tools/iio/iio_utils.c
    @@ -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)) {
    --
    2.20.1


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