Commit 208a68c8 authored Jun 27, 2019 by Bastien Nocera Committed by Jonathan Cameron Jun 27, 2019

iio: iio-utils: Fix possible incorrect mask calculation

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>

parent def914a4

tools/iio/iio_utils.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)) {

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