From: Bastien Nocera <[email protected]>
[ 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 <[email protected]> in
iio-sensor-proxy:
https://github.com/hadess/iio-sensor-proxy/commit/9615ceac7c134d838660e209726cd86aa2064fd3
Signed-off-by: Bastien Nocera <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
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)) {
--
2.20.1
On Fri, 19 Jul 2019 00:14:06 -0400
Sasha Levin <[email protected]> wrote:
> From: Bastien Nocera <[email protected]>
>
> [ 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 <[email protected]> in
> iio-sensor-proxy:
> https://github.com/hadess/iio-sensor-proxy/commit/9615ceac7c134d838660e209726cd86aa2064fd3
>
> Signed-off-by: Bastien Nocera <[email protected]>
> Signed-off-by: Jonathan Cameron <[email protected]>
> Signed-off-by: Sasha Levin <[email protected]>
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)) {