From: Andreas Klinger ak@it-klinger.de
[ Upstream commit dee2dabc0e4115b80945fe2c91603e634f4b4686 ]
Limit the output of humidity compensation to the range between 0 and 100 percent.
Depending on the calibration parameters of the individual sensor it happens, that a humidity above 100 percent or below 0 percent is calculated, which don't make sense in terms of relative humidity.
Add a clamp to the compensation formula as described in the datasheet of the sensor in chapter 4.2.3.
Although this clamp is documented, it was never in the driver of the kernel.
It depends on the circumstances (calibration parameters, temperature, humidity) if one can see a value above 100 percent without the clamp. The writer of this patch was working with this type of sensor without noting this error. So it seems to be a rare event when this bug occures.
Signed-off-by: Andreas Klinger ak@it-klinger.de Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iio/pressure/bmp280-core.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c index 36f03fdf4d4f..85b90b5939db 100644 --- a/drivers/iio/pressure/bmp280-core.c +++ b/drivers/iio/pressure/bmp280-core.c @@ -182,6 +182,8 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data, + (s32)2097152) * H2 + 8192) >> 14); var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)H1) >> 4;
+ var = clamp_val(var, 0, 419430400); + return var >> 12; };