[PATCH] IIO: bmp280-core.c: fix error in humidity calculation

[Andreas Klinger <ak@it-klinger.de>]

While calculating the compensation of the humidity there are negative
values interpreted as unsigned because of unsigned variables used.
These values need to be casted to signed as indicated by the documentation
of the sensor.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
---
 drivers/iio/pressure/bmp280-core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index 4d18826ac63c..73308f0ea260 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -177,9 +177,9 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data,
 
 	var = ((s32)data->t_fine) - 76800;
 	var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var)) + 16384) >> 15)
-		* (((((((var * H6) >> 10) * (((var * H3) >> 11) + 32768)) >> 10)
-		+ 2097152) * H2 + 8192) >> 14);
-	var -= ((((var >> 15) * (var >> 15)) >> 7) * H1) >> 4;
+		* (((((((var * H6) >> 10) * (((var * (s32)H3) >> 11) + 32768))
+		>> 10) + 2097152) * H2 + 8192) >> 14);
+	var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)H1) >> 4;
 
 	return var >> 12;
 };
-- 
2.1.4


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