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

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

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Matt Ranostay <matt.ranostay@konsulko.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Andreas Klinger 2017-04-10 19:00:01 +02:00 committed by Jonathan Cameron
parent 84ca8e364a
commit ed3730c435
1 changed files with 6 additions and 5 deletions
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11
drivers/iio/pressure/bmp280-core.c
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@ -175,11 +175,12 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data,
}
H6 = sign_extend32(tmp, 7);
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 = ((s32)data->t_fine) - (s32)76800;
var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var))
+ (s32)16384) >> 15) * (((((((var * H6) >> 10)
* (((var * (s32)H3) >> 11) + (s32)32768)) >> 10)
+ (s32)2097152) * H2 + 8192) >> 14);
var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)H1) >> 4;
return var >> 12;
};