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

From Andreas Klinger <ak@it-klinger.de>
Newsgroups linux.kernel
Subject [PATCH] IIO: bmp280-core.c: fix error in humidity calculation
Date 2017-03-27 12:10 +0200
Message-ID <tpzL5-6pP-41@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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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 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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Thread

[PATCH] IIO: bmp280-core.c: fix error in humidity calculation Andreas Klinger <ak@it-klinger.de> - 2017-03-27 12:10 +0200
  Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Jonathan Cameron <jic23@kernel.org> - 2017-04-02 11:40 +0200
    Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Linus Walleij <linus.walleij@linaro.org> - 2017-04-02 17:00 +0200
      Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Andreas Klinger <ak@it-klinger.de> - 2017-04-02 19:40 +0200
        Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Jonathan Cameron <jic23@jic23.retrosnub.co.uk> - 2017-04-02 19:50 +0200
        Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Matt Ranostay <matt.ranostay@konsulko.com> - 2017-04-04 08:20 +0200
          Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Matt Ranostay <matt.ranostay@konsulko.com> - 2017-04-07 08:20 +0200
            Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Andreas Klinger <ak@it-klinger.de> - 2017-04-07 21:30 +0200
              Re: [PATCH] IIO: bmp280-core.c: fix error in humidity calculation Matt Ranostay <matt.ranostay@konsulko.com> - 2017-04-08 23:40 +0200

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