linux-kernel - [PATCH v2] iio: bmp280: fix compensation of humidity

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Message-ID: <20200429184852.GA17547@arbad>
Date:   Wed, 29 Apr 2020 20:48:54 +0200
From:   Andreas Klinger <ak@...klinger.de>
To:     jic23@...nel.org
Cc:     knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        bgolaszewski@...libre.com, linus.walleij@...aro.org,
        tglx@...utronix.de, allison@...utok.net, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] iio: bmp280: fix compensation of humidity

Output of humidity compensation is limited to the range between 0 and
100 percent. Add this to the compensation formula as described in the
datasheet chapter 4.2.3.

Change to v1:
Thanks to Tomasz for suggesting the easier to use function clamp_val()
which is now used.

Signed-off-by: Andreas Klinger <ak@...klinger.de>
---
 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 29c209cc1108..297ee2205bf6 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -271,6 +271,8 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data,
 		+ (s32)2097152) * calib->H2 + 8192) >> 14);
 	var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)calib->H1) >> 4;
 
+	var = clamp_val(var, 0, 419430400);
+
 	return var >> 12;
 };
 
-- 
2.20.1