linux-kernel - [PATCH 4.9 018/102] iio: magnetometer: ak8974: Fix negative raw values in sysfs

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Message-Id: <20200401161536.017379826@linuxfoundation.org>
Date:   Wed,  1 Apr 2020 18:17:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephan Gerhold <stephan@...hold.net>,
        Linus Waleij <linus.walleij@...aro.org>,
        Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 4.9 018/102] iio: magnetometer: ak8974: Fix negative raw values in sysfs

From: Stephan Gerhold <stephan@...hold.net>

commit b500c086e4110829a308c23e83a7cdc65b26228a upstream.

At the moment, reading from in_magn_*_raw in sysfs tends to return
large values around 65000, even though the output of ak8974 is actually
limited to ±32768. This happens because the value is never converted
to the signed 16-bit integer variant.

Add an explicit cast to s16 to fix this.

Fixes: 7c94a8b2ee8c ("iio: magn: add a driver for AK8974")
Signed-off-by: Stephan Gerhold <stephan@...hold.net>
Reviewed-by: Linus Waleij <linus.walleij@...aro.org>
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/iio/magnetometer/ak8974.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/magnetometer/ak8974.c
+++ b/drivers/iio/magnetometer/ak8974.c
@@ -477,7 +477,7 @@ static int ak8974_read_raw(struct iio_de
 		 * We read all axes and discard all but one, for optimized
 		 * reading, use the triggered buffer.
 		 */
-		*val = le16_to_cpu(hw_values[chan->address]);
+		*val = (s16)le16_to_cpu(hw_values[chan->address]);
 
 		ret = IIO_VAL_INT;
 	}