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staging: iio: ad2s1200: Fix sign extension

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The line above makes vel a 12-bit quantity (st->rx[] is u8). The
intention is to sign-extend vel using bit 11 as the sign bit. But
because of C's promotion rules "vel = (vel << 4) >> 4;" is actually a
no-op, since vel is promoted to int before the inner
shift. sign_extend32 works equally well for 8 and 16 bits types, so
use that.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Rasmus Villemoes 2015-01-23 00:09:56 +01:00 committed by Jonathan Cameron
parent 89bb35e200
commit f7067a5ad7
1 changed files with 2 additions and 1 deletions
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3
drivers/staging/iio/resolver/ad2s1200.c
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@ -18,6 +18,7 @@
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
@ -68,7 +69,7 @@ static int ad2s1200_read_raw(struct iio_dev *indio_dev,
break;
case IIO_ANGL_VEL:
vel = (((s16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
vel = (vel << 4) >> 4;
vel = sign_extend32(vel, 11);
*val = vel;
break;
default: