From f7067a5ad717d4dbb4faa3ec56744152f6ba97ad Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 23 Jan 2015 00:09:56 +0100 Subject: [PATCH] staging: iio: ad2s1200: Fix sign extension 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 Acked-by: Lars-Peter Clausen Signed-off-by: Jonathan Cameron --- drivers/staging/iio/resolver/ad2s1200.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/staging/iio/resolver/ad2s1200.c b/drivers/staging/iio/resolver/ad2s1200.c index 017d2f8..c17893b 100644 --- a/drivers/staging/iio/resolver/ad2s1200.c +++ b/drivers/staging/iio/resolver/ad2s1200.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include @@ -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: -- 2.7.4