Re: [PATCH] iio: accel: sca3000: Use sign_extend32() instead of opencoding sign extension.

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 3 Oct 2021 20:03:10 +0200
Lars-Peter Clausen <lars@metafoo.de> wrote:

> On 6/3/21 6:47 PM, Jonathan Cameron wrote:
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > Whilst nice to get rid of this non obvious code, this also clears a
> > static checker warning:
> >
> > drivers/iio/accel/sca3000.c:734 sca3000_read_raw()
> > warn: no-op. '((*val) << 19) >> 19'
> >
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >   drivers/iio/accel/sca3000.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/iio/accel/sca3000.c b/drivers/iio/accel/sca3000.c
> > index cb753a43533c..0692ccb80293 100644
> > --- a/drivers/iio/accel/sca3000.c
> > +++ b/drivers/iio/accel/sca3000.c
> > @@ -731,8 +731,7 @@ static int sca3000_read_raw(struct iio_dev *indio_dev,
> >   				return ret;
> >   			}
> >   			*val = (be16_to_cpup((__be16 *)st->rx) >> 3) & 0x1FFF;
> > -			*val = ((*val) << (sizeof(*val) * 8 - 13)) >>
> > -				(sizeof(*val) * 8 - 13);
> > +			*val = sign_extend32(*val, 13);  
> Should be 12 I think. The index is 0 based.

Fine example of why everything needs a sanity check.  Indeed, should be 12
to sign extend a 13bit value.

Jonathan

> >   		} else {
> >   			/* get the temperature when available */
> >   			ret = sca3000_read_data_short(st,  
> 
>