[PATCH v2 07/13] staging: iio: ad2s1200: Improve readability with be16_to_cpup

[Jonathan Cameron]

On Fri, 20 Apr 2018 21:30:32 +0200
David Veenstra <davidjulianveenstra at gmail.com> wrote:

> The manual states that the data is contained in the upper 12 bits
> of the 16 bits read by spi. The code that extracts these 12 bits
> is correct for both be and le machines, but this is not clear
> from a first glance.
> 
> To improve readability the relevant expressions are replaced
> with equivalent expressions that use be16_to_cpup.
> 
> Signed-off-by: David Veenstra <davidjulianveenstra at gmail.com>
> ---
>  drivers/staging/iio/resolver/ad2s1200.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/iio/resolver/ad2s1200.c b/drivers/staging/iio/resolver/ad2s1200.c
> index 0a5fc9917e32..11ed9c7332e6 100644
> --- a/drivers/staging/iio/resolver/ad2s1200.c
> +++ b/drivers/staging/iio/resolver/ad2s1200.c
> @@ -57,7 +57,7 @@ static int ad2s1200_read_raw(struct iio_dev *indio_dev,
>  {
>  	struct ad2s1200_state *st = iio_priv(indio_dev);
>  	int ret = 0;
> -	s16 vel;
> +	u16 vel;
>  
>  	mutex_lock(&st->lock);
>  	gpio_set_value(st->sample, 0);
> @@ -73,14 +73,13 @@ static int ad2s1200_read_raw(struct iio_dev *indio_dev,
>  		return ret;
>  	}
>  
> +	vel = be16_to_cpup((__be16 *)st->rx);
Well it isn't vel (velocity) in one case so now the name is misleading.

Also that type cast suggests a fairly obvious cleanup associated with this one.
Why not make st->rx a __be16 in the first pace avoiding the need to cast at all?

Then you could just have *val = be16_to_cpu(st->rx) >> 4 and similar.

>  	switch (chan->type) {
>  	case IIO_ANGL:
> -		*val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
> +		*val = vel >> 4;
>  		break;
>  	case IIO_ANGL_VEL:
> -		vel = (((s16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
> -		vel = sign_extend32(vel, 11);
> -		*val = vel;
> +		*val = sign_extend32((s16)vel >> 4, 11);
If you were to use an intermediate that was s16 then the sign extend would
be automatic.  Perhaps it is clear to do it like this though.. 
Up to you.

>  		break;
>  	default:
>  		mutex_unlock(&st->lock);