Re: [PATCH 1/5] staging:iio:ad7298: Do not perform endianness conversion in buffered mode

[Jonathan Cameron <jic23@kernel.org>]

On 11/15/2012 01:15 PM, Lars-Peter Clausen wrote:
> For buffered mode we do not want to perform endianness conversion in the kernel,
> but rather offload it to user space, since it is not always required to do a
> conversion at all. It also greatly simplifies the kernel code since no
> post-processing has to be done and may allow future optimizations like streaming
> data directly to a storage device or over the network via DMA.
>
added to togreg branch of iio.git
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> ---
>  drivers/staging/iio/adc/ad7298.h      |  2 +-
>  drivers/staging/iio/adc/ad7298_core.c |  1 +
>  drivers/staging/iio/adc/ad7298_ring.c | 11 +++--------
>  3 files changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/ad7298.h b/drivers/staging/iio/adc/ad7298.h
> index 18f2787..0ce9031 100644
> --- a/drivers/staging/iio/adc/ad7298.h
> +++ b/drivers/staging/iio/adc/ad7298.h
> @@ -48,7 +48,7 @@ struct ad7298_state {
>  	 * DMA (thus cache coherency maintenance) requires the
>  	 * transfer buffers to live in their own cache lines.
>  	 */
> -	unsigned short			rx_buf[8] ____cacheline_aligned;
> +	unsigned short			rx_buf[12] ____cacheline_aligned;
>  	unsigned short			tx_buf[2];
>  };
>  
> diff --git a/drivers/staging/iio/adc/ad7298_core.c b/drivers/staging/iio/adc/ad7298_core.c
> index 4c75114..67082ad 100644
> --- a/drivers/staging/iio/adc/ad7298_core.c
> +++ b/drivers/staging/iio/adc/ad7298_core.c
> @@ -35,6 +35,7 @@
>  			.sign = 'u',					\
>  			.realbits = 12,					\
>  			.storagebits = 16,				\
> +			.endianness = IIO_BE,				\
>  		},							\
>  	}
>  
> diff --git a/drivers/staging/iio/adc/ad7298_ring.c b/drivers/staging/iio/adc/ad7298_ring.c
> index b3dd514..e387712 100644
> --- a/drivers/staging/iio/adc/ad7298_ring.c
> +++ b/drivers/staging/iio/adc/ad7298_ring.c
> @@ -76,8 +76,7 @@ static irqreturn_t ad7298_trigger_handler(int irq, void *p)
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct ad7298_state *st = iio_priv(indio_dev);
>  	s64 time_ns = 0;
> -	__u16 buf[16];
> -	int b_sent, i;
> +	int b_sent;
>  
>  	b_sent = spi_sync(st->spi, &st->ring_msg);
>  	if (b_sent)
> @@ -85,15 +84,11 @@ static irqreturn_t ad7298_trigger_handler(int irq, void *p)
>  
>  	if (indio_dev->scan_timestamp) {
>  		time_ns = iio_get_time_ns();
> -		memcpy((u8 *)buf + indio_dev->scan_bytes - sizeof(s64),
> +		memcpy((u8 *)st->rx_buf + indio_dev->scan_bytes - sizeof(s64),
>  			&time_ns, sizeof(time_ns));
>  	}
>  
> -	for (i = 0; i < bitmap_weight(indio_dev->active_scan_mask,
> -						 indio_dev->masklength); i++)
> -		buf[i] = be16_to_cpu(st->rx_buf[i]);
> -
> -	iio_push_to_buffers(indio_dev, (u8 *)buf);
> +	iio_push_to_buffers(indio_dev, (u8 *)st->rx_buf);
>  
>  done:
>  	iio_trigger_notify_done(indio_dev->trig);
>