Re: [PATCH 04/49] iio: fix opencoded for_each_set_bit()

[Andy Shevchenko]

On Thu, Feb 10, 2022 at 02:48:48PM -0800, Yury Norov wrote:
> iio_simple_dummy_trigger_h() is mostly an opencoded for_each_set_bit().
> Using for_each_set_bit() make code much cleaner, and more effective.

I would wait for some testing, but from code perspective looks good.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

> Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
> ---
>  drivers/iio/dummy/iio_simple_dummy_buffer.c | 48 ++++++++-------------
>  1 file changed, 19 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/iio/dummy/iio_simple_dummy_buffer.c b/drivers/iio/dummy/iio_simple_dummy_buffer.c
> index d81c2b2dad82..3bc1b7529e2a 100644
> --- a/drivers/iio/dummy/iio_simple_dummy_buffer.c
> +++ b/drivers/iio/dummy/iio_simple_dummy_buffer.c
> @@ -45,41 +45,31 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
>  {
>  	struct iio_poll_func *pf = p;
>  	struct iio_dev *indio_dev = pf->indio_dev;
> +	int i = 0, j;
>  	u16 *data;
>  
>  	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
>  	if (!data)
>  		goto done;
>  
> -	if (!bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) {
> -		/*
> -		 * Three common options here:
> -		 * hardware scans: certain combinations of channels make
> -		 *   up a fast read.  The capture will consist of all of them.
> -		 *   Hence we just call the grab data function and fill the
> -		 *   buffer without processing.
> -		 * software scans: can be considered to be random access
> -		 *   so efficient reading is just a case of minimal bus
> -		 *   transactions.
> -		 * software culled hardware scans:
> -		 *   occasionally a driver may process the nearest hardware
> -		 *   scan to avoid storing elements that are not desired. This
> -		 *   is the fiddliest option by far.
> -		 * Here let's pretend we have random access. And the values are
> -		 * in the constant table fakedata.
> -		 */
> -		int i, j;
> -
> -		for (i = 0, j = 0;
> -		     i < bitmap_weight(indio_dev->active_scan_mask,
> -				       indio_dev->masklength);
> -		     i++, j++) {
> -			j = find_next_bit(indio_dev->active_scan_mask,
> -					  indio_dev->masklength, j);
> -			/* random access read from the 'device' */
> -			data[i] = fakedata[j];
> -		}
> -	}
> +	/*
> +	 * Three common options here:
> +	 * hardware scans: certain combinations of channels make
> +	 *   up a fast read.  The capture will consist of all of them.
> +	 *   Hence we just call the grab data function and fill the
> +	 *   buffer without processing.
> +	 * software scans: can be considered to be random access
> +	 *   so efficient reading is just a case of minimal bus
> +	 *   transactions.
> +	 * software culled hardware scans:
> +	 *   occasionally a driver may process the nearest hardware
> +	 *   scan to avoid storing elements that are not desired. This
> +	 *   is the fiddliest option by far.
> +	 * Here let's pretend we have random access. And the values are
> +	 * in the constant table fakedata.
> +	 */
> +	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
> +		data[i++] = fakedata[j];
>  
>  	iio_push_to_buffers_with_timestamp(indio_dev, data,
>  					   iio_get_time_ns(indio_dev));
> -- 
> 2.32.0
> 

-- 
With Best Regards,
Andy Shevchenko