[PATCH 29/54] drivers/iio: replace bitmap_weight() with bitmap_weight_{eq,gt} where appropriate

[PATCH 29/54] drivers/iio: replace bitmap_weight() with bitmap_weight_{eq,gt} where appropriate

[Yury Norov]

drivers/iio calls bitmap_weight() to compare the weight of bitmap with
a given number. We can do it more efficiently with bitmap_weight_{eq, gt}
because conditional bitmap_weight may stop traversing the bitmap earlier,
as soon as condition is met.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 drivers/iio/dummy/iio_simple_dummy_buffer.c | 4 ++--
 drivers/iio/industrialio-trigger.c          | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/dummy/iio_simple_dummy_buffer.c b/drivers/iio/dummy/iio_simple_dummy_buffer.c
index d81c2b2dad82..670997301e47 100644
--- a/drivers/iio/dummy/iio_simple_dummy_buffer.c
+++ b/drivers/iio/dummy/iio_simple_dummy_buffer.c
@@ -71,8 +71,8 @@ static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
 		int i, j;
 
 		for (i = 0, j = 0;
-		     i < bitmap_weight(indio_dev->active_scan_mask,
-				       indio_dev->masklength);
+		     bitmap_weight_gt(indio_dev->active_scan_mask,
+				       indio_dev->masklength, i);
 		     i++, j++) {
 			j = find_next_bit(indio_dev->active_scan_mask,
 					  indio_dev->masklength, j);
diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
index f504ed351b3e..98c54022fecf 100644
--- a/drivers/iio/industrialio-trigger.c
+++ b/drivers/iio/industrialio-trigger.c
@@ -331,7 +331,7 @@ int iio_trigger_detach_poll_func(struct iio_trigger *trig,
 {
 	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(pf->indio_dev);
 	bool no_other_users =
-		bitmap_weight(trig->pool, CONFIG_IIO_CONSUMERS_PER_TRIGGER) == 1;
+		bitmap_weight_eq(trig->pool, CONFIG_IIO_CONSUMERS_PER_TRIGGER, 1);
 	int ret = 0;
 
 	if (trig->ops && trig->ops->set_trigger_state && no_other_users) {
-- 
2.30.2

Re: [PATCH 29/54] drivers/iio: replace bitmap_weight() with bitmap_weight_{eq,gt} where appropriate

[Andy Shevchenko]

On Sun, Jan 23, 2022 at 10:39:00AM -0800, Yury Norov wrote:
> drivers/iio calls bitmap_weight() to compare the weight of bitmap with
> a given number. We can do it more efficiently with bitmap_weight_{eq, gt}
> because conditional bitmap_weight may stop traversing the bitmap earlier,
> as soon as condition is met.

...

>  		int i, j;
>  
>  		for (i = 0, j = 0;
> -		     i < bitmap_weight(indio_dev->active_scan_mask,
> -				       indio_dev->masklength);
> +		     bitmap_weight_gt(indio_dev->active_scan_mask,
> +				       indio_dev->masklength, i);
>  		     i++, j++) {
>  			j = find_next_bit(indio_dev->active_scan_mask,
>  					  indio_dev->masklength, j);

This smells like room for improvement. Have you checked this deeply?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 29/54] drivers/iio: replace bitmap_weight() with bitmap_weight_{eq,gt} where appropriate

[Jonathan Cameron]

On Mon, 24 Jan 2022 14:46:43 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Sun, Jan 23, 2022 at 10:39:00AM -0800, Yury Norov wrote:
> > drivers/iio calls bitmap_weight() to compare the weight of bitmap with
> > a given number. We can do it more efficiently with bitmap_weight_{eq, gt}
> > because conditional bitmap_weight may stop traversing the bitmap earlier,
> > as soon as condition is met.  
> 
> ...
> 
> >  		int i, j;
> >  
> >  		for (i = 0, j = 0;
> > -		     i < bitmap_weight(indio_dev->active_scan_mask,
> > -				       indio_dev->masklength);
> > +		     bitmap_weight_gt(indio_dev->active_scan_mask,
> > +				       indio_dev->masklength, i);
> >  		     i++, j++) {
> >  			j = find_next_bit(indio_dev->active_scan_mask,
> >  					  indio_dev->masklength, j);  
> 
> This smells like room for improvement. Have you checked this deeply?
> 

I have no idea what I was smoking that day.
It was near 10 years ago, so I'll blame my younger self ;)

Jonathan