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

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 4 Jun 2022 16:41:13 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 11 Feb 2022 18:17:37 +0100
> Christophe JAILLET <christophe.jaillet@wanadoo.fr> wrote:
> 
> > Le 10/02/2022 à 23:48, Yury Norov a écrit :  
> > > 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.
> > > 
> > > Signed-off-by: Yury Norov <yury.norov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > > ---
> > >   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.
> > > +	 */    
> > 
> > Nitpicking: you could take advantage of the tab you save to use the full 
> > width of the line and save some lines of code.  
> 
> Tweaked whilst applying.
> 
> Sorry this one took so long. I marked it as a patch that I'd revisit if and
> tidy up if there was no v2 sent, but then managed to forget about it until
> I came to do a clean out of patchwork today.
> 
> Anyhow, now applied to the togreg branch of iio.git - initially pushed out
> as testing for 0-day to see if we missed anything.

And dropped again during a rebase as a different version has gone upstream
through a pull request to Linus.

Whilst I have no strong opinion on that in general, I am a little grumpy
that a version was merged that was never posted to the mailing lists (that
I can find on lore.kernel.org.)  Sure the changes were minor and easy to verify
as harmless, but none the less they should have been posted.

Jonathan

> 
> Thanks,
> 
> Jonathan
> 
> > 
> > Just my 2c.
> > 
> > CJ
> > 
> >   
> > > +	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));    
> >   
>