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SubjectRe: [PATCH 04/49] iio: fix opencoded for_each_set_bit()
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));
> >
>

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