linux-kernel - Re: [PATCH 04/49] iio: fix opencoded for_each_set

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Message-ID: <20220604164113.2ed4f681@jic23-huawei>
Date:   Sat, 4 Jun 2022 16:41:13 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-iio@...r.kernel.org
Subject: Re: [PATCH 04/49] iio: fix opencoded for_each_set_bit()

On Fri, 11 Feb 2022 18:17:37 +0100
Christophe JAILLET <christophe.jaillet@...adoo.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@...lic.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.

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));  
>