linux-kernel - Re: [PATCH v1 1/1] gpiolib: Deduplicate cleanup for-loop in gpiochip_add_data_with

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Date: Thu, 22 Feb 2024 15:40:22 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] gpiolib: Deduplicate cleanup for-loop in
 gpiochip_add_data_with_key()

On Thu, Feb 22, 2024 at 03:38:56PM +0200, Andy Shevchenko wrote:
> On Thu, Feb 22, 2024 at 02:30:03PM +0100, Bartosz Golaszewski wrote:
> > On Thu, Feb 22, 2024 at 2:28 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Thu, Feb 22, 2024 at 10:48:00AM +0100, Bartosz Golaszewski wrote:
> > > > On Wed, Feb 21, 2024 at 8:36 PM Andy Shevchenko
> > > > <andriy.shevchenko@...ux.intel.com> wrote:

..

> > > > > +       while (desc_index--)
> > > >
> > > > What about gdev->descs[0]?
> > >
> > > What about it? :-)
> > >
> > > for (i = i - 1; i >= 0; i--)
> > > while (--i >= 0)
> > > while (i--)
> > >
> > > are all equivalents.
> > >
> > > The difference is what the value will i get _after_ the loop.
> > 
> > Ugh of course. But the first one is more readable given I got tricked
> > by variant #3 at a quick glance but the for loop says out loud what it
> > does.
> 
> I disagree. `while (i--)` is very well known cleanup pattern.
> Less letters to parse, easier to understand.

$ git grep -n 'while (i--)' | wc -l
298
$ git grep -n 'while (--i >= 0)' | wc -l
246
$ git grep -n 'for (--i; i >= 0; i--)' | wc -l
29
$ git grep -n 'for (i = i - 1; i >= 0; i--)' | wc -l
17

-- 
With Best Regards,
Andy Shevchenko