linux-kernel - Re: [PATCH v1 1/1] drm/i915/selftests: Replace too verbose for-loop with simpler while

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Date:   Wed, 16 Feb 2022 10:55:11 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v1 1/1] drm/i915/selftests: Replace too verbose for-loop
 with simpler while

On Tue, 15 Feb 2022, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> On Tue, Feb 15, 2022 at 07:14:49PM +0200, Jani Nikula wrote:
>> On Tue, 15 Feb 2022, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>> > It's hard to parse for-loop which has some magic calculations inside.
>> > Much cleaner to use while-loop directly.
>> 
>> I assume you're trying to prove a point following our recent
>> for-vs-while loop discussion. I really can't think of any other reason
>> you'd end up looking at this file or this loop.
>> 
>> With the change, the loop indeed becomes simpler, but it also runs one
>> iteration further than the original. Whoops.
>
> Yeah, sorry for that, the initial condition should be d = depth - 1,
> of course.

Well, no, the condition should be while (--i) instead to also match the
values the original loop takes. ;D

Cheers,
Jani.


>
>> It's a selftest. The loop's been there for five years. What are we
>> trying to achieve here? So we disagree on loops, fine. Perhaps this is
>> not the best use of either of our time? Please just let the for loops in
>> i915 be.
>
> Yes, I'm pretty much was sure that no-one will go and apply this anyway
> (so I haven't paid too much attention), but to prove my point in the
> certain discussion.
>
> And yes, the point is for the new code, I'm not going to change existing
> suboptimal and too hard to read for-loops, it will consume my time later
> when I will try to understand the code.

-- 
Jani Nikula, Intel Open Source Graphics Center