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Date:   Thu, 3 Aug 2023 10:24:46 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Jani Nikula <jani.nikula@intel.com>,
        Imre Deak <imre.deak@intel.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Andi Shyti <andi.shyti@linux.intel.com>,
        Jiri Slaby <jirislaby@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
        linux-fbdev@vger.kernel.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, Helge Deller <deller@gmx.de>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH v4 1/1] drm/i915: Move abs_diff() to math.h
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In-Reply-To: <20230803131918.53727-1-andriy.shevchenko@linux.intel.com>
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On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> abs_diff() belongs to math.h. Move it there.
> This will allow others to use it.
> 
> ...
>
> --- a/include/linux/math.h
> +++ b/include/linux/math.h
> @@ -155,6 +155,13 @@ __STRUCT_FRACT(u32)
>  	__builtin_types_compatible_p(typeof(x), unsigned type),		\
>  	({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
>  
> +#define abs_diff(a, b) ({			\
> +	typeof(a) __a = (a);			\
> +	typeof(b) __b = (b);			\
> +	(void)(&__a == &__b);			\
> +	__a > __b ? (__a - __b) : (__b - __a);	\
> +})

Can we document it please?

Also, the open-coded type comparison could be replaced with __typecheck()?

And why the heck isn't __typecheck() in typecheck.h, to be included by
minmax.h.

etcetera.  Sigh.  I'll grab it, but please at least send along some
kerneldoc?