Re: [PATCH v4 1/1] drm/i915: Move abs_diff() to math.h

[Andrew Morton]

On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> 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?