[Intel-gfx] [PATCH 3/4] drm/i915: introduce range_overflows utility macros

[Chris Wilson]

On Tue, Dec 13, 2016 at 08:32:21PM +0000, Matthew Auld wrote:
> In a number places we hand-roll the overflow sanity check for ranges, so
> roll that into single macro, conceived by Chris, along with its typed
> variant.
> 
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 20bc04d5e617..47b5a9f1c9ed 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -218,6 +218,18 @@ static inline const char *enableddisabled(bool v)
>  	return v ? "enabled" : "disabled";
>  }
>  
> +#define range_overflows(start, size, max) ({ \
> +	typeof(start) start__ = (start); \
> +	typeof(size) size__ = (size); \
> +	typeof(max) max__ = (max); \
> +	(void)(&start__ == &size__); \
> +	(void)(&start__ == &max__); \
> +	start > max || size > max - start; \
> +})
> +
> +#define range_overflows_t(type, start, size, max) \
> +	range_overflows(((type)start), ((type)size), ((type)max))

Hmm, should be (type)(start) etc. Yeah, this is slightly more obvious
than min_t's method.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre