drm/i915: introduce range_overflows utility macros

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@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161213203222.32564-3-matthew.auld@intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

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))
+
 enum pipe {
 	INVALID_PIPE = -1,
 	PIPE_A = 0,