drm: Define drm_mm_for_each_node_in_range()

Some clients would like to iterate over every node within a certain
range. Make a nice little macro for them to hide the mixing of the
rbtree search and linear walk.

v2: Blurb

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161123141118.23876-1-chris@chris-wilson.co.uk

drivers/gpu/drm/drm_mm.c

@@ -174,19 +174,12 @@ INTERVAL_TREE_DEFINE(struct drm_mm_node, rb,
 		     START, LAST, static inline, drm_mm_interval_tree)
 
 struct drm_mm_node *
-drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last)
+__drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last)
 {
 	return drm_mm_interval_tree_iter_first(&mm->interval_tree,
 					       start, last);
 }
-EXPORT_SYMBOL(drm_mm_interval_first);
-
-struct drm_mm_node *
-drm_mm_interval_next(struct drm_mm_node *node, u64 start, u64 last)
-{
-	return drm_mm_interval_tree_iter_next(node, start, last);
-}
-EXPORT_SYMBOL(drm_mm_interval_next);
+EXPORT_SYMBOL(__drm_mm_interval_first);
 
 static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 					  struct drm_mm_node *node)

include/drm/drm_mm.h

@@ -308,10 +308,26 @@ void drm_mm_takedown(struct drm_mm *mm);
 bool drm_mm_clean(struct drm_mm *mm);
 
 struct drm_mm_node *
-drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last);
+__drm_mm_interval_first(struct drm_mm *mm, u64 start, u64 last);
 
-struct drm_mm_node *
-drm_mm_interval_next(struct drm_mm_node *node, u64 start, u64 last);
+/**
+ * drm_mm_for_each_node_in_range - iterator to walk over a range of
+ * allocated nodes
+ * @node: drm_mm_node structure to assign to in each iteration step
+ * @mm: drm_mm allocator to walk
+ * @start: starting offset, the first node will overlap this
+ * @end: ending offset, the last node will start before this (but may overlap)
+ *
+ * This iterator walks over all nodes in the range allocator that lie
+ * between @start and @end. It is implemented similarly to list_for_each(),
+ * but using the internal interval tree to accelerate the search for the
+ * starting node, and so not safe against removal of elements. It assumes
+ * that @end is within (or is the upper limit of) the drm_mm allocator.
+ */
+#define drm_mm_for_each_node_in_range(node, mm, start, end)		\
+	for (node = __drm_mm_interval_first((mm), (start), (end)-1);	\
+	     node && node->start < (end);				\
+	     node = list_next_entry(node, node_list))			\
 
 void drm_mm_init_scan(struct drm_mm *mm,
 		      u64 size,