drm: mm: add helper to unwind scan state

With the switch to implicit free space accounting one pointer
got unused when scanning. Use it to create a single-linked list
to ensure correct unwinding of the scan state.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
index 17a070e11d3c..b1e7809e5e15 100644
--- a/include/drm/drm_mm.h
+++ b/include/drm/drm_mm.h
@@ -72,6 +72,7 @@ struct drm_mm {
         unsigned scanned_blocks;
         unsigned long scan_start;
         unsigned long scan_end;
+        struct drm_mm_node *prev_scanned_node;
 };
 
 static inline bool drm_mm_node_allocated(struct drm_mm_node *node)
@@ -86,6 +87,13 @@ static inline bool drm_mm_initialized(struct drm_mm *mm)
 #define drm_mm_for_each_node(entry, mm) list_for_each_entry(entry, \
                                                 &(mm)->head_node.node_list, \
                                                 node_list);
+#define drm_mm_for_each_scanned_node_reverse(entry, n, mm) \
+        for (entry = (mm)->prev_scanned_node, \
+                next = entry ? list_entry(entry->node_list.next, \
+                        struct drm_mm_node, node_list) : NULL; \
+             entry != NULL; entry = next, \
+                next = entry ? list_entry(entry->node_list.next, \
+                        struct drm_mm_node, node_list) : NULL) \
 /*
  * Basic range manager support (drm_mm.c)
  */