drm/ttm: Balance ttm_resource_cursor_init() and ttm_resource_cursor_fini()

Make the interface more symmetric by providing and using a
ttm_resource_cursor_init().

v10:
- Fix a stray newline (Matthew Brost)
- Update kerneldoc (Matthew Brost)

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241217145852.37342-2-thomas.hellstrom@linux.intel.com
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -450,7 +450,8 @@ int ttm_bo_evict_first(struct ttm_device *bdev, struct ttm_resource_manager *man
 	int ret = 0;
 
 	spin_lock(&bdev->lru_lock);
-	res = ttm_resource_manager_first(man, &cursor);
+	ttm_resource_cursor_init(&cursor, man);
+	res = ttm_resource_manager_first(&cursor);
 	ttm_resource_cursor_fini(&cursor);
 	if (!res) {
 		ret = -ENOENT;

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -865,7 +865,8 @@ s64 ttm_lru_walk_for_evict(struct ttm_lru_walk *walk, struct ttm_device *bdev,
 	s64 lret;
 
 	spin_lock(&bdev->lru_lock);
-	ttm_resource_manager_for_each_res(man, &cursor, res) {
+	ttm_resource_cursor_init(&cursor, man);
+	ttm_resource_manager_for_each_res(&cursor, res) {
 		struct ttm_buffer_object *bo = res->bo;
 		bool bo_needs_unlock = false;
 		bool bo_locked = false;

drivers/gpu/drm/ttm/ttm_resource.c

@@ -81,6 +81,23 @@ static void ttm_bulk_move_drop_cursors(struct ttm_lru_bulk_move *bulk)
 		ttm_resource_cursor_clear_bulk(cursor);
 }
 
+/**
+ * ttm_resource_cursor_init() - Initialize a struct ttm_resource_cursor
+ * @cursor: The cursor to initialize.
+ * @man: The resource manager.
+ *
+ * Initialize the cursor before using it for iteration.
+ */
+void ttm_resource_cursor_init(struct ttm_resource_cursor *cursor,
+			      struct ttm_resource_manager *man)
+{
+	cursor->priority = 0;
+	cursor->man = man;
+	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
+	INIT_LIST_HEAD(&cursor->bulk_link);
+	INIT_LIST_HEAD(&cursor->hitch.link);
+}
+
 /**
  * ttm_resource_cursor_fini() - Finalize the LRU list cursor usage
  * @cursor: The struct ttm_resource_cursor to finalize.
@@ -593,7 +610,6 @@ ttm_resource_cursor_check_bulk(struct ttm_resource_cursor *cursor,
 /**
  * ttm_resource_manager_first() - Start iterating over the resources
  * of a resource manager
- * @man: resource manager to iterate over
  * @cursor: cursor to record the position
  *
  * Initializes the cursor and starts iterating. When done iterating,
@@ -602,17 +618,16 @@ ttm_resource_cursor_check_bulk(struct ttm_resource_cursor *cursor,
  * Return: The first resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_first(struct ttm_resource_manager *man,
-			   struct ttm_resource_cursor *cursor)
+ttm_resource_manager_first(struct ttm_resource_cursor *cursor)
 {
+	struct ttm_resource_manager *man = cursor->man;
+
+	if (WARN_ON_ONCE(!man))
+		return NULL;
+
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	cursor->priority = 0;
-	cursor->man = man;
-	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
-	INIT_LIST_HEAD(&cursor->bulk_link);
-	list_add(&cursor->hitch.link, &man->lru[cursor->priority]);
-
+	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
 	return ttm_resource_manager_next(cursor);
 }
 
@@ -648,8 +663,6 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 		ttm_resource_cursor_clear_bulk(cursor);
 	}
 
-	ttm_resource_cursor_fini(cursor);
-
 	return NULL;
 }
 

include/drm/ttm/ttm_resource.h

@@ -325,6 +325,9 @@ struct ttm_resource_cursor {
 	unsigned int priority;
 };
 
+void ttm_resource_cursor_init(struct ttm_resource_cursor *cursor,
+			      struct ttm_resource_manager *man);
+
 void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
 
 /**
@@ -456,8 +459,7 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 				struct drm_printer *p);
 
 struct ttm_resource *
-ttm_resource_manager_first(struct ttm_resource_manager *man,
-			   struct ttm_resource_cursor *cursor);
+ttm_resource_manager_first(struct ttm_resource_cursor *cursor);
 struct ttm_resource *
 ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
 
@@ -466,14 +468,13 @@ ttm_lru_first_res_or_null(struct list_head *head);
 
 /**
  * ttm_resource_manager_for_each_res - iterate over all resources
- * @man: the resource manager
  * @cursor: struct ttm_resource_cursor for the current position
  * @res: the current resource
  *
  * Iterate over all the evictable resources in a resource manager.
  */
-#define ttm_resource_manager_for_each_res(man, cursor, res)		\
-	for (res = ttm_resource_manager_first(man, cursor); res;	\
+#define ttm_resource_manager_for_each_res(cursor, res)	\
+	for (res = ttm_resource_manager_first(cursor); res;	\
 	     res = ttm_resource_manager_next(cursor))
 
 struct ttm_kmap_iter *