dma-buf: Split out dma fence array create into alloc and arm functions

Useful to preallocate dma fence array and then arm in path of reclaim or
a dma fence.

v2:
- s/arm/init (Christian)
- Drop !array warn (Christian)
v3:
- Fix kernel doc typos (dim)

Cc: Sumit Semwal <[e-mail]>
Cc: Christian König <[e-mail]>
Signed-off-by: Matthew Brost <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/dma-buf/dma-fence-array.c

···
 EXPORT_SYMBOL(dma_fence_array_ops);
 
 /**
- * dma_fence_array_create - Create a custom fence array
+ * dma_fence_array_alloc - Allocate a custom fence array
+ * @num_fences:		[in]	number of fences to add in the array
+ *
+ * Return dma fence array on success, NULL on failure
+ */
+struct dma_fence_array *dma_fence_array_alloc(int num_fences)
+{
+	struct dma_fence_array *array;
+
+	return kzalloc(struct_size(array, callbacks, num_fences), GFP_KERNEL);
+}
+EXPORT_SYMBOL(dma_fence_array_alloc);
+
+/**
+ * dma_fence_array_init - Init a custom fence array
+ * @array:		[in]	dma fence array to arm
  * @num_fences:		[in]	number of fences to add in the array
  * @fences:		[in]	array containing the fences
  * @context:		[in]	fence context to use
  * @seqno:		[in]	sequence number to use
  * @signal_on_any:	[in]	signal on any fence in the array
  *
- * Allocate a dma_fence_array object and initialize the base fence with
- * dma_fence_init().
- * In case of error it returns NULL.
- *
- * The caller should allocate the fences array with num_fences size
- * and fill it with the fences it wants to add to the object. Ownership of this
- * array is taken and dma_fence_put() is used on each fence on release.
- *
- * If @signal_on_any is true the fence array signals if any fence in the array
- * signals, otherwise it signals when all fences in the array signal.
+ * Implementation of @dma_fence_array_create without allocation. Useful to init
+ * a preallocated dma fence array in the path of reclaim or dma fence signaling.
  */
-struct dma_fence_array *dma_fence_array_create(int num_fences,
-					       struct dma_fence **fences,
-					       u64 context, unsigned seqno,
-					       bool signal_on_any)
+void dma_fence_array_init(struct dma_fence_array *array,
+			  int num_fences, struct dma_fence **fences,
+			  u64 context, unsigned seqno,
+			  bool signal_on_any)
 {
-	struct dma_fence_array *array;
-
 	WARN_ON(!num_fences || !fences);
-
-	array = kzalloc(struct_size(array, callbacks, num_fences), GFP_KERNEL);
-	if (!array)
-		return NULL;
 
 	array->num_fences = num_fences;
 
···
 	 */
 	while (num_fences--)
 		WARN_ON(dma_fence_is_container(fences[num_fences]));
+}
+EXPORT_SYMBOL(dma_fence_array_init);
+
+/**
+ * dma_fence_array_create - Create a custom fence array
+ * @num_fences:		[in]	number of fences to add in the array
+ * @fences:		[in]	array containing the fences
+ * @context:		[in]	fence context to use
+ * @seqno:		[in]	sequence number to use
+ * @signal_on_any:	[in]	signal on any fence in the array
+ *
+ * Allocate a dma_fence_array object and initialize the base fence with
+ * dma_fence_init().
+ * In case of error it returns NULL.
+ *
+ * The caller should allocate the fences array with num_fences size
+ * and fill it with the fences it wants to add to the object. Ownership of this
+ * array is taken and dma_fence_put() is used on each fence on release.
+ *
+ * If @signal_on_any is true the fence array signals if any fence in the array
+ * signals, otherwise it signals when all fences in the array signal.
+ */
+struct dma_fence_array *dma_fence_array_create(int num_fences,
+					       struct dma_fence **fences,
+					       u64 context, unsigned seqno,
+					       bool signal_on_any)
+{
+	struct dma_fence_array *array;
+
+	array = dma_fence_array_alloc(num_fences);
+	if (!array)
+		return NULL;
+
+	dma_fence_array_init(array, num_fences, fences,
+			     context, seqno, signal_on_any);
 
 	return array;
 }

include/linux/dma-fence-array.h

···
 	for (index = 0, fence = dma_fence_array_first(head); fence;	\
 	     ++(index), fence = dma_fence_array_next(head, index))
 
+struct dma_fence_array *dma_fence_array_alloc(int num_fences);
+void dma_fence_array_init(struct dma_fence_array *array,
+			  int num_fences, struct dma_fence **fences,
+			  u64 context, unsigned seqno,
+			  bool signal_on_any);
+
 struct dma_fence_array *dma_fence_array_create(int num_fences,
 					       struct dma_fence **fences,
 					       u64 context, unsigned seqno,