dma-buf: Add dma_fence_array_for_each (v2)

Add a helper to iterate over all fences in a dma_fence_array object.

v2 (Jason Ekstrand)
 - Return NULL from dma_fence_array_first if head == NULL.  This matches
   the iterator behavior of dma_fence_chain_for_each in that it iterates
   zero times if head == NULL.
 - Return NULL from dma_fence_array_next if index > array->num_fences.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210610210925.642582-2-jason@jlekstrand.net
Signed-off-by: Christian König <christian.koenig@amd.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index cb1bacb5a42b..52b85d292383 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -219,3 +219,30 @@ bool dma_fence_match_context(struct dma_fence *fence, u64 context)
 	return true;
 }
 EXPORT_SYMBOL(dma_fence_match_context);
+
+struct dma_fence *dma_fence_array_first(struct dma_fence *head)
+{
+	struct dma_fence_array *array;
+
+	if (!head)
+		return NULL;
+
+	array = to_dma_fence_array(head);
+	if (!array)
+		return head;
+
+	return array->fences[0];
+}
+EXPORT_SYMBOL(dma_fence_array_first);
+
+struct dma_fence *dma_fence_array_next(struct dma_fence *head,
+				       unsigned int index)
+{
+	struct dma_fence_array *array = to_dma_fence_array(head);
+
+	if (!array || index >= array->num_fences)
+		return NULL;
+
+	return array->fences[index];
+}
+EXPORT_SYMBOL(dma_fence_array_next);