[PATCH v3 3/4] dma-buf/sync_file: add sync_file_get_fence()

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Creates a function that given an sync file descriptor returns a
fence containing all fences in the sync_file.

v2: Comments by Daniel Vetter
	- Adapt to new version of fence_collection_init()
	- Hold a reference for the fence we return

v3:
	- Adapt to use fput() directly
	- rename to sync_file_get_fence() as we always return one fence

v4: Adapt to use fence_array

v5: set fence through fence_get()

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/dma-buf/sync_file.c | 23 +++++++++++++++++++++++
 include/linux/sync_file.h   |  1 +
 2 files changed, 24 insertions(+)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index a223f48..61a687c 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -116,6 +116,29 @@ err:
 	return NULL;
 }
 
+/**
+ * sync_file_get_fence - get the fence related to the sync_file fd
+ * @fd:		sync_file fd to get the fence from
+ *
+ * Ensures @fd references a valid sync_file and returns a fence that
+ * represents all fence in the sync_file. On error NULL is returned.
+ */
+struct fence *sync_file_get_fence(int fd)
+{
+	struct sync_file *sync_file;
+	struct fence *fence;
+
+	sync_file = sync_file_fdget(fd);
+	if (!sync_file)
+		return NULL;
+
+	fence = fence_get(sync_file->fence);
+	fput(sync_file->file);
+
+	return fence;
+}
+EXPORT_SYMBOL(sync_file_get_fence);
+
 static int sync_file_set_fence(struct sync_file *sync_file,
 			       struct fence **fences, int num_fences)
 {
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index 2efc5ec..f7de5a0 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -46,5 +46,6 @@ struct sync_file {
 };
 
 struct sync_file *sync_file_create(struct fence *fence);
+struct fence *sync_file_get_fence(int fd);
 
 #endif /* _LINUX_SYNC_H */
-- 
2.5.5