dma-buf/sync_file: add sync_file_get_fence()

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>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

2 files changed, 24 insertions, 0 deletions

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index ac9c250af302..2873760e02a9 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 2efc5ec60575..f7de5a0b3d12 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 */