[RFC 2/8] dma-buf/sync_file: add sync_file_fences_get()

[Gustavo Padovan]

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>

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

If there is only one fence in the sync_file this fence itself is returned,
however if there is more than one, a fence_collection fence is returned.

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
---
 drivers/dma-buf/sync_file.c | 37 +++++++++++++++++++++++++++++++++++++
 include/linux/sync_file.h   | 10 ++++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 4d2af24..926fafa 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -23,6 +23,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/anon_inodes.h>
+#include <linux/fence-collection.h>
 #include <linux/sync_file.h>
 #include <uapi/linux/sync_file.h>
 
@@ -122,6 +123,39 @@ void sync_file_install(struct sync_file *sync_file, int fd)
 }
 EXPORT_SYMBOL(sync_file_install);
 
+struct fence *sync_file_fences_get(int fd)
+{
+	struct sync_file *sync_file;
+	struct fence_collection *collection;
+	int i;
+
+	sync_file = sync_file_fdget(fd);
+	if (!sync_file)
+		return NULL;
+
+	if (sync_file->num_fences == 1) {
+		struct fence *fence = sync_file->cbs[0].fence;
+
+		sync_file_put(sync_file);
+		return fence;
+	}
+
+	collection = fence_collection_init(sync_file->num_fences);
+	if (!collection) {
+		sync_file_put(sync_file);
+		return NULL;
+	}
+
+	for (i = 0 ; i < sync_file->num_fences ; i++)
+		fence_collection_add(collection, sync_file->cbs[i].fence);
+
+	sync_file->collection = collection;
+	sync_file_put(sync_file);
+
+	return &collection->base;
+}
+EXPORT_SYMBOL(sync_file_fences_get);
+
 static void sync_file_add_pt(struct sync_file *sync_file, int *i,
 			     struct fence *fence)
 {
@@ -200,6 +234,9 @@ static void sync_file_free(struct kref *kref)
 						     kref);
 	int i;
 
+	if (sync_file->collection)
+		fence_collection_put(sync_file->collection);
+
 	for (i = 0; i < sync_file->num_fences; ++i) {
 		fence_remove_callback(sync_file->cbs[i].fence,
 				      &sync_file->cbs[i].cb);
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index 7b7a89d..2cb0486 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -49,6 +49,7 @@ struct sync_file {
 	wait_queue_head_t	wq;
 	atomic_t		status;
 
+	struct fence_collection *collection;
 	struct sync_file_cb	cbs[];
 };
 
@@ -103,4 +104,13 @@ void sync_file_put(struct sync_file *sync_file);
  */
 void sync_file_install(struct sync_file *sync_file, int fd);
 
+/**
+ * sync_file_fences_get - get the fence related to the fd
+ * @fd:		file descriptor to look for a fence collection
+ *
+ * Ensures @fd references a valid sync_file and returns the base object
+ * of the fence_collection that contains all fences in the sync_file
+ * or NULL in case of error.
+ */
+struct fence *sync_file_fences_get(int fd);
 #endif /* _LINUX_SYNC_H */
-- 
2.5.5