[RFC 3/5] dma-buf/fence: add .get_fences() ops

[Gustavo Padovan <gustavo@padovan.org>]

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

get_fences() should return a copy of all fences in the fence as some
fence subclass (such as fence_array) can store more than one fence at
time.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/dma-buf/fence.c | 14 ++++++++++++++
 include/linux/fence.h   |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/drivers/dma-buf/fence.c b/drivers/dma-buf/fence.c
index 4e61afb..f4094fd 100644
--- a/drivers/dma-buf/fence.c
+++ b/drivers/dma-buf/fence.c
@@ -185,6 +185,20 @@ void fence_release(struct kref *kref)
 }
 EXPORT_SYMBOL(fence_release);
 
+struct fence **fence_get_fences(struct fence *fence)
+{
+	if (fence->ops->get_fences) {
+		return fence->ops->get_fences(fence);
+	} else {
+		struct fence **fences = kmalloc(sizeof(**fences), GFP_KERNEL);
+		if (!fences)
+			return NULL;
+		fences[0] = fence;
+		return fences;
+	}
+}
+EXPORT_SYMBOL(fence_get_fences);
+
 void fence_teardown(struct fence *fence)
 {
 	if (fence->ops->teardown)
diff --git a/include/linux/fence.h b/include/linux/fence.h
index 1d3b671..a7a2fbc 100644
--- a/include/linux/fence.h
+++ b/include/linux/fence.h
@@ -111,6 +111,7 @@ struct fence_cb {
  * struct fence_ops - operations implemented for fence
  * @get_driver_name: returns the driver name.
  * @get_timeline_name: return the name of the context this fence belongs to.
+ * @get_fences: return an array with a copy of all fences in the fence.
  * @enable_signaling: enable software signaling of fence.
  * @signaled: [optional] peek whether the fence is signaled, can be null.
  * @wait: custom wait implementation, or fence_default_wait.
@@ -175,6 +176,7 @@ struct fence_cb {
 struct fence_ops {
 	const char * (*get_driver_name)(struct fence *fence);
 	const char * (*get_timeline_name)(struct fence *fence);
+	struct fence ** (*get_fences)(struct fence *fence);
 	bool (*enable_signaling)(struct fence *fence);
 	bool (*signaled)(struct fence *fence);
 	signed long (*wait)(struct fence *fence, bool intr, signed long timeout);
@@ -189,6 +191,7 @@ struct fence_ops {
 void fence_init(struct fence *fence, const struct fence_ops *ops,
 		spinlock_t *lock, u64 context, unsigned seqno);
 
+struct fence **fence_get_fences(struct fence *fence);
 void fence_release(struct kref *kref);
 void fence_teardown(struct fence *fence);
 void fence_free(struct fence *fence);
-- 
2.5.5