1 files changed, 64 insertions, 8 deletions

diff --git a/include/linux/dma-fence-chain.h b/include/linux/dma-fence-chain.h
index 10462a029da2..4bdf0b96da28 100644
--- a/include/linux/dma-fence-chain.h
+++ b/include/linux/dma-fence-chain.h
@@ -12,28 +12,43 @@
 
 #include <linux/dma-fence.h>
 #include <linux/irq_work.h>
+#include <linux/slab.h>
 
 /**
  * struct dma_fence_chain - fence to represent an node of a fence chain
  * @base: fence base class
- * @lock: spinlock for fence handling
  * @prev: previous fence of the chain
  * @prev_seqno: original previous seqno before garbage collection
  * @fence: encapsulated fence
- * @cb: callback structure for signaling
- * @work: irq work item for signaling
+ * @lock: spinlock for fence handling
  */
 struct dma_fence_chain {
 	struct dma_fence base;
-	spinlock_t lock;
 	struct dma_fence __rcu *prev;
 	u64 prev_seqno;
 	struct dma_fence *fence;
-	struct dma_fence_cb cb;
-	struct irq_work work;
+	union {
+		/**
+		 * @cb: callback for signaling
+		 *
+		 * This is used to add the callback for signaling the
+		 * complection of the fence chain. Never used at the same time
+		 * as the irq work.
+		 */
+		struct dma_fence_cb cb;
+
+		/**
+		 * @work: irq work item for signaling
+		 *
+		 * Irq work structure to allow us to add the callback without
+		 * running into lock inversion. Never used at the same time as
+		 * the callback.
+		 */
+		struct irq_work work;
+	};
+	spinlock_t lock;
 };
 
-extern const struct dma_fence_ops dma_fence_chain_ops;
 
 /**
  * to_dma_fence_chain - cast a fence to a dma_fence_chain
@@ -45,19 +60,60 @@ extern const struct dma_fence_ops dma_fence_chain_ops;
 static inline struct dma_fence_chain *
 to_dma_fence_chain(struct dma_fence *fence)
 {
-	if (!fence || fence->ops != &dma_fence_chain_ops)
+	if (!fence || !dma_fence_is_chain(fence))
 		return NULL;
 
 	return container_of(fence, struct dma_fence_chain, base);
 }
 
 /**
+ * dma_fence_chain_contained - return the contained fence
+ * @fence: the fence to test
+ *
+ * If the fence is a dma_fence_chain the function returns the fence contained
+ * inside the chain object, otherwise it returns the fence itself.
+ */
+static inline struct dma_fence *
+dma_fence_chain_contained(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain = to_dma_fence_chain(fence);
+
+	return chain ? chain->fence : fence;
+}
+
+/**
+ * dma_fence_chain_alloc
+ *
+ * Returns a new struct dma_fence_chain object or NULL on failure.
+ */
+static inline struct dma_fence_chain *dma_fence_chain_alloc(void)
+{
+	return kmalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
+};
+
+/**
+ * dma_fence_chain_free
+ * @chain: chain node to free
+ *
+ * Frees up an allocated but not used struct dma_fence_chain object. This
+ * doesn't need an RCU grace period since the fence was never initialized nor
+ * published. After dma_fence_chain_init() has been called the fence must be
+ * released by calling dma_fence_put(), and not through this function.
+ */
+static inline void dma_fence_chain_free(struct dma_fence_chain *chain)
+{
+	kfree(chain);
+};
+
+/**
  * dma_fence_chain_for_each - iterate over all fences in chain
  * @iter: current fence
  * @head: starting point
  *
  * Iterate over all fences in the chain. We keep a reference to the current
  * fence while inside the loop which must be dropped when breaking out.
+ *
+ * For a deep dive iterator see dma_fence_unwrap_for_each().
  */
 #define dma_fence_chain_for_each(iter, head)	\
 	for (iter = dma_fence_get(head); iter; \