+ if (!cursor->fence || !dma_fence_is_signaled(cursor->fence))
+ break;
+ } while (true);
+}
+
+/**
+ * dma_resv_iter_first_unlocked - first fence in an unlocked
dma_resv obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the first fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter
*cursor)
+{
+ rcu_read_lock();
+ do {
+ dma_resv_iter_restart_unlocked(cursor);
+ dma_resv_iter_walk_unlocked(cursor);
+ } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+ rcu_read_unlock();
+
+ return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_first_unlocked);
+
+/**
+ * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv
obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the next fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter
*cursor)
+{
+ bool restart;
+
+ rcu_read_lock();
+ cursor->is_restarted = false;
+ restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
+ do {
+ if (restart)
+ dma_resv_iter_restart_unlocked(cursor);
+ dma_resv_iter_walk_unlocked(cursor);
+ restart = true;
+ } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+ rcu_read_unlock();
+
+ return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
+
/**
* dma_resv_copy_fences - Copy all fences from src to dst.
* @dst: the destination reservation object
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index 9100dd3dc21f..5d7d28cb9008 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -149,6 +149,101 @@ struct dma_resv {
struct dma_resv_list __rcu *fence;
};
+/**
+ * struct dma_resv_iter - current position into the dma_resv fences
+ *
+ * Don't touch this directly in the driver, use the accessor
function instead.
+ */
+struct dma_resv_iter {
+ /** @obj: The dma_resv object we iterate over */
+ struct dma_resv *obj;
+
+ /** @all_fences: If all fences should be returned */
+ bool all_fences;
+
+ /** @fence: the currently handled fence */
+ struct dma_fence *fence;
+
+ /** @seq: sequence number to check for modifications */
+ unsigned int seq;
+
+ /** @index: index into the shared fences */
+ unsigned int index;
+
+ /** @fences: the shared fences */
+ struct dma_resv_list *fences;
+
+ /** @is_restarted: true if this is the first returned fence */
+ bool is_restarted;
+};
+
+struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter
*cursor);
+struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter
*cursor);
+
+/**
+ * dma_resv_iter_begin - initialize a dma_resv_iter object
+ * @cursor: The dma_resv_iter object to initialize
+ * @obj: The dma_resv object which we want to iterate over
+ * @all_fences: If all fences should be returned or just the
exclusive one
+ */
+static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
+ struct dma_resv *obj,
+ bool all_fences)
+{
+ cursor->obj = obj;
+ cursor->all_fences = all_fences;
+ cursor->fence = NULL;
+}
+
+/**
+ * dma_resv_iter_end - cleanup a dma_resv_iter object
+ * @cursor: the dma_resv_iter object which should be cleaned up
+ *
+ * Make sure that the reference to the fence in the cursor is properly
+ * dropped.
+ */
+static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
+{
+ dma_fence_put(cursor->fence);
+}
+
+/**
+ * dma_resv_iter_is_exclusive - test if the current fence is the
exclusive one
+ * @cursor: the cursor of the current position
+ *
+ * Returns true if the currently returned fence is the exclusive one.
+ */
+static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter
*cursor)
+{
+ return cursor->index == -1;
+}
+
+/**
+ * dma_resv_iter_is_restarted - test if this is the first fence
after a restart
+ * @cursor: the cursor with the current position
+ *
+ * Return true if this is the first fence in an iteration after a
restart.
+ */
+static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter
*cursor)
+{
+ return cursor->is_restarted;
+}
+
+/**
+ * dma_resv_for_each_fence_unlocked - unlocked fence iterator
+ * @cursor: a struct dma_resv_iter pointer
+ * @fence: the current fence
+ *
+ * Iterate over the fences in a struct dma_resv object without
holding the
+ * &dma_resv.lock and using RCU instead. The cursor needs to be
initialized
+ * with dma_resv_iter_begin() and cleaned up with
dma_resv_iter_end(). Inside
+ * the iterator a reference to the dma_fence is held and the RCU
lock dropped.
+ * When the dma_resv is modified the iteration starts over again.
+ */
+#define dma_resv_for_each_fence_unlocked(cursor, fence) \
+ for (fence = dma_resv_iter_first_unlocked(cursor); \
+ fence; fence = dma_resv_iter_next_unlocked(cursor))
+
#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
#define dma_resv_assert_held(obj)
lockdep_assert_held(&(obj)->lock.base)
