[RFC 2/9] dma-fence: Add callback initialization helper

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

In preparation of adding a new field to struct dma_fence_cb we will need
an initialization helper for those callers who add callbacks by open-
coding. That will ensure they initialize all the fields so common code
does not get confused by potential garbage in some fields.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/dma-buf/dma-fence.c | 10 ++++------
 include/linux/dma-fence.h   |  7 +++++++
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 41da0da17eba..ea4a1f82c9bf 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -662,21 +662,19 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
 	unsigned long flags;
 	int ret = 0;
 
+	__dma_fence_cb_init(cb, func);
+
 	if (WARN_ON(!fence || !func))
 		return -EINVAL;
 
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
-		INIT_LIST_HEAD(&cb->node);
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 		return -ENOENT;
-	}
 
 	spin_lock_irqsave(fence->lock, flags);
 
 	if (__dma_fence_enable_signaling(fence)) {
-		cb->func = func;
 		list_add_tail(&cb->node, &fence->cb_list);
 	} else {
-		INIT_LIST_HEAD(&cb->node);
 		ret = -ENOENT;
 	}
 
@@ -795,7 +793,7 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
 		goto out;
 	}
 
-	cb.base.func = dma_fence_default_wait_cb;
+	__dma_fence_cb_init(&cb.base, dma_fence_default_wait_cb);
 	cb.task = current;
 	list_add(&cb.base.node, &fence->cb_list);
 
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 2af328a89468..35933e0ae62c 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -629,4 +629,11 @@ static inline bool dma_fence_is_container(struct dma_fence *fence)
 	return dma_fence_is_array(fence) || dma_fence_is_chain(fence);
 }
 
+static inline void __dma_fence_cb_init(struct dma_fence_cb *cb,
+				       dma_fence_func_t func)
+{
+	INIT_LIST_HEAD(&cb->node);
+	cb->func = func;
+}
+
 #endif /* __LINUX_DMA_FENCE_H */
-- 
2.34.1