[PATCH 2/3] dma-fence: Wrap querying the fence->status

[Chris Wilson]

The fence->status is an optional field that is only valid once the fence
has been signaled. (Driver may fill the fence->status with an error code
prior to calling dma_fence_signal().) Given the restriction upon its
validity, wrap querying of the fence->status into a helper
dma_fence_get_status().

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/dma-buf/dma-fence.c  | 25 +++++++++++++++++++++++++
 drivers/dma-buf/sync_debug.c | 17 ++++++++---------
 drivers/dma-buf/sync_file.c  |  6 ++----
 include/linux/dma-fence.h    | 24 ++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 9130f790ebf3..7d936d19e659 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -275,6 +275,31 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
 EXPORT_SYMBOL(dma_fence_add_callback);
 
 /**
+ * dma_fence_get_status - returns the status upon completion
+ * @fence: [in]	the dma_fence to query
+ *
+ * This wraps dma_fence_get_status_locked() to return the error status
+ * condition on a signaled fence. See dma_fence_get_status_locked() for more
+ * details.
+ *
+ * Returns 0 if the fence has not yet been signaled, 1 if the fence has
+ * been signaled without an error condition, or a negative error code
+ * if the fence has been completed in err.
+ */
+int dma_fence_get_status(struct dma_fence *fence)
+{
+	unsigned long flags;
+	int status;
+
+	spin_lock_irqsave(fence->lock, flags);
+	status = dma_fence_get_status_locked(fence);
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return status;
+}
+EXPORT_SYMBOL(dma_fence_get_status);
+
+/**
  * dma_fence_remove_callback - remove a callback from the signaling list
  * @fence:	[in]	the fence to wait on
  * @cb:		[in]	the callback to remove
diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
index 48b20e34fb6d..c769dc653b34 100644
--- a/drivers/dma-buf/sync_debug.c
+++ b/drivers/dma-buf/sync_debug.c
@@ -62,30 +62,29 @@ void sync_file_debug_remove(struct sync_file *sync_file)
 
 static const char *sync_status_str(int status)
 {
-	if (status == 0)
-		return "signaled";
+	if (status < 0)
+		return "error";
 
 	if (status > 0)
-		return "active";
+		return "signaled";
 
-	return "error";
+	return "active";
 }
 
 static void sync_print_fence(struct seq_file *s,
 			     struct dma_fence *fence, bool show)
 {
-	int status = 1;
 	struct sync_timeline *parent = dma_fence_parent(fence);
+	int status;
 
-	if (dma_fence_is_signaled_locked(fence))
-		status = fence->status;
+	status = dma_fence_get_status_locked(fence);
 
 	seq_printf(s, "  %s%sfence %s",
 		   show ? parent->name : "",
 		   show ? "_" : "",
 		   sync_status_str(status));
 
-	if (status <= 0) {
+	if (status) {
 		struct timespec64 ts64 =
 			ktime_to_timespec64(fence->timestamp);
 
@@ -136,7 +135,7 @@ static void sync_print_sync_file(struct seq_file *s,
 	int i;
 
 	seq_printf(s, "[%p] %s: %s\n", sync_file, sync_file->name,
-		   sync_status_str(!dma_fence_is_signaled(sync_file->fence)));
+		   sync_status_str(dma_fence_get_status(sync_file->fence)));
 
 	if (dma_fence_is_array(sync_file->fence)) {
 		struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 07cb9b908f30..2321035f6204 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -373,10 +373,8 @@ static void sync_fill_fence_info(struct dma_fence *fence,
 		sizeof(info->obj_name));
 	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
 		sizeof(info->driver_name));
-	if (dma_fence_is_signaled(fence))
-		info->status = fence->status >= 0 ? 1 : fence->status;
-	else
-		info->status = 0;
+
+	info->status = dma_fence_get_status(fence);
 	info->timestamp_ns = ktime_to_ns(fence->timestamp);
 }
 
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index d51a7d23c358..19f7af905182 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -378,6 +378,30 @@ static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
 		return dma_fence_is_signaled(f2) ? NULL : f2;
 }
 
+/**
+ * dma_fence_get_status_locked - returns the status upon completion
+ * @fence: [in]	the dma_fence to query
+ *
+ * Drivers can supply an optional error status condition before they signal
+ * the fence (to indicate whether the fence was completed due to an error
+ * rather than success). The value of the status condition is only valid
+ * if the fence has been signaled, dma_fence_get_status_locked() first checks
+ * the signal state before reporting the error status.
+ *
+ * Returns 0 if the fence has not yet been signaled, 1 if the fence has
+ * been signaled without an error condition, or a negative error code
+ * if the fence has been completed in err.
+ */
+static inline int dma_fence_get_status_locked(struct dma_fence *fence)
+{
+	if (dma_fence_is_signaled_locked(fence))
+		return fence->status < 0 ? fence->status : 1;
+	else
+		return 0;
+}
+
+int dma_fence_get_status(struct dma_fence *fence);
+
 signed long dma_fence_wait_timeout(struct dma_fence *,
 				   bool intr, signed long timeout);
 signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
-- 
2.11.0