dma-fence: add dma_fence_match_context helper

Add a helper to check if all fences in a fence array are from a given
context. For convenience, the function can also handle being given a
non-array fence.

Signed-off-by: Philipp Zabel <[e-mail]>
Reviewed-by: Gustavo Padovan <[e-mail]>
Acked-by: Sumit Semwal <[e-mail]>
Signed-off-by: Sumit Semwal <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/dma-buf/dma-fence-array.c

···
 	return array;
 }
 EXPORT_SYMBOL(dma_fence_array_create);
+
+/**
+ * dma_fence_match_context - Check if all fences are from the given context
+ * @fence:		[in]	fence or fence array
+ * @context:		[in]	fence context to check all fences against
+ *
+ * Checks the provided fence or, for a fence array, all fences in the array
+ * against the given context. Returns false if any fence is from a different
+ * context.
+ */
+bool dma_fence_match_context(struct dma_fence *fence, u64 context)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+	unsigned i;
+
+	if (!dma_fence_is_array(fence))
+		return fence->context == context;
+
+	for (i = 0; i < array->num_fences; i++) {
+		if (array->fences[i]->context != context)
+			return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(dma_fence_match_context);

include/linux/dma-fence-array.h

···
 					       u64 context, unsigned seqno,
 					       bool signal_on_any);
 
+bool dma_fence_match_context(struct dma_fence *fence, u64 context);
+
 #endif /* __LINUX_DMA_FENCE_ARRAY_H */