batman-adv: add missing ewma compat declaration

Signed-off-by: NMarek Lindner <mareklindner@neomailbox.ch>

batman-adv/files/compat-hacks.h

@@ -36,6 +36,47 @@
 
 #define IFF_NO_QUEUE	0; dev->tx_queue_len = 0
 
+/* Exponentially weighted moving average (EWMA) */
+
+#define DECLARE_EWMA(name, _factor, _weight)				\
+	struct ewma_##name {						\
+		unsigned long internal;					\
+	};								\
+	static inline void ewma_##name##_init(struct ewma_##name *e)	\
+	{								\
+		BUILD_BUG_ON(!__builtin_constant_p(_factor));		\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight));		\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_factor);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight);			\
+		e->internal = 0;					\
+	}								\
+	static inline unsigned long					\
+	ewma_##name##_read(struct ewma_##name *e)			\
+	{								\
+		BUILD_BUG_ON(!__builtin_constant_p(_factor));		\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight));		\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_factor);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight);			\
+		return e->internal >> ilog2(_factor);			\
+	}								\
+	static inline void ewma_##name##_add(struct ewma_##name *e,	\
+					     unsigned long val)		\
+	{								\
+		unsigned long internal = ACCESS_ONCE(e->internal);	\
+		unsigned long weight = ilog2(_weight);			\
+		unsigned long factor = ilog2(_factor);			\
+									\
+		BUILD_BUG_ON(!__builtin_constant_p(_factor));		\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight));		\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_factor);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight);			\
+									\
+		ACCESS_ONCE(e->internal) = internal ?			\
+			(((internal << weight) - internal) +		\
+				(val << factor)) >> weight :		\
+			(val << factor);				\
+	}
+
 #endif /* < KERNEL_VERSION(4, 3, 0) */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0)