1 files changed, 38 insertions, 23 deletions
diff --git a/include/linux/average.h b/include/linux/average.h
index c6028fd74..d04aa5828 100644
--- a/include/linux/average.h
+++ b/include/linux/average.h
@@ -3,28 +3,43 @@
 
 /* Exponentially weighted moving average (EWMA) */
 
-/* For more documentation see lib/average.c */
-
-struct ewma {
-	unsigned long internal;
-	unsigned long factor;
-	unsigned long weight;
-};
-
-extern void ewma_init(struct ewma *avg, unsigned long factor,
-		      unsigned long weight);
-
-extern struct ewma *ewma_add(struct ewma *avg, unsigned long val);
-
-/**
- * ewma_read() - Get average value
- * @avg: Average structure
- *
- * Returns the average value held in @avg.
- */
-static inline unsigned long ewma_read(const struct ewma *avg)
-{
-	return avg->internal >> avg->factor;
-}
+#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 /* _LINUX_AVERAGE_H */