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authorBruno Randolf <br1@einfach.org>2010-11-16 10:58:37 +0900
committerJohn W. Linville <linville@tuxdriver.com>2010-11-18 14:21:52 -0500
commitc5485a7e7569ab32eea240c850198519e2a765ef (patch)
tree928a8556deaec0811d1b83102b33365aab28a270 /include
parent50a9432daeece6fc1309bef1dc0a7b8fde8204cb (diff)
lib: Add generic exponentially weighted moving average (EWMA) function
This adds generic functions for calculating Exponentially Weighted Moving Averages (EWMA). This implementation makes use of a structure which keeps the EWMA parameters and a scaled up internal representation to reduce rounding errors. The original idea for this implementation came from the rt2x00 driver (rt2x00link.c). I would like to use it in several places in the mac80211 and ath5k code and I hope it can be useful in many other places in the kernel code. Signed-off-by: Bruno Randolf <br1@einfach.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/average.h32
1 files changed, 32 insertions, 0 deletions
diff --git a/include/linux/average.h b/include/linux/average.h
new file mode 100644
index 00000000000..7706e40f95f
--- /dev/null
+++ b/include/linux/average.h
@@ -0,0 +1,32 @@
+#ifndef _LINUX_AVERAGE_H
+#define _LINUX_AVERAGE_H
+
+#include <linux/kernel.h>
+
+/* 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 DIV_ROUND_CLOSEST(avg->internal, avg->factor);
+}
+
+#endif /* _LINUX_AVERAGE_H */