compat: backport Generic exponentially weighted moving average (EWMA)

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

diff --git a/compat/Makefile b/compat/Makefile
index 46049af187febc6c4d1b8bde676c73971cee9aef..18a9afcc1bbf3c3585c0cc6860b71f940aa545c5 100644 (file)
--- a/compat/Makefile
+++ b/compat/Makefile
@@ -27,3 +27,4 @@ compat-$(CONFIG_COMPAT_KERNEL_33) += compat-2.6.33.o
 compat-$(CONFIG_COMPAT_KERNEL_35) += compat-2.6.35.o
 compat-$(CONFIG_COMPAT_KERNEL_36) += compat-2.6.36.o
 compat-$(CONFIG_COMPAT_KERNEL_37) += compat-2.6.37.o
+compat-$(CONFIG_COMPAT_KERNEL_38) += compat-2.6.38.o

diff --git a/compat/compat-2.6.38.c b/compat/compat-2.6.38.c
new file mode 100644 (file)
index 0000000..172aa19
--- /dev/null
+++ b/compat/compat-2.6.38.c
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2010    Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Compatibility file for Linux wireless for kernels 2.6.38.
+ */
+
+#include <linux/compat.h>
+#include <linux/module.h>
+#include <linux/bug.h>
+
+/**
+ * ewma_init() - Initialize EWMA parameters
+ * @avg: Average structure
+ * @factor: Factor to use for the scaled up internal value. The maximum value
+ *     of averages can be ULONG_MAX/(factor*weight).
+ * @weight: Exponential weight, or decay rate. This defines how fast the
+ *     influence of older values decreases. Has to be bigger than 1.
+ *
+ * Initialize the EWMA parameters for a given struct ewma @avg.
+ */
+void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight)
+{
+       WARN_ON(weight <= 1 || factor == 0);
+       avg->internal = 0;
+       avg->weight = weight;
+       avg->factor = factor;
+}
+EXPORT_SYMBOL(ewma_init);
+
+/**
+ * ewma_add() - Exponentially weighted moving average (EWMA)
+ * @avg: Average structure
+ * @val: Current value
+ *
+ * Add a sample to the average.
+ */
+struct ewma *ewma_add(struct ewma *avg, unsigned long val)
+{
+       avg->internal = avg->internal  ?
+               (((avg->internal * (avg->weight - 1)) +
+                       (val * avg->factor)) / avg->weight) :
+               (val * avg->factor);
+       return avg;
+}
+EXPORT_SYMBOL(ewma_add);
+

diff --git a/include/linux/average.h b/include/linux/average.h
new file mode 100644 (file)
index 0000000..ece86ca
--- /dev/null
+++ b/include/linux/average.h
@@ -0,0 +1,5 @@
+#include <linux/version.h>
+
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(2,6,37))
+#include_next <linux/average.h>
+#endif /* (LINUX_VERSION_CODE > KERNEL_VERSION(2,6,37)) */

diff --git a/include/linux/compat-2.6.38.h b/include/linux/compat-2.6.38.h
index fa77a89ed2a4d4d2161db5df8c880f647c23ef65..85eac512ac1be615665901a6a1b50e6640d75b12 100644 (file)
--- a/include/linux/compat-2.6.38.h
+++ b/include/linux/compat-2.6.38.h
@@ -5,6 +5,8 @@
 
 #if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,38))
 
+#include <linux/kernel.h>
+
 /*
  * This is not part of The 2.6.37 kernel yet but we
  * we use it to optimize the backport code we
@@ -25,6 +27,33 @@
 /* rename member in struct mmc_host in include/linux/mmc/host.h */
 #define max_segs       max_hw_segs
 
+
+/* 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_VERSION_CODE < KERNEL_VERSION(2,6,38)) */
 
 #endif /* LINUX_26_38_COMPAT_H */