From 063a8b5d2d3883fed89582d334ae0d39b814aa44 Mon Sep 17 00:00:00 2001
From: "Robert P. J. Day" <rpjday@mindspring.com>
Date: Tue, 16 Oct 2007 23:29:32 -0700
Subject: [PATCH] --- yaml --- r: 70660 b: refs/heads/master c:
 b311e921b385b5a848f0806df16276aca1ecae07 h: refs/heads/master v: v3

---
 [refs]                     |  2 +-
 trunk/include/linux/log2.h | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index d2c74ea2166e..d27bdfbccd5e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d9aacccf457d07d729cfc7bf20ff0c7428357a9f
+refs/heads/master: b311e921b385b5a848f0806df16276aca1ecae07
diff --git a/trunk/include/linux/log2.h b/trunk/include/linux/log2.h
index 1b8a2c1cb0e3..c8cf5e8ef171 100644
--- a/trunk/include/linux/log2.h
+++ b/trunk/include/linux/log2.h
@@ -63,6 +63,15 @@ unsigned long __roundup_pow_of_two(unsigned long n)
 	return 1UL << fls_long(n - 1);
 }
 
+/*
+ * round down to nearest power of two
+ */
+static inline __attribute__((const))
+unsigned long __rounddown_pow_of_two(unsigned long n)
+{
+	return 1UL << (fls_long(n) - 1);
+}
+
 /**
  * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
  * @n - parameter
@@ -165,4 +174,20 @@ unsigned long __roundup_pow_of_two(unsigned long n)
 	__roundup_pow_of_two(n)			\
  )
 
+/**
+ * rounddown_pow_of_two - round the given value down to nearest power of two
+ * @n - parameter
+ *
+ * round the given value down to the nearest power of two
+ * - the result is undefined when n == 0
+ * - this can be used to initialise global variables from constant data
+ */
+#define rounddown_pow_of_two(n)			\
+(						\
+	__builtin_constant_p(n) ? (		\
+		(n == 1) ? 0 :			\
+		(1UL << ilog2(n))) :		\
+	__rounddown_pow_of_two(n)		\
+ )
+
 #endif /* _LINUX_LOG2_H */