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authorRobert P. J. Day <rpjday@crashcourse.ca>2008-02-06 01:36:54 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-06 10:41:03 -0800
commitde9330d13eac1f331e63ab1d18c506365b0151f3 (patch)
tree67fc0eb97f706d8cb39485dba50da9f9918c3f3f /include/linux/log2.h
parent582539e5a0480f1e00e3b9ffbe50bd5b2f59a16f (diff)
log2.h: Define order_base_2() macro for convenience.
Given a number of places in the tree that need to calculate this value explicitly, might as well just create a macro for it. (akpm: must be implemented as a macro for callee typeof() usage) Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/log2.h')
-rw-r--r--include/linux/log2.h16
1 files changed, 16 insertions, 0 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h
index c8cf5e8ef171..25b808631cd9 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -190,4 +190,20 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
__rounddown_pow_of_two(n) \
)
+/**
+ * order_base_2 - calculate the (rounded up) base 2 order of the argument
+ * @n: parameter
+ *
+ * The first few values calculated by this routine:
+ * ob2(0) = 0
+ * ob2(1) = 0
+ * ob2(2) = 1
+ * ob2(3) = 2
+ * ob2(4) = 2
+ * ob2(5) = 3
+ * ... and so on.
+ */
+
+#define order_base_2(n) ilog2(roundup_pow_of_two(n))
+
#endif /* _LINUX_LOG2_H */