Mailing List Archive

Given a number of places in the tree that need to calculate this value
explicitly, might as well just create a macro for it.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

---

run-time tested for the first several values. note that this macro
is defined strictly in terms of rounding *up* -- i've seen no places
in the tree that require this expression to be rounded down, so i'm
not drawing that distinction.

diff --git a/include/linux/log2.h b/include/linux/log2.h
index c8cf5e8..ed121c0 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 */

--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://crashcourse.ca
========================================================================
-
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