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log2.h: Define order_base_2() macro for convenience.

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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>
This commit is contained in:
Robert P. J. Day 2008-02-06 01:36:54 -08:00 committed by Linus Torvalds
parent 582539e5a0
commit de9330d13e
1 changed files with 16 additions and 0 deletions
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16
include/linux/log2.h
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@ -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 */