From: "Robert P. J. Day" 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 Signed-off-by: Andrew Morton --- include/linux/log2.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff -puN include/linux/log2.h~log2h-define-order_base_2-macro-for-convenience include/linux/log2.h --- a/include/linux/log2.h~log2h-define-order_base_2-macro-for-convenience +++ a/include/linux/log2.h @@ -190,4 +190,20 @@ unsigned long __rounddown_pow_of_two(uns __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 */ _