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| author |   Robert P. J. Day <rpjday@crashcourse.ca> | 2008-02-06 01:36:54 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-06 10:41:03 -0800 |
| commit | de9330d13eac1f331e63ab1d18c506365b0151f3 (patch) | |
| tree | 67fc0eb97f706d8cb39485dba50da9f9918c3f3f /include/linux/log2.h | |
| parent | cciss: use upper_32_bits() macro to eliminate warnings (diff) | |
| download | linux-dev-de9330d13eac1f331e63ab1d18c506365b0151f3.tar.xz linux-dev-de9330d13eac1f331e63ab1d18c506365b0151f3.zip | |
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.h | 16 |
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 */ |