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| author | David Howells | 2006-12-08 11:37:51 +0100 |
|---|---|---|
| committer | Linus Torvalds | 2006-12-08 17:28:51 +0100 |
| commit | 312a0c170945b49f319960afd2e492c05f9dd551 (patch) | |
| tree | f3c122cc65d18bc647b45d89b3a8d0fb8492422b /include/linux/log2.h | |
| parent | [PATCH] LOG2: Implement a general integer log2 facility in the kernel (diff) | |
| download | kernel-qcow2-linux-312a0c170945b49f319960afd2e492c05f9dd551.tar.gz kernel-qcow2-linux-312a0c170945b49f319960afd2e492c05f9dd551.tar.xz kernel-qcow2-linux-312a0c170945b49f319960afd2e492c05f9dd551.zip | |
[PATCH] LOG2: Alter roundup_pow_of_two() so that it can use a ilog2() on a constant
Alter roundup_pow_of_two() so that it can make use of ilog2() on a constant to
produce a constant value, retaining the ability for an arch to override it in
the non-const case.
This permits the function to be used to initialise variables.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux/log2.h')
| -rw-r--r-- | include/linux/log2.h | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/log2.h b/include/linux/log2.h index 3979c60325ff..d02e1a547a7e 100644 --- a/include/linux/log2.h +++ b/include/linux/log2.h @@ -43,6 +43,15 @@ int __ilog2_u64(u64 n) } #endif +/* + * round up to nearest power of two + */ +static inline __attribute__((const)) +unsigned long __roundup_pow_of_two(unsigned long n) +{ + return 1UL << fls_long(n - 1); +} + /** * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value * @n - parameter @@ -128,4 +137,21 @@ int __ilog2_u64(u64 n) __ilog2_u64(n) \ ) +/** + * roundup_pow_of_two - round the given value up to nearest power of two + * @n - parameter + * + * round the given balue up to the nearest power of two + * - the result is undefined when n == 0 + * - this can be used to initialise global variables from constant data + */ +#define roundup_pow_of_two(n) \ +( \ + __builtin_constant_p(n) ? ( \ + (n == 1) ? 0 : \ + (1UL << (ilog2((n) - 1) + 1)) \ + ) : \ + __roundup_pow_of_two(n) \ + ) + #endif /* _LINUX_LOG2_H */ |