提交 312a0c17 编写于 作者: D David Howells 提交者: Linus Torvalds

[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: NDavid Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
上级 f0d1b0b3
......@@ -158,12 +158,6 @@ static inline int printk(const char *s, ...) { return 0; }
unsigned long int_sqrt(unsigned long);
static inline unsigned long
__attribute_const__ roundup_pow_of_two(unsigned long x)
{
return 1UL << fls_long(x - 1);
}
extern int printk_ratelimit(void);
extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
......
......@@ -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 */
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