From: David Howells 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 Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Signed-off-by: Andrew Morton --- include/linux/kernel.h | 6 ------ include/linux/log2.h | 26 ++++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 6 deletions(-) diff -puN include/linux/kernel.h~log2-alter-roundup_pow_of_two-so-that-it-can-use-a-ilog2-on-a-constant include/linux/kernel.h --- a/include/linux/kernel.h~log2-alter-roundup_pow_of_two-so-that-it-can-use-a-ilog2-on-a-constant +++ a/include/linux/kernel.h @@ -156,12 +156,6 @@ static inline int printk(const char *s, 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, diff -puN include/linux/log2.h~log2-alter-roundup_pow_of_two-so-that-it-can-use-a-ilog2-on-a-constant include/linux/log2.h --- a/include/linux/log2.h~log2-alter-roundup_pow_of_two-so-that-it-can-use-a-ilog2-on-a-constant +++ a/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 */ _