diff options
Diffstat (limited to 'lib/math/div64.c')
| -rw-r--r-- | lib/math/div64.c | 61 |
1 files changed, 47 insertions, 14 deletions
diff --git a/lib/math/div64.c b/lib/math/div64.c index 368ca7fd0d82..55a81782e271 100644 --- a/lib/math/div64.c +++ b/lib/math/div64.c @@ -18,9 +18,11 @@ * or by defining a preprocessor macro in arch/include/asm/div64.h. */ +#include <linux/bitops.h> #include <linux/export.h> -#include <linux/kernel.h> +#include <linux/math.h> #include <linux/math64.h> +#include <linux/log2.h> /* Not needed on 64bit architectures */ #if BITS_PER_LONG == 32 @@ -61,12 +63,6 @@ uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) EXPORT_SYMBOL(__div64_32); #endif -/** - * div_s64_rem - signed 64bit divide with 64bit divisor and remainder - * @dividend: 64bit dividend - * @divisor: 64bit divisor - * @remainder: 64bit remainder - */ #ifndef div_s64_rem s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) { @@ -87,7 +83,7 @@ s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) EXPORT_SYMBOL(div_s64_rem); #endif -/** +/* * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder * @dividend: 64bit dividend * @divisor: 64bit divisor @@ -127,7 +123,7 @@ u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) EXPORT_SYMBOL(div64_u64_rem); #endif -/** +/* * div64_u64 - unsigned 64bit divide with 64bit divisor * @dividend: 64bit dividend * @divisor: 64bit divisor @@ -161,11 +157,6 @@ u64 div64_u64(u64 dividend, u64 divisor) EXPORT_SYMBOL(div64_u64); #endif -/** - * div64_s64 - signed 64bit divide with 64bit divisor - * @dividend: 64bit dividend - * @divisor: 64bit divisor - */ #ifndef div64_s64 s64 div64_s64(s64 dividend, s64 divisor) { @@ -190,3 +181,45 @@ u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) return __iter_div_u64_rem(dividend, divisor, remainder); } EXPORT_SYMBOL(iter_div_u64_rem); + +#ifndef mul_u64_u64_div_u64 +u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c) +{ + u64 res = 0, div, rem; + int shift; + + /* can a * b overflow ? */ + if (ilog2(a) + ilog2(b) > 62) { + /* + * (b * a) / c is equal to + * + * (b / c) * a + + * (b % c) * a / c + * + * if nothing overflows. Can the 1st multiplication + * overflow? Yes, but we do not care: this can only + * happen if the end result can't fit in u64 anyway. + * + * So the code below does + * + * res = (b / c) * a; + * b = b % c; + */ + div = div64_u64_rem(b, c, &rem); + res = div * a; + b = rem; + + shift = ilog2(a) + ilog2(b) - 62; + if (shift > 0) { + /* drop precision */ + b >>= shift; + c >>= shift; + if (!c) + return res; + } + } + + return res + div64_u64(a * b, c); +} +EXPORT_SYMBOL(mul_u64_u64_div_u64); +#endif |