Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid
[linux-2.6-block.git] / lib / div64.c
CommitLineData
b2441318 1// SPDX-License-Identifier: GPL-2.0
1da177e4
LT
2/*
3 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
4 *
5 * Based on former do_div() implementation from asm-parisc/div64.h:
6 * Copyright (C) 1999 Hewlett-Packard Co
7 * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
8 *
9 *
10 * Generic C version of 64bit/32bit division and modulo, with
11 * 64bit result and 32bit remainder.
12 *
13 * The fast case for (n>>32 == 0) is handled inline by do_div().
14 *
15 * Code generated for this function might be very inefficient
16 * for some CPUs. __div64_32() can be overridden by linking arch-specific
dce1eb93
NP
17 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
18 * or by defining a preprocessor macro in arch/include/asm/div64.h.
1da177e4
LT
19 */
20
8bc3bcc9
PG
21#include <linux/export.h>
22#include <linux/kernel.h>
2418f4f2 23#include <linux/math64.h>
1da177e4
LT
24
25/* Not needed on 64bit architectures */
26#if BITS_PER_LONG == 32
27
dce1eb93 28#ifndef __div64_32
cb8c181f 29uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
1da177e4
LT
30{
31 uint64_t rem = *n;
32 uint64_t b = base;
33 uint64_t res, d = 1;
34 uint32_t high = rem >> 32;
35
36 /* Reduce the thing a bit first */
37 res = 0;
38 if (high >= base) {
39 high /= base;
40 res = (uint64_t) high << 32;
41 rem -= (uint64_t) (high*base) << 32;
42 }
43
44 while ((int64_t)b > 0 && b < rem) {
45 b = b+b;
46 d = d+d;
47 }
48
49 do {
50 if (rem >= b) {
51 rem -= b;
52 res += d;
53 }
54 b >>= 1;
55 d >>= 1;
56 } while (d);
57
58 *n = res;
59 return rem;
60}
1da177e4 61EXPORT_SYMBOL(__div64_32);
dce1eb93 62#endif
1da177e4 63
6ec72e61
RD
64/**
65 * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
66 * @dividend: 64bit dividend
67 * @divisor: 64bit divisor
68 * @remainder: 64bit remainder
69 */
2418f4f2
RZ
70#ifndef div_s64_rem
71s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
72{
73 u64 quotient;
74
75 if (dividend < 0) {
76 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
77 *remainder = -*remainder;
78 if (divisor > 0)
79 quotient = -quotient;
80 } else {
81 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
82 if (divisor < 0)
83 quotient = -quotient;
84 }
85 return quotient;
86}
87EXPORT_SYMBOL(div_s64_rem);
88#endif
89
eb18cba7
MS
90/**
91 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
92 * @dividend: 64bit dividend
93 * @divisor: 64bit divisor
94 * @remainder: 64bit remainder
95 *
96 * This implementation is a comparable to algorithm used by div64_u64.
97 * But this operation, which includes math for calculating the remainder,
98 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
99 * systems.
100 */
101#ifndef div64_u64_rem
102u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
103{
104 u32 high = divisor >> 32;
105 u64 quot;
106
107 if (high == 0) {
108 u32 rem32;
109 quot = div_u64_rem(dividend, divisor, &rem32);
110 *remainder = rem32;
111 } else {
112 int n = 1 + fls(high);
113 quot = div_u64(dividend >> n, divisor >> n);
114
115 if (quot != 0)
116 quot--;
117
118 *remainder = dividend - quot * divisor;
119 if (*remainder >= divisor) {
120 quot++;
121 *remainder -= divisor;
122 }
123 }
124
125 return quot;
126}
127EXPORT_SYMBOL(div64_u64_rem);
128#endif
129
658716d1 130/**
f3002134 131 * div64_u64 - unsigned 64bit divide with 64bit divisor
658716d1
BB
132 * @dividend: 64bit dividend
133 * @divisor: 64bit divisor
134 *
135 * This implementation is a modified version of the algorithm proposed
136 * by the book 'Hacker's Delight'. The original source and full proof
137 * can be found here and is available for use without restriction.
138 *
28ca84e0 139 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
658716d1 140 */
f3002134
SG
141#ifndef div64_u64
142u64 div64_u64(u64 dividend, u64 divisor)
3927f2e8 143{
658716d1
BB
144 u32 high = divisor >> 32;
145 u64 quot;
3927f2e8 146
658716d1 147 if (high == 0) {
f3002134 148 quot = div_u64(dividend, divisor);
658716d1
BB
149 } else {
150 int n = 1 + fls(high);
151 quot = div_u64(dividend >> n, divisor >> n);
3927f2e8 152
658716d1
BB
153 if (quot != 0)
154 quot--;
f3002134 155 if ((dividend - quot * divisor) >= divisor)
658716d1
BB
156 quot++;
157 }
3927f2e8 158
658716d1 159 return quot;
3927f2e8 160}
f3002134 161EXPORT_SYMBOL(div64_u64);
6f6d6a1a 162#endif
3927f2e8 163
658716d1
BB
164/**
165 * div64_s64 - signed 64bit divide with 64bit divisor
166 * @dividend: 64bit dividend
167 * @divisor: 64bit divisor
168 */
169#ifndef div64_s64
170s64 div64_s64(s64 dividend, s64 divisor)
171{
172 s64 quot, t;
173
79211c8e 174 quot = div64_u64(abs(dividend), abs(divisor));
658716d1
BB
175 t = (dividend ^ divisor) >> 63;
176
177 return (quot ^ t) - t;
178}
179EXPORT_SYMBOL(div64_s64);
180#endif
181
1da177e4 182#endif /* BITS_PER_LONG == 32 */
f595ec96
JF
183
184/*
185 * Iterative div/mod for use when dividend is not expected to be much
186 * bigger than divisor.
187 */
188u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
189{
d5e181f7 190 return __iter_div_u64_rem(dividend, divisor, remainder);
f595ec96
JF
191}
192EXPORT_SYMBOL(iter_div_u64_rem);