Commit | Line | Data |
---|---|---|
3e9b3112 JK |
1 | /* |
2 | * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name> | |
3 | * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com> | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License version 2 | |
7 | * as published by the Free Software Foundation | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | */ | |
14 | ||
15 | #ifndef _LINUX_BITFIELD_H | |
16 | #define _LINUX_BITFIELD_H | |
17 | ||
18 | #include <linux/bug.h> | |
19 | ||
20 | /* | |
21 | * Bitfield access macros | |
22 | * | |
23 | * FIELD_{GET,PREP} macros take as first parameter shifted mask | |
24 | * from which they extract the base mask and shift amount. | |
25 | * Mask must be a compilation time constant. | |
26 | * | |
27 | * Example: | |
28 | * | |
29 | * #define REG_FIELD_A GENMASK(6, 0) | |
30 | * #define REG_FIELD_B BIT(7) | |
31 | * #define REG_FIELD_C GENMASK(15, 8) | |
32 | * #define REG_FIELD_D GENMASK(31, 16) | |
33 | * | |
34 | * Get: | |
35 | * a = FIELD_GET(REG_FIELD_A, reg); | |
36 | * b = FIELD_GET(REG_FIELD_B, reg); | |
37 | * | |
38 | * Set: | |
39 | * reg = FIELD_PREP(REG_FIELD_A, 1) | | |
40 | * FIELD_PREP(REG_FIELD_B, 0) | | |
41 | * FIELD_PREP(REG_FIELD_C, c) | | |
42 | * FIELD_PREP(REG_FIELD_D, 0x40); | |
43 | * | |
44 | * Modify: | |
45 | * reg &= ~REG_FIELD_C; | |
46 | * reg |= FIELD_PREP(REG_FIELD_C, c); | |
47 | */ | |
48 | ||
49 | #define __bf_shf(x) (__builtin_ffsll(x) - 1) | |
50 | ||
51 | #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ | |
52 | ({ \ | |
53 | BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ | |
54 | _pfx "mask is not constant"); \ | |
55 | BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \ | |
56 | BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ | |
57 | ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ | |
58 | _pfx "value too large for the field"); \ | |
59 | BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ | |
60 | _pfx "type of reg too small for mask"); \ | |
61 | __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ | |
62 | (1ULL << __bf_shf(_mask))); \ | |
63 | }) | |
64 | ||
1697599e JK |
65 | /** |
66 | * FIELD_FIT() - check if value fits in the field | |
67 | * @_mask: shifted mask defining the field's length and position | |
68 | * @_val: value to test against the field | |
69 | * | |
70 | * Return: true if @_val can fit inside @_mask, false if @_val is too big. | |
71 | */ | |
72 | #define FIELD_FIT(_mask, _val) \ | |
73 | ({ \ | |
74 | __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ | |
75 | !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ | |
76 | }) | |
77 | ||
3e9b3112 JK |
78 | /** |
79 | * FIELD_PREP() - prepare a bitfield element | |
80 | * @_mask: shifted mask defining the field's length and position | |
81 | * @_val: value to put in the field | |
82 | * | |
83 | * FIELD_PREP() masks and shifts up the value. The result should | |
84 | * be combined with other fields of the bitfield using logical OR. | |
85 | */ | |
86 | #define FIELD_PREP(_mask, _val) \ | |
87 | ({ \ | |
88 | __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ | |
89 | ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ | |
90 | }) | |
91 | ||
92 | /** | |
93 | * FIELD_GET() - extract a bitfield element | |
94 | * @_mask: shifted mask defining the field's length and position | |
72407674 | 95 | * @_reg: value of entire bitfield |
3e9b3112 JK |
96 | * |
97 | * FIELD_GET() extracts the field specified by @_mask from the | |
98 | * bitfield passed in as @_reg by masking and shifting it down. | |
99 | */ | |
100 | #define FIELD_GET(_mask, _reg) \ | |
101 | ({ \ | |
102 | __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ | |
103 | (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ | |
104 | }) | |
105 | ||
106 | #endif |