1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
4 * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
5 */
6
7 #ifndef _LINUX_BITFIELD_H
8 #define _LINUX_BITFIELD_H
9
10 #include <linux/build_bug.h>
11 #include <asm/byteorder.h>
12
13 /*
14 * Bitfield access macros
15 *
16 * FIELD_{GET,PREP} macros take as first parameter shifted mask
17 * from which they extract the base mask and shift amount.
18 * Mask must be a compilation time constant.
19 *
20 * Example:
21 *
22 * #define REG_FIELD_A GENMASK(6, 0)
23 * #define REG_FIELD_B BIT(7)
24 * #define REG_FIELD_C GENMASK(15, 8)
25 * #define REG_FIELD_D GENMASK(31, 16)
26 *
27 * Get:
28 * a = FIELD_GET(REG_FIELD_A, reg);
29 * b = FIELD_GET(REG_FIELD_B, reg);
30 *
31 * Set:
32 * reg = FIELD_PREP(REG_FIELD_A, 1) |
33 * FIELD_PREP(REG_FIELD_B, 0) |
34 * FIELD_PREP(REG_FIELD_C, c) |
35 * FIELD_PREP(REG_FIELD_D, 0x40);
36 *
37 * Modify:
38 * reg &= ~REG_FIELD_C;
39 * reg |= FIELD_PREP(REG_FIELD_C, c);
40 */
41
42 #define __bf_shf(x) (__builtin_ffsll(x) - 1)
43
44 #define __scalar_type_to_unsigned_cases(type) \
45 unsigned type: (unsigned type)0, \
46 signed type: (unsigned type)0
47
48 #define __unsigned_scalar_typeof(x) typeof( \
49 _Generic((x), \
50 char: (unsigned char)0, \
51 __scalar_type_to_unsigned_cases(char), \
52 __scalar_type_to_unsigned_cases(short), \
53 __scalar_type_to_unsigned_cases(int), \
54 __scalar_type_to_unsigned_cases(long), \
55 __scalar_type_to_unsigned_cases(long long), \
56 default: (x)))
57
58 #define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
59
60 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
61 ({ \
62 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
63 _pfx "mask is not constant"); \
64 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
65 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
66 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
67 _pfx "value too large for the field"); \
68 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
69 __bf_cast_unsigned(_reg, ~0ull), \
70 _pfx "type of reg too small for mask"); \
71 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
72 (1ULL << __bf_shf(_mask))); \
73 })
74
75 /**
76 * FIELD_MAX() - produce the maximum value representable by a field
77 * @_mask: shifted mask defining the field's length and position
78 *
79 * FIELD_MAX() returns the maximum value that can be held in the field
80 * specified by @_mask.
81 */
82 #define FIELD_MAX(_mask) \
83 ({ \
84 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
85 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
86 })
87
88 /**
89 * FIELD_FIT() - check if value fits in the field
90 * @_mask: shifted mask defining the field's length and position
91 * @_val: value to test against the field
92 *
93 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
94 */
95 #define FIELD_FIT(_mask, _val) \
96 ({ \
97 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
98 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
99 })
100
101 /**
102 * FIELD_PREP() - prepare a bitfield element
103 * @_mask: shifted mask defining the field's length and position
104 * @_val: value to put in the field
105 *
106 * FIELD_PREP() masks and shifts up the value. The result should
107 * be combined with other fields of the bitfield using logical OR.
108 */
109 #define FIELD_PREP(_mask, _val) \
110 ({ \
111 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
112 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
113 })
114
115 /**
116 * FIELD_GET() - extract a bitfield element
117 * @_mask: shifted mask defining the field's length and position
118 * @_reg: value of entire bitfield
119 *
120 * FIELD_GET() extracts the field specified by @_mask from the
121 * bitfield passed in as @_reg by masking and shifting it down.
122 */
123 #define FIELD_GET(_mask, _reg) \
124 ({ \
125 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
126 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
127 })
128
129 extern void __compiletime_error("value doesn't fit into mask")
130 __field_overflow(void);
131 extern void __compiletime_error("bad bitfield mask")
132 __bad_mask(void);
field_multiplier(u64 field)133 static __always_inline u64 field_multiplier(u64 field)
134 {
135 if ((field | (field - 1)) & ((field | (field - 1)) + 1))
136 __bad_mask();
137 return field & -field;
138 }
field_mask(u64 field)139 static __always_inline u64 field_mask(u64 field)
140 {
141 return field / field_multiplier(field);
142 }
143 #define field_max(field) ((typeof(field))field_mask(field))
144 #define ____MAKE_OP(type,base,to,from) \
145 static __always_inline __##type type##_encode_bits(base v, base field) \
146 { \
147 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
148 __field_overflow(); \
149 return to((v & field_mask(field)) * field_multiplier(field)); \
150 } \
151 static __always_inline __##type type##_replace_bits(__##type old, \
152 base val, base field) \
153 { \
154 return (old & ~to(field)) | type##_encode_bits(val, field); \
155 } \
156 static __always_inline void type##p_replace_bits(__##type *p, \
157 base val, base field) \
158 { \
159 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \
160 } \
161 static __always_inline base type##_get_bits(__##type v, base field) \
162 { \
163 return (from(v) & field)/field_multiplier(field); \
164 }
165 #define __MAKE_OP(size) \
166 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
167 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
168 ____MAKE_OP(u##size,u##size,,)
169 ____MAKE_OP(u8,u8,,)
170 __MAKE_OP(16)
171 __MAKE_OP(32)
172 __MAKE_OP(64)
173 #undef __MAKE_OP
174 #undef ____MAKE_OP
175
176 #endif
177
