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 <linux/kernel.h>
12 #include <asm/byteorder.h>
13
14 /*
15 * Bitfield access macros
16 *
17 * FIELD_{GET,PREP} macros take as first parameter shifted mask
18 * from which they extract the base mask and shift amount.
19 * Mask must be a compilation time constant.
20 *
21 * Example:
22 *
23 * #define REG_FIELD_A GENMASK(6, 0)
24 * #define REG_FIELD_B BIT(7)
25 * #define REG_FIELD_C GENMASK(15, 8)
26 * #define REG_FIELD_D GENMASK(31, 16)
27 *
28 * Get:
29 * a = FIELD_GET(REG_FIELD_A, reg);
30 * b = FIELD_GET(REG_FIELD_B, reg);
31 *
32 * Set:
33 * reg = FIELD_PREP(REG_FIELD_A, 1) |
34 * FIELD_PREP(REG_FIELD_B, 0) |
35 * FIELD_PREP(REG_FIELD_C, c) |
36 * FIELD_PREP(REG_FIELD_D, 0x40);
37 *
38 * Modify:
39 * reg &= ~REG_FIELD_C;
40 * reg |= FIELD_PREP(REG_FIELD_C, c);
41 */
42
43 #define __bf_shf(x) (__builtin_ffsll(x) - 1)
44
45 #define __scalar_type_to_unsigned_cases(type) \
46 unsigned type: (unsigned type)0, \
47 signed type: (unsigned type)0
48
49 #define __unsigned_scalar_typeof(x) typeof( \
50 _Generic((x), \
51 char: (unsigned char)0, \
52 __scalar_type_to_unsigned_cases(char), \
53 __scalar_type_to_unsigned_cases(short), \
54 __scalar_type_to_unsigned_cases(int), \
55 __scalar_type_to_unsigned_cases(long), \
56 __scalar_type_to_unsigned_cases(long long), \
57 default: (x)))
58
59 #define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
60
61 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
62 ({ \
63 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
64 _pfx "mask is not constant"); \
65 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
66 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
67 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
68 _pfx "value too large for the field"); \
69 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
70 __bf_cast_unsigned(_reg, ~0ull), \
71 _pfx "type of reg too small for mask"); \
72 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
73 (1ULL << __bf_shf(_mask))); \
74 })
75
76 /**
77 * FIELD_MAX() - produce the maximum value representable by a field
78 * @_mask: shifted mask defining the field's length and position
79 *
80 * FIELD_MAX() returns the maximum value that can be held in the field
81 * specified by @_mask.
82 */
83 #define FIELD_MAX(_mask) \
84 ({ \
85 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
86 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
87 })
88
89 /**
90 * FIELD_FIT() - check if value fits in the field
91 * @_mask: shifted mask defining the field's length and position
92 * @_val: value to test against the field
93 *
94 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
95 */
96 #define FIELD_FIT(_mask, _val) \
97 ({ \
98 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
99 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
100 })
101
102 /**
103 * FIELD_PREP() - prepare a bitfield element
104 * @_mask: shifted mask defining the field's length and position
105 * @_val: value to put in the field
106 *
107 * FIELD_PREP() masks and shifts up the value. The result should
108 * be combined with other fields of the bitfield using logical OR.
109 */
110 #define FIELD_PREP(_mask, _val) \
111 ({ \
112 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
113 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
114 })
115
116 /**
117 * FIELD_GET() - extract a bitfield element
118 * @_mask: shifted mask defining the field's length and position
119 * @_reg: value of entire bitfield
120 *
121 * FIELD_GET() extracts the field specified by @_mask from the
122 * bitfield passed in as @_reg by masking and shifting it down.
123 */
124 #define FIELD_GET(_mask, _reg) \
125 ({ \
126 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
127 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
128 })
129
130 extern void __compiletime_error("value doesn't fit into mask")
131 __field_overflow(void);
132 extern void __compiletime_error("bad bitfield mask")
133 __bad_mask(void);
field_multiplier(u64 field)134 static __always_inline u64 field_multiplier(u64 field)
135 {
136 if ((field | (field - 1)) & ((field | (field - 1)) + 1))
137 __bad_mask();
138 return field & -field;
139 }
field_mask(u64 field)140 static __always_inline u64 field_mask(u64 field)
141 {
142 return field / field_multiplier(field);
143 }
144 #define field_max(field) ((typeof(field))field_mask(field))
145 #define ____MAKE_OP(type,base,to,from) \
146 static __always_inline __##type type##_encode_bits(base v, base field) \
147 { \
148 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
149 __field_overflow(); \
150 return to((v & field_mask(field)) * field_multiplier(field)); \
151 } \
152 static __always_inline __##type type##_replace_bits(__##type old, \
153 base val, base field) \
154 { \
155 return (old & ~to(field)) | type##_encode_bits(val, field); \
156 } \
157 static __always_inline void type##p_replace_bits(__##type *p, \
158 base val, base field) \
159 { \
160 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \
161 } \
162 static __always_inline base type##_get_bits(__##type v, base field) \
163 { \
164 return (from(v) & field)/field_multiplier(field); \
165 }
166 #define __MAKE_OP(size) \
167 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
168 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
169 ____MAKE_OP(u##size,u##size,,)
170 ____MAKE_OP(u8,u8,,)
171 __MAKE_OP(16)
172 __MAKE_OP(32)
173 __MAKE_OP(64)
174 #undef __MAKE_OP
175 #undef ____MAKE_OP
176
177 #endif
178