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_FIT() - check if value fits in the field
77 * @_mask: shifted mask defining the field's length and position
78 * @_val: value to test against the field
79 *
80 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
81 */
82 #define FIELD_FIT(_mask, _val) \
83 ({ \
84 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
85 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
86 })
87
88 /**
89 * FIELD_PREP() - prepare a bitfield element
90 * @_mask: shifted mask defining the field's length and position
91 * @_val: value to put in the field
92 *
93 * FIELD_PREP() masks and shifts up the value. The result should
94 * be combined with other fields of the bitfield using logical OR.
95 */
96 #define FIELD_PREP(_mask, _val) \
97 ({ \
98 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
99 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
100 })
101
102 /**
103 * FIELD_GET() - extract a bitfield element
104 * @_mask: shifted mask defining the field's length and position
105 * @_reg: value of entire bitfield
106 *
107 * FIELD_GET() extracts the field specified by @_mask from the
108 * bitfield passed in as @_reg by masking and shifting it down.
109 */
110 #define FIELD_GET(_mask, _reg) \
111 ({ \
112 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
113 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
114 })
115
116 extern void __compiletime_error("value doesn't fit into mask")
117 __field_overflow(void);
118 extern void __compiletime_error("bad bitfield mask")
119 __bad_mask(void);
field_multiplier(u64 field)120 static __always_inline u64 field_multiplier(u64 field)
121 {
122 if ((field | (field - 1)) & ((field | (field - 1)) + 1))
123 __bad_mask();
124 return field & -field;
125 }
field_mask(u64 field)126 static __always_inline u64 field_mask(u64 field)
127 {
128 return field / field_multiplier(field);
129 }
130 #define ____MAKE_OP(type,base,to,from) \
131 static __always_inline __##type type##_encode_bits(base v, base field) \
132 { \
133 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
134 __field_overflow(); \
135 return to((v & field_mask(field)) * field_multiplier(field)); \
136 } \
137 static __always_inline __##type type##_replace_bits(__##type old, \
138 base val, base field) \
139 { \
140 return (old & ~to(field)) | type##_encode_bits(val, field); \
141 } \
142 static __always_inline void type##p_replace_bits(__##type *p, \
143 base val, base field) \
144 { \
145 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \
146 } \
147 static __always_inline base type##_get_bits(__##type v, base field) \
148 { \
149 return (from(v) & field)/field_multiplier(field); \
150 }
151 #define __MAKE_OP(size) \
152 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
153 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
154 ____MAKE_OP(u##size,u##size,,)
155 ____MAKE_OP(u8,u8,,)
156 __MAKE_OP(16)
157 __MAKE_OP(32)
158 __MAKE_OP(64)
159 #undef __MAKE_OP
160 #undef ____MAKE_OP
161
162 #endif
163