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 * #include <linux/bitfield.h>
23 * #include <linux/bits.h>
24 *
25 * #define REG_FIELD_A GENMASK(6, 0)
26 * #define REG_FIELD_B BIT(7)
27 * #define REG_FIELD_C GENMASK(15, 8)
28 * #define REG_FIELD_D GENMASK(31, 16)
29 *
30 * Get:
31 * a = FIELD_GET(REG_FIELD_A, reg);
32 * b = FIELD_GET(REG_FIELD_B, reg);
33 *
34 * Set:
35 * reg = FIELD_PREP(REG_FIELD_A, 1) |
36 * FIELD_PREP(REG_FIELD_B, 0) |
37 * FIELD_PREP(REG_FIELD_C, c) |
38 * FIELD_PREP(REG_FIELD_D, 0x40);
39 *
40 * Modify:
41 * reg &= ~REG_FIELD_C;
42 * reg |= FIELD_PREP(REG_FIELD_C, c);
43 */
44
45 #define __bf_shf(x) (__builtin_ffsll(x) - 1)
46
47 #define __scalar_type_to_unsigned_cases(type) \
48 unsigned type: (unsigned type)0, \
49 signed type: (unsigned type)0
50
51 #define __unsigned_scalar_typeof(x) typeof( \
52 _Generic((x), \
53 char: (unsigned char)0, \
54 __scalar_type_to_unsigned_cases(char), \
55 __scalar_type_to_unsigned_cases(short), \
56 __scalar_type_to_unsigned_cases(int), \
57 __scalar_type_to_unsigned_cases(long), \
58 __scalar_type_to_unsigned_cases(long long), \
59 default: (x)))
60
61 #define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
62
63 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
64 ({ \
65 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
66 _pfx "mask is not constant"); \
67 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
68 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
69 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
70 _pfx "value too large for the field"); \
71 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
72 __bf_cast_unsigned(_reg, ~0ull), \
73 _pfx "type of reg too small for mask"); \
74 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
75 (1ULL << __bf_shf(_mask))); \
76 })
77
78 /**
79 * FIELD_MAX() - produce the maximum value representable by a field
80 * @_mask: shifted mask defining the field's length and position
81 *
82 * FIELD_MAX() returns the maximum value that can be held in the field
83 * specified by @_mask.
84 */
85 #define FIELD_MAX(_mask) \
86 ({ \
87 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
88 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
89 })
90
91 /**
92 * FIELD_FIT() - check if value fits in the field
93 * @_mask: shifted mask defining the field's length and position
94 * @_val: value to test against the field
95 *
96 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
97 */
98 #define FIELD_FIT(_mask, _val) \
99 ({ \
100 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
101 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
102 })
103
104 /**
105 * FIELD_PREP() - prepare a bitfield element
106 * @_mask: shifted mask defining the field's length and position
107 * @_val: value to put in the field
108 *
109 * FIELD_PREP() masks and shifts up the value. The result should
110 * be combined with other fields of the bitfield using logical OR.
111 */
112 #define FIELD_PREP(_mask, _val) \
113 ({ \
114 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
115 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
116 })
117
118 #define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
119
120 /**
121 * FIELD_PREP_CONST() - prepare a constant bitfield element
122 * @_mask: shifted mask defining the field's length and position
123 * @_val: value to put in the field
124 *
125 * FIELD_PREP_CONST() masks and shifts up the value. The result should
126 * be combined with other fields of the bitfield using logical OR.
127 *
128 * Unlike FIELD_PREP() this is a constant expression and can therefore
129 * be used in initializers. Error checking is less comfortable for this
130 * version, and non-constant masks cannot be used.
131 */
132 #define FIELD_PREP_CONST(_mask, _val) \
133 ( \
134 /* mask must be non-zero */ \
135 BUILD_BUG_ON_ZERO((_mask) == 0) + \
136 /* check if value fits */ \
137 BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
138 /* check if mask is contiguous */ \
139 __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \
140 /* and create the value */ \
141 (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)) \
142 )
143
144 /**
145 * FIELD_GET() - extract a bitfield element
146 * @_mask: shifted mask defining the field's length and position
147 * @_reg: value of entire bitfield
148 *
149 * FIELD_GET() extracts the field specified by @_mask from the
150 * bitfield passed in as @_reg by masking and shifting it down.
151 */
152 #define FIELD_GET(_mask, _reg) \
153 ({ \
154 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
155 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
156 })
157
158 extern void __compiletime_error("value doesn't fit into mask")
159 __field_overflow(void);
160 extern void __compiletime_error("bad bitfield mask")
161 __bad_mask(void);
field_multiplier(u64 field)162 static __always_inline u64 field_multiplier(u64 field)
163 {
164 if ((field | (field - 1)) & ((field | (field - 1)) + 1))
165 __bad_mask();
166 return field & -field;
167 }
field_mask(u64 field)168 static __always_inline u64 field_mask(u64 field)
169 {
170 return field / field_multiplier(field);
171 }
172 #define field_max(field) ((typeof(field))field_mask(field))
173 #define ____MAKE_OP(type,base,to,from) \
174 static __always_inline __##type type##_encode_bits(base v, base field) \
175 { \
176 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
177 __field_overflow(); \
178 return to((v & field_mask(field)) * field_multiplier(field)); \
179 } \
180 static __always_inline __##type type##_replace_bits(__##type old, \
181 base val, base field) \
182 { \
183 return (old & ~to(field)) | type##_encode_bits(val, field); \
184 } \
185 static __always_inline void type##p_replace_bits(__##type *p, \
186 base val, base field) \
187 { \
188 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \
189 } \
190 static __always_inline base type##_get_bits(__##type v, base field) \
191 { \
192 return (from(v) & field)/field_multiplier(field); \
193 }
194 #define __MAKE_OP(size) \
195 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
196 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
197 ____MAKE_OP(u##size,u##size,,)
198 ____MAKE_OP(u8,u8,,)
199 __MAKE_OP(16)
200 __MAKE_OP(32)
201 __MAKE_OP(64)
202 #undef __MAKE_OP
203 #undef ____MAKE_OP
204
205 #endif
206