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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/typecheck.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 * field_{get,prep} are variants that take a non-const mask.
21 *
22 * Example:
23 *
24 * #include <linux/bitfield.h>
25 * #include <linux/bits.h>
26 *
27 * #define REG_FIELD_A GENMASK(6, 0)
28 * #define REG_FIELD_B BIT(7)
29 * #define REG_FIELD_C GENMASK(15, 8)
30 * #define REG_FIELD_D GENMASK(31, 16)
31 *
32 * Get:
33 * a = FIELD_GET(REG_FIELD_A, reg);
34 * b = FIELD_GET(REG_FIELD_B, reg);
35 *
36 * Set:
37 * reg = FIELD_PREP(REG_FIELD_A, 1) |
38 * FIELD_PREP(REG_FIELD_B, 0) |
39 * FIELD_PREP(REG_FIELD_C, c) |
40 * FIELD_PREP(REG_FIELD_D, 0x40);
41 *
42 * Modify:
43 * FIELD_MODIFY(REG_FIELD_C, &reg, c);
44 */
45
46#define __bf_shf(x) (__builtin_ffsll(x) - 1)
47
48#define __scalar_type_to_unsigned_cases(type) \
49 unsigned type: (unsigned type)0, \
50 signed type: (unsigned type)0
51
52#define __unsigned_scalar_typeof(x) typeof( \
53 _Generic((x), \
54 char: (unsigned char)0, \
55 __scalar_type_to_unsigned_cases(char), \
56 __scalar_type_to_unsigned_cases(short), \
57 __scalar_type_to_unsigned_cases(int), \
58 __scalar_type_to_unsigned_cases(long), \
59 __scalar_type_to_unsigned_cases(long long), \
60 default: (x)))
61
62#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
63
64#define __BF_FIELD_CHECK_MASK(_mask, _val, _pfx) \
65 ({ \
66 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
67 _pfx "mask is not constant"); \
68 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \
69 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
70 ~((_mask) >> __bf_shf(_mask)) & \
71 (0 + (_val)) : 0, \
72 _pfx "value too large for the field"); \
73 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
74 (1ULL << __bf_shf(_mask))); \
75 })
76
77#define __BF_FIELD_CHECK_REG(mask, reg, pfx) \
78 BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) > \
79 __bf_cast_unsigned(reg, ~0ull), \
80 pfx "type of reg too small for mask")
81
82#define __BF_FIELD_CHECK(mask, reg, val, pfx) \
83 ({ \
84 __BF_FIELD_CHECK_MASK(mask, val, pfx); \
85 __BF_FIELD_CHECK_REG(mask, reg, pfx); \
86 })
87
88#define __FIELD_PREP(mask, val, pfx) \
89 ({ \
90 __BF_FIELD_CHECK_MASK(mask, val, pfx); \
91 ((typeof(mask))(val) << __bf_shf(mask)) & (mask); \
92 })
93
94#define __FIELD_GET(mask, reg, pfx) \
95 ({ \
96 __BF_FIELD_CHECK_MASK(mask, 0U, pfx); \
97 (typeof(mask))(((reg) & (mask)) >> __bf_shf(mask)); \
98 })
99
100/**
101 * FIELD_MAX() - produce the maximum value representable by a field
102 * @_mask: shifted mask defining the field's length and position
103 *
104 * FIELD_MAX() returns the maximum value that can be held in the field
105 * specified by @_mask.
106 */
107#define FIELD_MAX(_mask) \
108 ({ \
109 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
110 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
111 })
112
113/**
114 * FIELD_FIT() - check if value fits in the field
115 * @_mask: shifted mask defining the field's length and position
116 * @_val: value to test against the field
117 *
118 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
119 */
120#define FIELD_FIT(_mask, _val) \
121 ({ \
122 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
123 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
124 })
125
126/**
127 * FIELD_PREP() - prepare a bitfield element
128 * @_mask: shifted mask defining the field's length and position
129 * @_val: value to put in the field
130 *
131 * FIELD_PREP() masks and shifts up the value. The result should
132 * be combined with other fields of the bitfield using logical OR.
133 */
134#define FIELD_PREP(_mask, _val) \
135 ({ \
136 __BF_FIELD_CHECK_REG(_mask, 0ULL, "FIELD_PREP: "); \
137 __FIELD_PREP(_mask, _val, "FIELD_PREP: "); \
138 })
139
140#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
141
142/**
143 * FIELD_PREP_CONST() - prepare a constant bitfield element
144 * @_mask: shifted mask defining the field's length and position
145 * @_val: value to put in the field
146 *
147 * FIELD_PREP_CONST() masks and shifts up the value. The result should
148 * be combined with other fields of the bitfield using logical OR.
149 *
150 * Unlike FIELD_PREP() this is a constant expression and can therefore
151 * be used in initializers. Error checking is less comfortable for this
152 * version, and non-constant masks cannot be used.
153 */
154#define FIELD_PREP_CONST(_mask, _val) \
155 ( \
156 /* mask must be non-zero */ \
157 BUILD_BUG_ON_ZERO((_mask) == 0) + \
158 /* check if value fits */ \
159 BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
160 /* check if mask is contiguous */ \
161 __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \
162 /* and create the value */ \
163 (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)) \
164 )
165
166/**
167 * FIELD_GET() - extract a bitfield element
168 * @_mask: shifted mask defining the field's length and position
169 * @_reg: value of entire bitfield
170 *
171 * FIELD_GET() extracts the field specified by @_mask from the
172 * bitfield passed in as @_reg by masking and shifting it down.
173 */
174#define FIELD_GET(_mask, _reg) \
175 ({ \
176 __BF_FIELD_CHECK_REG(_mask, _reg, "FIELD_GET: "); \
177 __FIELD_GET(_mask, _reg, "FIELD_GET: "); \
178 })
179
180/**
181 * FIELD_MODIFY() - modify a bitfield element
182 * @_mask: shifted mask defining the field's length and position
183 * @_reg_p: pointer to the memory that should be updated
184 * @_val: value to store in the bitfield
185 *
186 * FIELD_MODIFY() modifies the set of bits in @_reg_p specified by @_mask,
187 * by replacing them with the bitfield value passed in as @_val.
188 */
189#define FIELD_MODIFY(_mask, _reg_p, _val) \
190 ({ \
191 typecheck_pointer(_reg_p); \
192 __BF_FIELD_CHECK(_mask, *(_reg_p), _val, "FIELD_MODIFY: "); \
193 *(_reg_p) &= ~(_mask); \
194 *(_reg_p) |= (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)); \
195 })
196
197extern void __compiletime_error("value doesn't fit into mask")
198__field_overflow(void);
199extern void __compiletime_error("bad bitfield mask")
200__bad_mask(void);
201static __always_inline u64 field_multiplier(u64 field)
202{
203 if ((field | (field - 1)) & ((field | (field - 1)) + 1))
204 __bad_mask();
205 return field & -field;
206}
207static __always_inline u64 field_mask(u64 field)
208{
209 return field / field_multiplier(field);
210}
211#define field_max(field) ((typeof(field))field_mask(field))
212#define ____MAKE_OP(type,base,to,from) \
213static __always_inline __##type __must_check type##_encode_bits(base v, base field) \
214{ \
215 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
216 __field_overflow(); \
217 return to((v & field_mask(field)) * field_multiplier(field)); \
218} \
219static __always_inline __##type __must_check type##_replace_bits(__##type old, \
220 base val, base field) \
221{ \
222 return (old & ~to(field)) | type##_encode_bits(val, field); \
223} \
224static __always_inline void type##p_replace_bits(__##type *p, \
225 base val, base field) \
226{ \
227 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \
228} \
229static __always_inline base __must_check type##_get_bits(__##type v, base field) \
230{ \
231 return (from(v) & field)/field_multiplier(field); \
232}
233#define __MAKE_OP(size) \
234 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
235 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
236 ____MAKE_OP(u##size,u##size,,)
237____MAKE_OP(u8,u8,,)
238__MAKE_OP(16)
239__MAKE_OP(32)
240__MAKE_OP(64)
241#undef __MAKE_OP
242#undef ____MAKE_OP
243
244#define __field_prep(mask, val) \
245 ({ \
246 __auto_type __mask = (mask); \
247 typeof(__mask) __val = (val); \
248 unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ? \
249 __ffs(__mask) : __ffs64(__mask); \
250 (__val << __shift) & __mask; \
251 })
252
253#define __field_get(mask, reg) \
254 ({ \
255 __auto_type __mask = (mask); \
256 typeof(__mask) __reg = (reg); \
257 unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ? \
258 __ffs(__mask) : __ffs64(__mask); \
259 (__reg & __mask) >> __shift; \
260 })
261
262/**
263 * field_prep() - prepare a bitfield element
264 * @mask: shifted mask defining the field's length and position, must be
265 * non-zero
266 * @val: value to put in the field
267 *
268 * Return: field value masked and shifted to its final destination
269 *
270 * field_prep() masks and shifts up the value. The result should be
271 * combined with other fields of the bitfield using logical OR.
272 * Unlike FIELD_PREP(), @mask is not limited to a compile-time constant.
273 * Typical usage patterns are a value stored in a table, or calculated by
274 * shifting a constant by a variable number of bits.
275 * If you want to ensure that @mask is a compile-time constant, please use
276 * FIELD_PREP() directly instead.
277 */
278#define field_prep(mask, val) \
279 (__builtin_constant_p(mask) ? __FIELD_PREP(mask, val, "field_prep: ") \
280 : __field_prep(mask, val))
281
282/**
283 * field_get() - extract a bitfield element
284 * @mask: shifted mask defining the field's length and position, must be
285 * non-zero
286 * @reg: value of entire bitfield
287 *
288 * Return: extracted field value
289 *
290 * field_get() extracts the field specified by @mask from the
291 * bitfield passed in as @reg by masking and shifting it down.
292 * Unlike FIELD_GET(), @mask is not limited to a compile-time constant.
293 * Typical usage patterns are a value stored in a table, or calculated by
294 * shifting a constant by a variable number of bits.
295 * If you want to ensure that @mask is a compile-time constant, please use
296 * FIELD_GET() directly instead.
297 */
298#define field_get(mask, reg) \
299 (__builtin_constant_p(mask) ? __FIELD_GET(mask, reg, "field_get: ") \
300 : __field_get(mask, reg))
301
302#endif
303

source code of linux/include/linux/bitfield.h