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 __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ 45 ({ \ 46 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ 47 _pfx "mask is not constant"); \ 48 BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \ 49 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ 50 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ 51 _pfx "value too large for the field"); \ 52 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ 53 _pfx "type of reg too small for mask"); \ 54 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ 55 (1ULL << __bf_shf(_mask))); \ 56 }) 57 58 /** 59 * FIELD_MAX() - produce the maximum value representable by a field 60 * @_mask: shifted mask defining the field's length and position 61 * 62 * FIELD_MAX() returns the maximum value that can be held in the field 63 * specified by @_mask. 64 */ 65 #define FIELD_MAX(_mask) \ 66 ({ \ 67 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \ 68 (typeof(_mask))((_mask) >> __bf_shf(_mask)); \ 69 }) 70 71 /** 72 * FIELD_FIT() - check if value fits in the field 73 * @_mask: shifted mask defining the field's length and position 74 * @_val: value to test against the field 75 * 76 * Return: true if @_val can fit inside @_mask, false if @_val is too big. 77 */ 78 #define FIELD_FIT(_mask, _val) \ 79 ({ \ 80 __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ 81 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ 82 }) 83 84 /** 85 * FIELD_PREP() - prepare a bitfield element 86 * @_mask: shifted mask defining the field's length and position 87 * @_val: value to put in the field 88 * 89 * FIELD_PREP() masks and shifts up the value. The result should 90 * be combined with other fields of the bitfield using logical OR. 91 */ 92 #define FIELD_PREP(_mask, _val) \ 93 ({ \ 94 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ 95 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ 96 }) 97 98 /** 99 * FIELD_GET() - extract a bitfield element 100 * @_mask: shifted mask defining the field's length and position 101 * @_reg: value of entire bitfield 102 * 103 * FIELD_GET() extracts the field specified by @_mask from the 104 * bitfield passed in as @_reg by masking and shifting it down. 105 */ 106 #define FIELD_GET(_mask, _reg) \ 107 ({ \ 108 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ 109 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ 110 }) 111 112 extern void __compiletime_error("value doesn't fit into mask") 113 __field_overflow(void); 114 extern void __compiletime_error("bad bitfield mask") 115 __bad_mask(void); 116 static __always_inline u64 field_multiplier(u64 field) 117 { 118 if ((field | (field - 1)) & ((field | (field - 1)) + 1)) 119 __bad_mask(); 120 return field & -field; 121 } 122 static __always_inline u64 field_mask(u64 field) 123 { 124 return field / field_multiplier(field); 125 } 126 #define field_max(field) ((typeof(field))field_mask(field)) 127 #define ____MAKE_OP(type,base,to,from) \ 128 static __always_inline __##type type##_encode_bits(base v, base field) \ 129 { \ 130 if (__builtin_constant_p(v) && (v & ~field_mask(field))) \ 131 __field_overflow(); \ 132 return to((v & field_mask(field)) * field_multiplier(field)); \ 133 } \ 134 static __always_inline __##type type##_replace_bits(__##type old, \ 135 base val, base field) \ 136 { \ 137 return (old & ~to(field)) | type##_encode_bits(val, field); \ 138 } \ 139 static __always_inline void type##p_replace_bits(__##type *p, \ 140 base val, base field) \ 141 { \ 142 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \ 143 } \ 144 static __always_inline base type##_get_bits(__##type v, base field) \ 145 { \ 146 return (from(v) & field)/field_multiplier(field); \ 147 } 148 #define __MAKE_OP(size) \ 149 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \ 150 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \ 151 ____MAKE_OP(u##size,u##size,,) 152 ____MAKE_OP(u8,u8,,) 153 __MAKE_OP(16) 154 __MAKE_OP(32) 155 __MAKE_OP(64) 156 #undef __MAKE_OP 157 #undef ____MAKE_OP 158 159 #endif 160