1 /* 2 * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name> 3 * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 7 * as published by the Free Software Foundation 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 */ 14 15 #ifndef _LINUX_BITFIELD_H 16 #define _LINUX_BITFIELD_H 17 18 #include <linux/build_bug.h> 19 #include <asm/byteorder.h> 20 21 /* 22 * Bitfield access macros 23 * 24 * FIELD_{GET,PREP} macros take as first parameter shifted mask 25 * from which they extract the base mask and shift amount. 26 * Mask must be a compilation time constant. 27 * 28 * Example: 29 * 30 * #define REG_FIELD_A GENMASK(6, 0) 31 * #define REG_FIELD_B BIT(7) 32 * #define REG_FIELD_C GENMASK(15, 8) 33 * #define REG_FIELD_D GENMASK(31, 16) 34 * 35 * Get: 36 * a = FIELD_GET(REG_FIELD_A, reg); 37 * b = FIELD_GET(REG_FIELD_B, reg); 38 * 39 * Set: 40 * reg = FIELD_PREP(REG_FIELD_A, 1) | 41 * FIELD_PREP(REG_FIELD_B, 0) | 42 * FIELD_PREP(REG_FIELD_C, c) | 43 * FIELD_PREP(REG_FIELD_D, 0x40); 44 * 45 * Modify: 46 * reg &= ~REG_FIELD_C; 47 * reg |= FIELD_PREP(REG_FIELD_C, c); 48 */ 49 50 #define __bf_shf(x) (__builtin_ffsll(x) - 1) 51 52 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ 53 ({ \ 54 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ 55 _pfx "mask is not constant"); \ 56 BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \ 57 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ 58 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ 59 _pfx "value too large for the field"); \ 60 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ 61 _pfx "type of reg too small for mask"); \ 62 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ 63 (1ULL << __bf_shf(_mask))); \ 64 }) 65 66 /** 67 * FIELD_FIT() - check if value fits in the field 68 * @_mask: shifted mask defining the field's length and position 69 * @_val: value to test against the field 70 * 71 * Return: true if @_val can fit inside @_mask, false if @_val is too big. 72 */ 73 #define FIELD_FIT(_mask, _val) \ 74 ({ \ 75 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ 76 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ 77 }) 78 79 /** 80 * FIELD_PREP() - prepare a bitfield element 81 * @_mask: shifted mask defining the field's length and position 82 * @_val: value to put in the field 83 * 84 * FIELD_PREP() masks and shifts up the value. The result should 85 * be combined with other fields of the bitfield using logical OR. 86 */ 87 #define FIELD_PREP(_mask, _val) \ 88 ({ \ 89 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ 90 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ 91 }) 92 93 /** 94 * FIELD_GET() - extract a bitfield element 95 * @_mask: shifted mask defining the field's length and position 96 * @_reg: value of entire bitfield 97 * 98 * FIELD_GET() extracts the field specified by @_mask from the 99 * bitfield passed in as @_reg by masking and shifting it down. 100 */ 101 #define FIELD_GET(_mask, _reg) \ 102 ({ \ 103 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ 104 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ 105 }) 106 107 extern void __compiletime_warning("value doesn't fit into mask") 108 __field_overflow(void); 109 extern void __compiletime_error("bad bitfield mask") 110 __bad_mask(void); 111 static __always_inline u64 field_multiplier(u64 field) 112 { 113 if ((field | (field - 1)) & ((field | (field - 1)) + 1)) 114 __bad_mask(); 115 return field & -field; 116 } 117 static __always_inline u64 field_mask(u64 field) 118 { 119 return field / field_multiplier(field); 120 } 121 #define ____MAKE_OP(type,base,to,from) \ 122 static __always_inline __##type type##_encode_bits(base v, base field) \ 123 { \ 124 if (__builtin_constant_p(v) && (v & ~field_multiplier(field))) \ 125 __field_overflow(); \ 126 return to((v & field_mask(field)) * field_multiplier(field)); \ 127 } \ 128 static __always_inline __##type type##_replace_bits(__##type old, \ 129 base val, base field) \ 130 { \ 131 return (old & ~to(field)) | type##_encode_bits(val, field); \ 132 } \ 133 static __always_inline void type##p_replace_bits(__##type *p, \ 134 base val, base field) \ 135 { \ 136 *p = (*p & ~to(field)) | type##_encode_bits(val, field); \ 137 } \ 138 static __always_inline base type##_get_bits(__##type v, base field) \ 139 { \ 140 return (from(v) & field)/field_multiplier(field); \ 141 } 142 #define __MAKE_OP(size) \ 143 ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \ 144 ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \ 145 ____MAKE_OP(u##size,u##size,,) 146 __MAKE_OP(16) 147 __MAKE_OP(32) 148 __MAKE_OP(64) 149 #undef __MAKE_OP 150 #undef ____MAKE_OP 151 152 #endif 153