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/bug.h> 19 20 /* 21 * Bitfield access macros 22 * 23 * FIELD_{GET,PREP} macros take as first parameter shifted mask 24 * from which they extract the base mask and shift amount. 25 * Mask must be a compilation time constant. 26 * 27 * Example: 28 * 29 * #define REG_FIELD_A GENMASK(6, 0) 30 * #define REG_FIELD_B BIT(7) 31 * #define REG_FIELD_C GENMASK(15, 8) 32 * #define REG_FIELD_D GENMASK(31, 16) 33 * 34 * Get: 35 * a = FIELD_GET(REG_FIELD_A, reg); 36 * b = FIELD_GET(REG_FIELD_B, reg); 37 * 38 * Set: 39 * reg = FIELD_PREP(REG_FIELD_A, 1) | 40 * FIELD_PREP(REG_FIELD_B, 0) | 41 * FIELD_PREP(REG_FIELD_C, c) | 42 * FIELD_PREP(REG_FIELD_D, 0x40); 43 * 44 * Modify: 45 * reg &= ~REG_FIELD_C; 46 * reg |= FIELD_PREP(REG_FIELD_C, c); 47 */ 48 49 #define __bf_shf(x) (__builtin_ffsll(x) - 1) 50 51 #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ 52 ({ \ 53 BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ 54 _pfx "mask is not constant"); \ 55 BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \ 56 BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ 57 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ 58 _pfx "value too large for the field"); \ 59 BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ 60 _pfx "type of reg too small for mask"); \ 61 __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ 62 (1ULL << __bf_shf(_mask))); \ 63 }) 64 65 /** 66 * FIELD_FIT() - check if value fits in the field 67 * @_mask: shifted mask defining the field's length and position 68 * @_val: value to test against the field 69 * 70 * Return: true if @_val can fit inside @_mask, false if @_val is too big. 71 */ 72 #define FIELD_FIT(_mask, _val) \ 73 ({ \ 74 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ 75 !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ 76 }) 77 78 /** 79 * FIELD_PREP() - prepare a bitfield element 80 * @_mask: shifted mask defining the field's length and position 81 * @_val: value to put in the field 82 * 83 * FIELD_PREP() masks and shifts up the value. The result should 84 * be combined with other fields of the bitfield using logical OR. 85 */ 86 #define FIELD_PREP(_mask, _val) \ 87 ({ \ 88 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ 89 ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ 90 }) 91 92 /** 93 * FIELD_GET() - extract a bitfield element 94 * @_mask: shifted mask defining the field's length and position 95 * @_reg: 32bit value of entire bitfield 96 * 97 * FIELD_GET() extracts the field specified by @_mask from the 98 * bitfield passed in as @_reg by masking and shifting it down. 99 */ 100 #define FIELD_GET(_mask, _reg) \ 101 ({ \ 102 __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ 103 (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ 104 }) 105 106 #endif 107