| Jakub Kicinski | 3e9b311 | 2016-08-31 12:46:44 +0100 | [diff] [blame^] | 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_PREP() - prepare a bitfield element |
| 67 | * @_mask: shifted mask defining the field's length and position |
| 68 | * @_val: value to put in the field |
| 69 | * |
| 70 | * FIELD_PREP() masks and shifts up the value. The result should |
| 71 | * be combined with other fields of the bitfield using logical OR. |
| 72 | */ |
| 73 | #define FIELD_PREP(_mask, _val) \ |
| 74 | ({ \ |
| 75 | __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ |
| 76 | ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ |
| 77 | }) |
| 78 | |
| 79 | /** |
| 80 | * FIELD_GET() - extract a bitfield element |
| 81 | * @_mask: shifted mask defining the field's length and position |
| 82 | * @_reg: 32bit value of entire bitfield |
| 83 | * |
| 84 | * FIELD_GET() extracts the field specified by @_mask from the |
| 85 | * bitfield passed in as @_reg by masking and shifting it down. |
| 86 | */ |
| 87 | #define FIELD_GET(_mask, _reg) \ |
| 88 | ({ \ |
| 89 | __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ |
| 90 | (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ |
| 91 | }) |
| 92 | |
| 93 | #endif |