/* * Copyright (C) 2014 Felix Fietkau * Copyright (C) 2004 - 2009 Ivo van Doorn * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 * as published by the Free Software Foundation * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #ifndef _LINUX_BITFIELD_H #define _LINUX_BITFIELD_H #include /* * Bitfield access macros * * FIELD_{GET,PREP} macros take as first parameter shifted mask * from which they extract the base mask and shift amount. * Mask must be a compilation time constant. * * Example: * * #define REG_FIELD_A GENMASK(6, 0) * #define REG_FIELD_B BIT(7) * #define REG_FIELD_C GENMASK(15, 8) * #define REG_FIELD_D GENMASK(31, 16) * * Get: * a = FIELD_GET(REG_FIELD_A, reg); * b = FIELD_GET(REG_FIELD_B, reg); * * Set: * reg = FIELD_PREP(REG_FIELD_A, 1) | * FIELD_PREP(REG_FIELD_B, 0) | * FIELD_PREP(REG_FIELD_C, c) | * FIELD_PREP(REG_FIELD_D, 0x40); * * Modify: * reg &= ~REG_FIELD_C; * reg |= FIELD_PREP(REG_FIELD_C, c); */ #define __bf_shf(x) (__builtin_ffsll(x) - 1) #define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \ ({ \ BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \ _pfx "mask is not constant"); \ BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \ BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ _pfx "value too large for the field"); \ BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ _pfx "type of reg too small for mask"); \ __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ (1ULL << __bf_shf(_mask))); \ }) /** * FIELD_FIT() - check if value fits in the field * @_mask: shifted mask defining the field's length and position * @_val: value to test against the field * * Return: true if @_val can fit inside @_mask, false if @_val is too big. */ #define FIELD_FIT(_mask, _val) \ ({ \ __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ }) /** * FIELD_PREP() - prepare a bitfield element * @_mask: shifted mask defining the field's length and position * @_val: value to put in the field * * FIELD_PREP() masks and shifts up the value. The result should * be combined with other fields of the bitfield using logical OR. */ #define FIELD_PREP(_mask, _val) \ ({ \ __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ }) /** * FIELD_GET() - extract a bitfield element * @_mask: shifted mask defining the field's length and position * @_reg: value of entire bitfield * * FIELD_GET() extracts the field specified by @_mask from the * bitfield passed in as @_reg by masking and shifting it down. */ #define FIELD_GET(_mask, _reg) \ ({ \ __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ }) #endif