153 строки
4.7 KiB
C
153 строки
4.7 KiB
C
/*
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* Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
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* Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#ifndef _LINUX_BITFIELD_H
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#define _LINUX_BITFIELD_H
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#include <linux/build_bug.h>
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#include <asm/byteorder.h>
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/*
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* Bitfield access macros
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*
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* FIELD_{GET,PREP} macros take as first parameter shifted mask
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* from which they extract the base mask and shift amount.
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* Mask must be a compilation time constant.
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*
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* Example:
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*
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* #define REG_FIELD_A GENMASK(6, 0)
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* #define REG_FIELD_B BIT(7)
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* #define REG_FIELD_C GENMASK(15, 8)
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* #define REG_FIELD_D GENMASK(31, 16)
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*
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* Get:
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* a = FIELD_GET(REG_FIELD_A, reg);
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* b = FIELD_GET(REG_FIELD_B, reg);
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*
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* Set:
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* reg = FIELD_PREP(REG_FIELD_A, 1) |
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* FIELD_PREP(REG_FIELD_B, 0) |
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* FIELD_PREP(REG_FIELD_C, c) |
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* FIELD_PREP(REG_FIELD_D, 0x40);
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*
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* Modify:
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* reg &= ~REG_FIELD_C;
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* reg |= FIELD_PREP(REG_FIELD_C, c);
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*/
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#define __bf_shf(x) (__builtin_ffsll(x) - 1)
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#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx) \
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({ \
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BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
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_pfx "mask is not constant"); \
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BUILD_BUG_ON_MSG(!(_mask), _pfx "mask is zero"); \
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BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
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~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
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_pfx "value too large for the field"); \
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BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \
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_pfx "type of reg too small for mask"); \
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__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
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(1ULL << __bf_shf(_mask))); \
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})
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/**
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* FIELD_FIT() - check if value fits in the field
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* @_mask: shifted mask defining the field's length and position
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* @_val: value to test against the field
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*
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* Return: true if @_val can fit inside @_mask, false if @_val is too big.
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*/
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#define FIELD_FIT(_mask, _val) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \
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!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
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})
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/**
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* FIELD_PREP() - prepare a bitfield element
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* @_mask: shifted mask defining the field's length and position
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* @_val: value to put in the field
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*
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* FIELD_PREP() masks and shifts up the value. The result should
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* be combined with other fields of the bitfield using logical OR.
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*/
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#define FIELD_PREP(_mask, _val) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
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((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
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})
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/**
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* FIELD_GET() - extract a bitfield element
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* @_mask: shifted mask defining the field's length and position
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* @_reg: value of entire bitfield
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*
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* FIELD_GET() extracts the field specified by @_mask from the
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* bitfield passed in as @_reg by masking and shifting it down.
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*/
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#define FIELD_GET(_mask, _reg) \
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({ \
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__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \
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(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
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})
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extern void __compiletime_warning("value doesn't fit into mask")
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__field_overflow(void);
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extern void __compiletime_error("bad bitfield mask")
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__bad_mask(void);
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static __always_inline u64 field_multiplier(u64 field)
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{
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if ((field | (field - 1)) & ((field | (field - 1)) + 1))
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__bad_mask();
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return field & -field;
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}
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static __always_inline u64 field_mask(u64 field)
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{
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return field / field_multiplier(field);
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}
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#define ____MAKE_OP(type,base,to,from) \
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static __always_inline __##type type##_encode_bits(base v, base field) \
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{ \
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if (__builtin_constant_p(v) && (v & ~field_multiplier(field))) \
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__field_overflow(); \
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return to((v & field_mask(field)) * field_multiplier(field)); \
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} \
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static __always_inline __##type type##_replace_bits(__##type old, \
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base val, base field) \
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{ \
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return (old & ~to(field)) | type##_encode_bits(val, field); \
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} \
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static __always_inline void type##p_replace_bits(__##type *p, \
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base val, base field) \
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{ \
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*p = (*p & ~to(field)) | type##_encode_bits(val, field); \
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} \
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static __always_inline base type##_get_bits(__##type v, base field) \
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{ \
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return (from(v) & field)/field_multiplier(field); \
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}
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#define __MAKE_OP(size) \
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____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
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____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
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____MAKE_OP(u##size,u##size,,)
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__MAKE_OP(16)
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__MAKE_OP(32)
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__MAKE_OP(64)
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#undef __MAKE_OP
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#undef ____MAKE_OP
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#endif
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