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e2192de59e
Neither FIELD_PREP() nor *_encode_bits() can be used in constant contexts (such as initializers), but we don't want to define shift constants for all masks just for use in initializers, and having checks that the values fit is also useful. Therefore, add FIELD_PREP_CONST() which is a smaller version of FIELD_PREP() that can only take constant arguments and has less friendly (but not less strict) error checks, and expands to a constant value. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Link: https://lore.kernel.org/r/20230118142652.53f20593504b.Iaeea0aee77a6493d70e573b4aa55c91c00e01e4b@changeid Signed-off-by: Johannes Berg <johannes.berg@intel.com>
205 lines
6.4 KiB
C
205 lines
6.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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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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#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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* #include <linux/bitfield.h>
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* #include <linux/bits.h>
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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 __scalar_type_to_unsigned_cases(type) \
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unsigned type: (unsigned type)0, \
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signed type: (unsigned type)0
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#define __unsigned_scalar_typeof(x) typeof( \
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_Generic((x), \
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char: (unsigned char)0, \
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__scalar_type_to_unsigned_cases(char), \
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__scalar_type_to_unsigned_cases(short), \
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__scalar_type_to_unsigned_cases(int), \
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__scalar_type_to_unsigned_cases(long), \
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__scalar_type_to_unsigned_cases(long long), \
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default: (x)))
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#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
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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) == 0, _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(__bf_cast_unsigned(_mask, _mask) > \
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__bf_cast_unsigned(_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_MAX() - produce the maximum value representable by a field
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* @_mask: shifted mask defining the field's length and position
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*
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* FIELD_MAX() returns the maximum value that can be held in the field
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* specified by @_mask.
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*/
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#define FIELD_MAX(_mask) \
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({ \
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__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
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(typeof(_mask))((_mask) >> __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, 0ULL, "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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#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
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/**
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* FIELD_PREP_CONST() - prepare a constant 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_CONST() 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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* Unlike FIELD_PREP() this is a constant expression and can therefore
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* be used in initializers. Error checking is less comfortable for this
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* version, and non-constant masks cannot be used.
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*/
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#define FIELD_PREP_CONST(_mask, _val) \
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( \
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/* mask must be non-zero */ \
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BUILD_BUG_ON_ZERO((_mask) == 0) + \
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/* check if value fits */ \
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BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
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/* check if mask is contiguous */ \
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__BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \
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/* and create the value */ \
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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_error("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 field_max(field) ((typeof(field))field_mask(field))
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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_mask(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(u8,u8,,)
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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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