1/* SPDX-License-Identifier: GPL-2.0-only */
  2/*
  3 * Copyright (C) 2014 Felix Fietkau <nbd@nbd.name>
  4 * Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
  5 */
  6
  7#ifndef _LINUX_BITFIELD_H
  8#define _LINUX_BITFIELD_H
  9
 10#include <linux/build_bug.h>
 11#include <asm/byteorder.h>
 12
 13/*
 14 * Bitfield access macros
 15 *
 16 * FIELD_{GET,PREP} macros take as first parameter shifted mask
 17 * from which they extract the base mask and shift amount.
 18 * Mask must be a compilation time constant.
 19 *
 20 * Example:
 21 *
 22 *  #define REG_FIELD_A  GENMASK(6, 0)
 23 *  #define REG_FIELD_B  BIT(7)
 24 *  #define REG_FIELD_C  GENMASK(15, 8)
 25 *  #define REG_FIELD_D  GENMASK(31, 16)
 26 *
 27 * Get:
 28 *  a = FIELD_GET(REG_FIELD_A, reg);
 29 *  b = FIELD_GET(REG_FIELD_B, reg);
 30 *
 31 * Set:
 32 *  reg = FIELD_PREP(REG_FIELD_A, 1) |
 33 *	  FIELD_PREP(REG_FIELD_B, 0) |
 34 *	  FIELD_PREP(REG_FIELD_C, c) |
 35 *	  FIELD_PREP(REG_FIELD_D, 0x40);
 36 *
 37 * Modify:
 38 *  reg &= ~REG_FIELD_C;
 39 *  reg |= FIELD_PREP(REG_FIELD_C, c);
 40 */
 41
 42#define __bf_shf(x) (__builtin_ffsll(x) - 1)
 43
 44#define __scalar_type_to_unsigned_cases(type)				\
 45		unsigned type:	(unsigned type)0,			\
 46		signed type:	(unsigned type)0
 47
 48#define __unsigned_scalar_typeof(x) typeof(				\
 49		_Generic((x),						\
 50			char:	(unsigned char)0,			\
 51			__scalar_type_to_unsigned_cases(char),		\
 52			__scalar_type_to_unsigned_cases(short),		\
 53			__scalar_type_to_unsigned_cases(int),		\
 54			__scalar_type_to_unsigned_cases(long),		\
 55			__scalar_type_to_unsigned_cases(long long),	\
 56			default: (x)))
 57
 58#define __bf_cast_unsigned(type, x)	((__unsigned_scalar_typeof(type))(x))
 59
 60#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)			\
 61	({								\
 62		BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),		\
 63				 _pfx "mask is not constant");		\
 64		BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");	\
 65		BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?		\
 66				 ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
 67				 _pfx "value too large for the field"); \
 68		BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >	\
 69				 __bf_cast_unsigned(_reg, ~0ull),	\
 70				 _pfx "type of reg too small for mask"); \
 71		__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +			\
 72					      (1ULL << __bf_shf(_mask))); \
 73	})
 74
 75/**
 76 * FIELD_MAX() - produce the maximum value representable by a field
 77 * @_mask: shifted mask defining the field's length and position
 78 *
 79 * FIELD_MAX() returns the maximum value that can be held in the field
 80 * specified by @_mask.
 81 */
 82#define FIELD_MAX(_mask)						\
 83	({								\
 84		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");	\
 85		(typeof(_mask))((_mask) >> __bf_shf(_mask));		\
 86	})
 87
 88/**
 89 * FIELD_FIT() - check if value fits in the field
 90 * @_mask: shifted mask defining the field's length and position
 91 * @_val:  value to test against the field
 92 *
 93 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
 94 */
 95#define FIELD_FIT(_mask, _val)						\
 96	({								\
 97		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");	\
 98		!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
 99	})
100
101/**
102 * FIELD_PREP() - prepare a bitfield element
103 * @_mask: shifted mask defining the field's length and position
104 * @_val:  value to put in the field
105 *
106 * FIELD_PREP() masks and shifts up the value.  The result should
107 * be combined with other fields of the bitfield using logical OR.
108 */
109#define FIELD_PREP(_mask, _val)						\
110	({								\
111		__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");	\
112		((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);	\
113	})
114
115/**
116 * FIELD_GET() - extract a bitfield element
117 * @_mask: shifted mask defining the field's length and position
118 * @_reg:  value of entire bitfield
119 *
120 * FIELD_GET() extracts the field specified by @_mask from the
121 * bitfield passed in as @_reg by masking and shifting it down.
122 */
123#define FIELD_GET(_mask, _reg)						\
124	({								\
125		__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");	\
126		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask));	\
127	})
128
129extern void __compiletime_error("value doesn't fit into mask")
130__field_overflow(void);
131extern void __compiletime_error("bad bitfield mask")
132__bad_mask(void);
133static __always_inline u64 field_multiplier(u64 field)
134{
135	if ((field | (field - 1)) & ((field | (field - 1)) + 1))
136		__bad_mask();
137	return field & -field;
138}
139static __always_inline u64 field_mask(u64 field)
140{
141	return field / field_multiplier(field);
142}
143#define field_max(field)	((typeof(field))field_mask(field))
144#define ____MAKE_OP(type,base,to,from)					\
145static __always_inline __##type type##_encode_bits(base v, base field)	\
146{									\
147	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
148		__field_overflow();					\
149	return to((v & field_mask(field)) * field_multiplier(field));	\
150}									\
151static __always_inline __##type type##_replace_bits(__##type old,	\
152					base val, base field)		\
153{									\
154	return (old & ~to(field)) | type##_encode_bits(val, field);	\
155}									\
156static __always_inline void type##p_replace_bits(__##type *p,		\
157					base val, base field)		\
158{									\
159	*p = (*p & ~to(field)) | type##_encode_bits(val, field);	\
160}									\
161static __always_inline base type##_get_bits(__##type v, base field)	\
162{									\
163	return (from(v) & field)/field_multiplier(field);		\
164}
165#define __MAKE_OP(size)							\
166	____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu)	\
167	____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu)	\
168	____MAKE_OP(u##size,u##size,,)
169____MAKE_OP(u8,u8,,)
170__MAKE_OP(16)
171__MAKE_OP(32)
172__MAKE_OP(64)
173#undef __MAKE_OP
174#undef ____MAKE_OP
175
176#endif