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 *  #include <linux/bitfield.h>
23 *  #include <linux/bits.h>
24 *
25 *  #define REG_FIELD_A  GENMASK(6, 0)
26 *  #define REG_FIELD_B  BIT(7)
27 *  #define REG_FIELD_C  GENMASK(15, 8)
28 *  #define REG_FIELD_D  GENMASK(31, 16)
29 *
30 * Get:
31 *  a = FIELD_GET(REG_FIELD_A, reg);
32 *  b = FIELD_GET(REG_FIELD_B, reg);
33 *
34 * Set:
35 *  reg = FIELD_PREP(REG_FIELD_A, 1) |
36 *	  FIELD_PREP(REG_FIELD_B, 0) |
37 *	  FIELD_PREP(REG_FIELD_C, c) |
38 *	  FIELD_PREP(REG_FIELD_D, 0x40);
39 *
40 * Modify:
41 *  reg &= ~REG_FIELD_C;
42 *  reg |= FIELD_PREP(REG_FIELD_C, c);
43 */
44
45#define __bf_shf(x) (__builtin_ffsll(x) - 1)
46
47#define __scalar_type_to_unsigned_cases(type)				\
48		unsigned type:	(unsigned type)0,			\
49		signed type:	(unsigned type)0
50
51#define __unsigned_scalar_typeof(x) typeof(				\
52		_Generic((x),						\
53			char:	(unsigned char)0,			\
54			__scalar_type_to_unsigned_cases(char),		\
55			__scalar_type_to_unsigned_cases(short),		\
56			__scalar_type_to_unsigned_cases(int),		\
57			__scalar_type_to_unsigned_cases(long),		\
58			__scalar_type_to_unsigned_cases(long long),	\
59			default: (x)))
60
61#define __bf_cast_unsigned(type, x)	((__unsigned_scalar_typeof(type))(x))
62
63#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)			\
64	({								\
65		BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),		\
66				 _pfx "mask is not constant");		\
67		BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");	\
68		BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?		\
69				 ~((_mask) >> __bf_shf(_mask)) &	\
70					(0 + (_val)) : 0,		\
71				 _pfx "value too large for the field"); \
72		BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >	\
73				 __bf_cast_unsigned(_reg, ~0ull),	\
74				 _pfx "type of reg too small for mask"); \
75		__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +			\
76					      (1ULL << __bf_shf(_mask))); \
77	})
78
79/**
80 * FIELD_MAX() - produce the maximum value representable by a field
81 * @_mask: shifted mask defining the field's length and position
82 *
83 * FIELD_MAX() returns the maximum value that can be held in the field
84 * specified by @_mask.
85 */
86#define FIELD_MAX(_mask)						\
87	({								\
88		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: ");	\
89		(typeof(_mask))((_mask) >> __bf_shf(_mask));		\
90	})
91
92/**
93 * FIELD_FIT() - check if value fits in the field
94 * @_mask: shifted mask defining the field's length and position
95 * @_val:  value to test against the field
96 *
97 * Return: true if @_val can fit inside @_mask, false if @_val is too big.
98 */
99#define FIELD_FIT(_mask, _val)						\
100	({								\
101		__BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: ");	\
102		!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
103	})
104
105/**
106 * FIELD_PREP() - prepare a bitfield element
107 * @_mask: shifted mask defining the field's length and position
108 * @_val:  value to put in the field
109 *
110 * FIELD_PREP() masks and shifts up the value.  The result should
111 * be combined with other fields of the bitfield using logical OR.
112 */
113#define FIELD_PREP(_mask, _val)						\
114	({								\
115		__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");	\
116		((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);	\
117	})
118
119#define __BF_CHECK_POW2(n)	BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
120
121/**
122 * FIELD_PREP_CONST() - prepare a constant bitfield element
123 * @_mask: shifted mask defining the field's length and position
124 * @_val:  value to put in the field
125 *
126 * FIELD_PREP_CONST() masks and shifts up the value.  The result should
127 * be combined with other fields of the bitfield using logical OR.
128 *
129 * Unlike FIELD_PREP() this is a constant expression and can therefore
130 * be used in initializers. Error checking is less comfortable for this
131 * version, and non-constant masks cannot be used.
132 */
133#define FIELD_PREP_CONST(_mask, _val)					\
134	(								\
135		/* mask must be non-zero */				\
136		BUILD_BUG_ON_ZERO((_mask) == 0) +			\
137		/* check if value fits */				\
138		BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
139		/* check if mask is contiguous */			\
140		__BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) +	\
141		/* and create the value */				\
142		(((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask))	\
143	)
144
145/**
146 * FIELD_GET() - extract a bitfield element
147 * @_mask: shifted mask defining the field's length and position
148 * @_reg:  value of entire bitfield
149 *
150 * FIELD_GET() extracts the field specified by @_mask from the
151 * bitfield passed in as @_reg by masking and shifting it down.
152 */
153#define FIELD_GET(_mask, _reg)						\
154	({								\
155		__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");	\
156		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask));	\
157	})
158
159extern void __compiletime_error("value doesn't fit into mask")
160__field_overflow(void);
161extern void __compiletime_error("bad bitfield mask")
162__bad_mask(void);
163static __always_inline u64 field_multiplier(u64 field)
164{
165	if ((field | (field - 1)) & ((field | (field - 1)) + 1))
166		__bad_mask();
167	return field & -field;
168}
169static __always_inline u64 field_mask(u64 field)
170{
171	return field / field_multiplier(field);
172}
173#define field_max(field)	((typeof(field))field_mask(field))
174#define ____MAKE_OP(type,base,to,from)					\
175static __always_inline __##type type##_encode_bits(base v, base field)	\
176{									\
177	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
178		__field_overflow();					\
179	return to((v & field_mask(field)) * field_multiplier(field));	\
180}									\
181static __always_inline __##type type##_replace_bits(__##type old,	\
182					base val, base field)		\
183{									\
184	return (old & ~to(field)) | type##_encode_bits(val, field);	\
185}									\
186static __always_inline void type##p_replace_bits(__##type *p,		\
187					base val, base field)		\
188{									\
189	*p = (*p & ~to(field)) | type##_encode_bits(val, field);	\
190}									\
191static __always_inline base type##_get_bits(__##type v, base field)	\
192{									\
193	return (from(v) & field)/field_multiplier(field);		\
194}
195#define __MAKE_OP(size)							\
196	____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu)	\
197	____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu)	\
198	____MAKE_OP(u##size,u##size,,)
199____MAKE_OP(u8,u8,,)
200__MAKE_OP(16)
201__MAKE_OP(32)
202__MAKE_OP(64)
203#undef __MAKE_OP
204#undef ____MAKE_OP
205
206#endif
207