[PATCH v2 1/2] linux/bitfield.h: sync <linux/bitfield.h> from Linux 6.15
Christian Marangi
ansuelsmth at gmail.com
Wed Jun 4 19:02:38 CEST 2025
Sync bitfield.h header with Linux 6.15 version. Mainly is to permit the
introduction of FIELD_PREP_CONST. The bug.h header changed to
build_bug.h doesn't cause any regression as we also ship split header
similar to how it's done with in Linux.
Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
---
Changes v2:
- Copy the full file instead of cherry-pick Changes
This is being CI tested on [1]. Locally compile and works on
my build system.
[1] https://github.com/u-boot/u-boot/pull/777
include/linux/bitfield.h | 103 ++++++++++++++++++++++++++++-----------
1 file changed, 75 insertions(+), 28 deletions(-)
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 7ad02f8cbb9..63928f17322 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -1,21 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2014 Felix Fietkau <nbd at nbd.name>
* Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn at gmail.com>
- *
- * 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 <linux/bug.h>
+#include <linux/build_bug.h>
#include <asm/byteorder.h>
/*
@@ -27,6 +19,9 @@
*
* Example:
*
+ * #include <linux/bitfield.h>
+ * #include <linux/bits.h>
+ *
* #define REG_FIELD_A GENMASK(6, 0)
* #define REG_FIELD_B BIT(7)
* #define REG_FIELD_C GENMASK(15, 8)
@@ -49,20 +44,51 @@
#define __bf_shf(x) (__builtin_ffsll(x) - 1)
+#define __scalar_type_to_unsigned_cases(type) \
+ unsigned type: (unsigned type)0, \
+ signed type: (unsigned type)0
+
+#define __unsigned_scalar_typeof(x) typeof( \
+ _Generic((x), \
+ char: (unsigned char)0, \
+ __scalar_type_to_unsigned_cases(char), \
+ __scalar_type_to_unsigned_cases(short), \
+ __scalar_type_to_unsigned_cases(int), \
+ __scalar_type_to_unsigned_cases(long), \
+ __scalar_type_to_unsigned_cases(long long), \
+ default: (x)))
+
+#define __bf_cast_unsigned(type, x) ((__unsigned_scalar_typeof(type))(x))
+
#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((_mask) == 0, _pfx "mask is zero"); \
BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
- ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
+ ~((_mask) >> __bf_shf(_mask)) & \
+ (0 + (_val)) : 0, \
_pfx "value too large for the field"); \
- BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \
+ BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \
+ __bf_cast_unsigned(_reg, ~0ull), \
_pfx "type of reg too small for mask"); \
__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \
(1ULL << __bf_shf(_mask))); \
})
+/**
+ * FIELD_MAX() - produce the maximum value representable by a field
+ * @_mask: shifted mask defining the field's length and position
+ *
+ * FIELD_MAX() returns the maximum value that can be held in the field
+ * specified by @_mask.
+ */
+#define FIELD_MAX(_mask) \
+ ({ \
+ __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_MAX: "); \
+ (typeof(_mask))((_mask) >> __bf_shf(_mask)); \
+ })
+
/**
* FIELD_FIT() - check if value fits in the field
* @_mask: shifted mask defining the field's length and position
@@ -72,7 +98,7 @@
*/
#define FIELD_FIT(_mask, _val) \
({ \
- __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \
+ __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \
!((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \
})
@@ -90,10 +116,36 @@
((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \
})
+#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
+
+/**
+ * FIELD_PREP_CONST() - prepare a constant bitfield element
+ * @_mask: shifted mask defining the field's length and position
+ * @_val: value to put in the field
+ *
+ * FIELD_PREP_CONST() masks and shifts up the value. The result should
+ * be combined with other fields of the bitfield using logical OR.
+ *
+ * Unlike FIELD_PREP() this is a constant expression and can therefore
+ * be used in initializers. Error checking is less comfortable for this
+ * version, and non-constant masks cannot be used.
+ */
+#define FIELD_PREP_CONST(_mask, _val) \
+ ( \
+ /* mask must be non-zero */ \
+ BUILD_BUG_ON_ZERO((_mask) == 0) + \
+ /* check if value fits */ \
+ BUILD_BUG_ON_ZERO(~((_mask) >> __bf_shf(_mask)) & (_val)) + \
+ /* check if mask is contiguous */ \
+ __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) + \
+ /* and create the value */ \
+ (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask)) \
+ )
+
/**
* FIELD_GET() - extract a bitfield element
* @_mask: shifted mask defining the field's length and position
- * @_reg: 32bit value of entire bitfield
+ * @_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.
@@ -108,20 +160,18 @@ extern void __compiletime_error("value doesn't fit into mask")
__field_overflow(void);
extern void __compiletime_error("bad bitfield mask")
__bad_mask(void);
-
static __always_inline u64 field_multiplier(u64 field)
{
if ((field | (field - 1)) & ((field | (field - 1)) + 1))
__bad_mask();
return field & -field;
}
-
static __always_inline u64 field_mask(u64 field)
{
return field / field_multiplier(field);
}
-
-#define ____MAKE_OP(type, base, to, from) \
+#define field_max(field) ((typeof(field))field_mask(field))
+#define ____MAKE_OP(type,base,to,from) \
static __always_inline __##type type##_encode_bits(base v, base field) \
{ \
if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
@@ -133,26 +183,23 @@ static __always_inline __##type type##_replace_bits(__##type old, \
{ \
return (old & ~to(field)) | type##_encode_bits(val, field); \
} \
-static __always_inline void type##p_replace_bits(__##type * p, \
+static __always_inline void type##p_replace_bits(__##type *p, \
base val, base field) \
{ \
*p = (*p & ~to(field)) | type##_encode_bits(val, field); \
} \
static __always_inline base type##_get_bits(__##type v, base field) \
{ \
- return (from(v) & field) / field_multiplier(field); \
+ return (from(v) & field)/field_multiplier(field); \
}
-
#define __MAKE_OP(size) \
- ____MAKE_OP(le##size, u##size, cpu_to_le##size, le##size##_to_cpu) \
- ____MAKE_OP(be##size, u##size, cpu_to_be##size, be##size##_to_cpu) \
- ____MAKE_OP(u##size, u##size, ,)
-
-____MAKE_OP(u8, u8, ,)
+ ____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu) \
+ ____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu) \
+ ____MAKE_OP(u##size,u##size,,)
+____MAKE_OP(u8,u8,,)
__MAKE_OP(16)
__MAKE_OP(32)
__MAKE_OP(64)
-
#undef __MAKE_OP
#undef ____MAKE_OP
--
2.48.1
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