[PATCH v2 08/16] bitfield: Simplify __BF_FIELD_CHECK_REG()

david.laight.linux
2025-12-12T19:38:15Z

From: David Laight <david.laight.linux@gmail.com>

Simplify the check for 'reg' being large enough to hold 'mask' using
sizeof (reg) rather than a convoluted scheme to generate an unsigned
type the same size as 'reg'.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
include/linux/bitfield.h | 20 ++------------------
1 file changed, 2 insertions(+), 18 deletions(-)

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index c354ca2ef1a0..7160b762c979 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -45,22 +45,6 @@

#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(_mask, _val, _pfx) \
({ \
BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask), \
@@ -75,8 +59,8 @@
})

#define __BF_FIELD_CHECK_REG(mask, reg, pfx) \
- BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) > \
- __bf_cast_unsigned(reg, ~0ull), \
+ BUILD_BUG_ON_MSG((mask) + 0U + 0UL + 0ULL > \
+ ~0ULL >> (64 - 8 * sizeof (reg)), \
pfx "type of reg too small for mask")

#define __BF_FIELD_CHECK(mask, reg, val, pfx) \
--
2.39.5