From: Nicolas Saenz Julienne nsaenzjulienne@suse.de
Imports Al Viro's original Linux commit 00b0c9b82663a, which contains an in depth explanation and two fixes from Johannes Berg: e7d4a95da86e0 "bitfield: fix *_encode_bits()", 37a3862e12382 "bitfield: add u8 helpers".
Signed-off-by: Nicolas Saenz Julienne nsaenzjulienne@suse.de [s.nawrocki: added empty lines between functions and macros] Signed-off-by: Sylwester Nawrocki s.nawrocki@samsung.com --- Changes since v3: - none. Changes since v2: - added some more missing whitespaces as pointed out by checkpatch.pl. Changes since v1: - added empty lines between functions and macros. Changes since RFC: - new patch. --- include/linux/bitfield.h | 52 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+)
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index 8b9d6ff..7ad8b08 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -103,4 +103,56 @@ (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ })
+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) \ +static __always_inline __##type type##_encode_bits(base v, base field) \ +{ \ + if (__builtin_constant_p(v) && (v & ~field_mask(field))) \ + __field_overflow(); \ + return to((v & field_mask(field)) * field_multiplier(field)); \ +} \ +static __always_inline __##type type##_replace_bits(__##type old, \ + base val, base field) \ +{ \ + return (old & ~to(field)) | type##_encode_bits(val, field); \ +} \ +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); \ +} + +#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(16) +__MAKE_OP(32) +__MAKE_OP(64) + +#undef __MAKE_OP +#undef ____MAKE_OP + #endif