From: Johannes Berg <[email protected]> John Garry requested to be able to use FIELD_PREP() and friends in constant initializers, so the thing we can do is switch all the compile-time assertions to use BUILD_BUG_ON_ZERO() instead of regular BUILD_BUG_ON().
The only downside is that we lose all the error messages, but it doesn't seem worthwhile to duplicate all of this into e.g. CONST_FIELD_PREP() (for constants) just for that. Requested-by: John Garry <[email protected]> Signed-off-by: Johannes Berg <[email protected]> --- include/linux/bitfield.h | 40 +++++++++++++++------------------------- 1 file changed, 15 insertions(+), 25 deletions(-) diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index 3f1ef4450a7c..1840dae6448a 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -49,19 +49,15 @@ #define __bf_shf(x) (__builtin_ffsll(x) - 1) -#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) == 0, _pfx "mask is zero"); \ - BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ - ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ - _pfx "value too large for the field"); \ - BUILD_BUG_ON_MSG((_mask) > (typeof(_reg))~0ull, \ - _pfx "type of reg too small for mask"); \ - __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) + \ - (1ULL << __bf_shf(_mask))); \ - }) +#define __BF_CHECK_POW2(n) BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0) + +#define __BF_FIELD_CHECK(_mask, _reg, _val) \ + BUILD_BUG_ON_ZERO(!__builtin_constant_p(_mask)) + \ + BUILD_BUG_ON_ZERO((_mask) == 0) + \ + BUILD_BUG_ON_ZERO(__builtin_constant_p(_val) ? \ + ~((_mask) >> __bf_shf(_mask)) & (_val) : 0) + \ + BUILD_BUG_ON_ZERO((_mask) > (typeof(_reg))~0ull) + \ + __BF_CHECK_POW2((_mask) + (1ULL << __bf_shf(_mask))) /** * FIELD_FIT() - check if value fits in the field @@ -71,10 +67,8 @@ * Return: true if @_val can fit inside @_mask, false if @_val is too big. */ #define FIELD_FIT(_mask, _val) \ - ({ \ - __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ - !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ - }) + (__BF_FIELD_CHECK(_mask, 0ULL, _val) + \ + !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask))) /** * FIELD_PREP() - prepare a bitfield element @@ -85,10 +79,8 @@ * be combined with other fields of the bitfield using logical OR. */ #define FIELD_PREP(_mask, _val) \ - ({ \ - __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \ - ((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask); \ - }) + (__BF_FIELD_CHECK(_mask, 0ULL, _val) + \ + (((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask))) /** * FIELD_GET() - extract a bitfield element @@ -99,10 +91,8 @@ * bitfield passed in as @_reg by masking and shifting it down. */ #define FIELD_GET(_mask, _reg) \ - ({ \ - __BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: "); \ - (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \ - }) + (__BF_FIELD_CHECK(_mask, _reg, 0U) + \ + ((typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)))) extern void __compiletime_error("value doesn't fit into mask") __field_overflow(void); -- 2.14.4
