Implement fixed-type BIT() to help drivers add stricter checks, like was done for GENMASK. Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx> --- include/linux/bits.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/linux/bits.h b/include/linux/bits.h index bd56f32de44e..811846ce110e 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -24,12 +24,16 @@ #define GENMASK_INPUT_CHECK(h, l) \ (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ __is_constexpr((l) > (h)), (l) > (h), 0))) +#define BIT_INPUT_CHECK(type, b) \ + ((BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ + __is_constexpr(b), (b) >= BITS_PER_TYPE(type), 0)))) #else /* * BUILD_BUG_ON_ZERO is not available in h files included from asm files, * disable the input check if that is the case. */ #define GENMASK_INPUT_CHECK(h, l) 0 +#define BIT_INPUT_CHECK(type, b) 0 #endif /* @@ -54,4 +58,17 @@ #define GENMASK_U32(h, l) __GENMASK(u32, h, l) #define GENMASK_U64(h, l) __GENMASK(u64, h, l) +/* + * Fixed-type variants of BIT(), with additional checks like __GENMASK(). The + * following examples generate compiler warnings due to shift-count-overflow: + * + * - BIT_U8(8) + * - BIT_U32(-1) + * - BIT_U32(40) + */ +#define BIT_U8(b) ((u8)(BIT_INPUT_CHECK(u8, b) + BIT(b))) +#define BIT_U16(b) ((u16)(BIT_INPUT_CHECK(u16, b) + BIT(b))) +#define BIT_U32(b) ((u32)(BIT_INPUT_CHECK(u32, b) + BIT(b))) +#define BIT_U64(b) ((u64)(BIT_INPUT_CHECK(u64, b) + BIT(b))) + #endif /* __LINUX_BITS_H */ -- 2.43.0
