From: Vincent Mailhol mailhol.vincent@wanadoo.fr
[ Upstream commit 19408200c094858d952a90bf4977733dc89a4df5 ]
Add GENMASK_TYPE() which generalizes __GENMASK() to support different types, and implement fixed-types versions of GENMASK() based on it. The fixed-type version allows more strict checks to the min/max values accepted, which is useful for defining registers like implemented by i915 and xe drivers with their REG_GENMASK*() macros.
The strict checks rely on shift-count-overflow compiler check to fail the build if a number outside of the range allowed is passed. Example:
#define FOO_MASK GENMASK_U32(33, 4)
will generate a warning like:
include/linux/bits.h:51:27: error: right shift count >= width of type [-Werror=shift-count-overflow] 51 | type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h))))) | ^~
The result is casted to the corresponding fixed width type. For example, GENMASK_U8() returns an u8. Note that because of the C promotion rules, GENMASK_U8() and GENMASK_U16() will immediately be promoted to int if used in an expression. Regardless, the main goal is not to get the correct type, but rather to enforce more checks at compile time.
While GENMASK_TYPE() is crafted to cover all variants, including the already existing GENMASK(), GENMASK_ULL() and GENMASK_U128(), for the moment, only use it for the newly introduced GENMASK_U*(). The consolidation will be done in a separate change.
Co-developed-by: Yury Norov yury.norov@gmail.com Signed-off-by: Lucas De Marchi lucas.demarchi@intel.com Acked-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Vincent Mailhol mailhol.vincent@wanadoo.fr Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Yury Norov yury.norov@gmail.com Stable-dep-of: 2ba5772e530f ("gpio: idio-16: Define fixed direction of the GPIO lines") Signed-off-by: William Breathitt Gray wbg@kernel.org --- include/linux/bitops.h | 1 - include/linux/bits.h | 30 ++++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index ba35bbf07798..65d084abbc2c 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -8,7 +8,6 @@
#include <uapi/linux/kernel.h>
-#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) #define BITS_TO_LONGS(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long)) #define BITS_TO_U64(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u64)) #define BITS_TO_U32(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u32)) diff --git a/include/linux/bits.h b/include/linux/bits.h index 18143b536d9d..b48aa3209c2e 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -12,6 +12,7 @@ #define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG)) #define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG) #define BITS_PER_BYTE 8 +#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
/* * Create a contiguous bitmask starting at bit position @l and ending at @@ -20,11 +21,40 @@ */ #if !defined(__ASSEMBLY__)
+/* + * Missing asm support + * + * GENMASK_U*() depend on BITS_PER_TYPE() which relies on sizeof(), + * something not available in asm. Nevertheless, fixed width integers is a C + * concept. Assembly code can rely on the long and long long versions instead. + */ + #include <linux/build_bug.h> +#include <linux/overflow.h> #define GENMASK_INPUT_CHECK(h, l) \ (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ __is_constexpr((l) > (h)), (l) > (h), 0)))
+/* + * Generate a mask for the specified type @t. Additional checks are made to + * guarantee the value returned fits in that type, relying on + * -Wshift-count-overflow compiler check to detect incompatible arguments. + * For example, all these create build errors or warnings: + * + * - GENMASK(15, 20): wrong argument order + * - GENMASK(72, 15): doesn't fit unsigned long + * - GENMASK_U32(33, 15): doesn't fit in a u32 + */ +#define GENMASK_TYPE(t, h, l) \ + ((t)(GENMASK_INPUT_CHECK(h, l) + \ + (type_max(t) << (l) & \ + type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h))))) + +#define GENMASK_U8(h, l) GENMASK_TYPE(u8, h, l) +#define GENMASK_U16(h, l) GENMASK_TYPE(u16, h, l) +#define GENMASK_U32(h, l) GENMASK_TYPE(u32, h, l) +#define GENMASK_U64(h, l) GENMASK_TYPE(u64, h, l) + #else /* defined(__ASSEMBLY__) */
/*