From: Yury Norov <yury.no...@gmail.com>
Generalize __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:41:31: error: left shift count >= width of type
[-Werror=shift-count-overflow]
41 | (((t)~0ULL - ((t)(1) << (l)) + 1) & \
| ^~
Signed-off-by: Yury Norov <yury.no...@gmail.com>
Signed-off-by: Lucas De Marchi <lucas.demar...@intel.com>
Acked-by: Jani Nikula <jani.nik...@intel.com>
---
include/linux/bitops.h | 1 -
include/linux/bits.h | 32 ++++++++++++++++++++++----------
2 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 2ba557e067fe..1db50c69cfdb 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -15,7 +15,6 @@
# define aligned_byte_mask(n) (~0xffUL << (BITS_PER_LONG - 8 - 8*(n)))
#endif
-#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 7c0cf5031abe..bd56f32de44e 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -6,6 +6,8 @@
#include <vdso/bits.h>
#include <asm/bitsperlong.h>
+#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
+
#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
@@ -30,16 +32,26 @@
#define GENMASK_INPUT_CHECK(h, l) 0
#endif
-#define __GENMASK(h, l) \
- (((~UL(0)) - (UL(1) << (l)) + 1) & \
- (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
-#define GENMASK(h, l) \
- (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
+/*
+ * Generate a mask for the specified type @t. Additional checks are made to
+ * guarantee the value returned fits in that type, relying on
+ * shift-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(t, h, l) \
+ (GENMASK_INPUT_CHECK(h, l) + \
+ (((t)~0ULL - ((t)(1) << (l)) + 1) & \
+ ((t)~0ULL >> (BITS_PER_TYPE(t) - 1 - (h)))))
-#define __GENMASK_ULL(h, l) \
- (((~ULL(0)) - (ULL(1) << (l)) + 1) & \
- (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
-#define GENMASK_ULL(h, l) \
- (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
+#define GENMASK(h, l) __GENMASK(unsigned long, h, l)
+#define GENMASK_ULL(h, l) __GENMASK(unsigned long long, h, l)
+#define GENMASK_U8(h, l) __GENMASK(u8, h, l)
+#define GENMASK_U16(h, l) __GENMASK(u16, h, l)
+#define GENMASK_U32(h, l) __GENMASK(u32, h, l)
+#define GENMASK_U64(h, l) __GENMASK(u64, h, l)
#endif /* __LINUX_BITS_H */
--
2.43.0
