[PATCH 2/3] linux/bits.h: Add fixed-width GENMASK and BIT macros

[Lucas De Marchi]

Add GENMASK_U32(), GENMASK_U16() and GENMASK_U8()  macros to create
masks for fixed-width types and also the corresponding BIT_U32(),
BIT_U16() and BIT_U8().

All of those depend on a new "U" suffix added to the integer constant.
Due to naming clashes it's better to call the macro U32. Since C doesn't
have a proper suffix for short and char types, the U16 and U18 variants
just use U32 with one additional check in the BIT_* macros to make
sure the compiler gives an error when the those types overflow.

The following test source is now possible and also breaks the build
when the comments are removed:

	$ cat mask.c
	#include <linux/types.h>
	#include <linux/bits.h>

	static const u32 a = GENMASK_U32(31, 0);
	// static const u32 a2 = GENMASK_U32(32, 0);
	static const u16 b = GENMASK_U16(15, 0);
	// static const u16 b2 = GENMASK_U16(1, 0);
	static const u8 c = GENMASK_U8(7, 0);
	// static const u8 c2 = GENMASK_U8(8, 0);

	static const u32 x = BIT_U32(31);
	// static const u32 x2 = BIT_U32(32);
	static const u16 y = BIT_U16(15);
	//static const u16 y2 = BIT_U16(16);
	static const u8 z = BIT_U8(7);
	// static const u8 z2 = BIT_U8(8);

Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
---
 include/linux/bits.h       | 22 ++++++++++++++++++++++
 include/uapi/linux/const.h |  2 ++
 include/vdso/const.h       |  1 +
 3 files changed, 25 insertions(+)

diff --git a/include/linux/bits.h b/include/linux/bits.h
index 7c0cf5031abe..ff4786c99b8c 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -42,4 +42,26 @@
 #define GENMASK_ULL(h, l) \
 	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
 
+#define __GENMASK_U32(h, l) \
+	(((~U32(0)) - (U32(1) << (l)) + 1) & \
+	 (~U32(0) >> (32 - 1 - (h))))
+#define GENMASK_U32(h, l) \
+	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_U32(h, l))
+
+#define __GENMASK_U16(h, l) \
+	((U32(0xffff) - (U32(1) << (l)) + 1) & \
+	 (U32(0xffff) >> (16 - 1 - (h))))
+#define GENMASK_U16(h, l) \
+	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_U16(h, l))
+
+#define __GENMASK_U8(h, l) \
+	(((U32(0xff)) - (U32(1) << (l)) + 1) & \
+	 (U32(0xff) >> (8 - 1 - (h))))
+#define GENMASK_U8(h, l) \
+	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_U8(h, l))
+
+#define BIT_U32(nr)	_BITU32(nr)
+#define BIT_U16(nr)	(GENMASK_INPUT_CHECK(16 - 1, nr) + (U32(1) << (nr)))
+#define BIT_U8(nr)	(GENMASK_INPUT_CHECK(32 - 1, nr) + (U32(1) << (nr)))
+
 #endif	/* __LINUX_BITS_H */
diff --git a/include/uapi/linux/const.h b/include/uapi/linux/const.h
index a429381e7ca5..3a4e152520f4 100644
--- a/include/uapi/linux/const.h
+++ b/include/uapi/linux/const.h
@@ -22,9 +22,11 @@
 #define _AT(T,X)	((T)(X))
 #endif
 
+#define _U32(x)		(_AC(x, U))
 #define _UL(x)		(_AC(x, UL))
 #define _ULL(x)		(_AC(x, ULL))
 
+#define _BITU32(x)	(_U32(1) << (x))
 #define _BITUL(x)	(_UL(1) << (x))
 #define _BITULL(x)	(_ULL(1) << (x))
 
diff --git a/include/vdso/const.h b/include/vdso/const.h
index 94b385ad438d..417384a9795b 100644
--- a/include/vdso/const.h
+++ b/include/vdso/const.h
@@ -4,6 +4,7 @@
 
 #include <uapi/linux/const.h>
 
+#define U32(x)		(_U32(x))
 #define UL(x)		(_UL(x))
 #define ULL(x)		(_ULL(x))
 
-- 
2.40.1