kernel.h: define u8, s8, u32, etc. limits

Create constants that define the maximum and minimum values
representable by the kernel types u8, s8, u16, s16, and so on.

Signed-off-by: Alex Elder <elder@linaro.org>
Cc: Sage Weil <sage@inktank.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -29,6 +29,19 @@
 #define ULLONG_MAX	(~0ULL)
 #define SIZE_MAX	(~(size_t)0)
 
+#define U8_MAX		((u8)~0U)
+#define S8_MAX		((s8)(U8_MAX>>1))
+#define S8_MIN		((s8)(-S8_MAX - 1))
+#define U16_MAX		((u16)~0U)
+#define S16_MAX		((s16)(U16_MAX>>1))
+#define S16_MIN		((s16)(-S16_MAX - 1))
+#define U32_MAX		((u32)~0U)
+#define S32_MAX		((s32)(U32_MAX>>1))
+#define S32_MIN		((s32)(-S32_MAX - 1))
+#define U64_MAX		((u64)~0ULL)
+#define S64_MAX		((s64)(U64_MAX>>1))
+#define S64_MIN		((s64)(-S64_MAX - 1))
+
 #define STACK_MAGIC	0xdeadbeef
 
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))