1 files changed, 32 insertions, 0 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2aa3d4b000e6..196d1ea86df0 100644
--- a/include/linux/kernel.h
+++ b/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))
@@ -193,6 +206,25 @@ extern int _cond_resched(void);
                 (__x < 0) ? -__x : __x;         \
         })
 
+/**
+ * reciprocal_scale - "scale" a value into range [0, ep_ro)
+ * @val: value
+ * @ep_ro: right open interval endpoint
+ *
+ * Perform a "reciprocal multiplication" in order to "scale" a value into
+ * range [0, ep_ro), where the upper interval endpoint is right-open.
+ * This is useful, e.g. for accessing a index of an array containing
+ * ep_ro elements, for example. Think of it as sort of modulus, only that
+ * the result isn't that of modulo. ;) Note that if initial input is a
+ * small value, then result will return 0.
+ *
+ * Return: a result based on val in interval [0, ep_ro).
+ */
+static inline u32 reciprocal_scale(u32 val, u32 ep_ro)
+{
+        return (u32)(((u64) val * ep_ro) >> 32);
+}
+
 #if defined(CONFIG_MMU) && \
         (defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP))
 void might_fault(void);