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authorChris Zankel2014-02-24 00:34:36 -0800
committerChris Zankel2014-02-24 00:34:36 -0800
commitb3fdfc1b4b641d372e35ced98814289bc60bc5d1 (patch)
tree5f11d5ba885031dde45690745646519fb887f447 /include/linux/random.h
parentc0e50d41126e4786d9cf1105bdf783e55c99f915 (diff)
parentf63b6d7555cd4064554b39da4d44c4cbbc9d6a4a (diff)
Merge tag 'xtensa-for-next-20140221-1' into for_next
Xtensa fixes for 3.14: - allow booting xtfpga on boards with new uBoot and >128MBytes memory; - drop nonexistent GPIO32 support from fsf variant; - don't select USE_GENERIC_SMP_HELPERS; - enable common clock framework support, set up ethoc clock on xtfpga; - wire up sched_setattr and sched_getattr syscalls. Signed-off-by: Chris Zankel <chris@zankel.net>
Diffstat (limited to 'include/linux/random.h')
-rw-r--r--include/linux/random.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/random.h b/include/linux/random.h
index 4002b3df4c85..1cfce0e24dbd 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -8,7 +8,6 @@
#include <uapi/linux/random.h>
-
extern void add_device_randomness(const void *, unsigned int);
extern void add_input_randomness(unsigned int type, unsigned int code,
unsigned int value);
@@ -38,6 +37,23 @@ struct rnd_state {
u32 prandom_u32_state(struct rnd_state *state);
void prandom_bytes_state(struct rnd_state *state, void *buf, int nbytes);
+/**
+ * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)
+ * @ep_ro: right open interval endpoint
+ *
+ * Returns a pseudo-random number that is in interval [0, ep_ro). Note
+ * that the result depends on PRNG being well distributed in [0, ~0U]
+ * u32 space. Here we use maximally equidistributed combined Tausworthe
+ * generator, that is, prandom_u32(). This is useful when requesting a
+ * random index of an array containing ep_ro elements, for example.
+ *
+ * Returns: pseudo-random number in interval [0, ep_ro)
+ */
+static inline u32 prandom_u32_max(u32 ep_ro)
+{
+ return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
+}
+
/*
* Handle minimum values for seeds
*/