It is useful for test modules that make use of random numbers to allow the exact same series of test cases to be repeated (e.g., after fixing a bug in the code being tested). For that, the test module needs to obtain its random numbers from a private state that can be seeded by a known seed, e.g. given as a module parameter (and using a random seed when that parameter is not given).
There's a few test modules I'm going to modify to follow that scheme. As preparation, add a _state variant of the existing prandom_u32_max(), and for convenience, also add a variant that produces a value in a given range.
Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk --- include/linux/prandom.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)
diff --git a/include/linux/prandom.h b/include/linux/prandom.h index aa16e6468f91e79e1f31..58ffcd56c705be34fb98 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -46,6 +46,35 @@ static inline u32 prandom_u32_max(u32 ep_ro) return (u32)(((u64) prandom_u32() * ep_ro) >> 32); }
+/** + * prandom_u32_max_state - get pseudo-random number in internal [0, hi) + * + * Like prandom_u32_max, but use the given state structure. + * @state: pointer to state structure + * @hi: (exclusive) upper bound + * + * Exception: If @hi == 0, this returns 0. + */ +static inline u32 prandom_u32_max_state(struct rnd_state *state, u32 hi) +{ + return ((u64)prandom_u32_state(state) * hi) >> 32; +} + +/** + * prandom_u32_range_state - get pseudo-random number in internal [lo, hi) + * + * @state: pointer to state structure + * @lo: (inclusive) lower bound + * @hi: (exclusive) upper bound + * + * Exception: If @lo == @hi, this returns @lo. Results are unspecified + * for @lo > @hi. + */ +static inline u32 prandom_u32_range_state(struct rnd_state *state, u32 lo, u32 hi) +{ + return lo + prandom_u32_max_state(state, hi - lo); +} + /* * Handle minimum values for seeds */