From a33d42dd03352d2e9d3d2c00bfa435c7a5ebab25 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 22 Dec 2016 08:36:08 +0000 Subject: drm: Add a simple generator of random permutations When testing, we want a random but yet reproducible order in which to process elements. Here we create an array which is a random (using the Tausworthe PRNG) permutation of the order in which to execute. Note these are simple helpers intended to be merged upstream in lib/ v2: Tidier code by David Herrmann v3: Add reminder that this code is intended to be temporary, with at least the bulk of the prandom changes going to lib/ Signed-off-by: Chris Wilson Cc: Joonas Lahtinen Cc: David Herrmann Reviewed-by: Joonas Lahtinen Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-6-chris@chris-wilson.co.uk --- drivers/gpu/drm/lib/drm_random.c | 41 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 drivers/gpu/drm/lib/drm_random.c (limited to 'drivers/gpu/drm/lib/drm_random.c') diff --git a/drivers/gpu/drm/lib/drm_random.c b/drivers/gpu/drm/lib/drm_random.c new file mode 100644 index 000000000000..7b12a68c3b54 --- /dev/null +++ b/drivers/gpu/drm/lib/drm_random.c @@ -0,0 +1,41 @@ +#include +#include +#include +#include +#include + +#include "drm_random.h" + +static inline u32 drm_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state) +{ + return upper_32_bits((u64)prandom_u32_state(state) * ep_ro); +} + +void drm_random_reorder(unsigned int *order, unsigned int count, + struct rnd_state *state) +{ + unsigned int i, j; + + for (i = 0; i < count; ++i) { + BUILD_BUG_ON(sizeof(unsigned int) > sizeof(u32)); + j = drm_prandom_u32_max_state(count, state); + swap(order[i], order[j]); + } +} +EXPORT_SYMBOL(drm_random_reorder); + +unsigned int *drm_random_order(unsigned int count, struct rnd_state *state) +{ + unsigned int *order, i; + + order = kmalloc_array(count, sizeof(*order), GFP_TEMPORARY); + if (!order) + return order; + + for (i = 0; i < count; i++) + order[i] = i; + + drm_random_reorder(order, count, state); + return order; +} +EXPORT_SYMBOL(drm_random_order); -- cgit v1.2.3