drivers/gpu/drm/lib/drm_random.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/bitops.h>
   3 #include <linux/kernel.h>
   4 #include <linux/random.h>
   5 #include <linux/slab.h>
   6 #include <linux/types.h>
   7
   8 #include "drm_random.h"
   9
  10 static inline u32 drm_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
  11 {
  12         return upper_32_bits((u64)prandom_u32_state(state) * ep_ro);
  13 }
  14
  15 void drm_random_reorder(unsigned int *order, unsigned int count,
  16                         struct rnd_state *state)
  17 {
  18         unsigned int i, j;
  19
  20         for (i = 0; i < count; ++i) {
  21                 BUILD_BUG_ON(sizeof(unsigned int) > sizeof(u32));
  22                 j = drm_prandom_u32_max_state(count, state);
  23                 swap(order[i], order[j]);
  24         }
  25 }
  26 EXPORT_SYMBOL(drm_random_reorder);
  27
  28 unsigned int *drm_random_order(unsigned int count, struct rnd_state *state)
  29 {
  30         unsigned int *order, i;
  31
  32         order = kmalloc_array(count, sizeof(*order), GFP_KERNEL);
  33         if (!order)
  34                 return order;
  35
  36         for (i = 0; i < count; i++)
  37                 order[i] = i;
  38
  39         drm_random_reorder(order, count, state);
  40         return order;
  41 }
  42 EXPORT_SYMBOL(drm_random_order);