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/*
* Copyright © 2016 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
*/
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/types.h>
#include "i915_random.h"
u64 i915_prandom_u64_state(struct rnd_state *rnd)
{
u64 x;
x = prandom_u32_state(rnd);
x <<= 32;
x |= prandom_u32_state(rnd);
return x;
}
void i915_prandom_shuffle(void *arr, size_t elsz, size_t count,
struct rnd_state *state)
{
char stack[128];
if (WARN_ON(elsz > sizeof(stack) || count > U32_MAX))
return;
if (!elsz || !count)
return;
/* Fisher-Yates shuffle courtesy of Knuth */
while (--count) {
size_t swp;
swp = i915_prandom_u32_max_state(count + 1, state);
if (swp == count)
continue;
memcpy(stack, arr + count * elsz, elsz);
memcpy(arr + count * elsz, arr + swp * elsz, elsz);
memcpy(arr + swp * elsz, stack, elsz);
}
}
void i915_random_reorder(unsigned int *order, unsigned int count,
struct rnd_state *state)
{
i915_prandom_shuffle(order, sizeof(*order), count, state);
}
unsigned int *i915_random_order(unsigned int count, struct rnd_state *state)
{
unsigned int *order, i;
order = kmalloc_array(count, sizeof(*order),
GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
if (!order)
return order;
for (i = 0; i < count; i++)
order[i] = i;
i915_random_reorder(order, count, state);
return order;
}
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