LXR linux/drivers/infiniband/hw/cxgb4/id

   1/*
   2 * Copyright (c) 2011 Chelsio Communications.  All rights reserved.
   3 *
   4 * This software is available to you under a choice of one of two
   5 * licenses.  You may choose to be licensed under the terms of the GNU
   6 * General Public License (GPL) Version 2, available from the file
   7 * COPYING in the main directory of this source tree, or the
   8 * OpenIB.org BSD license below:
   9 *
  10 *     Redistribution and use in source and binary forms, with or
  11 *     without modification, are permitted provided that the following
  12 *     conditions are met:
  13 *
  14 *      - Redistributions of source code must retain the above
  15 *        copyright notice, this list of conditions and the following
  16 *        disclaimer.
  17 *
  18 *      - Redistributions in binary form must reproduce the above
  19 *        copyright notice, this list of conditions and the following
  20 *        disclaimer in the documentation and/or other materials
  21 *        provided with the distribution.
  22 *
  23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30 * SOFTWARE.
  31 */
  32#include <linux/kernel.h>
  33#include <linux/random.h>
  34#include "iw_cxgb4.h"
  35
  36#define RANDOM_SKIP 16
  37
  38/*
  39 * Trivial bitmap-based allocator. If the random flag is set, the
  40 * allocator is designed to:
  41 * - pseudo-randomize the id returned such that it is not trivially predictable.
  42 * - avoid reuse of recently used id (at the expense of predictability)
  43 */
  44u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
  45{
  46        unsigned long flags;
  47        u32 obj;
  48
  49        spin_lock_irqsave(&alloc->lock, flags);
  50
  51        obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
  52        if (obj >= alloc->max)
  53                obj = find_first_zero_bit(alloc->table, alloc->max);
  54
  55        if (obj < alloc->max) {
  56                if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
  57                        alloc->last += prandom_u32() % RANDOM_SKIP;
  58                else
  59                        alloc->last = obj + 1;
  60                if (alloc->last >= alloc->max)
  61                        alloc->last = 0;
  62                set_bit(obj, alloc->table);
  63                obj += alloc->start;
  64        } else
  65                obj = -1;
  66
  67        spin_unlock_irqrestore(&alloc->lock, flags);
  68        return obj;
  69}
  70
  71void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
  72{
  73        unsigned long flags;
  74
  75        obj -= alloc->start;
  76        BUG_ON((int)obj < 0);
  77
  78        spin_lock_irqsave(&alloc->lock, flags);
  79        clear_bit(obj, alloc->table);
  80        spin_unlock_irqrestore(&alloc->lock, flags);
  81}
  82
  83int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
  84                        u32 reserved, u32 flags)
  85{
  86        int i;
  87
  88        alloc->start = start;
  89        alloc->flags = flags;
  90        if (flags & C4IW_ID_TABLE_F_RANDOM)
  91                alloc->last = prandom_u32() % RANDOM_SKIP;
  92        else
  93                alloc->last = 0;
  94        alloc->max  = num;
  95        spin_lock_init(&alloc->lock);
  96        alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
  97                                GFP_KERNEL);
  98        if (!alloc->table)
  99                return -ENOMEM;
 100
 101        bitmap_zero(alloc->table, num);
 102        if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
 103                for (i = 0; i < reserved; ++i)
 104                        set_bit(i, alloc->table);
 105
 106        return 0;
 107}
 108
 109void c4iw_id_table_free(struct c4iw_id_table *alloc)
 110{
 111        kfree(alloc->table);
 112}
 113