drivers/infiniband/hw/cxgb4/id_table.c

   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  */
  44 u32 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
  71 void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
  72 {
  73         unsigned long flags;
  74
  75         obj -= alloc->start;
  76
  77         spin_lock_irqsave(&alloc->lock, flags);
  78         clear_bit(obj, alloc->table);
  79         spin_unlock_irqrestore(&alloc->lock, flags);
  80 }
  81
  82 int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
  83                         u32 reserved, u32 flags)
  84 {
  85         int i;
  86
  87         alloc->start = start;
  88         alloc->flags = flags;
  89         if (flags & C4IW_ID_TABLE_F_RANDOM)
  90                 alloc->last = prandom_u32() % RANDOM_SKIP;
  91         else
  92                 alloc->last = 0;
  93         alloc->max  = num;
  94         spin_lock_init(&alloc->lock);
  95         alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
  96                                 GFP_KERNEL);
  97         if (!alloc->table)
  98                 return -ENOMEM;
  99
 100         bitmap_zero(alloc->table, num);
 101         if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
 102                 for (i = 0; i < reserved; ++i)
 103                         set_bit(i, alloc->table);
 104
 105         return 0;
 106 }
 107
 108 void c4iw_id_table_free(struct c4iw_id_table *alloc)
 109 {
 110         kfree(alloc->table);
 111 }