linux/net/wimax/id-table.c
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   1/*
   2 * Linux WiMAX
   3 * Mappping of generic netlink family IDs to net devices
   4 *
   5 *
   6 * Copyright (C) 2005-2006 Intel Corporation <linux-wimax@intel.com>
   7 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   8 *
   9 * This program is free software; you can redistribute it and/or
  10 * modify it under the terms of the GNU General Public License version
  11 * 2 as published by the Free Software Foundation.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program; if not, write to the Free Software
  20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  21 * 02110-1301, USA.
  22 *
  23 *
  24 * We assign a single generic netlink family ID to each device (to
  25 * simplify lookup).
  26 *
  27 * We need a way to map family ID to a wimax_dev pointer.
  28 *
  29 * The idea is to use a very simple lookup. Using a netlink attribute
  30 * with (for example) the interface name implies a heavier search over
  31 * all the network devices; seemed kind of a waste given that we know
  32 * we are looking for a WiMAX device and that most systems will have
  33 * just a single WiMAX adapter.
  34 *
  35 * We put all the WiMAX devices in the system in a linked list and
  36 * match the generic link family ID against the list.
  37 *
  38 * By using a linked list, the case of a single adapter in the system
  39 * becomes (almost) no overhead, while still working for many more. If
  40 * it ever goes beyond two, I'll be surprised.
  41 */
  42#include <linux/device.h>
  43#include <net/genetlink.h>
  44#include <linux/netdevice.h>
  45#include <linux/list.h>
  46#include <linux/wimax.h>
  47#include "wimax-internal.h"
  48
  49
  50#define D_SUBMODULE id_table
  51#include "debug-levels.h"
  52
  53
  54static DEFINE_SPINLOCK(wimax_id_table_lock);
  55static struct list_head wimax_id_table = LIST_HEAD_INIT(wimax_id_table);
  56
  57
  58/*
  59 * wimax_id_table_add - add a gennetlink familiy ID / wimax_dev mapping
  60 *
  61 * @wimax_dev: WiMAX device descriptor to associate to the Generic
  62 *     Netlink family ID.
  63 *
  64 * Look for an empty spot in the ID table; if none found, double the
  65 * table's size and get the first spot.
  66 */
  67void wimax_id_table_add(struct wimax_dev *wimax_dev)
  68{
  69        d_fnstart(3, NULL, "(wimax_dev %p)\n", wimax_dev);
  70        spin_lock(&wimax_id_table_lock);
  71        list_add(&wimax_dev->id_table_node, &wimax_id_table);
  72        spin_unlock(&wimax_id_table_lock);
  73        d_fnend(3, NULL, "(wimax_dev %p)\n", wimax_dev);
  74}
  75
  76
  77/*
  78 * wimax_get_netdev_by_info - lookup a wimax_dev from the gennetlink info
  79 *
  80 * The generic netlink family ID has been filled out in the
  81 * nlmsghdr->nlmsg_type field, so we pull it from there, look it up in
  82 * the mapping table and reference the wimax_dev.
  83 *
  84 * When done, the reference should be dropped with
  85 * 'dev_put(wimax_dev->net_dev)'.
  86 */
  87struct wimax_dev *wimax_dev_get_by_genl_info(
  88        struct genl_info *info, int ifindex)
  89{
  90        struct wimax_dev *wimax_dev = NULL;
  91
  92        d_fnstart(3, NULL, "(info %p ifindex %d)\n", info, ifindex);
  93        spin_lock(&wimax_id_table_lock);
  94        list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
  95                if (wimax_dev->net_dev->ifindex == ifindex) {
  96                        dev_hold(wimax_dev->net_dev);
  97                        goto found;
  98                }
  99        }
 100        wimax_dev = NULL;
 101        d_printf(1, NULL, "wimax: no devices found with ifindex %d\n",
 102                 ifindex);
 103found:
 104        spin_unlock(&wimax_id_table_lock);
 105        d_fnend(3, NULL, "(info %p ifindex %d) = %p\n",
 106                info, ifindex, wimax_dev);
 107        return wimax_dev;
 108}
 109
 110
 111/*
 112 * wimax_id_table_rm - Remove a gennetlink familiy ID / wimax_dev mapping
 113 *
 114 * @id: family ID to remove from the table
 115 */
 116void wimax_id_table_rm(struct wimax_dev *wimax_dev)
 117{
 118        spin_lock(&wimax_id_table_lock);
 119        list_del_init(&wimax_dev->id_table_node);
 120        spin_unlock(&wimax_id_table_lock);
 121}
 122
 123
 124/*
 125 * Release the gennetlink family id / mapping table
 126 *
 127 * On debug, verify that the table is empty upon removal. We want the
 128 * code always compiled, to ensure it doesn't bit rot. It will be
 129 * compiled out if CONFIG_BUG is disabled.
 130 */
 131void wimax_id_table_release(void)
 132{
 133        struct wimax_dev *wimax_dev;
 134
 135#ifndef CONFIG_BUG
 136        return;
 137#endif
 138        spin_lock(&wimax_id_table_lock);
 139        list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
 140                printk(KERN_ERR "BUG: %s wimax_dev %p ifindex %d not cleared\n",
 141                       __func__, wimax_dev, wimax_dev->net_dev->ifindex);
 142                WARN_ON(1);
 143        }
 144        spin_unlock(&wimax_id_table_lock);
 145}
 146
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