net/wimax/id-table.c

   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
  54 static DEFINE_SPINLOCK(wimax_id_table_lock);
  55 static 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  */
  67 void 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  */
  87 struct 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);
 103 found:
 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  */
 116 void 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  */
 131 void 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                 pr_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 }