net/wimax/id-table.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Linux WiMAX
   4  * Mappping of generic netlink family IDs to net devices
   5  *
   6  * Copyright (C) 2005-2006 Intel Corporation <linux-wimax@intel.com>
   7  * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   8  *
   9  * We assign a single generic netlink family ID to each device (to
  10  * simplify lookup).
  11  *
  12  * We need a way to map family ID to a wimax_dev pointer.
  13  *
  14  * The idea is to use a very simple lookup. Using a netlink attribute
  15  * with (for example) the interface name implies a heavier search over
  16  * all the network devices; seemed kind of a waste given that we know
  17  * we are looking for a WiMAX device and that most systems will have
  18  * just a single WiMAX adapter.
  19  *
  20  * We put all the WiMAX devices in the system in a linked list and
  21  * match the generic link family ID against the list.
  22  *
  23  * By using a linked list, the case of a single adapter in the system
  24  * becomes (almost) no overhead, while still working for many more. If
  25  * it ever goes beyond two, I'll be surprised.
  26  */
  27 #include <linux/device.h>
  28 #include <net/genetlink.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/list.h>
  31 #include <linux/wimax.h>
  32 #include "wimax-internal.h"
  33
  34
  35 #define D_SUBMODULE id_table
  36 #include "debug-levels.h"
  37
  38
  39 static DEFINE_SPINLOCK(wimax_id_table_lock);
  40 static struct list_head wimax_id_table = LIST_HEAD_INIT(wimax_id_table);
  41
  42
  43 /*
  44  * wimax_id_table_add - add a gennetlink familiy ID / wimax_dev mapping
  45  *
  46  * @wimax_dev: WiMAX device descriptor to associate to the Generic
  47  *     Netlink family ID.
  48  *
  49  * Look for an empty spot in the ID table; if none found, double the
  50  * table's size and get the first spot.
  51  */
  52 void wimax_id_table_add(struct wimax_dev *wimax_dev)
  53 {
  54         d_fnstart(3, NULL, "(wimax_dev %p)\n", wimax_dev);
  55         spin_lock(&wimax_id_table_lock);
  56         list_add(&wimax_dev->id_table_node, &wimax_id_table);
  57         spin_unlock(&wimax_id_table_lock);
  58         d_fnend(3, NULL, "(wimax_dev %p)\n", wimax_dev);
  59 }
  60
  61
  62 /*
  63  * wimax_get_netdev_by_info - lookup a wimax_dev from the gennetlink info
  64  *
  65  * The generic netlink family ID has been filled out in the
  66  * nlmsghdr->nlmsg_type field, so we pull it from there, look it up in
  67  * the mapping table and reference the wimax_dev.
  68  *
  69  * When done, the reference should be dropped with
  70  * 'dev_put(wimax_dev->net_dev)'.
  71  */
  72 struct wimax_dev *wimax_dev_get_by_genl_info(
  73         struct genl_info *info, int ifindex)
  74 {
  75         struct wimax_dev *wimax_dev = NULL;
  76
  77         d_fnstart(3, NULL, "(info %p ifindex %d)\n", info, ifindex);
  78         spin_lock(&wimax_id_table_lock);
  79         list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
  80                 if (wimax_dev->net_dev->ifindex == ifindex) {
  81                         dev_hold(wimax_dev->net_dev);
  82                         goto found;
  83                 }
  84         }
  85         wimax_dev = NULL;
  86         d_printf(1, NULL, "wimax: no devices found with ifindex %d\n",
  87                  ifindex);
  88 found:
  89         spin_unlock(&wimax_id_table_lock);
  90         d_fnend(3, NULL, "(info %p ifindex %d) = %p\n",
  91                 info, ifindex, wimax_dev);
  92         return wimax_dev;
  93 }
  94
  95
  96 /*
  97  * wimax_id_table_rm - Remove a gennetlink familiy ID / wimax_dev mapping
  98  *
  99  * @id: family ID to remove from the table
 100  */
 101 void wimax_id_table_rm(struct wimax_dev *wimax_dev)
 102 {
 103         spin_lock(&wimax_id_table_lock);
 104         list_del_init(&wimax_dev->id_table_node);
 105         spin_unlock(&wimax_id_table_lock);
 106 }
 107
 108
 109 /*
 110  * Release the gennetlink family id / mapping table
 111  *
 112  * On debug, verify that the table is empty upon removal. We want the
 113  * code always compiled, to ensure it doesn't bit rot. It will be
 114  * compiled out if CONFIG_BUG is disabled.
 115  */
 116 void wimax_id_table_release(void)
 117 {
 118         struct wimax_dev *wimax_dev;
 119
 120 #ifndef CONFIG_BUG
 121         return;
 122 #endif
 123         spin_lock(&wimax_id_table_lock);
 124         list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
 125                 pr_err("BUG: %s wimax_dev %p ifindex %d not cleared\n",
 126                        __func__, wimax_dev, wimax_dev->net_dev->ifindex);
 127                 WARN_ON(1);
 128         }
 129         spin_unlock(&wimax_id_table_lock);
 130 }