/*
   * Linux WiMAX
   * Mappping of generic netlink family IDs to net devices
   *
   *
   * Copyright (C) 2005-2006 Intel Corporation <linux-wimax@intel.com>
   * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License version
   * 2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   * 02110-1301, USA.
   *
   *
   * We assign a single generic netlink family ID to each device (to
   * simplify lookup).
   *
   * We need a way to map family ID to a wimax_dev pointer.
   *
   * The idea is to use a very simple lookup. Using a netlink attribute
   * with (for example) the interface name implies a heavier search over
   * all the network devices; seemed kind of a waste given that we know
   * we are looking for a WiMAX device and that most systems will have
   * just a single WiMAX adapter.
   *
   * We put all the WiMAX devices in the system in a linked list and
   * match the generic link family ID against the list.
   *
   * By using a linked list, the case of a single adapter in the system
   * becomes (almost) no overhead, while still working for many more. If
   * it ever goes beyond two, I'll be surprised.
   */
  #include <linux/device.h>
  #include <net/genetlink.h>
  #include <linux/netdevice.h>
  #include <linux/list.h>
  #include <linux/wimax.h>
  #include "wimax-internal.h"
  
  
  #define D_SUBMODULE id_table
  #include "debug-levels.h"
  
  
  static DEFINE_SPINLOCK(wimax_id_table_lock);
  static struct list_head wimax_id_table = LIST_HEAD_INIT(wimax_id_table);
  
  
  /*
   * wimax_id_table_add - add a gennetlink familiy ID / wimax_dev mapping
   *
   * @wimax_dev: WiMAX device descriptor to associate to the Generic
   *     Netlink family ID.
   *
   * Look for an empty spot in the ID table; if none found, double the
   * table's size and get the first spot.
   */
  void wimax_id_table_add(struct wimax_dev *wimax_dev)
  {
  	d_fnstart(3, NULL, "(wimax_dev %p)
  ", wimax_dev);
  	spin_lock(&wimax_id_table_lock);
  	list_add(&wimax_dev->id_table_node, &wimax_id_table);
  	spin_unlock(&wimax_id_table_lock);
  	d_fnend(3, NULL, "(wimax_dev %p)
  ", wimax_dev);
  }
  
  
  /*
   * wimax_get_netdev_by_info - lookup a wimax_dev from the gennetlink info
   *
   * The generic netlink family ID has been filled out in the
   * nlmsghdr->nlmsg_type field, so we pull it from there, look it up in
   * the mapping table and reference the wimax_dev.
   *
   * When done, the reference should be dropped with
   * 'dev_put(wimax_dev->net_dev)'.
   */
  struct wimax_dev *wimax_dev_get_by_genl_info(
  	struct genl_info *info, int ifindex)
  {
  	struct wimax_dev *wimax_dev = NULL;
  
  	d_fnstart(3, NULL, "(info %p ifindex %d)
  ", info, ifindex);
  	spin_lock(&wimax_id_table_lock);
  	list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
  		if (wimax_dev->net_dev->ifindex == ifindex) {
  			dev_hold(wimax_dev->net_dev);
  			goto found;
  		}
  	}
  	wimax_dev = NULL;
  	d_printf(1, NULL, "wimax: no devices found with ifindex %d
  ",
  		 ifindex);
  found:
  	spin_unlock(&wimax_id_table_lock);
  	d_fnend(3, NULL, "(info %p ifindex %d) = %p
  ",
  		info, ifindex, wimax_dev);
  	return wimax_dev;
  }
  
  
  /*
   * wimax_id_table_rm - Remove a gennetlink familiy ID / wimax_dev mapping
   *
   * @id: family ID to remove from the table
   */
  void wimax_id_table_rm(struct wimax_dev *wimax_dev)
  {
  	spin_lock(&wimax_id_table_lock);
  	list_del_init(&wimax_dev->id_table_node);
  	spin_unlock(&wimax_id_table_lock);
  }
  
  
  /*
   * Release the gennetlink family id / mapping table
   *
   * On debug, verify that the table is empty upon removal. We want the
   * code always compiled, to ensure it doesn't bit rot. It will be
   * compiled out if CONFIG_BUG is disabled.
   */
  void wimax_id_table_release(void)
  {
  	struct wimax_dev *wimax_dev;
  
  #ifndef CONFIG_BUG
  	return;
  #endif
  	spin_lock(&wimax_id_table_lock);
  	list_for_each_entry(wimax_dev, &wimax_id_table, id_table_node) {
  		printk(KERN_ERR "BUG: %s wimax_dev %p ifindex %d not cleared
  ",
  		       __func__, wimax_dev, wimax_dev->net_dev->ifindex);
  		WARN_ON(1);
  	}
  	spin_unlock(&wimax_id_table_lock);
  }