wimax: generic device management (registration, deregistration, lookup)

Implements the basic life cycles of a 'struct wimax_dev', some common
generic netlink functionality for marshalling calls to user space,
and the device state machine.

For looking up net devices based on their generic netlink family IDs,
use a low overhead method that optimizes for the case where most
systems have a single WiMAX device, or at most, a very low number of
WiMAX adaptors.
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/wimax/id-table.c

+/*
+ * 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)\n", 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)\n", 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)\n", 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);
+			break;
+		}
+	}
+	if (wimax_dev == NULL)
+		d_printf(1, NULL, "wimax: no devices found with ifindex %d\n",
+			 ifindex);
+	spin_unlock(&wimax_id_table_lock);
+	d_fnend(3, NULL, "(info %p ifindex %d) = %p\n",
+		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.
+ */
+void wimax_id_table_release(void)
+{
+#ifndef CONFIG_BUG
+	return;
+#endif
+	struct wimax_dev *wimax_dev;
+
+	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\n",
+		       __func__, wimax_dev, wimax_dev->net_dev->ifindex);
+		WARN_ON(1);
+	}
+	spin_unlock(&wimax_id_table_lock);
+}