drivers/connector/connector.c - kernel/msm-4.19 - Gitiles

 /*
  * 	connector.c
  *
  * 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
  * All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/skbuff.h>
 #include <linux/netlink.h>
 #include <linux/moduleparam.h>
 #include <linux/connector.h>
 #include <linux/mutex.h>

 #include <net/sock.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");

 static u32 cn_idx = CN_IDX_CONNECTOR;
 static u32 cn_val = CN_VAL_CONNECTOR;

 module_param(cn_idx, uint, 0);
 module_param(cn_val, uint, 0);
 MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
 MODULE_PARM_DESC(cn_val, "Connector's main device val.");

 static DEFINE_MUTEX(notify_lock);
 static LIST_HEAD(notify_list);

 static struct cn_dev cdev;

 int cn_already_initialized = 0;

 /*
  * msg->seq and msg->ack are used to determine message genealogy.
  * When someone sends message it puts there locally unique sequence
  * and random acknowledge numbers.  Sequence number may be copied into
  * nlmsghdr->nlmsg_seq too.
  *
  * Sequence number is incremented with each message to be sent.
  *
  * If we expect reply to our message then the sequence number in
  * received message MUST be the same as in original message, and
  * acknowledge number MUST be the same + 1.
  *
  * If we receive a message and its sequence number is not equal to the
  * one we are expecting then it is a new message.
  *
  * If we receive a message and its sequence number is the same as one
  * we are expecting but it's acknowledgement number is not equal to
  * the acknowledgement number in the original message + 1, then it is
  * a new message.
  *
  */
 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
 {
 	struct cn_callback_entry *__cbq;
 	unsigned int size;
 	struct sk_buff *skb;
 	struct nlmsghdr *nlh;
 	struct cn_msg *data;
 	struct cn_dev *dev = &cdev;
 	u32 group = 0;
 	int found = 0;

 	if (!__group) {
 		spin_lock_bh(&dev->cbdev->queue_lock);
 		list_for_each_entry(__cbq, &dev->cbdev->queue_list,
 				    callback_entry) {
 			if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 				found = 1;
 				group = __cbq->group;
 			}
 		}
 		spin_unlock_bh(&dev->cbdev->queue_lock);

 		if (!found)
 			return -ENODEV;
 	} else {
 		group = __group;
 	}

 	if (!netlink_has_listeners(dev->nls, group))
 		return -ESRCH;

 	size = NLMSG_SPACE(sizeof(*msg) + msg->len);

 	skb = alloc_skb(size, gfp_mask);
 	if (!skb)
 		return -ENOMEM;

 	nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));

 	data = NLMSG_DATA(nlh);

 	memcpy(data, msg, sizeof(*data) + msg->len);

 	NETLINK_CB(skb).dst_group = group;

 	return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);

 nlmsg_failure:
 	kfree_skb(skb);
 	return -EINVAL;
 }
 EXPORT_SYMBOL_GPL(cn_netlink_send);

 /*
  * Callback helper - queues work and setup destructor for given data.
  */
 static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
 {
 	struct cn_callback_entry *__cbq, *__new_cbq;
 	struct cn_dev *dev = &cdev;
 	int err = -ENODEV;

 	spin_lock_bh(&dev->cbdev->queue_lock);
 	list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 		if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 			if (likely(!work_pending(&__cbq->work) &&
 					__cbq->data.ddata == NULL)) {
 				__cbq->data.callback_priv = msg;

 				__cbq->data.ddata = data;
 				__cbq->data.destruct_data = destruct_data;

 				if (queue_work(dev->cbdev->cn_queue,
 							&__cbq->work))
 					err = 0;
 			} else {
 				struct cn_callback_data *d;

 				err = -ENOMEM;
 				__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
 				if (__new_cbq) {
 					d = &__new_cbq->data;
 					d->callback_priv = msg;
 					d->callback = __cbq->data.callback;
 					d->ddata = data;
 					d->destruct_data = destruct_data;
 					d->free = __new_cbq;

 					INIT_WORK(&__new_cbq->work,
 							&cn_queue_wrapper);

 					if (queue_work(dev->cbdev->cn_queue,
 						    &__new_cbq->work))
 						err = 0;
 					else {
 						kfree(__new_cbq);
 						err = -EINVAL;
 					}
 				}
 			}
 			break;
 		}
 	}
 	spin_unlock_bh(&dev->cbdev->queue_lock);

 	return err;
 }

 /*
  * Skb receive helper - checks skb and msg size and calls callback
  * helper.
  */
 static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
 	u32 pid, uid, seq, group;
 	struct cn_msg *msg;

 	pid = NETLINK_CREDS(skb)->pid;
 	uid = NETLINK_CREDS(skb)->uid;
 	seq = nlh->nlmsg_seq;
 	group = NETLINK_CB((skb)).dst_group;
 	msg = NLMSG_DATA(nlh);

 	return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
 }

 /*
  * Main netlink receiving function.
  *
  * It checks skb and netlink header sizes and calls the skb receive
  * helper with a shared skb.
  */
 static void cn_rx_skb(struct sk_buff *__skb)
 {
 	struct nlmsghdr *nlh;
 	u32 len;
 	int err;
 	struct sk_buff *skb;

 	skb = skb_get(__skb);

 	if (skb->len >= NLMSG_SPACE(0)) {
 		nlh = (struct nlmsghdr *)skb->data;

 		if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 		    skb->len < nlh->nlmsg_len ||
 		    nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 			kfree_skb(skb);
 			goto out;
 		}

 		len = NLMSG_ALIGN(nlh->nlmsg_len);
 		if (len > skb->len)
 			len = skb->len;

 		err = __cn_rx_skb(skb, nlh);
 		if (err < 0)
 			kfree_skb(skb);
 	}

 out:
 	kfree_skb(__skb);
 }

 /*
  * Netlink socket input callback - dequeues the skbs and calls the
  * main netlink receiving function.
  */
 static void cn_input(struct sock *sk, int len)
 {
 	struct sk_buff *skb;

 	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
 		cn_rx_skb(skb);
 }

 /*
  * Notification routing.
  *
  * Gets id and checks if there are notification request for it's idx
  * and val.  If there are such requests notify the listeners with the
  * given notify event.
  *
  */
 static void cn_notify(struct cb_id *id, u32 notify_event)
 {
 	struct cn_ctl_entry *ent;

 	mutex_lock(&notify_lock);
 	list_for_each_entry(ent, &notify_list, notify_entry) {
 		int i;
 		struct cn_notify_req *req;
 		struct cn_ctl_msg *ctl = ent->msg;
 		int idx_found, val_found;

 		idx_found = val_found = 0;

 		req = (struct cn_notify_req *)ctl->data;
 		for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 			if (id->idx >= req->first &&
 					id->idx < req->first + req->range) {
 				idx_found = 1;
 				break;
 			}
 		}

 		for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 			if (id->val >= req->first &&
 					id->val < req->first + req->range) {
 				val_found = 1;
 				break;
 			}
 		}

 		if (idx_found && val_found) {
 			struct cn_msg m = { .ack = notify_event, };

 			memcpy(&m.id, id, sizeof(m.id));
 			cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 		}
 	}
 	mutex_unlock(&notify_lock);
 }

 /*
  * Callback add routing - adds callback with given ID and name.
  * If there is registered callback with the same ID it will not be added.
  *
  * May sleep.
  */
 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 {
 	int err;
 	struct cn_dev *dev = &cdev;

 	if (!cn_already_initialized)
 		return -EAGAIN;

 	err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 	if (err)
 		return err;

 	cn_notify(id, 0);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(cn_add_callback);

 /*
  * Callback remove routing - removes callback
  * with given ID.
  * If there is no registered callback with given
  * ID nothing happens.
  *
  * May sleep while waiting for reference counter to become zero.
  */
 void cn_del_callback(struct cb_id *id)
 {
 	struct cn_dev *dev = &cdev;

 	cn_queue_del_callback(dev->cbdev, id);
 	cn_notify(id, 1);
 }
 EXPORT_SYMBOL_GPL(cn_del_callback);

 /*
  * Checks two connector's control messages to be the same.
  * Returns 1 if they are the same or if the first one is corrupted.
  */
 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 {
 	int i;
 	struct cn_notify_req *req1, *req2;

 	if (m1->idx_notify_num != m2->idx_notify_num)
 		return 0;

 	if (m1->val_notify_num != m2->val_notify_num)
 		return 0;

 	if (m1->len != m2->len)
 		return 0;

 	if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 	    m1->len)
 		return 1;

 	req1 = (struct cn_notify_req *)m1->data;
 	req2 = (struct cn_notify_req *)m2->data;

 	for (i = 0; i < m1->idx_notify_num; ++i) {
 		if (req1->first != req2->first || req1->range != req2->range)
 			return 0;
 		req1++;
 		req2++;
 	}

 	for (i = 0; i < m1->val_notify_num; ++i) {
 		if (req1->first != req2->first || req1->range != req2->range)
 			return 0;
 		req1++;
 		req2++;
 	}

 	return 1;
 }

 /*
  * Main connector device's callback.
  *
  * Used for notification of a request's processing.
  */
 static void cn_callback(void *data)
 {
 	struct cn_msg *msg = data;
 	struct cn_ctl_msg *ctl;
 	struct cn_ctl_entry *ent;
 	u32 size;

 	if (msg->len < sizeof(*ctl))
 		return;

 	ctl = (struct cn_ctl_msg *)msg->data;

 	size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 				 ctl->val_notify_num) *
 				sizeof(struct cn_notify_req)));

 	if (msg->len != size)
 		return;

 	if (ctl->len + sizeof(*ctl) != msg->len)
 		return;

 	/*
 	 * Remove notification.
 	 */
 	if (ctl->group == 0) {
 		struct cn_ctl_entry *n;

 		mutex_lock(&notify_lock);
 		list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 			if (cn_ctl_msg_equals(ent->msg, ctl)) {
 				list_del(&ent->notify_entry);
 				kfree(ent);
 			}
 		}
 		mutex_unlock(&notify_lock);

 		return;
 	}

 	size += sizeof(*ent);

 	ent = kzalloc(size, GFP_KERNEL);
 	if (!ent)
 		return;

 	ent->msg = (struct cn_ctl_msg *)(ent + 1);

 	memcpy(ent->msg, ctl, size - sizeof(*ent));

 	mutex_lock(&notify_lock);
 	list_add(&ent->notify_entry, &notify_list);
 	mutex_unlock(&notify_lock);
 }

 static int __devinit cn_init(void)
 {
 	struct cn_dev *dev = &cdev;
 	int err;

 	dev->input = cn_input;
 	dev->id.idx = cn_idx;
 	dev->id.val = cn_val;

 	dev->nls = netlink_kernel_create(NETLINK_CONNECTOR,
 					 CN_NETLINK_USERS + 0xf,
 					 dev->input, THIS_MODULE);
 	if (!dev->nls)
 		return -EIO;

 	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 	if (!dev->cbdev) {
 		if (dev->nls->sk_socket)
 			sock_release(dev->nls->sk_socket);
 		return -EINVAL;
 	}

 	cn_already_initialized = 1;

 	err = cn_add_callback(&dev->id, "connector", &cn_callback);
 	if (err) {
 		cn_already_initialized = 0;
 		cn_queue_free_dev(dev->cbdev);
 		if (dev->nls->sk_socket)
 			sock_release(dev->nls->sk_socket);
 		return -EINVAL;
 	}

 	return 0;
 }

 static void __devexit cn_fini(void)
 {
 	struct cn_dev *dev = &cdev;

 	cn_already_initialized = 0;

 	cn_del_callback(&dev->id);
 	cn_queue_free_dev(dev->cbdev);
 	if (dev->nls->sk_socket)
 		sock_release(dev->nls->sk_socket);
 }

 subsys_initcall(cn_init);
 module_exit(cn_fini);
	/*
	* connector.c
	*
	* 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
	* All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/list.h>
	#include <linux/skbuff.h>
	#include <linux/netlink.h>
	#include <linux/moduleparam.h>
	#include <linux/connector.h>
	#include <linux/mutex.h>

	#include <net/sock.h>

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
	MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");

	static u32 cn_idx = CN_IDX_CONNECTOR;
	static u32 cn_val = CN_VAL_CONNECTOR;

	module_param(cn_idx, uint, 0);
	module_param(cn_val, uint, 0);
	MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
	MODULE_PARM_DESC(cn_val, "Connector's main device val.");

	static DEFINE_MUTEX(notify_lock);
	static LIST_HEAD(notify_list);

	static struct cn_dev cdev;

	int cn_already_initialized = 0;

	/*
	* msg->seq and msg->ack are used to determine message genealogy.
	* When someone sends message it puts there locally unique sequence
	* and random acknowledge numbers. Sequence number may be copied into
	* nlmsghdr->nlmsg_seq too.
	*
	* Sequence number is incremented with each message to be sent.
	*
	* If we expect reply to our message then the sequence number in
	* received message MUST be the same as in original message, and
	* acknowledge number MUST be the same + 1.
	*
	* If we receive a message and its sequence number is not equal to the
	* one we are expecting then it is a new message.
	*
	* If we receive a message and its sequence number is the same as one
	* we are expecting but it's acknowledgement number is not equal to
	* the acknowledgement number in the original message + 1, then it is
	* a new message.
	*
	*/
	int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
	{
	struct cn_callback_entry *__cbq;
	unsigned int size;
	struct sk_buff *skb;
	struct nlmsghdr *nlh;
	struct cn_msg *data;
	struct cn_dev *dev = &cdev;
	u32 group = 0;
	int found = 0;

	if (!__group) {
	spin_lock_bh(&dev->cbdev->queue_lock);
	list_for_each_entry(__cbq, &dev->cbdev->queue_list,
	callback_entry) {
	if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
	found = 1;
	group = __cbq->group;
	}
	}
	spin_unlock_bh(&dev->cbdev->queue_lock);

	if (!found)
	return -ENODEV;
	} else {
	group = __group;
	}

	if (!netlink_has_listeners(dev->nls, group))
	return -ESRCH;

	size = NLMSG_SPACE(sizeof(*msg) + msg->len);

	skb = alloc_skb(size, gfp_mask);
	if (!skb)
	return -ENOMEM;

	nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));

	data = NLMSG_DATA(nlh);

	memcpy(data, msg, sizeof(*data) + msg->len);

	NETLINK_CB(skb).dst_group = group;

	return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);

	nlmsg_failure:
	kfree_skb(skb);
	return -EINVAL;
	}
	EXPORT_SYMBOL_GPL(cn_netlink_send);

	/*
	* Callback helper - queues work and setup destructor for given data.
	*/
	static int cn_call_callback(struct cn_msg msg, void (destruct_data)(void ), void data)
	{
	struct cn_callback_entry __cbq, __new_cbq;
	struct cn_dev *dev = &cdev;
	int err = -ENODEV;

	spin_lock_bh(&dev->cbdev->queue_lock);
	list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
	if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
	if (likely(!work_pending(&__cbq->work) &&
	__cbq->data.ddata == NULL)) {
	__cbq->data.callback_priv = msg;

	__cbq->data.ddata = data;
	__cbq->data.destruct_data = destruct_data;

	if (queue_work(dev->cbdev->cn_queue,
	&__cbq->work))
	err = 0;
	} else {
	struct cn_callback_data *d;

	err = -ENOMEM;
	__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
	if (__new_cbq) {
	d = &__new_cbq->data;
	d->callback_priv = msg;
	d->callback = __cbq->data.callback;
	d->ddata = data;
	d->destruct_data = destruct_data;
	d->free = __new_cbq;

	INIT_WORK(&__new_cbq->work,
	&cn_queue_wrapper);

	if (queue_work(dev->cbdev->cn_queue,
	&__new_cbq->work))
	err = 0;
	else {
	kfree(__new_cbq);
	err = -EINVAL;
	}
	}
	}
	break;
	}
	}
	spin_unlock_bh(&dev->cbdev->queue_lock);

	return err;
	}

	/*
	* Skb receive helper - checks skb and msg size and calls callback
	* helper.
	*/
	static int __cn_rx_skb(struct sk_buff skb, struct nlmsghdr nlh)
	{
	u32 pid, uid, seq, group;
	struct cn_msg *msg;

	pid = NETLINK_CREDS(skb)->pid;
	uid = NETLINK_CREDS(skb)->uid;
	seq = nlh->nlmsg_seq;
	group = NETLINK_CB((skb)).dst_group;
	msg = NLMSG_DATA(nlh);

	return cn_call_callback(msg, (void ()(void ))kfree_skb, skb);
	}

	/*
	* Main netlink receiving function.
	*
	* It checks skb and netlink header sizes and calls the skb receive
	* helper with a shared skb.
	*/
	static void cn_rx_skb(struct sk_buff *__skb)
	{
	struct nlmsghdr *nlh;
	u32 len;
	int err;
	struct sk_buff *skb;

	skb = skb_get(__skb);

	if (skb->len >= NLMSG_SPACE(0)) {
	nlh = (struct nlmsghdr *)skb->data;

	if (nlh->nlmsg_len < sizeof(struct cn_msg) \|\|
	skb->len < nlh->nlmsg_len \|\|
	nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
	kfree_skb(skb);
	goto out;
	}

	len = NLMSG_ALIGN(nlh->nlmsg_len);
	if (len > skb->len)
	len = skb->len;

	err = __cn_rx_skb(skb, nlh);
	if (err < 0)
	kfree_skb(skb);
	}

	out:
	kfree_skb(__skb);
	}

	/*
	* Netlink socket input callback - dequeues the skbs and calls the
	* main netlink receiving function.
	*/
	static void cn_input(struct sock *sk, int len)
	{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
	cn_rx_skb(skb);
	}

	/*
	* Notification routing.
	*
	* Gets id and checks if there are notification request for it's idx
	* and val. If there are such requests notify the listeners with the
	* given notify event.
	*
	*/
	static void cn_notify(struct cb_id *id, u32 notify_event)
	{
	struct cn_ctl_entry *ent;

	mutex_lock(&notify_lock);
	list_for_each_entry(ent, &notify_list, notify_entry) {
	int i;
	struct cn_notify_req *req;
	struct cn_ctl_msg *ctl = ent->msg;
	int idx_found, val_found;

	idx_found = val_found = 0;

	req = (struct cn_notify_req *)ctl->data;
	for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
	if (id->idx >= req->first &&
	id->idx < req->first + req->range) {
	idx_found = 1;
	break;
	}
	}

	for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
	if (id->val >= req->first &&
	id->val < req->first + req->range) {
	val_found = 1;
	break;
	}
	}

	if (idx_found && val_found) {
	struct cn_msg m = { .ack = notify_event, };

	memcpy(&m.id, id, sizeof(m.id));
	cn_netlink_send(&m, ctl->group, GFP_KERNEL);
	}
	}
	mutex_unlock(&notify_lock);
	}

	/*
	* Callback add routing - adds callback with given ID and name.
	* If there is registered callback with the same ID it will not be added.
	*
	* May sleep.
	*/
	int cn_add_callback(struct cb_id id, char name, void (callback)(void ))
	{
	int err;
	struct cn_dev *dev = &cdev;

	if (!cn_already_initialized)
	return -EAGAIN;

	err = cn_queue_add_callback(dev->cbdev, name, id, callback);
	if (err)
	return err;

	cn_notify(id, 0);

	return 0;
	}
	EXPORT_SYMBOL_GPL(cn_add_callback);

	/*
	* Callback remove routing - removes callback
	* with given ID.
	* If there is no registered callback with given
	* ID nothing happens.
	*
	* May sleep while waiting for reference counter to become zero.
	*/
	void cn_del_callback(struct cb_id *id)
	{
	struct cn_dev *dev = &cdev;

	cn_queue_del_callback(dev->cbdev, id);
	cn_notify(id, 1);
	}
	EXPORT_SYMBOL_GPL(cn_del_callback);

	/*
	* Checks two connector's control messages to be the same.
	* Returns 1 if they are the same or if the first one is corrupted.
	*/
	static int cn_ctl_msg_equals(struct cn_ctl_msg m1, struct cn_ctl_msg m2)
	{
	int i;
	struct cn_notify_req req1, req2;

	if (m1->idx_notify_num != m2->idx_notify_num)
	return 0;

	if (m1->val_notify_num != m2->val_notify_num)
	return 0;

	if (m1->len != m2->len)
	return 0;

	if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
	m1->len)
	return 1;

	req1 = (struct cn_notify_req *)m1->data;
	req2 = (struct cn_notify_req *)m2->data;

	for (i = 0; i < m1->idx_notify_num; ++i) {
	if (req1->first != req2->first \|\| req1->range != req2->range)
	return 0;
	req1++;
	req2++;
	}

	for (i = 0; i < m1->val_notify_num; ++i) {
	if (req1->first != req2->first \|\| req1->range != req2->range)
	return 0;
	req1++;
	req2++;
	}

	return 1;
	}

	/*
	* Main connector device's callback.
	*
	* Used for notification of a request's processing.
	*/
	static void cn_callback(void *data)
	{
	struct cn_msg *msg = data;
	struct cn_ctl_msg *ctl;
	struct cn_ctl_entry *ent;
	u32 size;

	if (msg->len < sizeof(*ctl))
	return;

	ctl = (struct cn_ctl_msg *)msg->data;

	size = (sizeof(*ctl) + ((ctl->idx_notify_num +
	ctl->val_notify_num) *
	sizeof(struct cn_notify_req)));

	if (msg->len != size)
	return;

	if (ctl->len + sizeof(*ctl) != msg->len)
	return;

	/*
	* Remove notification.
	*/
	if (ctl->group == 0) {
	struct cn_ctl_entry *n;

	mutex_lock(&notify_lock);
	list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
	if (cn_ctl_msg_equals(ent->msg, ctl)) {
	list_del(&ent->notify_entry);
	kfree(ent);
	}
	}
	mutex_unlock(&notify_lock);

	return;
	}

	size += sizeof(*ent);

	ent = kzalloc(size, GFP_KERNEL);
	if (!ent)
	return;

	ent->msg = (struct cn_ctl_msg *)(ent + 1);

	memcpy(ent->msg, ctl, size - sizeof(*ent));

	mutex_lock(&notify_lock);
	list_add(&ent->notify_entry, &notify_list);
	mutex_unlock(&notify_lock);
	}

	static int __devinit cn_init(void)
	{
	struct cn_dev *dev = &cdev;
	int err;

	dev->input = cn_input;
	dev->id.idx = cn_idx;
	dev->id.val = cn_val;

	dev->nls = netlink_kernel_create(NETLINK_CONNECTOR,
	CN_NETLINK_USERS + 0xf,
	dev->input, THIS_MODULE);
	if (!dev->nls)
	return -EIO;

	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
	if (!dev->cbdev) {
	if (dev->nls->sk_socket)
	sock_release(dev->nls->sk_socket);
	return -EINVAL;
	}

	cn_already_initialized = 1;

	err = cn_add_callback(&dev->id, "connector", &cn_callback);
	if (err) {
	cn_already_initialized = 0;
	cn_queue_free_dev(dev->cbdev);
	if (dev->nls->sk_socket)
	sock_release(dev->nls->sk_socket);
	return -EINVAL;
	}

	return 0;
	}

	static void __devexit cn_fini(void)
	{
	struct cn_dev *dev = &cdev;

	cn_already_initialized = 0;

	cn_del_callback(&dev->id);
	cn_queue_free_dev(dev->cbdev);
	if (dev->nls->sk_socket)
	sock_release(dev->nls->sk_socket);
	}

	subsys_initcall(cn_init);
	module_exit(cn_fini);