Commit 2c8e1411 authored by David Herrmann's avatar David Herrmann Committed by Gustavo Padovan
Browse files

Bluetooth: l2cap: add l2cap_user sub-modules 



Several sub-modules like HIDP, rfcomm, ... need to track l2cap
connections. The l2cap_conn->hcon->dev object is used as parent for sysfs
devices so the sub-modules need to be notified when the hci_conn object is
removed from sysfs.

As submodules normally use the l2cap layer, the l2cap_user objects are
registered there instead of on the underlying hci_conn object. This avoids
any direct dependency on the HCI layer and lets the l2cap core handle any
specifics.

This patch introduces l2cap_user objects which contain a "probe" and
"remove" callback. You can register them on any l2cap_conn object and if
it is active, the "probe" callback will get called. Otherwise, an error is
returned.

The l2cap_conn object will call your "remove" callback directly before it
is removed from user-space. This allows you to remove your submodules
_before_ the parent l2cap_conn and hci_conn object is removed.

At any time you can asynchronously unregister your l2cap_user object if
your submodule vanishes before the l2cap_conn object does.

There is no way around l2cap_user. If we want wire-protocols in the
kernel, we always want the hci_conn object as parent in the sysfs tree. We
cannot use a channel here since we might need multiple channels for a
single protocol.
But the problem is, we _must_ get notified when an l2cap_conn object is
removed. We cannot use reference-counting for object-removal! This is not
how it works. If a hardware is removed, we should immediately remove the
object from sysfs. Any other behavior would be inconsistent with the rest
of the system. Also note that device_del() might sleep, but it doesn't
wait for user-space or block very long. It only _unlinks_ the object from
sysfs and the whole device-tree. Everything else is handled by ref-counts!
This is exactly what the other sub-modules must do: unlink their devices
when the "remove" l2cap_user callback is called. They should not do any
cleanup or synchronous shutdowns.

Signed-off-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
Acked-by: default avatarMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: default avatarGustavo Padovan <gustavo.padovan@collabora.co.uk>
parent 9c903e37

include/net/bluetooth/l2cap.h

+10 −0
Original line number Diff line number Diff line
@@ -584,6 +584,13 @@ struct l2cap_conn { 
	struct list_head	chan_l;

	struct mutex		chan_lock;

	struct kref		ref;

	struct list_head	users;

};



struct l2cap_user {

	struct list_head list;

	int (*probe) (struct l2cap_conn *conn, struct l2cap_user *user);

	void (*remove) (struct l2cap_conn *conn, struct l2cap_user *user);

};



#define L2CAP_INFO_CL_MTU_REQ_SENT	0x01
@@ -817,4 +824,7 @@ void __l2cap_physical_cfm(struct l2cap_chan *chan, int result); 
void l2cap_conn_get(struct l2cap_conn *conn);

void l2cap_conn_put(struct l2cap_conn *conn);



int l2cap_register_user(struct l2cap_conn *conn, struct l2cap_user *user);

void l2cap_unregister_user(struct l2cap_conn *conn, struct l2cap_user *user);



#endif /* __L2CAP_H */

net/bluetooth/l2cap_core.c

+86 −0
Original line number Diff line number Diff line
@@ -1446,6 +1446,89 @@ static void l2cap_info_timeout(struct work_struct *work) 
	l2cap_conn_start(conn);

}



/*

 * l2cap_user

 * External modules can register l2cap_user objects on l2cap_conn. The ->probe

 * callback is called during registration. The ->remove callback is called

 * during unregistration.

 * An l2cap_user object can either be explicitly unregistered or when the

 * underlying l2cap_conn object is deleted. This guarantees that l2cap->hcon,

 * l2cap->hchan, .. are valid as long as the remove callback hasn't been called.

 * External modules must own a reference to the l2cap_conn object if they intend

 * to call l2cap_unregister_user(). The l2cap_conn object might get destroyed at

 * any time if they don't.

 */



int l2cap_register_user(struct l2cap_conn *conn, struct l2cap_user *user)

{

	struct hci_dev *hdev = conn->hcon->hdev;

	int ret;



	/* We need to check whether l2cap_conn is registered. If it is not, we

	 * must not register the l2cap_user. l2cap_conn_del() is unregisters

	 * l2cap_conn objects, but doesn't provide its own locking. Instead, it

	 * relies on the parent hci_conn object to be locked. This itself relies

	 * on the hci_dev object to be locked. So we must lock the hci device

	 * here, too. */



	hci_dev_lock(hdev);



	if (user->list.next || user->list.prev) {

		ret = -EINVAL;

		goto out_unlock;

	}



	/* conn->hchan is NULL after l2cap_conn_del() was called */

	if (!conn->hchan) {

		ret = -ENODEV;

		goto out_unlock;

	}



	ret = user->probe(conn, user);

	if (ret)

		goto out_unlock;



	list_add(&user->list, &conn->users);

	ret = 0;



out_unlock:

	hci_dev_unlock(hdev);

	return ret;

}

EXPORT_SYMBOL(l2cap_register_user);



void l2cap_unregister_user(struct l2cap_conn *conn, struct l2cap_user *user)

{

	struct hci_dev *hdev = conn->hcon->hdev;



	hci_dev_lock(hdev);



	if (!user->list.next || !user->list.prev)

		goto out_unlock;



	list_del(&user->list);

	user->list.next = NULL;

	user->list.prev = NULL;

	user->remove(conn, user);



out_unlock:

	hci_dev_unlock(hdev);

}

EXPORT_SYMBOL(l2cap_unregister_user);



static void l2cap_unregister_all_users(struct l2cap_conn *conn)

{

	struct l2cap_user *user;



	while (!list_empty(&conn->users)) {

		user = list_first_entry(&conn->users, struct l2cap_user, list);

		list_del(&user->list);

		user->list.next = NULL;

		user->list.prev = NULL;

		user->remove(conn, user);

	}

}



static void l2cap_conn_del(struct hci_conn *hcon, int err)

{

	struct l2cap_conn *conn = hcon->l2cap_data;
@@ -1458,6 +1541,8 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) 


	kfree_skb(conn->rx_skb);



	l2cap_unregister_all_users(conn);



	mutex_lock(&conn->chan_lock);



	/* Kill channels */
@@ -1550,6 +1635,7 @@ static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon) 
	mutex_init(&conn->chan_lock);



	INIT_LIST_HEAD(&conn->chan_l);

	INIT_LIST_HEAD(&conn->users);



	if (hcon->type == LE_LINK)

		INIT_DELAYED_WORK(&conn->security_timer, security_timeout);

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