From 2c8e1411e93391c5a78f55b09697a997474a4707 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Sat, 6 Apr 2013 20:28:45 +0200 Subject: [PATCH] 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: David Herrmann Acked-by: Marcel Holtmann Signed-off-by: Gustavo Padovan --- include/net/bluetooth/l2cap.h | 10 ++++ net/bluetooth/l2cap_core.c | 86 +++++++++++++++++++++++++++++++++++ 2 files changed, 96 insertions(+) diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index 7b4cc5b98535..fb94cf13c777 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -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 */ diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index be9ad89339cd..eae1d9f90b68 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -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); -- 2.39.5