atm: propagate signal changes via notifier

Add notifier chain for changes in atm_dev.

Clients like br2684 will call register_atmdevice_notifier() to be notified of
changes. Drivers will call atm_dev_signal_change() to notify clients like
br2684 of the change.

On DSL and ATM devices it's usefull to have a know if you have a carrier
signal. netdevice LOWER_UP changes can be propagated to userspace via netlink
monitor.

Signed-off-by: Karl Hiramoto <karl@hiramoto.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/atmdev.h

@@ -431,6 +431,14 @@ struct atm_dev *atm_dev_register(const char *type,const struct atmdev_ops *ops,
     int number,unsigned long *flags); /* number == -1: pick first available */
 struct atm_dev *atm_dev_lookup(int number);
 void atm_dev_deregister(struct atm_dev *dev);
+
+/* atm_dev_signal_change
+ *
+ * Propagate lower layer signal change in atm_dev->signal to netdevice.
+ * The event will be sent via a notifier call chain.
+ */
+void atm_dev_signal_change(struct atm_dev *dev, char signal);
+
 void vcc_insert_socket(struct sock *sk);
 
 
@@ -510,6 +518,15 @@ void register_atm_ioctl(struct atm_ioctl *);
  */
 void deregister_atm_ioctl(struct atm_ioctl *);
 
+
+/* register_atmdevice_notifier - register atm_dev notify events
+ *
+ * Clients like br2684 will register notify events
+ * Currently we notify of signal found/lost
+ */
+int register_atmdevice_notifier(struct notifier_block *nb);
+void unregister_atmdevice_notifier(struct notifier_block *nb);
+
 #endif /* __KERNEL__ */
 
 #endif

net/atm/common.c

@@ -37,6 +37,8 @@ EXPORT_SYMBOL(vcc_hash);
 DEFINE_RWLOCK(vcc_sklist_lock);
 EXPORT_SYMBOL(vcc_sklist_lock);
 
+static ATOMIC_NOTIFIER_HEAD(atm_dev_notify_chain);
+
 static void __vcc_insert_socket(struct sock *sk)
 {
 	struct atm_vcc *vcc = atm_sk(sk);
@@ -212,6 +214,22 @@ void vcc_release_async(struct atm_vcc *vcc, int reply)
 }
 EXPORT_SYMBOL(vcc_release_async);
 
+void atm_dev_signal_change(struct atm_dev *dev, char signal)
+{
+	pr_debug("%s signal=%d dev=%p number=%d dev->signal=%d\n",
+		__func__, signal, dev, dev->number, dev->signal);
+
+	/* atm driver sending invalid signal */
+	WARN_ON(signal < ATM_PHY_SIG_LOST || signal > ATM_PHY_SIG_FOUND);
+
+	if (dev->signal == signal)
+		return; /* no change */
+
+	dev->signal = signal;
+
+	atomic_notifier_call_chain(&atm_dev_notify_chain, signal, dev);
+}
+EXPORT_SYMBOL(atm_dev_signal_change);
 
 void atm_dev_release_vccs(struct atm_dev *dev)
 {
@@ -781,6 +799,18 @@ int vcc_getsockopt(struct socket *sock, int level, int optname,
 	return vcc->dev->ops->getsockopt(vcc, level, optname, optval, len);
 }
 
+int register_atmdevice_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&atm_dev_notify_chain, nb);
+}
+EXPORT_SYMBOL_GPL(register_atmdevice_notifier);
+
+void unregister_atmdevice_notifier(struct notifier_block *nb)
+{
+	atomic_notifier_chain_unregister(&atm_dev_notify_chain, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_atmdevice_notifier);
+
 static int __init atm_init(void)
 {
 	int error;