Bluetooth: Notify adv monitor removed event

This notifies management sockets on MGMT_EV_ADV_MONITOR_REMOVED event.

The following test was performed.
- Start two btmgmt consoles, issue a btmgmt advmon-remove command on one
console and observe a MGMT_EV_ADV_MONITOR_REMOVED event on the other.
Signed-off-by: Miao-chen Chou <mcchou@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

net/bluetooth/mgmt.c

@@ -192,6 +192,7 @@ static const u16 mgmt_untrusted_events[] = {
 	MGMT_EV_EXT_INFO_CHANGED,
 	MGMT_EV_EXP_FEATURE_CHANGED,
 	MGMT_EV_ADV_MONITOR_ADDED,
+	MGMT_EV_ADV_MONITOR_REMOVED,
 };
 
 #define CACHE_TIMEOUT	msecs_to_jiffies(2 * 1000)
@@ -3988,6 +3989,16 @@ static void mgmt_adv_monitor_added(struct sock *sk, struct hci_dev *hdev,
 	mgmt_event(MGMT_EV_ADV_MONITOR_ADDED, hdev, &ev, sizeof(ev), sk);
 }
 
+static void mgmt_adv_monitor_removed(struct sock *sk, struct hci_dev *hdev,
+				     u16 handle)
+{
+	struct mgmt_ev_adv_monitor_added ev;
+
+	ev.monitor_handle = cpu_to_le16(handle);
+
+	mgmt_event(MGMT_EV_ADV_MONITOR_REMOVED, hdev, &ev, sizeof(ev), sk);
+}
+
 static int read_adv_mon_features(struct sock *sk, struct hci_dev *hdev,
 				 void *data, u16 len)
 {
@@ -4140,6 +4151,7 @@ static int remove_adv_monitor(struct sock *sk, struct hci_dev *hdev,
 {
 	struct mgmt_cp_remove_adv_monitor *cp = data;
 	struct mgmt_rp_remove_adv_monitor rp;
+	unsigned int prev_adv_monitors_cnt;
 	u16 handle;
 	int err;
 
@@ -4148,6 +4160,7 @@ static int remove_adv_monitor(struct sock *sk, struct hci_dev *hdev,
 	hci_dev_lock(hdev);
 
 	handle = __le16_to_cpu(cp->monitor_handle);
+	prev_adv_monitors_cnt = hdev->adv_monitors_cnt;
 
 	err = hci_remove_adv_monitor(hdev, handle);
 	if (err == -ENOENT) {
@@ -4156,6 +4169,9 @@ static int remove_adv_monitor(struct sock *sk, struct hci_dev *hdev,
 		goto unlock;
 	}
 
+	if (hdev->adv_monitors_cnt < prev_adv_monitors_cnt)
+		mgmt_adv_monitor_removed(sk, hdev, handle);
+
 	hci_dev_unlock(hdev);
 
 	rp.monitor_handle = cp->monitor_handle;