Bluetooth: Keep MSFT ext info throughout a hci_dev's life cycle

This splits the msft_do_{open/close} to msft_do_{open/close} and
msft_{register/unregister}. With this change it is possible to retain
the MSFT extension info irrespective of controller power on/off state.
This helps bluetoothd to report correct 'supported features' of the
controller to the D-Bus clients event if the controller is off. It also
re-reads the MSFT info upon every msft_do_open().

The following test steps were performed.
1. Boot the test device and verify the MSFT support debug log in syslog.
2. Power off the controller and read the 'supported features', power on
   and read again.
3. Restart the bluetoothd and verify the 'supported features' value.

Signed-off-by: Miao-chen Chou <mcchou@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Alain Michaud <alainm@chromium.org>
Signed-off-by: Manish Mandlik <mmandlik@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_core.c

@@ -3990,6 +3990,7 @@ int hci_register_dev(struct hci_dev *hdev)
 	queue_work(hdev->req_workqueue, &hdev->power_on);
 
 	idr_init(&hdev->adv_monitors_idr);
+	msft_register(hdev);
 
 	return id;
 
@@ -4022,6 +4023,8 @@ void hci_unregister_dev(struct hci_dev *hdev)
 		cancel_work_sync(&hdev->suspend_prepare);
 	}
 
+	msft_unregister(hdev);
+
 	hci_dev_do_close(hdev);
 
 	if (!test_bit(HCI_INIT, &hdev->flags) &&

net/bluetooth/msft.c

@@ -184,28 +184,36 @@ static void reregister_monitor_on_restart(struct hci_dev *hdev, int handle)
 
 void msft_do_open(struct hci_dev *hdev)
 {
-	struct msft_data *msft;
+	struct msft_data *msft = hdev->msft_data;
 
 	if (hdev->msft_opcode == HCI_OP_NOP)
 		return;
 
+	if (!msft) {
+		bt_dev_err(hdev, "MSFT extension not registered");
+		return;
+	}
+
 	bt_dev_dbg(hdev, "Initialize MSFT extension");
 
-	msft = kzalloc(sizeof(*msft), GFP_KERNEL);
-	if (!msft)
-		return;
+	/* Reset existing MSFT data before re-reading */
+	kfree(msft->evt_prefix);
+	msft->evt_prefix = NULL;
+	msft->evt_prefix_len = 0;
+	msft->features = 0;
 
 	if (!read_supported_features(hdev, msft)) {
+		hdev->msft_data = NULL;
 		kfree(msft);
 		return;
 	}
 
-	INIT_LIST_HEAD(&msft->handle_map);
-	hdev->msft_data = msft;
-
 	if (msft_monitor_supported(hdev)) {
 		msft->reregistering = true;
 		msft_set_filter_enable(hdev, true);
+		/* Monitors get removed on power off, so we need to explicitly
+		 * tell the controller to re-monitor.
+		 */
 		reregister_monitor_on_restart(hdev, 0);
 	}
 }
@@ -221,8 +229,9 @@ void msft_do_close(struct hci_dev *hdev)
 
 	bt_dev_dbg(hdev, "Cleanup of MSFT extension");
 
-	hdev->msft_data = NULL;
-
+	/* The controller will silently remove all monitors on power off.
+	 * Therefore, remove handle_data mapping and reset monitor state.
+	 */
 	list_for_each_entry_safe(handle_data, tmp, &msft->handle_map, list) {
 		monitor = idr_find(&hdev->adv_monitors_idr,
 				   handle_data->mgmt_handle);
@@ -233,6 +242,34 @@ void msft_do_close(struct hci_dev *hdev)
 		list_del(&handle_data->list);
 		kfree(handle_data);
 	}
+}
+
+void msft_register(struct hci_dev *hdev)
+{
+	struct msft_data *msft = NULL;
+
+	bt_dev_dbg(hdev, "Register MSFT extension");
+
+	msft = kzalloc(sizeof(*msft), GFP_KERNEL);
+	if (!msft) {
+		bt_dev_err(hdev, "Failed to register MSFT extension");
+		return;
+	}
+
+	INIT_LIST_HEAD(&msft->handle_map);
+	hdev->msft_data = msft;
+}
+
+void msft_unregister(struct hci_dev *hdev)
+{
+	struct msft_data *msft = hdev->msft_data;
+
+	if (!msft)
+		return;
+
+	bt_dev_dbg(hdev, "Unregister MSFT extension");
+
+	hdev->msft_data = NULL;
 
 	kfree(msft->evt_prefix);
 	kfree(msft);

net/bluetooth/msft.h

@@ -13,6 +13,8 @@
 #if IS_ENABLED(CONFIG_BT_MSFTEXT)
 
 bool msft_monitor_supported(struct hci_dev *hdev);
+void msft_register(struct hci_dev *hdev);
+void msft_unregister(struct hci_dev *hdev);
 void msft_do_open(struct hci_dev *hdev);
 void msft_do_close(struct hci_dev *hdev);
 void msft_vendor_evt(struct hci_dev *hdev, struct sk_buff *skb);
@@ -31,6 +33,8 @@ static inline bool msft_monitor_supported(struct hci_dev *hdev)
 	return false;
 }
 
+static inline void msft_register(struct hci_dev *hdev) {}
+static inline void msft_unregister(struct hci_dev *hdev) {}
 static inline void msft_do_open(struct hci_dev *hdev) {}
 static inline void msft_do_close(struct hci_dev *hdev) {}
 static inline void msft_vendor_evt(struct hci_dev *hdev, struct sk_buff *skb) {}