Bluetooth: Add discovery state tracking

This patch adds proper state tracking to the device discovery process.
This makes it possible to return appropriate errors when trying to stop
a non-active discovery or start discovery when it is already ongoing.
Once name resolving is implemented this also makes it possible to know
what the right action to do is when a remote name lookup is cancelled.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 894f11b..590966d 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -1918,6 +1918,12 @@
 		goto failed;
 	}
 
+	if (hdev->discovery.state != DISCOVERY_STOPPED) {
+		err = cmd_status(sk, index, MGMT_OP_START_DISCOVERY,
+						MGMT_STATUS_BUSY);
+		goto failed;
+	}
+
 	cmd = mgmt_pending_add(sk, MGMT_OP_START_DISCOVERY, hdev, NULL, 0);
 	if (!cmd) {
 		err = -ENOMEM;
@@ -1927,6 +1933,8 @@
 	err = hci_do_inquiry(hdev, INQUIRY_LEN_BREDR);
 	if (err < 0)
 		mgmt_pending_remove(cmd);
+	else
+		hci_discovery_set_state(hdev, DISCOVERY_STARTING);
 
 failed:
 	hci_dev_unlock(hdev);
@@ -1950,6 +1958,12 @@
 
 	hci_dev_lock(hdev);
 
+	if (hdev->discovery.state != DISCOVERY_ACTIVE) {
+		err = cmd_status(sk, index, MGMT_OP_STOP_DISCOVERY,
+						MGMT_STATUS_REJECTED);
+		goto failed;
+	}
+
 	cmd = mgmt_pending_add(sk, MGMT_OP_STOP_DISCOVERY, hdev, NULL, 0);
 	if (!cmd) {
 		err = -ENOMEM;
@@ -1959,6 +1973,8 @@
 	err = hci_cancel_inquiry(hdev);
 	if (err < 0)
 		mgmt_pending_remove(cmd);
+	else
+		hci_discovery_set_state(hdev, DISCOVERY_STOPPING);
 
 failed:
 	hci_dev_unlock(hdev);