TTY: add tty_port_tty_hangup helper

It allows for cleaning up on a considerable amount of places. They did
port_get, hangup, kref_put. Now the only thing needed is to call
tty_port_tty_hangup which does exactly that. And they can also decide
whether to consider CLOCAL or completely ignore that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_port.c

@@ -232,6 +232,23 @@ void tty_port_hangup(struct tty_port *port)
 }
 EXPORT_SYMBOL(tty_port_hangup);
 
+/**
+ * tty_port_tty_hangup - helper to hang up a tty
+ *
+ * @port: tty port
+ * @check_clocal: hang only ttys with CLOCAL unset?
+ */
+void tty_port_tty_hangup(struct tty_port *port, bool check_clocal)
+{
+	struct tty_struct *tty = tty_port_tty_get(port);
+
+	if (tty && (!check_clocal || !C_CLOCAL(tty))) {
+		tty_hangup(tty);
+		tty_kref_put(tty);
+	}
+}
+EXPORT_SYMBOL_GPL(tty_port_tty_hangup);
+
 /**
  * tty_port_tty_wakeup - helper to wake up a tty
  *