TTY: n_gsm, use tty_port_install

We need to link a port to a tty in install. And since dlci is
allocated even in open, we need to create gsmtty_install, allocate
dlci there and create also the link.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_gsm.c

@@ -2868,14 +2868,14 @@ static const struct tty_port_operations gsm_port_ops = {
 	.dtr_rts = gsm_dtr_rts,
 };
 
-
-static int gsmtty_open(struct tty_struct *tty, struct file *filp)
+static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
 {
 	struct gsm_mux *gsm;
 	struct gsm_dlci *dlci;
-	struct tty_port *port;
 	unsigned int line = tty->index;
 	unsigned int mux = line >> 6;
+	bool alloc = false;
+	int ret;
 
 	line = line & 0x3F;
 
@@ -2890,13 +2890,30 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
 	if (gsm->dead)
 		return -EL2HLT;
 	dlci = gsm->dlci[line];
-	if (dlci == NULL)
+	if (dlci == NULL) {
+		alloc = true;
 		dlci = gsm_dlci_alloc(gsm, line);
+	}
 	if (dlci == NULL)
 		return -ENOMEM;
-	port = &dlci->port;
-	port->count++;
+	ret = tty_port_install(&dlci->port, driver, tty);
+	if (ret) {
+		if (alloc)
+			dlci_put(dlci);
+		return ret;
+	}
+
 	tty->driver_data = dlci;
+
+	return 0;
+}
+
+static int gsmtty_open(struct tty_struct *tty, struct file *filp)
+{
+	struct gsm_dlci *dlci = tty->driver_data;
+	struct tty_port *port = &dlci->port;
+
+	port->count++;
 	dlci_get(dlci);
 	dlci_get(dlci->gsm->dlci[0]);
 	mux_get(dlci->gsm);
@@ -3085,6 +3102,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
 
 /* Virtual ttys for the demux */
 static const struct tty_operations gsmtty_ops = {
+	.install		= gsmtty_install,
 	.open			= gsmtty_open,
 	.close			= gsmtty_close,
 	.write			= gsmtty_write,