usb-serial: begin switching to ->[sg]et_serial()

add such methods for usb_serial_driver, provide tty_operations
->[sg]et_serial() calling those.  For now the lack of methods
in driver means ENOIOCTLCMD from usb-serial ->[sg]et_serial(),
making tty_ioctl() fall back to calling ->ioctl().  Once all
drivers are converted, we'll be returning -ENOTTY instead,
completing the switchover.
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/usb/serial/usb-serial.c

@@ -396,6 +396,24 @@ static void serial_unthrottle(struct tty_struct *tty)
 		port->serial->type->unthrottle(tty);
 }
 
+static int serial_get_serial(struct tty_struct *tty, struct serial_struct *ss)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	if (port->serial->type->get_serial)
+		return port->serial->type->get_serial(tty, ss);
+	return -ENOIOCTLCMD;
+}
+
+static int serial_set_serial(struct tty_struct *tty, struct serial_struct *ss)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	if (port->serial->type->set_serial)
+		return port->serial->type->set_serial(tty, ss);
+	return -ENOIOCTLCMD;
+}
+
 static int serial_ioctl(struct tty_struct *tty,
 					unsigned int cmd, unsigned long arg)
 {
@@ -1177,6 +1195,8 @@ static const struct tty_operations serial_ops = {
 	.tiocmget =		serial_tiocmget,
 	.tiocmset =		serial_tiocmset,
 	.get_icount =		serial_get_icount,
+	.set_serial =		serial_set_serial,
+	.get_serial =		serial_get_serial,
 	.cleanup =		serial_cleanup,
 	.install =		serial_install,
 	.proc_show =		serial_proc_show,

include/linux/usb/serial.h

@@ -285,6 +285,8 @@ struct usb_serial_driver {
 	int  (*write_room)(struct tty_struct *tty);
 	int  (*ioctl)(struct tty_struct *tty,
 		      unsigned int cmd, unsigned long arg);
+	int  (*get_serial)(struct tty_struct *tty, struct serial_struct *ss);
+	int  (*set_serial)(struct tty_struct *tty, struct serial_struct *ss);
 	void (*set_termios)(struct tty_struct *tty,
 			struct usb_serial_port *port, struct ktermios *old);
 	void (*break_ctl)(struct tty_struct *tty, int break_state);