USB: serial: add sysrq break-handler dummy

Add inline sysrq break-handler dummy to allow the compiler to eliminate
further code when either console or sysrq support isn't enabled and to
clearly mark the two sysrq functions as belonging together.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/generic.c

@@ -585,11 +585,10 @@ int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(usb_serial_handle_sysrq_char);
-#endif
 
 int usb_serial_handle_break(struct usb_serial_port *port)
 {
-	if (!port->port.console || !IS_ENABLED(CONFIG_MAGIC_SYSRQ))
+	if (!port->port.console)
 		return 0;
 
 	if (!port->sysrq) {
@@ -600,6 +599,7 @@ int usb_serial_handle_break(struct usb_serial_port *port)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(usb_serial_handle_break);
+#endif
 
 /**
  * usb_serial_handle_dcd_change - handle a change of carrier detect state

include/linux/usb/serial.h

@@ -369,14 +369,18 @@ extern int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
 #if defined(CONFIG_USB_SERIAL_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
 extern int usb_serial_handle_sysrq_char(struct usb_serial_port *port,
 					unsigned int ch);
+extern int usb_serial_handle_break(struct usb_serial_port *port);
 #else
 static inline int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
 {
 	return 0;
 }
+static inline int usb_serial_handle_break(struct usb_serial_port *port)
+{
+	return 0;
+}
 #endif
 
-extern int usb_serial_handle_break(struct usb_serial_port *port);
 extern void usb_serial_handle_dcd_change(struct usb_serial_port *usb_port,
 					 struct tty_struct *tty,
 					 unsigned int status);