USB: serial: export usb_serial_generic_write_start

Export usb_serial_generic_write_start which is needed when implementing
a custom resume function while still relying on the generic write
implementation.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/generic.c

@@ -129,7 +129,7 @@ int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
  *
  * Return: Zero on success or if busy, otherwise a negative errno value.
  */
-static int usb_serial_generic_write_start(struct usb_serial_port *port,
+int usb_serial_generic_write_start(struct usb_serial_port *port,
 							gfp_t mem_flags)
 {
 	struct urb *urb;
@@ -184,6 +184,7 @@ static int usb_serial_generic_write_start(struct usb_serial_port *port,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(usb_serial_generic_write_start);
 
 /**
  * usb_serial_generic_write - generic write function

include/linux/usb/serial.h

@@ -320,6 +320,8 @@ extern struct usb_serial_port *usb_serial_port_get_by_minor(unsigned int minor);
 extern void usb_serial_put(struct usb_serial *serial);
 extern int usb_serial_generic_open(struct tty_struct *tty,
 	struct usb_serial_port *port);
+extern int usb_serial_generic_write_start(struct usb_serial_port *port,
+							gfp_t mem_flags);
 extern int usb_serial_generic_write(struct tty_struct *tty,
 	struct usb_serial_port *port, const unsigned char *buf, int count);
 extern void usb_serial_generic_close(struct usb_serial_port *port);