USB: serial: generalise generic read implementation

Add process_read_urb to usb_serial_driver so that a driver can rely on
the generic read (and throttle) mechanism but still do device specific
processing of incoming data (such as adding tty_flags before pushing to
line discipline).

The default generic implementation handles sysrq for consoles but
otherwise simply pushes to tty.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index 53f6dc6..ff8872e 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -272,6 +272,8 @@
 	void (*write_int_callback)(struct urb *urb);
 	void (*read_bulk_callback)(struct urb *urb);
 	void (*write_bulk_callback)(struct urb *urb);
+	/* Called by the generic read bulk callback */
+	void (*process_read_urb)(struct urb *urb);
 };
 #define to_usb_serial_driver(d) \
 	container_of(d, struct usb_serial_driver, driver)
@@ -323,6 +325,7 @@
 extern void usb_serial_generic_deregister(void);
 extern int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
 						 gfp_t mem_flags);
+extern void usb_serial_generic_process_read_urb(struct urb *urb);
 extern int usb_serial_handle_sysrq_char(struct tty_struct *tty,
 					struct usb_serial_port *port,
 					unsigned int ch);