TTY: switch tty_flip_buffer_push

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.

IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.

Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/ssu100.c b/drivers/usb/serial/ssu100.c
index 3871315..58bc7e7 100644
--- a/drivers/usb/serial/ssu100.c
+++ b/drivers/usb/serial/ssu100.c
@@ -582,7 +582,7 @@
 
 }
 
-static int ssu100_process_packet(struct urb *urb)
+static void ssu100_process_read_urb(struct urb *urb)
 {
 	struct usb_serial_port *port = urb->context;
 	char *packet = (char *)urb->transfer_buffer;
@@ -609,7 +609,7 @@
 		ch = packet;
 
 	if (!len)
-		return 0;	/* status only */
+		return;	/* status only */
 
 	if (port->port.console && port->sysrq) {
 		for (i = 0; i < len; i++, ch++) {
@@ -619,24 +619,7 @@
 	} else
 		tty_insert_flip_string_fixed_flag(&port->port, ch, flag, len);
 
-	return len;
-}
-
-static void ssu100_process_read_urb(struct urb *urb)
-{
-	struct usb_serial_port *port = urb->context;
-	struct tty_struct *tty;
-	int count;
-
-	tty = tty_port_tty_get(&port->port);
-	if (!tty)
-		return;
-
-	count = ssu100_process_packet(urb);
-
-	if (count)
-		tty_flip_buffer_push(tty);
-	tty_kref_put(tty);
+	tty_flip_buffer_push(&port->port);
 }
 
 static struct usb_serial_driver ssu100_device = {