USB: ftdi_sio: remove obsolete port data refcounting

Remove the port data refcounting and release the private data
explicitly at port remove.

The port data refcounting was used to make sure the port data was not
freed until the last tty reference was closed. Since moving over to tty
ports, the underlying assumptions are no longer valid as close is now
called as part of tty port shutdown, which can occur before the final
tty reference is dropped on device disconnect.

This means that the private port data refcounting is now completely
useless, as the last reference will always be dropped on port_remove.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/ftdi_sio.c

@@ -55,7 +55,6 @@ static __u16 vendor = FTDI_VID;
 static __u16 product;
 
 struct ftdi_private {
-	struct kref kref;
 	enum ftdi_chip_type chip_type;
 				/* type of device, either SIO or FT8U232AM */
 	int baud_base;		/* baud base clock for divisor setting */
@@ -910,7 +909,6 @@ static int  ftdi_sio_probe(struct usb_serial *serial,
 static int  ftdi_sio_port_probe(struct usb_serial_port *port);
 static int  ftdi_sio_port_remove(struct usb_serial_port *port);
 static int  ftdi_open(struct tty_struct *tty, struct usb_serial_port *port);
-static void ftdi_close(struct usb_serial_port *port);
 static void ftdi_dtr_rts(struct usb_serial_port *port, int on);
 static void ftdi_process_read_urb(struct urb *urb);
 static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
@@ -950,7 +948,6 @@ static struct usb_serial_driver ftdi_sio_device = {
 	.port_probe =		ftdi_sio_port_probe,
 	.port_remove =		ftdi_sio_port_remove,
 	.open =			ftdi_open,
-	.close =		ftdi_close,
 	.dtr_rts =		ftdi_dtr_rts,
 	.throttle =		usb_serial_generic_throttle,
 	.unthrottle =		usb_serial_generic_unthrottle,
@@ -1687,7 +1684,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
 		return -ENOMEM;
 	}
 
-	kref_init(&priv->kref);
 	mutex_init(&priv->cfg_lock);
 
 	priv->flags = ASYNC_LOW_LATENCY;
@@ -1825,13 +1821,6 @@ static int ftdi_mtxorb_hack_setup(struct usb_serial *serial)
 	return 0;
 }
 
-static void ftdi_sio_priv_release(struct kref *k)
-{
-	struct ftdi_private *priv = container_of(k, struct ftdi_private, kref);
-
-	kfree(priv);
-}
-
 static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
@@ -1840,7 +1829,7 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
 
 	remove_sysfs_attrs(port);
 
-	kref_put(&priv->kref, ftdi_sio_priv_release);
+	kfree(priv);
 
 	return 0;
 }
@@ -1850,7 +1839,6 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 	struct ktermios dummy;
 	struct usb_device *dev = port->serial->dev;
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
-	int result;
 
 	/* No error checking for this (will get errors later anyway) */
 	/* See ftdi_sio.h for description of what is reset */
@@ -1869,12 +1857,7 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 		ftdi_set_termios(tty, port, &dummy);
 	}
 
-	/* Start reading from the device */
-	result = usb_serial_generic_open(tty, port);
-	if (!result)
-		kref_get(&priv->kref);
-
-	return result;
+	return usb_serial_generic_open(tty, port);
 }
 
 static void ftdi_dtr_rts(struct usb_serial_port *port, int on)
@@ -1899,19 +1882,6 @@ static void ftdi_dtr_rts(struct usb_serial_port *port, int on)
 		clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
 }
 
-/*
- * usbserial:__serial_close  only calls ftdi_close if the point is open
- *
- *   This only gets called when it is the last close
- */
-static void ftdi_close(struct usb_serial_port *port)
-{
-	struct ftdi_private *priv = usb_get_serial_port_data(port);
-
-	usb_serial_generic_close(port);
-	kref_put(&priv->kref, ftdi_sio_priv_release);
-}
-
 /* The SIO requires the first byte to have:
  *  B0 1
  *  B1 0