USB: serial: mos7720: fix parallel probe

A static usb-serial-driver structure that is used to initialise the
interrupt URB was modified during probe depending on the currently
probed device type, something which could break a parallel probe of a
device of a different type.

Fix this up by overriding the default completion callback for MCS7715
devices in attach() instead. We may want to use two usb-serial driver
instances for the two types later.

Fixes: fb088e335d78 ("USB: serial: add support for serial port on the
moschip 7715")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/mos7720.c

@@ -65,8 +65,6 @@ struct moschip_port {
 	struct urb		*write_urb_pool[NUM_URBS];
 };
 
-static struct usb_serial_driver moschip7720_2port_driver;
-
 #define USB_VENDOR_ID_MOSCHIP		0x9710
 #define MOSCHIP_DEVICE_ID_7720		0x7720
 #define MOSCHIP_DEVICE_ID_7715		0x7715
@@ -970,25 +968,6 @@ static void mos7720_bulk_out_data_callback(struct urb *urb)
 		tty_port_tty_wakeup(&mos7720_port->port->port);
 }
 
-/*
- * mos77xx_probe
- *	this function installs the appropriate read interrupt endpoint callback
- *	depending on whether the device is a 7720 or 7715, thus avoiding costly
- *	run-time checks in the high-frequency callback routine itself.
- */
-static int mos77xx_probe(struct usb_serial *serial,
-			 const struct usb_device_id *id)
-{
-	if (id->idProduct == MOSCHIP_DEVICE_ID_7715)
-		moschip7720_2port_driver.read_int_callback =
-			mos7715_interrupt_callback;
-	else
-		moschip7720_2port_driver.read_int_callback =
-			mos7720_interrupt_callback;
-
-	return 0;
-}
-
 static int mos77xx_calc_num_ports(struct usb_serial *serial)
 {
 	u16 product = le16_to_cpu(serial->dev->descriptor.idProduct);
@@ -1946,6 +1925,12 @@ static int mos7720_startup(struct usb_serial *serial)
 			tmp->interrupt_in_endpointAddress;
 		serial->port[1]->interrupt_in_urb = NULL;
 		serial->port[1]->interrupt_in_buffer = NULL;
+
+		if (serial->port[0]->interrupt_in_urb) {
+			struct urb *urb = serial->port[0]->interrupt_in_urb;
+
+			urb->complete = mos7715_interrupt_callback;
+		}
 	}
 
 	/* setting configuration feature to one */
@@ -2060,7 +2045,6 @@ static struct usb_serial_driver moschip7720_2port_driver = {
 	.close			= mos7720_close,
 	.throttle		= mos7720_throttle,
 	.unthrottle		= mos7720_unthrottle,
-	.probe			= mos77xx_probe,
 	.attach			= mos7720_startup,
 	.release		= mos7720_release,
 	.port_probe		= mos7720_port_probe,
@@ -2074,7 +2058,7 @@ static struct usb_serial_driver moschip7720_2port_driver = {
 	.chars_in_buffer	= mos7720_chars_in_buffer,
 	.break_ctl		= mos7720_break,
 	.read_bulk_callback	= mos7720_bulk_in_callback,
-	.read_int_callback	= NULL  /* dynamically assigned in probe() */
+	.read_int_callback	= mos7720_interrupt_callback,
 };
 
 static struct usb_serial_driver * const serial_drivers[] = {