USB: stop io performed by mos7720 upon close()

This fixes a problem where the mos7720 driver will make io to a device from
which it has been logically disconnected. It does so by introducing a flag by
which the generic usb serial code can signal the subdrivers their
disconnection and appropriate locking.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/mos7720.c

@@ -564,14 +564,16 @@ static void mos7720_close(struct usb_serial_port *port, struct file *filp)
 	}
 
 	/* While closing port, shutdown all bulk read, write  *
-	 * and interrupt read if they exists                  */
-	if (serial->dev) {
+	 * and interrupt read if they exists, otherwise nop   */
 	dbg("Shutdown bulk write");
 	usb_kill_urb(port->write_urb);
 	dbg("Shutdown bulk read");
 	usb_kill_urb(port->read_urb);
-	}
 
+	mutex_lock(&serial->disc_mutex);
+	/* these commands must not be issued if the device has
+	 * been disconnected */
+	if (!serial->disconnected) {
 		data = 0x00;
 		send_mos_cmd(serial, MOS_WRITE, port->number - port->serial->minor,
 			     0x04, &data);
@@ -579,7 +581,8 @@ static void mos7720_close(struct usb_serial_port *port, struct file *filp)
 		data = 0x00;
 		send_mos_cmd(serial, MOS_WRITE, port->number - port->serial->minor,
 			     0x01, &data);
-
+	}
+	mutex_unlock(&serial->disc_mutex);
 	mos7720_port->open = 0;
 
 	dbg("Leaving %s", __FUNCTION__);

drivers/usb/serial/usb-serial.c

@@ -634,6 +634,7 @@ static struct usb_serial * create_serial (struct usb_device *dev,
 	serial->type = driver;
 	serial->interface = interface;
 	kref_init(&serial->kref);
+	mutex_init(&serial->disc_mutex);
 
 	return serial;
 }
@@ -1089,8 +1090,10 @@ void usb_serial_disconnect(struct usb_interface *interface)
 	usb_serial_console_disconnect(serial);
 	dbg ("%s", __FUNCTION__);
 
+	mutex_lock(&serial->disc_mutex);
 	usb_set_intfdata (interface, NULL);
-	if (serial) {
+	/* must set a flag, to signal subdrivers */
+	serial->disconnected = 1;
 	for (i = 0; i < serial->num_ports; ++i) {
 		port = serial->port[i];
 		if (port) {
@@ -1101,8 +1104,8 @@ void usb_serial_disconnect(struct usb_interface *interface)
 	}
 	/* let the last holder of this object
 	 * cause it to be cleaned up */
+	mutex_unlock(&serial->disc_mutex);
 	usb_serial_put(serial);
-	}
 	dev_info(dev, "device disconnected\n");
 }
 
@@ -1112,9 +1115,6 @@ int usb_serial_suspend(struct usb_interface *intf, pm_message_t message)
 	struct usb_serial_port *port;
 	int i, r = 0;
 
-	if (!serial) /* device has been disconnected */
-		return 0;
-
 	for (i = 0; i < serial->num_ports; ++i) {
 		port = serial->port[i];
 		if (port)

include/linux/usb/serial.h

@@ -129,6 +129,7 @@ struct usb_serial {
 	struct usb_device *		dev;
 	struct usb_serial_driver *	type;
 	struct usb_interface *		interface;
+	unsigned char			disconnected;
 	unsigned char			minor;
 	unsigned char			num_ports;
 	unsigned char			num_port_pointers;
@@ -138,6 +139,7 @@ struct usb_serial {
 	char				num_bulk_out;
 	struct usb_serial_port *	port[MAX_NUM_PORTS];
 	struct kref			kref;
+	struct mutex			disc_mutex;
 	void *				private;
 };
 #define to_usb_serial(d) container_of(d, struct usb_serial, kref)