usb: core: hub: controller driver name may be NULL

The controller driver may be NULL if the controller device
is the middle device between platform device and roothub.
This middle device may not need a device driver due to all
hardware control can be at platform device driver, this
platform device is usually a dual-role USB controller device.

The benefit of using this middle device is we can keep both
controller device's private data (known as struct usb_hcd)
for USB core use, and platform device's private data for
platform driver use.
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hub.c

@@ -4342,6 +4342,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 	enum usb_device_speed	oldspeed = udev->speed;
 	const char		*speed;
 	int			devnum = udev->devnum;
+	const char		*driver_name;
 
 	/* root hub ports have a slightly longer reset period
 	 * (from USB 2.0 spec, section 7.1.7.5)
@@ -4409,11 +4410,23 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 	else
 		speed = usb_speed_string(udev->speed);
 
+	/*
+	 * The controller driver may be NULL if the controller device
+	 * is the middle device between platform device and roothub.
+	 * This middle device may not need a device driver due to
+	 * all hardware control can be at platform device driver, this
+	 * platform device is usually a dual-role USB controller device.
+	 */
+	if (udev->bus->controller->driver)
+		driver_name = udev->bus->controller->driver->name;
+	else
+		driver_name = udev->bus->sysdev->driver->name;
+
 	if (udev->speed < USB_SPEED_SUPER)
 		dev_info(&udev->dev,
 				"%s %s USB device number %d using %s\n",
 				(udev->config) ? "reset" : "new", speed,
-				devnum, udev->bus->controller->driver->name);
+				devnum, driver_name);
 
 	/* Set up TT records, if needed  */
 	if (hdev->tt) {
@@ -4545,7 +4558,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 						"%s SuperSpeed%s USB device number %d using %s\n",
 						(udev->config) ? "reset" : "new",
 					 (udev->speed == USB_SPEED_SUPER_PLUS) ? "Plus" : "",
-						devnum, udev->bus->controller->driver->name);
+					 devnum, driver_name);
 			}
 
 			/* cope with hardware quirkiness: