usb: gadget: udc-core: add utility for bus reset

The udc driver can notify the udc core that bus reset occurs by
calling this utility, the core will notify gadget driver this
information and update gadget state accordingly.

Signed-off-by: Peter Chen <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/udc/udc-core.c

···
 /* ------------------------------------------------------------------------- */
 
 /**
+ * usb_gadget_udc_reset - notifies the udc core that bus reset occurs
+ * @gadget: The gadget which bus reset occurs
+ * @driver: The gadget driver we want to notify
+ *
+ * If the udc driver has bus reset handler, it needs to call this when the bus
+ * reset occurs, it notifies the gadget driver that the bus reset occurs as
+ * well as updates gadget state.
+ */
+void usb_gadget_udc_reset(struct usb_gadget *gadget,
+		struct usb_gadget_driver *driver)
+{
+	driver->reset(gadget);
+	usb_gadget_set_state(gadget, USB_STATE_DEFAULT);
+}
+EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
+
+/**
  * usb_gadget_udc_start - tells usb device controller to start up
  * @gadget: The gadget we want to get started
  * @driver: The driver we want to bind to @gadget

include/linux/usb/gadget.h

···
 
 /*-------------------------------------------------------------------------*/
 
+/* utility to tell udc core that the bus reset occurs */
+extern void usb_gadget_udc_reset(struct usb_gadget *gadget,
+		struct usb_gadget_driver *driver);
+
+/*-------------------------------------------------------------------------*/
+
 /* utility wrapping a simple endpoint selection policy */
 
 extern struct usb_ep *usb_ep_autoconfig(struct usb_gadget *,