usb: gadget: introduce UDC Class

this class will be used to abstract away several of the duplicated
operations scattered among the USB gadget controller drivers.

Later, we can add an atomic notifier to tell interested drivers about
what's happening with the controller. Notifications such as suspend,
resume, enumerated, etc. will be useful, at a minimum, for implementing
usb charger detection.

As part of the converting process usb_gadget_probe_driver() is no longer
part of each udc but pushed into the ->stap() callback. The same for his
couterpart.

The core is currently set explicit to 'n'. It will be changed to 'y' once
all users are converted since it provides functions which clash with
other drivers.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/usb/gadget.h

@@ -418,6 +418,7 @@ static inline void usb_ep_fifo_flush(struct usb_ep *ep)
 /*-------------------------------------------------------------------------*/
 
 struct usb_gadget;
+struct usb_gadget_driver;
 
 /* the rest of the api to the controller hardware: device operations,
  * which don't involve endpoints (or i/o).
@@ -431,6 +432,9 @@ struct usb_gadget_ops {
 	int	(*pullup) (struct usb_gadget *, int is_on);
 	int	(*ioctl)(struct usb_gadget *,
 				unsigned code, unsigned long param);
+	int	(*start)(struct usb_gadget_driver *,
+			int (*bind)(struct usb_gadget *));
+	int	(*stop)(struct usb_gadget_driver *);
 };
 
 /**
@@ -822,6 +826,9 @@ int usb_gadget_probe_driver(struct usb_gadget_driver *driver,
  */
 int usb_gadget_unregister_driver(struct usb_gadget_driver *driver);
 
+extern int usb_add_gadget_udc(struct device *parent, struct usb_gadget *gadget);
+extern void usb_del_gadget_udc(struct usb_gadget *gadget);
+
 /*-------------------------------------------------------------------------*/
 
 /* utility to simplify dealing with string descriptors */