usb: gadget: add usb_gadget_activate/deactivate functions

These functions allows to deactivate gadget to make it not visible to
host and make it active again when gadget driver is finally ready.

They are needed to fix usb_function_activate() and usb_function_deactivate()
functions which currently are not working as usb_gadget_connect() is
called immediately after function bind regardless to previous calls of
usb_gadget_disconnect() function.

Signed-off-by: Robert Baldyga <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

include/linux/usb/gadget.h

···
  * @quirk_ep_out_aligned_size: epout requires buffer size to be aligned to
  *	MaxPacketSize.
  * @is_selfpowered: if the gadget is self-powered.
+ * @deactivated: True if gadget is deactivated - in deactivated state it cannot
+ *	be connected.
+ * @connected: True if gadget is connected.
  *
  * Gadgets have a mostly-portable "gadget driver" implementing device
  * functions, handling all usb configurations and interfaces.  Gadget
···
 	unsigned			a_alt_hnp_support:1;
 	unsigned			quirk_ep_out_aligned_size:1;
 	unsigned			is_selfpowered:1;
+	unsigned			deactivated:1;
+	unsigned			connected:1;
 };
 #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
 
···
  */
 static inline int usb_gadget_connect(struct usb_gadget *gadget)
 {
+	int ret;
+
 	if (!gadget->ops->pullup)
 		return -EOPNOTSUPP;
-	return gadget->ops->pullup(gadget, 1);
+
+	if (gadget->deactivated) {
+		/*
+		 * If gadget is deactivated we only save new state.
+		 * Gadget will be connected automatically after activation.
+		 */
+		gadget->connected = true;
+		return 0;
+	}
+
+	ret = gadget->ops->pullup(gadget, 1);
+	if (!ret)
+		gadget->connected = 1;
+	return ret;
 }
 
 /**
···
  * as a disconnect (when a VBUS session is active).  Not all systems
  * support software pullup controls.
  *
- * This routine may be used during the gadget driver bind() call to prevent
- * the peripheral from ever being visible to the USB host, unless later
- * usb_gadget_connect() is called.  For example, user mode components may
- * need to be activated before the system can talk to hosts.
- *
  * Returns zero on success, else negative errno.
  */
 static inline int usb_gadget_disconnect(struct usb_gadget *gadget)
 {
+	int ret;
+
 	if (!gadget->ops->pullup)
 		return -EOPNOTSUPP;
-	return gadget->ops->pullup(gadget, 0);
+
+	if (gadget->deactivated) {
+		/*
+		 * If gadget is deactivated we only save new state.
+		 * Gadget will stay disconnected after activation.
+		 */
+		gadget->connected = false;
+		return 0;
+	}
+
+	ret = gadget->ops->pullup(gadget, 0);
+	if (!ret)
+		gadget->connected = 0;
+	return ret;
 }
 
+/**
+ * usb_gadget_deactivate - deactivate function which is not ready to work
+ * @gadget: the peripheral being deactivated
+ *
+ * This routine may be used during the gadget driver bind() call to prevent
+ * the peripheral from ever being visible to the USB host, unless later
+ * usb_gadget_activate() is called.  For example, user mode components may
+ * need to be activated before the system can talk to hosts.
+ *
+ * Returns zero on success, else negative errno.
+ */
+static inline int usb_gadget_deactivate(struct usb_gadget *gadget)
+{
+	int ret;
+
+	if (gadget->deactivated)
+		return 0;
+
+	if (gadget->connected) {
+		ret = usb_gadget_disconnect(gadget);
+		if (ret)
+			return ret;
+		/*
+		 * If gadget was being connected before deactivation, we want
+		 * to reconnect it in usb_gadget_activate().
+		 */
+		gadget->connected = true;
+	}
+	gadget->deactivated = true;
+
+	return 0;
+}
+
+/**
+ * usb_gadget_activate - activate function which is not ready to work
+ * @gadget: the peripheral being activated
+ *
+ * This routine activates gadget which was previously deactivated with
+ * usb_gadget_deactivate() call. It calls usb_gadget_connect() if needed.
+ *
+ * Returns zero on success, else negative errno.
+ */
+static inline int usb_gadget_activate(struct usb_gadget *gadget)
+{
+	if (!gadget->deactivated)
+		return 0;
+
+	gadget->deactivated = false;
+
+	/*
+	 * If gadget has been connected before deactivation, or became connected
+	 * while it was being deactivated, we call usb_gadget_connect().
+	 */
+	if (gadget->connected)
+		return usb_gadget_connect(gadget);
+
+	return 0;
+}
 
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