usb: gadget: udc: Fix permanent block caused by 'deactivated' flag

When setting a new USB configuration, some functions (e.g., UVC) can call usb_function_deactivate() to set the gadget->deactivated flag to true, intentionally blocking enumeration until a userspace daemon (e.g., UVC service) is ready.

This deactivated=true state becomes a permanent block if this flag is not cleared by usb_function_activate() (e.g., UVC service failure or config set while unplugged). This blocked state persists even if the cable is plugged/unplugged, as the vbus_event_work() handler is still blocked by the gadget->deactivated flag, preventing pullup() from being called.

This patch fixes this by modifying vbus_event_work() to clear the gadget->deactivated flag *before* usb_udc_connect_control_locked(). This breaks the permanent block, so pullup() can now be called.

---
 drivers/usb/gadget/udc/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

index 8dbe79bdc0f9..0195540d511a 100644
@@ -1151,8 +1151,17 @@ static int usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc-
 static void vbus_event_work(struct work_struct *work)
 {
 	struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
+	struct usb_gadget *gadget = udc->gadget;
 
 	mutex_lock(&udc->connect_lock);
+
+	/*
+	 * Clear the 'deactivated' flag on a VBUS event
+	 * to break the blocked state.
+	 */
+	if (gadget->deactivated)
+		gadget->deactivated = false;
+
 	usb_udc_connect_control_locked(udc);
 	mutex_unlock(&udc->connect_lock);
 }

2.52.0.rc1.455.g30608eb744-goog

I do not believe this is the right approach. It will fail in situations where the cable is plugged in and then unplugged before the function driver is ready -- the deactivated flag will be cleared while the driver still is not ready.

The proper fix is to make sure that the situation never arises. In other words, if the ucv driver calls usb_function_deactivate() then it must guarantee that it will call usb_function_activate() at an appropriate time later.

Another approach would be for the composite driver to keep track of which function drivers have called usb_function_deactivate(), and have it automatically clear the deactivated flag once those drivers are all unbound. But this wouldn't be necessary if the function drivers all behaved properly.

Alan Stern