f_dfu_snippet1.c

static int
dfu_handle(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
	struct usb_gadget *gadget = f->config->cdev->gadget;
	struct usb_request *req = f->config->cdev->req;
	struct f_dfu *f_dfu = f->config->cdev->req->context;
	…
	if (req_type == USB_TYPE_STANDARD) {
		…
	} else /* DFU specific request */
		value = dfu_state[f_dfu->dfu_state] (f_dfu, ctrl, gadget, req);

	if (value >= 0) {
		req->length = value;
		req->zero = value < len;
		value = usb_ep_queue(gadget->ep0, req, 0);
		if (value < 0) {
			debug("ep_queue --> %d\n", value);
			req->status = 0;
		}
	}

	return value;
}