usbd_xfer_max_len
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_len(xfer));
usbd_xfer_max_len(xfer));
usb_frlength_t usbd_xfer_max_len(struct usb_xfer *xfer);