public static extern int usb_reap_async_nocancel(LibUsb_Context context, int timeout);
public static extern int usb_isochronous_setup_async(LibUsb_DevHandle dev, ref LibUsb_Context context, byte ep, int pktsize);
public static extern int usb_interrupt_setup_async(LibUsb_DevHandle dev, ref LibUsb_Context context, byte ep);
public static extern int usb_free_async(ref LibUsb_Context context);
public static extern int usb_cancel_async(LibUsb_Context context);
public static extern int usb_submit_async(LibUsb_Context context, IntPtr bytes, int size);