GUARD_BYTE
memset(urb->transfer_buffer, GUARD_BYTE, offset);
usb_pipein(urb->pipe) ? GUARD_BYTE : 0,
memset(urb->transfer_buffer, GUARD_BYTE, offset);
usb_pipein(urb->pipe) ? GUARD_BYTE : 0,
if (*guard != GUARD_BYTE) {
i, *guard, GUARD_BYTE);