PROTOCOL_OVERHEAD
fw_transaction_time = (((len + PROTOCOL_OVERHEAD) * 11) >> 4);
fw_transaction_time = ((len + PROTOCOL_OVERHEAD) * 6);
if (usb->actual_frame->total_bytes + len + PROTOCOL_OVERHEAD >=
usb->actual_frame->total_bytes += (len + PROTOCOL_OVERHEAD);
usb->actual_frame->total_bytes -= (len + PROTOCOL_OVERHEAD);