D-Port is a new port type created with the intention of running link
level diagnostic tests like loopback, traffic test. In static D-port
mode, user configures the port to D-port mode and starts the test, but
in dynamic D-port, once the Brocade switch port is configured to
D-port, it will reject the regular FLOGI from HBA with reason that it is
in D-port mode. So based on the reason code HBA port will turn itself into
D-port and start diagnostic test.