NAME
       TD_EJECT -- eject (or load) the disk in the drive, if possible.

   FUNCTION
        This command causes the drive to attempt to eject the disk in
        it, if any.  Note that the current trackdisk.device does not
        implement this command, but it might in the future, and other
        trackdisk-compatible drivers may implement this command.  Some
        devices may be able to load disks on command also.

   IO REQUEST INPUT
        io_Device       preset by the call to opendevice()
        io_Unit         preset by the call to opendevice()
        io_Command      TD_EJECT
        io_Flags        0 or IOF_QUICK
        io_Length       0 (load, if supported) or 1 (eject)

   IO REQUEST RESULT
        io_Error - 0 for success, or an error code as defined in
                   <devices/trackdisk.h>

   BUGS
        The pre-V40 autodoc didn't mention io_Length.  Because of this, for
        devices that can never support load, a driver might want to eject if
        io_Length is 0.