NAME
       TD_GETGEOMETRY -- return the geometry of the drive.

   FUNCTION
        This command returns a full set of information about the
        layout of the drive. The information is returned in the
        drivegeometry structure pointed to by io_data.

   IO REQUEST INPUT
        io_Device       preset by the call to opendevice()
        io_Unit         preset by the call to opendevice()
        io_Command      TD_GETGEOMETRY
        io_Flags        0 or IOF_QUICK
        io_Data         Pointer to a drivegeometry structure
        io_Length       sizeof(struct DriveGeometry)

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

   NOTE
        This information may change when a disk in inserted when
        certain hardware is present.

   SEE ALSO
        td_getdrivetype, td_getnumtracks