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