NAME
       CD_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      CD_GETGEOMETRY
       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/cd.h>
       io_Actual - length of data transferred.

   SEE ALSO
       CD_GETNUMTRACKS, <devices/trackdisk.h>