Passing a pointer to a cstruct

[basho1600 at pm.me]

I am using SBCL and trying to pass a pointer to a c-struct to
a CFFI routine.  The difficulty I am having is in formulating the
function call correctly.  I have tried 'define-alien-routine' but
was getting nowhere.  So now I am using cffi:foreign-funcall directly.
Here is the call:

    (cffi:foreign-funcall
    "v4lconvert_convert"
    :POINTER convert-info
    :POINTER *camera-format*
    :POINTER *display-format*
    :POINTER raw-image
    :INT *local-length*
    :POINTER pixdata
    :INT pixbuf-size
    :INT)

It is the pointers to the two '-format' items that are causing the
trouble I think.  Both of them were defined using defcstruct.

But the error message I get is complaining about the expansion of
the foreign-funcall macro and makes no sense at all to me.  Can
somebody help me interpret this?

;     (CFFI:FOREIGN-FUNCALL "v4lconvert_convert"
;        :POINTER ENCOMM.GUI::CONVERT-INFO
;        :POINTER ENCOMM.GUI::*CAMERA-FORMAT* :POINTER
;        ENCOMM.GUI::*DISPLAY-FORMAT* :POINTER
;        ENCOMM.GUI::RAW-IMAGE :INT ENCOMM.GUI::*LOCAL-LENGTH*
;                           ...)
; --> LET LET LET LET LET LET LET CFFI-SYS:%FOREIGN-FUNCALL
; --> CFFI-SYS::%%FOREIGN-FUNCALL ALIEN-FUNCALL
; --> SB-ALIEN-INTERNALS:INVOKE-WITH-SAVED-FP-AND-PC LAMBDA FUNCTION
; --> SB-ALIEN-INTERNALS:NATURALIZE LET LET LET LET LET LET LET
; --> SB-ALIEN-INTERNALS:MAYBE-WITH-PINNED-OBJECTS PROGN
SB-C:%ALIEN-FUNCALL
; ==>
;   (SB-ALIEN-INTERNALS:DEPORT #:G77
; '#<SB-ALIEN::ALIEN-SYSTEM-AREA-POINTER-TYPE SB-SYS:SYSTEM-AREA-POINTER>)
;
; caught WARNING:
;   Derived type of #:G77 is
;     (VALUES (ALIEN (* T)) &OPTIONAL),
;   conflicting with its asserted type
;     SB-SYS:SYSTEM-AREA-POINTER.
;   See also:
;     The SBCL Manual, Node "Handling of Types"