midi input in LWW / fli reference-return

Hi,
I was thinking of reading input from a midi device, but have some
basic problems with the fli.

I have the following:

(defconstant +max-pname-len+ 32)

(fli:define-c-typedef word
  (:unsigned :short))

(fli:define-c-typedef dword
  (:unsigned :long))

(fli:define-c-typedef mmversion
  (:unsigned :int))

;;; typedef struct {
;;;     WORD      wMid;
;;;     WORD      wPid;
;;;     MMVERSION vDriverVersion;
;;;     TCHAR     szPname[MAXPNAMELEN];
;;;     DWORD     dwSupport;
;;; } MIDIINCAPS;

(fli:define-c-struct midi-in-caps
  (mid word)
  (pid word)
  (driver-version mmversion)
  (p-name (:ef-mb-string :limit +max-pname-len+))
  (support dword))

;;; UINT midiInGetNumDevs(VOID);

(fli:define-foreign-function (midi-in-get-num-devs "midiInGetNumDevs")
    ()
  :result-type :unsigned
  :language :ansi-c)

;;; MMRESULT midiInGetDevCaps(
;;;   UINT_PTR     uDeviceID,
;;;   LPMIDIINCAPS lpMidiInCaps,
;;;   UINT         cbMidiInCaps
;;; );

(fli:define-foreign-function (midi-in-get-dev-caps "midiInGetDevCapsA")
    ((i dword)
     (midi-in-caps (:reference-return midi-in-caps))
     (size-of dword))
  :result-type :unsigned
  :language :ansi-c)


(defun print-dev-stats (id)
       (fli:with-dynamic-foreign-objects ()
         (let ((lp-midi-dev (fli:allocate-dynamic-foreign-object :type
'midi-in-caps)))
           (setf (fli:foreign-slot-value lp-midi-dev 'mid) 0
                 (fli:foreign-slot-value lp-midi-dev 'pid) 0
                 (fli:foreign-slot-value lp-midi-dev 'support) 0)
           (if (= 0 (midi-in-get-dev-caps id lp-midi-dev (fli:size-of
'midi-in-caps)))
             (format t "~a ~a ~a ~a ~%"
                     (fli:foreign-slot-value lp-midi-dev 'mid)
                     (fli:foreign-slot-value lp-midi-dev 'pid)
                     (fli:convert-from-foreign-string
(fli:foreign-slot-pointer lp-midi-dev 'p-name))
                     (fli:foreign-slot-value lp-midi-dev 'support))))))


The midi-in-get-num-devs works reasonably well, but if a midi device
is attached or
removed while the lisp image is running, the number returned from the
function stays
the same. print-dev-stats on the other hand does not work. The fli
call returns 0
indicating success, but the struct slots do not get updated. I'm
guessing I have
misunderstood the way to use reference-return somehow.

MIDI-MON 6 > (midi-in-get-num-devs)
2

MIDI-MON 7 > (print-dev-stats 0)
0 0 etNumDevs 0
NIL

MIDI-MON 8 > (print-dev-stats 1)
0 0 etNumDevs 0


If anyone has any better approach to using midi, I'm all ears btw. All I want
to do at the moment is to open a midi device an read in messages.
-- 
  -asbjxrn