呼び出しテーブル

こんな感じ
struct {
  const int   if_version;  /* interface version */
  const int   lib_version; /* library version */
  const char *name;        /* camera name */
    :
  int  (*alloc) (usbcam_dev_t *);  /* alloc device
                                      depended area */
  int  (*probe) (usbcam_dev_t *, char *);
                                   /* probe usb cam */
  int  (*dev_init) (usbcam_dev_t *, int);
                                   /* device init * /
  int  (*grab_image) (usbcam_dev_t *);
                                   /* get data image */
  void (*free) (usbcam_dev_t *);   /* device close and free */
    :