container-of-example.c

struct MyCustomType {
    int misc;
    struct ExistingType m0;
    void *data;
};

void my_callback(struct ExistingType *e)
{
   struct MyCustomType *p = containter_of(e, struct MyCustomType, m0);
   /* access p->data ... */
}

/* See http://www.kroah.com/log/linux/container_of.html
   for how the container_of() macro is implemented. */