get_offset
cb->get_offset(&md, &dpos, v3, i);
int (*get_offset)(struct mbuf **md, caddr_t *dpos, int v3, struct
softc->callbacks.get_offset = fhanew_get_offset;
{name, true, false, value, 0, 0, get_offset(var, bool)}
{name, true, true, false, 0, 0, get_offset(var, bool)}
{name, false, false, false, min, max, get_offset(var, int)}