OK, explain this:

4.7 BSD:

/sys/dev/wi/if_wi.c ... Lucent/prism2 802.11b device driver:

loadable modules (device drivers) are now placed in /sys/dev
stored in /modules, and can be loaded with kldload at boot.
This one is lucent/orinoco/prism2 802.11 device driver.

# kldload  if_wi.ko  (if necessary)
# kldstat

Can also be statically linked into kernel.

---------------------------------------------------------
wi_rxeof(sc)

...
                /* first allocate mbuf for packet storage */
                MGETHDR(m, M_DONTWAIT, MT_DATA);
                if (m == NULL) {
                        ifp->if_ierrors++;
                        return;
                }
                MCLGET(m, M_DONTWAIT);
                if (!(m->m_flags & M_EXT)) {
                        m_freem(m);
                        ifp->if_ierrors++;
                        return;
                }

                m->m_pkthdr.rcvif = ifp;

                /* now read wi_frame first so we know how much data to read */
                if (wi_read_data(sc, id, 0, mtod(m, caddr_t),
                    sizeof(struct wi_frame))) {
                        m_freem(m);
                        ifp->if_ierrors++;
                        return;
                }

...