Big polling(4) cleanup.

o Axe poll in trap.

o Axe IFF_POLLING flag from if_flags.

o Rework revision 1.21 (Giant removal), in such a way that
  poll_mtx is not dropped during call to polling handler.
  This fixes problem with idle polling.

o Make registration and deregistration from polling in a
  functional way, insted of next tick/interrupt.

o Obsolete kern.polling.enable. Polling is turned on/off
  with ifconfig.

Detailed kern_poll.c changes:
  - Remove polling handler flags, introduced in 1.21. The are not
    needed now.
  - Forget and do not check if_flags, if_capenable and if_drv_flags.
  - Call all registered polling handlers unconditionally.
  - Do not drop poll_mtx, when entering polling handlers.
  - In ether_poll() NET_LOCK_GIANT prior to locking poll_mtx.
  - In netisr_poll() axe the block, where polling code asks drivers
    to unregister.
  - In netisr_poll() and ether_poll() do polling always, if any
    handlers are present.
  - In ether_poll_[de]register() remove a lot of error hiding code. Assert
    that arguments are correct, instead.
  - In ether_poll_[de]register() use standard return values in case of
    error or success.
  - Introduce poll_switch() that is a sysctl handler for kern.polling.enable.
    poll_switch() goes through interface list and enabled/disables polling.
    A message that kern.polling.enable is deprecated is printed.

Detailed driver changes:
  - On attach driver announces IFCAP_POLLING in if_capabilities, but
    not in if_capenable.
  - On detach driver calls ether_poll_deregister() if polling is enabled.
  - In polling handler driver obtains its lock and checks IFF_DRV_RUNNING
    flag. If there is no, then unlocks and returns.
  - In ioctl handler driver checks for IFCAP_POLLING flag requested to
    be set or cleared. Driver first calls ether_poll_[de]register(), then
    obtains driver lock and [dis/en]ables interrupts.
  - In interrupt handler driver checks IFCAP_POLLING flag in if_capenable.
    If present, then returns.This is important to protect from spurious
    interrupts.

Reviewed by:	ru, sam, jhb

7 files changed, 295 insertions, 243 deletions

diff --git a/sys/pci/if_dc.c b/sys/pci/if_dc.c
index 8a9e8c6..a6f4304 100644
--- a/sys/pci/if_dc.c
+++ b/sys/pci/if_dc.c
@@ -2265,10 +2265,10 @@ dc_attach(device_t dev)
 	 */
 	ifp->if_data.ifi_hdrlen = sizeof(struct ether_vlan_header);
 	ifp->if_capabilities |= IFCAP_VLAN_MTU;
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
 #endif
-	ifp->if_capenable = ifp->if_capabilities;
 
 	callout_init_mtx(&sc->dc_stat_ch, &sc->dc_mtx, 0);
 
@@ -2339,6 +2339,11 @@ dc_detach(device_t dev)
 
 	ifp = sc->dc_ifp;
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+
 	/* These should only be active if attach succeeded */
 	if (device_is_attached(dev)) {
 		DC_LOCK(sc);
@@ -2704,7 +2709,7 @@ dc_rxeof(struct dc_softc *sc)
 	while (!(le32toh(sc->dc_ldata->dc_rx_list[i].dc_status) &
 	    DC_RXSTAT_OWN)) {
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
@@ -3038,16 +3043,13 @@ dc_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 {
 	struct dc_softc *sc = ifp->if_softc;
 
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-	if (cmd == POLL_DEREGISTER) { /* final call, enable interrupts */
-		/* Re-enable interrupts. */
-		CSR_WRITE_4(sc, DC_IMR, DC_INTRS);
+	DC_LOCK(sc);
+
+	if (!(ifp->if_drv_flags & IFF_DRV_RUNNING)) {
+		DC_UNLOCK(sc);
 		return;
 	}
-	DC_LOCK(sc);
+
 	sc->rxcycles = count;
 	dc_rxeof(sc);
 	dc_txeof(sc);
@@ -3111,12 +3113,9 @@ dc_intr(void *arg)
 	DC_LOCK(sc);
 	ifp = sc->dc_ifp;
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING)
-		goto done;
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(dc_poll, ifp)) { /* ok, disable interrupts */
-		CSR_WRITE_4(sc, DC_IMR, 0x00000000);
-		goto done;
+	if (ifp->if_capenable & IFCAP_POLLING) {
+		DC_UNLOCK(sc);
+		return;
 	}
 #endif
 
@@ -3183,10 +3182,6 @@ dc_intr(void *arg)
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		dc_start_locked(ifp);
 
-#ifdef DEVICE_POLLING
-done:
-#endif
-
 	DC_UNLOCK(sc);
 }
 
@@ -3534,7 +3529,7 @@ dc_init_locked(struct dc_softc *sc)
 	 * the case of polling. Some cards (e.g. fxp) turn interrupts on
 	 * after a reset.
 	 */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_4(sc, DC_IMR, 0x00000000);
 	else
 #endif
@@ -3686,10 +3681,31 @@ dc_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
 #endif
 		break;
 	case SIOCSIFCAP:
-		DC_LOCK(sc);
-		ifp->if_capenable &= ~IFCAP_POLLING;
-		ifp->if_capenable |= ifr->ifr_reqcap & IFCAP_POLLING;
-		DC_UNLOCK(sc);
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(dc_poll, ifp);
+			if (error)
+				return(error);
+			DC_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_4(sc, DC_IMR, 0x00000000);
+			ifp->if_capenable |= IFCAP_POLLING;
+			DC_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			DC_LOCK(sc);
+			CSR_WRITE_4(sc, DC_IMR, DC_INTRS);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			DC_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
@@ -3744,9 +3760,6 @@ dc_stop(struct dc_softc *sc)
 	callout_stop(&sc->dc_stat_ch);
 
 	ifp->if_drv_flags &= ~(IFF_DRV_RUNNING | IFF_DRV_OACTIVE);
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif
 
 	DC_CLRBIT(sc, DC_NETCFG, (DC_NETCFG_RX_ON | DC_NETCFG_TX_ON));
 	CSR_WRITE_4(sc, DC_IMR, 0x00000000);
diff --git a/sys/pci/if_rl.c b/sys/pci/if_rl.c
index c0e42e9..a35e999 100644
--- a/sys/pci/if_rl.c
+++ b/sys/pci/if_rl.c
@@ -195,10 +195,8 @@ static int rl_miibus_readreg(device_t, int, int);
 static void rl_miibus_statchg(device_t);
 static int rl_miibus_writereg(device_t, int, int, int);
 #ifdef DEVICE_POLLING
-static void rl_poll(struct ifnet *ifp, enum poll_cmd cmd,
-				 int count);
-static void rl_poll_locked(struct ifnet *ifp, enum poll_cmd cmd,
-				 int count);
+static void rl_poll(struct ifnet *ifp, enum poll_cmd cmd, int count);
+static void rl_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count);
 #endif
 static int rl_probe(device_t);
 static void rl_read_eeprom(struct rl_softc *, uint8_t *, int, int, int);
@@ -956,10 +954,10 @@ rl_attach(device_t dev)
 	ifp->if_init = rl_init;
 	ifp->if_baudrate = 10000000;
 	ifp->if_capabilities = IFCAP_VLAN_MTU;
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
 #endif
-	ifp->if_capenable = ifp->if_capabilities;
 	IFQ_SET_MAXLEN(&ifp->if_snd, IFQ_MAXLEN);
 	ifp->if_snd.ifq_drv_maxlen = IFQ_MAXLEN;
 	IFQ_SET_READY(&ifp->if_snd);
@@ -1002,6 +1000,10 @@ rl_detach(device_t dev)
 
 	KASSERT(mtx_initialized(&sc->rl_mtx), ("rl mutex not initialized"));
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
 	/* These should only be active if attach succeeded */
 	if (device_is_attached(dev)) {
 		RL_LOCK(sc);
@@ -1115,12 +1117,12 @@ rl_rxeof(struct rl_softc *sc)
 
 	while((CSR_READ_1(sc, RL_COMMAND) & RL_CMD_EMPTY_RXBUF) == 0) {
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 		rxbufpos = sc->rl_cdata.rl_rx_buf + cur_rx;
 		rxstat = le32toh(*(uint32_t *)rxbufpos);
 
@@ -1283,7 +1285,8 @@ rl_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct rl_softc *sc = ifp->if_softc;
 
 	RL_LOCK(sc);
-	rl_poll_locked(ifp, cmd, count);
+	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
+		rl_poll_locked(ifp, cmd, count);
 	RL_UNLOCK(sc);
 }
 
@@ -1294,17 +1297,6 @@ rl_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 
 	RL_LOCK_ASSERT(sc);
 
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-
-	if (cmd == POLL_DEREGISTER) {
-		/* Final call; enable interrupts. */
-		CSR_WRITE_2(sc, RL_IMR, RL_INTRS);
-		return;
-	}
-
 	sc->rxcycles = count;
 	rl_rxeof(sc);
 	rl_txeof(sc);
@@ -1345,17 +1337,9 @@ rl_intr(void *arg)
 		goto done_locked;
 
 #ifdef DEVICE_POLLING
-	if  (ifp->if_flags & IFF_POLLING)
+	if  (ifp->if_capenable & IFCAP_POLLING)
 		goto done_locked;
-
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(rl_poll, ifp)) {
-		/* Disable interrupts. */
-		CSR_WRITE_2(sc, RL_IMR, 0x0000);
-		rl_poll_locked(ifp, 0, 1);
-		goto done_locked;
-	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	for (;;) {
 		status = CSR_READ_2(sc, RL_ISR);
@@ -1574,10 +1558,10 @@ rl_init_locked(struct rl_softc *sc)
 
 #ifdef DEVICE_POLLING
 	/* Disable interrupts if we are polling. */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_2(sc, RL_IMR, 0);
 	else
-#endif /* DEVICE_POLLING */
+#endif
 	/* Enable interrupts. */
 	CSR_WRITE_2(sc, RL_IMR, RL_INTRS);
 
@@ -1669,8 +1653,31 @@ rl_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
 		error = ifmedia_ioctl(ifp, ifr, &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
-		ifp->if_capenable &= ~IFCAP_POLLING;
-		ifp->if_capenable |= ifr->ifr_reqcap & IFCAP_POLLING;
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(rl_poll, ifp);
+			if (error)
+				return(error);
+			RL_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_2(sc, RL_IMR, 0x0000);
+			ifp->if_capenable |= IFCAP_POLLING;
+			RL_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			RL_LOCK(sc);
+			CSR_WRITE_2(sc, RL_IMR, RL_INTRS);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			RL_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
@@ -1712,9 +1719,6 @@ rl_stop(struct rl_softc *sc)
 	ifp->if_timer = 0;
 	callout_stop(&sc->rl_stat_callout);
 	ifp->if_drv_flags &= ~(IFF_DRV_RUNNING | IFF_DRV_OACTIVE);
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif /* DEVICE_POLLING */
 
 	CSR_WRITE_1(sc, RL_COMMAND, 0x00);
 	CSR_WRITE_2(sc, RL_IMR, 0x0000);
diff --git a/sys/pci/if_sf.c b/sys/pci/if_sf.c
index fa7eb83..691a0f6 100644
--- a/sys/pci/if_sf.c
+++ b/sys/pci/if_sf.c
@@ -165,11 +165,9 @@ static int sf_miibus_readreg(device_t, int, int);
 static int sf_miibus_writereg(device_t, int, int, int);
 static void sf_miibus_statchg(device_t);
 #ifdef DEVICE_POLLING
-static void sf_poll(struct ifnet *ifp, enum poll_cmd cmd,
-				 int count);
-static void sf_poll_locked(struct ifnet *ifp, enum poll_cmd cmd,
-				 int count);
-#endif /* DEVICE_POLLING */
+static void sf_poll(struct ifnet *ifp, enum poll_cmd cmd, int count);
+static void sf_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count);
+#endif
 
 static u_int32_t csr_read_4(struct sf_softc *, int);
 static void csr_write_4(struct sf_softc *, int, u_int32_t);
@@ -560,10 +558,31 @@ sf_ioctl(ifp, command, data)
 		error = ifmedia_ioctl(ifp, ifr, &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
-		SF_LOCK(sc);
-		ifp->if_capenable &= ~IFCAP_POLLING;
-		ifp->if_capenable |= ifr->ifr_reqcap & IFCAP_POLLING;
-		SF_UNLOCK(sc);
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(sf_poll, ifp);
+			if (error)
+				return(error);
+			SF_LOCK(sc);
+			/* Disable interrupts */
+			csr_write_4(sc, SF_IMR, 0x00000000);
+			ifp->if_capenable |= IFCAP_POLLING;
+			SF_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			SF_LOCK(sc);
+			csr_write_4(sc, SF_IMR, SF_INTRS);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			SF_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
@@ -749,10 +768,10 @@ sf_attach(dev)
 	IFQ_SET_MAXLEN(&ifp->if_snd, SF_TX_DLIST_CNT - 1);
 	ifp->if_snd.ifq_drv_maxlen = SF_TX_DLIST_CNT - 1;
 	IFQ_SET_READY(&ifp->if_snd);
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
-#endif /* DEVICE_POLLING */
-	ifp->if_capenable = ifp->if_capabilities;
+#endif
 
 	/*
 	 * Call MI attach routine.
@@ -794,6 +813,11 @@ sf_detach(dev)
 	KASSERT(mtx_initialized(&sc->sf_mtx), ("sf mutex not initialized"));
 	ifp = sc->sf_ifp;
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+	
 	/* These should only be active if attach succeeded */
 	if (device_is_attached(dev)) {
 		SF_LOCK(sc);
@@ -946,12 +970,12 @@ sf_rxeof(sc)
 		struct mbuf		*m0;
 
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 
 		cur_rx = &sc->sf_ldata->sf_rx_clist[cmpconsidx];
 		desc = &sc->sf_ldata->sf_rx_dlist_big[cur_rx->sf_endidx];
@@ -1068,7 +1092,8 @@ sf_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct sf_softc *sc = ifp->if_softc;
 
 	SF_LOCK(sc);
-	sf_poll_locked(ifp, cmd, count);
+	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
+		sf_poll_locked(ifp, cmd, count);
 	SF_UNLOCK(sc);
 }
 
@@ -1079,17 +1104,6 @@ sf_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 
 	SF_LOCK_ASSERT(sc);
 
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-
-	if (cmd == POLL_DEREGISTER) {
-		/* Final call, enable interrupts. */
-		csr_write_4(sc, SF_IMR, SF_INTRS);
-		return;
-	}
-
 	sc->rxcycles = count;
 	sf_rxeof(sc);
 	sf_txeof(sc);
@@ -1131,17 +1145,11 @@ sf_intr(arg)
 	ifp = sc->sf_ifp;
 
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING)
-		goto done_locked;
-
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(sf_poll, ifp)) {
-		/* OK, disable interrupts. */
-		csr_write_4(sc, SF_IMR, 0x00000000);
-		sf_poll_locked(ifp, 0, 1);
-		goto done_locked;
+	if (ifp->if_capenable & IFCAP_POLLING) {
+		SF_UNLOCK(sc);
+		return;
 	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	if (!(csr_read_4(sc, SF_ISR_SHADOW) & SF_ISR_PCIINT_ASSERTED)) {
 		SF_UNLOCK(sc);
@@ -1185,9 +1193,6 @@ sf_intr(arg)
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		sf_start_locked(ifp);
 
-#ifdef DEVICE_POLLING
-done_locked:
-#endif /* DEVICE_POLLING */
 	SF_UNLOCK(sc);
 }
 
@@ -1296,10 +1301,10 @@ sf_init_locked(sc)
 
 #ifdef DEVICE_POLLING
 	/* Disable interrupts if we are polling. */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		csr_write_4(sc, SF_IMR, 0x00000000);
 	else
-#endif /* DEVICE_POLLING */
+#endif
 
 	/* Enable interrupts. */
 	csr_write_4(sc, SF_IMR, SF_INTRS);
@@ -1478,10 +1483,6 @@ sf_stop(sc)
 
 	callout_stop(&sc->sf_stat_callout);
 
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif /* DEVICE_POLLING */
-	
 	csr_write_4(sc, SF_GEN_ETH_CTL, 0);
 	csr_write_4(sc, SF_CQ_CONSIDX, 0);
 	csr_write_4(sc, SF_CQ_PRODIDX, 0);
diff --git a/sys/pci/if_sis.c b/sys/pci/if_sis.c
index 117a46a..c0417be 100644
--- a/sys/pci/if_sis.c
+++ b/sys/pci/if_sis.c
@@ -1217,11 +1217,10 @@ sis_attach(device_t dev)
 	 */
 	ifp->if_data.ifi_hdrlen = sizeof(struct ether_vlan_header);
 	ifp->if_capabilities |= IFCAP_VLAN_MTU;
-
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
 #endif
-	ifp->if_capenable = ifp->if_capabilities;
 
 	/* Hook interrupt last to avoid having to lock softc */
 	error = bus_setup_intr(dev, sc->sis_res[1], INTR_TYPE_NET | INTR_MPSAFE,
@@ -1257,6 +1256,11 @@ sis_detach(device_t dev)
 	KASSERT(mtx_initialized(&sc->sis_mtx), ("sis mutex not initialized"));
 	ifp = sc->sis_ifp;
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+
 	/* These should only be active if attach succeeded. */
 	if (device_is_attached(dev)) {
 		SIS_LOCK(sc);
@@ -1404,12 +1408,12 @@ sis_rxeof(struct sis_softc *sc)
 	    cur_rx = cur_rx->sis_nextdesc) {
 
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 		rxstat = cur_rx->sis_rxstat;
 		bus_dmamap_sync(sc->sis_tag,
 		    cur_rx->sis_map, BUS_DMASYNC_POSTWRITE);
@@ -1574,13 +1578,9 @@ sis_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct	sis_softc *sc = ifp->if_softc;
 
 	SIS_LOCK(sc);
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-	if (cmd == POLL_DEREGISTER) { /* final call, enable interrupts */
-		CSR_WRITE_4(sc, SIS_IER, 1);
-		goto done;
+	if (!(ifp->if_drv_flags & IFF_DRV_RUNNING)) {
+		SIS_UNLOCK(sc);
+		return;
 	}
 
 	/*
@@ -1613,7 +1613,7 @@ sis_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 			sis_initl(sc);
 		}
 	}
-done:
+
 	SIS_UNLOCK(sc);
 }
 #endif /* DEVICE_POLLING */
@@ -1633,14 +1633,11 @@ sis_intr(void *arg)
 
 	SIS_LOCK(sc);
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING)
-		goto done;
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(sis_poll, ifp)) { /* ok, disable interrupts */
-		CSR_WRITE_4(sc, SIS_IER, 0);
-		goto done;
+	if (ifp->if_capenable & IFCAP_POLLING) {
+		SIS_UNLOCK(sc);
+		return;
 	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	/* Disable interrupts. */
 	CSR_WRITE_4(sc, SIS_IER, 0);
@@ -1679,9 +1676,6 @@ sis_intr(void *arg)
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		sis_startl(ifp);
 
-#ifdef DEVICE_POLLING
-done:
-#endif /* DEVICE_POLLING */
 	SIS_UNLOCK(sc);
 }
 
@@ -2033,10 +2027,10 @@ sis_initl(struct sis_softc *sc)
 	 * ... only enable interrupts if we are not polling, make sure
 	 * they are off otherwise.
 	 */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_4(sc, SIS_IER, 0);
 	else
-#endif /* DEVICE_POLLING */
+#endif
 	CSR_WRITE_4(sc, SIS_IER, 1);
 
 	/* Enable receiver and transmitter. */
@@ -2133,10 +2127,32 @@ sis_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
 		error = ifmedia_ioctl(ifp, ifr, &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
-		SIS_LOCK(sc);
-		ifp->if_capenable &= ~IFCAP_POLLING;
-		ifp->if_capenable |= ifr->ifr_reqcap & IFCAP_POLLING;
-		SIS_UNLOCK(sc);
+		/* ok, disable interrupts */
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(sis_poll, ifp);
+			if (error)
+				return(error);
+			SIS_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_4(sc, SIS_IER, 0);
+			ifp->if_capenable |= IFCAP_POLLING;
+			SIS_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			SIS_LOCK(sc);
+			CSR_WRITE_4(sc, SIS_IER, 1);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			SIS_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
@@ -2192,9 +2208,6 @@ sis_stop(struct sis_softc *sc)
 	callout_stop(&sc->sis_stat_ch);
 
 	ifp->if_drv_flags &= ~(IFF_DRV_RUNNING | IFF_DRV_OACTIVE);
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif
 	CSR_WRITE_4(sc, SIS_IER, 0);
 	CSR_WRITE_4(sc, SIS_IMR, 0);
 	CSR_READ_4(sc, SIS_ISR); /* clear any interrupts already pending */
diff --git a/sys/pci/if_ste.c b/sys/pci/if_ste.c
index eca7e11..f80e676 100644
--- a/sys/pci/if_ste.c
+++ b/sys/pci/if_ste.c
@@ -621,7 +621,8 @@ ste_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct ste_softc *sc = ifp->if_softc;
 
 	STE_LOCK(sc);
-	ste_poll_locked(ifp, cmd, count);
+	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
+		ste_poll_locked(ifp, cmd, count);
 	STE_UNLOCK(sc);
 }
 
@@ -631,14 +632,6 @@ ste_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct ste_softc *sc = ifp->if_softc;
 
 	STE_LOCK_ASSERT(sc);
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-	if (cmd == POLL_DEREGISTER) { /* final call, enable interrupts */
-		CSR_WRITE_2(sc, STE_IMR, STE_INTRS);
-		return;
-	}
 
 	sc->rxcycles = count;
 	if (cmd == POLL_AND_CHECK_STATUS)
@@ -685,15 +678,11 @@ ste_intr(xsc)
 	ifp = sc->ste_ifp;
 
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING)
-		goto done;
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(ste_poll, ifp)) { /* ok, disable interrupts */
-		CSR_WRITE_2(sc, STE_IMR, 0);
-		ste_poll_locked(ifp, 0, 1);
-		goto done;
+	if (ifp->if_capenable & IFCAP_POLLING) {
+		STE_UNLOCK(sc);
+		return;
 	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	/* See if this is really our interrupt. */
 	if (!(CSR_READ_2(sc, STE_ISR) & STE_ISR_INTLATCH)) {
@@ -739,9 +728,6 @@ ste_intr(xsc)
 	if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
 		ste_start_locked(ifp);
 
-#ifdef DEVICE_POLLING
-done:
-#endif /* DEVICE_POLLING */
 	STE_UNLOCK(sc);
 
 	return;
@@ -791,12 +777,12 @@ ste_rxeof(sc)
 	while((rxstat = sc->ste_cdata.ste_rx_head->ste_ptr->ste_status)
 	      & STE_RXSTAT_DMADONE) {
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 		if ((STE_RX_LIST_CNT - count) < 3) {
 			break;
 		}
@@ -1115,10 +1101,10 @@ ste_attach(dev)
 	 */
 	ifp->if_data.ifi_hdrlen = sizeof(struct ether_vlan_header);
 	ifp->if_capabilities |= IFCAP_VLAN_MTU;
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
 #endif
-	ifp->if_capenable = ifp->if_capabilities;
 
 	/* Hook interrupt last to avoid having to lock softc */
 	error = bus_setup_intr(dev, sc->ste_irq, INTR_TYPE_NET | INTR_MPSAFE,
@@ -1155,6 +1141,11 @@ ste_detach(dev)
 	KASSERT(mtx_initialized(&sc->ste_mtx), ("ste mutex not initialized"));
 	ifp = sc->ste_ifp;
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+
 	/* These should only be active if attach succeeded */
 	if (device_is_attached(dev)) {
 		STE_LOCK(sc);
@@ -1386,10 +1377,10 @@ ste_init_locked(sc)
 	CSR_WRITE_2(sc, STE_ISR, 0xFFFF);
 #ifdef DEVICE_POLLING
 	/* Disable interrupts if we are polling. */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_2(sc, STE_IMR, 0);
 	else   
-#endif /* DEVICE_POLLING */
+#endif
 	/* Enable interrupts. */
 	CSR_WRITE_2(sc, STE_IMR, STE_INTRS);
 
@@ -1418,9 +1409,6 @@ ste_stop(sc)
 
 	callout_stop(&sc->ste_stat_callout);
 	ifp->if_drv_flags &= ~(IFF_DRV_RUNNING|IFF_DRV_OACTIVE);
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif /* DEVICE_POLLING */
 
 	CSR_WRITE_2(sc, STE_IMR, 0);
 	STE_SETBIT2(sc, STE_MACCTL1, STE_MACCTL1_TX_DISABLE);
@@ -1539,10 +1527,31 @@ ste_ioctl(ifp, command, data)
 		error = ifmedia_ioctl(ifp, ifr, &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
-		STE_LOCK(sc);
-		ifp->if_capenable &= ~IFCAP_POLLING;
-		ifp->if_capenable |= ifr->ifr_reqcap & IFCAP_POLLING;
-		STE_UNLOCK(sc);
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(ste_poll, ifp);
+			if (error)
+				return(error);
+			STE_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_2(sc, STE_IMR, 0);
+			ifp->if_capenable |= IFCAP_POLLING;
+			STE_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			STE_LOCK(sc);
+			CSR_WRITE_2(sc, STE_IMR, STE_INTRS);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			STE_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
diff --git a/sys/pci/if_vr.c b/sys/pci/if_vr.c
index 5eabc21..b3c92ea 100644
--- a/sys/pci/if_vr.c
+++ b/sys/pci/if_vr.c
@@ -742,10 +742,10 @@ vr_attach(dev)
 	IFQ_SET_MAXLEN(&ifp->if_snd, VR_TX_LIST_CNT - 1);
 	ifp->if_snd.ifq_maxlen = VR_TX_LIST_CNT - 1;
 	IFQ_SET_READY(&ifp->if_snd);
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
 #endif
-	ifp->if_capenable = ifp->if_capabilities;
 
 	/* Do MII setup. */
 	if (mii_phy_probe(dev, &sc->vr_miibus,
@@ -794,6 +794,11 @@ vr_detach(device_t dev)
 
 	KASSERT(mtx_initialized(&sc->vr_mtx), ("vr mutex not initialized"));
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+
 	VR_LOCK(sc);
 
 	sc->suspended = 1;
@@ -952,12 +957,12 @@ vr_rxeof(struct vr_softc *sc)
 	while (!((rxstat = sc->vr_cdata.vr_rx_head->vr_ptr->vr_status) &
 	    VR_RXSTAT_OWN)) {
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 		m0 = NULL;
 		cur_rx = sc->vr_cdata.vr_rx_head;
 		sc->vr_cdata.vr_rx_head = cur_rx->vr_nextdesc;
@@ -1151,7 +1156,8 @@ vr_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct vr_softc *sc = ifp->if_softc;
 
 	VR_LOCK(sc);
-	vr_poll_locked(ifp, cmd, count);
+	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
+		vr_poll_locked(ifp, cmd, count);
 	VR_UNLOCK(sc);
 }
 
@@ -1162,17 +1168,6 @@ vr_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 
 	VR_LOCK_ASSERT(sc);
 
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-
-	if (cmd == POLL_DEREGISTER) {
-		/* Final call, enable interrupts. */
-		CSR_WRITE_2(sc, VR_IMR, VR_INTRS);
-		return;
-	}
-
 	sc->rxcycles = count;
 	vr_rxeof(sc);
 	vr_txeof(sc);
@@ -1249,17 +1244,9 @@ vr_intr(void *arg)
 	}
 
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		goto done_locked;
-
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(vr_poll, ifp)) {
-		/* OK, disable interrupts. */
-		CSR_WRITE_2(sc, VR_IMR, 0x0000);
-		vr_poll_locked(ifp, 0, 1);
-		goto done_locked;
-	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	/* Suppress unwanted interrupts. */
 	if (!(ifp->if_flags & IFF_UP)) {
@@ -1534,10 +1521,10 @@ vr_init_locked(struct vr_softc *sc)
 	/*
 	 * Disable interrupts if we are polling.
 	 */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_2(sc, VR_IMR, 0);
 	else
-#endif /* DEVICE_POLLING */
+#endif
 	/*
 	 * Enable interrupts.
 	 */
@@ -1615,7 +1602,31 @@ vr_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
 		error = ifmedia_ioctl(ifp, ifr, &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
-		ifp->if_capenable = ifr->ifr_reqcap;
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(vr_poll, ifp);
+			if (error)
+				return(error);
+			VR_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_2(sc, VR_IMR, 0x0000);
+			ifp->if_capenable |= IFCAP_POLLING;
+			VR_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			VR_LOCK(sc);
+			CSR_WRITE_2(sc, VR_IMR, VR_INTRS);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			VR_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		break;
 	default:
 		error = ether_ioctl(ifp, command, data);
@@ -1662,9 +1673,6 @@ vr_stop(struct vr_softc *sc)
 
 	untimeout(vr_tick, sc, sc->vr_stat_ch);
 	ifp->if_drv_flags &= ~(IFF_DRV_RUNNING | IFF_DRV_OACTIVE);
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif /* DEVICE_POLLING */
 
 	VR_SETBIT16(sc, VR_COMMAND, VR_CMD_STOP);
 	VR_CLRBIT16(sc, VR_COMMAND, (VR_CMD_RX_ON|VR_CMD_TX_ON));
diff --git a/sys/pci/if_xl.c b/sys/pci/if_xl.c
index 520f668..e49997a 100644
--- a/sys/pci/if_xl.c
+++ b/sys/pci/if_xl.c
@@ -249,7 +249,7 @@ static int xl_resume(device_t);
 #ifdef DEVICE_POLLING
 static void xl_poll(struct ifnet *ifp, enum poll_cmd cmd, int count);
 static void xl_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count);
-#endif /* DEVICE_POLLING */
+#endif
 
 static int xl_ifmedia_upd(struct ifnet *);
 static void xl_ifmedia_sts(struct ifnet *, struct ifmediareq *);
@@ -1487,9 +1487,10 @@ xl_attach(device_t dev)
 		ifp->if_capabilities |= IFCAP_HWCSUM;
 #endif
 	}
+	ifp->if_capenable = ifp->if_capabilities;
 #ifdef DEVICE_POLLING
 	ifp->if_capabilities |= IFCAP_POLLING;
-#endif /* DEVICE_POLLING */
+#endif
 	ifp->if_start = xl_start;
 	ifp->if_watchdog = xl_watchdog;
 	ifp->if_init = xl_init;
@@ -1497,7 +1498,6 @@ xl_attach(device_t dev)
 	IFQ_SET_MAXLEN(&ifp->if_snd, XL_TX_LIST_CNT - 1);
 	ifp->if_snd.ifq_drv_maxlen = XL_TX_LIST_CNT - 1;
 	IFQ_SET_READY(&ifp->if_snd);
-	ifp->if_capenable = ifp->if_capabilities;
 
 	/*
 	 * Now we have to see what sort of media we have.
@@ -1690,6 +1690,11 @@ xl_detach(device_t dev)
 
 	KASSERT(mtx_initialized(&sc->xl_mtx), ("xl mutex not initialized"));
 
+#ifdef DEVICE_POLLING
+	if (ifp->if_capenable & IFCAP_POLLING)
+		ether_poll_deregister(ifp);
+#endif
+
 	if (sc->xl_flags & XL_FLAG_USE_MMIO) {
 		rid = XL_PCI_LOMEM;
 		res = SYS_RES_MEMORY;
@@ -1960,12 +1965,12 @@ again:
 	    BUS_DMASYNC_POSTREAD);
 	while ((rxstat = le32toh(sc->xl_cdata.xl_rx_head->xl_ptr->xl_status))) {
 #ifdef DEVICE_POLLING
-		if (ifp->if_flags & IFF_POLLING) {
+		if (ifp->if_capenable & IFCAP_POLLING) {
 			if (sc->rxcycles <= 0)
 				break;
 			sc->rxcycles--;
 		}
-#endif /* DEVICE_POLLING */
+#endif
 		cur_rx = sc->xl_cdata.xl_rx_head;
 		sc->xl_cdata.xl_rx_head = cur_rx->xl_next;
 		total_len = rxstat & XL_RXSTAT_LENMASK;
@@ -2275,24 +2280,11 @@ xl_intr(void *arg)
 	XL_LOCK(sc);
 
 #ifdef DEVICE_POLLING
-	if (ifp->if_flags & IFF_POLLING) {
+	if (ifp->if_capenable & IFCAP_POLLING) {
 		XL_UNLOCK(sc);
 		return;
 	}
-
-	if ((ifp->if_capenable & IFCAP_POLLING) &&
-	    ether_poll_register(xl_poll, ifp)) {
-		/* Disable interrupts. */
-		CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|0);
-		CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ACK|0xFF);
-		if (sc->xl_flags & XL_FLAG_FUNCREG)
-			bus_space_write_4(sc->xl_ftag, sc->xl_fhandle,
-			    4, 0x8000);
-		xl_poll_locked(ifp, 0, 1);
-		XL_UNLOCK(sc);
-		return;
-	}
-#endif /* DEVICE_POLLING */
+#endif
 
 	while ((status = CSR_READ_2(sc, XL_STATUS)) & XL_INTRS &&
 	    status != 0xFFFF) {
@@ -2351,7 +2343,8 @@ xl_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	struct xl_softc *sc = ifp->if_softc;
 
 	XL_LOCK(sc);
-	xl_poll_locked(ifp, cmd, count);
+	if (ifp->if_drv_flags & IFF_DRV_RUNNING)
+		xl_poll_locked(ifp, cmd, count);
 	XL_UNLOCK(sc);
 }
 
@@ -2362,21 +2355,6 @@ xl_poll_locked(struct ifnet *ifp, enum poll_cmd cmd, int count)
 
 	XL_LOCK_ASSERT(sc);
 
-	if (!(ifp->if_capenable & IFCAP_POLLING)) {
-		ether_poll_deregister(ifp);
-		cmd = POLL_DEREGISTER;
-	}
-
-	if (cmd == POLL_DEREGISTER) {
-		/* Final call; enable interrupts. */
-		CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ACK|0xFF);
-		CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|XL_INTRS);
-		if (sc->xl_flags & XL_FLAG_FUNCREG)
-			bus_space_write_4(sc->xl_ftag, sc->xl_fhandle,
-			    4, 0x8000);
-		return;
-	}
-
 	sc->rxcycles = count;
 	xl_rxeof(sc);
 	if (sc->xl_type == XL_TYPE_905B)
@@ -2989,10 +2967,10 @@ xl_init_locked(struct xl_softc *sc)
 	CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_STAT_ENB|XL_INTRS);
 #ifdef DEVICE_POLLING
 	/* Disable interrupts if we are polling. */
-	if (ifp->if_flags & IFF_POLLING)
+	if (ifp->if_capenable & IFCAP_POLLING)
 		CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|0);
 	else
-#endif /* DEVICE_POLLING */
+#endif
 	CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|XL_INTRS);
 	if (sc->xl_flags & XL_FLAG_FUNCREG)
 	    bus_space_write_4(sc->xl_ftag, sc->xl_fhandle, 4, 0x8000);
@@ -3204,6 +3182,35 @@ xl_ioctl(struct ifnet *ifp, u_long command, caddr_t data)
 			    &mii->mii_media, command);
 		break;
 	case SIOCSIFCAP:
+#ifdef DEVICE_POLLING
+		if (ifr->ifr_reqcap & IFCAP_POLLING &&
+		    !(ifp->if_capenable & IFCAP_POLLING)) {
+			error = ether_poll_register(xl_poll, ifp);
+			if (error)
+				return(error);
+			XL_LOCK(sc);
+			/* Disable interrupts */
+			CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|0);
+			ifp->if_capenable |= IFCAP_POLLING;
+			XL_UNLOCK(sc);
+			return (error);
+			
+		}
+		if (!(ifr->ifr_reqcap & IFCAP_POLLING) &&
+		    ifp->if_capenable & IFCAP_POLLING) {
+			error = ether_poll_deregister(ifp);
+			/* Enable interrupts. */
+			XL_LOCK(sc);
+			CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ACK|0xFF);
+			CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_INTR_ENB|XL_INTRS);
+			if (sc->xl_flags & XL_FLAG_FUNCREG)
+				bus_space_write_4(sc->xl_ftag, sc->xl_fhandle,
+				    4, 0x8000);
+			ifp->if_capenable &= ~IFCAP_POLLING;
+			XL_UNLOCK(sc);
+			return (error);
+		}
+#endif /* DEVICE_POLLING */
 		XL_LOCK(sc);
 		ifp->if_capenable = ifr->ifr_reqcap;
 		if (ifp->if_capenable & IFCAP_TXCSUM)
@@ -3268,9 +3275,6 @@ xl_stop(struct xl_softc *sc)
 	XL_LOCK_ASSERT(sc);
 
 	ifp->if_timer = 0;
-#ifdef DEVICE_POLLING
-	ether_poll_deregister(ifp);
-#endif /* DEVICE_POLLING */
 
 	CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_RX_DISABLE);
 	CSR_WRITE_2(sc, XL_COMMAND, XL_CMD_STATS_DISABLE);