Index: head/sys/dev/sfxge/common/efx_impl.h
===================================================================
--- head/sys/dev/sfxge/common/efx_impl.h
+++ head/sys/dev/sfxge/common/efx_impl.h
@@ -462,6 +462,7 @@
 	void		(*emco_fini)(efx_nic_t *);
 	efx_rc_t	(*emco_fw_update_supported)(efx_nic_t *, boolean_t *);
 	efx_rc_t	(*emco_macaddr_change_supported)(efx_nic_t *, boolean_t *);
+	efx_rc_t	(*emco_link_control_supported)(efx_nic_t *, boolean_t *);
 } efx_mcdi_ops_t;
 
 typedef struct efx_mcdi_s {
Index: head/sys/dev/sfxge/common/efx_mcdi.h
===================================================================
--- head/sys/dev/sfxge/common/efx_mcdi.h
+++ head/sys/dev/sfxge/common/efx_mcdi.h
@@ -151,6 +151,11 @@
 	__in			efx_nic_t *enp,
 	__out			boolean_t *supportedp);
 
+extern	__checkReturn		efx_rc_t
+efx_mcdi_link_control_supported(
+	__in			efx_nic_t *enp,
+	__out			boolean_t *supportedp);
+
 #if EFSYS_OPT_BIST
 #if EFSYS_OPT_HUNTINGTON
 extern	__checkReturn		efx_rc_t
Index: head/sys/dev/sfxge/common/efx_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/efx_mcdi.c
+++ head/sys/dev/sfxge/common/efx_mcdi.c
@@ -53,6 +53,8 @@
 	siena_mcdi_fw_update_supported,	/* emco_fw_update_supported */
 	siena_mcdi_macaddr_change_supported,
 				/* emco_macaddr_change_supported */
+	siena_mcdi_link_control_supported,
+				/* emco_link_control_supported */
 };
 
 #endif	/* EFSYS_OPT_SIENA */
@@ -69,6 +71,8 @@
 	hunt_mcdi_fw_update_supported,	/* emco_fw_update_supported */
 	hunt_mcdi_macaddr_change_supported,
 				/* emco_macaddr_change_supported */
+	hunt_mcdi_link_control_supported,
+				/* emco_link_control_supported */
 };
 
 #endif	/* EFSYS_OPT_HUNTINGTON */
@@ -1169,6 +1173,31 @@
 	return (rc);
 }
 
+	__checkReturn		efx_rc_t
+efx_mcdi_link_control_supported(
+	__in			efx_nic_t *enp,
+	__out			boolean_t *supportedp)
+{
+	efx_mcdi_ops_t *emcop = enp->en_mcdi.em_emcop;
+	efx_rc_t rc;
+
+	if (emcop != NULL && emcop->emco_link_control_supported != NULL) {
+		if ((rc = emcop->emco_link_control_supported(enp, supportedp))
+		    != 0)
+			goto fail1;
+	} else {
+		/* Earlier devices always supported link control */
+		*supportedp = B_TRUE;
+	}
+
+	return (0);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
 #if EFSYS_OPT_BIST
 
 #if EFSYS_OPT_HUNTINGTON
Index: head/sys/dev/sfxge/common/hunt_impl.h
===================================================================
--- head/sys/dev/sfxge/common/hunt_impl.h
+++ head/sys/dev/sfxge/common/hunt_impl.h
@@ -286,6 +286,11 @@
 	__in		efx_nic_t *enp,
 	__out		boolean_t *supportedp);
 
+extern	__checkReturn	efx_rc_t
+hunt_mcdi_link_control_supported(
+	__in		efx_nic_t *enp,
+	__out		boolean_t *supportedp);
+
 #endif /* EFSYS_OPT_MCDI */
 
 /* NVRAM */
Index: head/sys/dev/sfxge/common/hunt_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/hunt_mcdi.c
+++ head/sys/dev/sfxge/common/hunt_mcdi.c
@@ -471,6 +471,30 @@
 	return (0);
 }
 
+	__checkReturn	efx_rc_t
+hunt_mcdi_link_control_supported(
+	__in		efx_nic_t *enp,
+	__out		boolean_t *supportedp)
+{
+	efx_nic_cfg_t *encp = &(enp->en_nic_cfg);
+	uint32_t privilege_mask = encp->enc_privilege_mask;
+
+	EFSYS_ASSERT3U(enp->en_family, ==, EFX_FAMILY_HUNTINGTON);
+
+	/*
+	 * Use privilege mask state at MCDI attach.
+	 * Admin privilege used prior to introduction of
+	 * specific flag.
+	 */
+	*supportedp =
+	    ((privilege_mask & MC_CMD_PRIVILEGE_MASK_IN_GRP_LINK) ==
+	    MC_CMD_PRIVILEGE_MASK_IN_GRP_LINK) ||
+	    ((privilege_mask & MC_CMD_PRIVILEGE_MASK_IN_GRP_ADMIN) ==
+	    MC_CMD_PRIVILEGE_MASK_IN_GRP_ADMIN);
+
+	return (0);
+}
+
 #endif	/* EFSYS_OPT_MCDI */
 
 #endif	/* EFSYS_OPT_HUNTINGTON */
Index: head/sys/dev/sfxge/common/siena_impl.h
===================================================================
--- head/sys/dev/sfxge/common/siena_impl.h
+++ head/sys/dev/sfxge/common/siena_impl.h
@@ -148,6 +148,11 @@
 	__in		efx_nic_t *enp,
 	__out		boolean_t *supportedp);
 
+extern	__checkReturn	efx_rc_t
+siena_mcdi_link_control_supported(
+	__in		efx_nic_t *enp,
+	__out		boolean_t *supportedp);
+
 #endif /* EFSYS_OPT_MCDI */
 
 #if EFSYS_OPT_NVRAM || EFSYS_OPT_VPD
Index: head/sys/dev/sfxge/common/siena_mcdi.c
===================================================================
--- head/sys/dev/sfxge/common/siena_mcdi.c
+++ head/sys/dev/sfxge/common/siena_mcdi.c
@@ -351,4 +351,16 @@
 	return (0);
 }
 
+	__checkReturn	efx_rc_t
+siena_mcdi_link_control_supported(
+	__in		efx_nic_t *enp,
+	__out		boolean_t *supportedp)
+{
+	EFSYS_ASSERT3U(enp->en_family, ==, EFX_FAMILY_SIENA);
+
+	*supportedp = B_TRUE;
+
+	return (0);
+}
+
 #endif	/* EFSYS_OPT_SIENA && EFSYS_OPT_MCDI */