Index: head/sys/dev/sfxge/common/mcdi_mon.c
===================================================================
--- head/sys/dev/sfxge/common/mcdi_mon.c
+++ head/sys/dev/sfxge/common/mcdi_mon.c
@@ -50,6 +50,9 @@
 #define	MCDI_MON_PORT_P4	(0x08)
 #define	MCDI_MON_PORT_Px	(0xFFFF)
 
+/* Get port mask from one-based MCDI port number */
+#define	MCDI_MON_PORT_MASK(_emip) (1U << ((_emip)->emi_port - 1))
+
 /* Entry for MCDI sensor in sensor map */
 #define	STAT(portmask, stat)	\
 	{ (MCDI_MON_PORT_##portmask), (EFX_MON_STAT_##stat) }
@@ -166,10 +169,10 @@
 static						void
 mcdi_mon_decode_stats(
 	__in					efx_nic_t *enp,
-	__in_ecount(sensor_mask_size)		uint32_t *sensor_mask,
+	__in_bcount(sensor_mask_size)		uint32_t *sensor_mask,
 	__in					size_t sensor_mask_size,
 	__in_opt				efsys_mem_t *esmp,
-	__out_ecount_opt(sensor_mask_size)	uint32_t *stat_maskp,
+	__out_bcount_opt(sensor_mask_size)	uint32_t *stat_maskp,
 	__inout_ecount_opt(EFX_MON_NSTATS)	efx_mon_stat_value_t *stat)
 {
 	efx_mcdi_iface_t *emip = &(enp->en_mcdi.em_emip);
@@ -192,7 +195,8 @@
 	sensor_max =
 	    MIN((8 * sensor_mask_size), EFX_ARRAY_SIZE(mcdi_sensor_map));
 
-	port_mask = 1U << emip->emi_port;
+	EFSYS_ASSERT(emip->emi_port > 0); /* MCDI port number is one-based */
+	port_mask = MCDI_MON_PORT_MASK(emip);
 
 	memset(stat_mask, 0, sizeof (stat_mask));
 
@@ -269,9 +273,8 @@
 	efx_mon_stat_t id;
 	efx_rc_t rc;
 
-	port_mask = (emip->emi_port == 1)
-	    ? MCDI_MON_PORT_P1
-	    : MCDI_MON_PORT_P2;
+	EFSYS_ASSERT(emip->emi_port > 0); /* MCDI port number is one-based */
+	port_mask = MCDI_MON_PORT_MASK(emip);
 
 	sensor = (uint16_t)MCDI_EV_FIELD(eqp, SENSOREVT_MONITOR);
 	state = (uint16_t)MCDI_EV_FIELD(eqp, SENSOREVT_STATE);