Index: sys/kern/subr_intr.c
===================================================================
--- sys/kern/subr_intr.c
+++ sys/kern/subr_intr.c
@@ -103,6 +103,7 @@
 /* Interrupt controller definition. */
 struct intr_pic {
 	SLIST_ENTRY(intr_pic)	pic_next;
+#define XREF_INVALID	(-1)
 	intptr_t		pic_xref;	/* hardware identification */
 	device_t		pic_dev;
 /* Only one of FLAG_PIC or FLAG_MSI may be set */
@@ -696,8 +697,8 @@
 
 	mtx_assert(&pic_list_lock, MA_OWNED);
 
-	if (dev == NULL && xref == 0)
-		return (NULL);
+	KASSERT(dev != NULL || xref != XREF_INVALID,
+	    ("pic_lookup_locked: Either the device or the xref must be valid"));
 
 	/* Note that pic->pic_dev is never NULL on registered PIC. */
 	SLIST_FOREACH(pic, &pic_list, pic_next) {
@@ -706,13 +707,17 @@
 			continue;
 
 		if (dev == NULL) {
+			/* No dev, check the xref */
 			if (xref == pic->pic_xref)
 				return (pic);
-		} else if (xref == 0 || pic->pic_xref == 0) {
+		} else if (xref == XREF_INVALID) {
+			/* No xref, check the dev */
 			if (dev == pic->pic_dev)
 				return (pic);
-		} else if (xref == pic->pic_xref && dev == pic->pic_dev)
-				return (pic);
+		} else if (xref == pic->pic_xref && dev == pic->pic_dev) {
+			/* Have both, check both */
+			return (pic);
+		}
 	}
 	return (NULL);
 }
@@ -739,6 +744,8 @@
 {
 	struct intr_pic *pic;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
+
 	mtx_lock(&pic_list_lock);
 	pic = pic_lookup_locked(dev, xref, flags);
 	if (pic != NULL) {
@@ -768,6 +775,8 @@
 {
 	struct intr_pic *pic;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
+
 	mtx_lock(&pic_list_lock);
 	pic = pic_lookup_locked(dev, xref, flags);
 	if (pic == NULL) {
@@ -827,6 +836,7 @@
 {
 	struct intr_pic *pic;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(dev, xref, FLAG_PIC);
 	if (pic == NULL) {
 		device_printf(dev, "not registered\n");
@@ -876,7 +886,7 @@
 #endif
 
 	/* Find the parent PIC */
-	parent_pic = pic_lookup(parent, 0, FLAG_PIC);
+	parent_pic = pic_lookup(parent, XREF_INVALID, FLAG_PIC);
 	if (parent_pic == NULL)
 		return (NULL);
 
@@ -910,6 +920,7 @@
 	if (data == NULL)
 		return (EINVAL);
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(dev, xref,
 	    (data->type == INTR_MAP_DATA_MSI) ? FLAG_MSI : FLAG_PIC);
 	if (pic == NULL)
@@ -1281,6 +1292,7 @@
 	struct intr_map_data_msi *msi;
 	int err, i;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(NULL, xref, FLAG_MSI);
 	if (pic == NULL)
 		return (ESRCH);
@@ -1318,6 +1330,7 @@
 	struct intr_map_data_msi *msi;
 	int i, err;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(NULL, xref, FLAG_MSI);
 	if (pic == NULL)
 		return (ESRCH);
@@ -1357,6 +1370,7 @@
 	struct intr_map_data_msi *msi;
 	int err;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(NULL, xref, FLAG_MSI);
 	if (pic == NULL)
 		return (ESRCH);
@@ -1385,6 +1399,7 @@
 	struct intr_map_data_msi *msi;
 	int err;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(NULL, xref, FLAG_MSI);
 	if (pic == NULL)
 		return (ESRCH);
@@ -1418,6 +1433,7 @@
 	struct intr_pic *pic;
 	int err;
 
+	KASSERT(xref != XREF_INVALID, ("%s: Invalid xref", __func__));
 	pic = pic_lookup(NULL, xref, FLAG_MSI);
 	if (pic == NULL)
 		return (ESRCH);