Index: sys/kern/subr_bus.c
===================================================================
--- sys/kern/subr_bus.c
+++ sys/kern/subr_bus.c
@@ -6039,6 +6039,113 @@
 	    UID_ROOT, GID_WHEEL, 0600, "devctl2");
 }
 
+/*
+ * For maintaining device 'at' location info to avoid recomputing it
+ */
+struct device_location_node {
+	const char *dln_locator;
+	const char *dln_path;
+	TAILQ_ENTRY(device_location_node) dln_link;
+};
+typedef TAILQ_HEAD(device_location_list, device_location_node) device_location_list_t;
+
+struct device_location_cache {
+	device_location_list_t dlc_list;
+};
+
+
+/*
+ * Location cache for wired devices...  Maybe need a better name?
+ */
+device_location_cache_t *
+dev_wired_cache_init(void)
+{
+	device_location_cache_t *dcp;
+
+	dcp = malloc(sizeof(*dcp), M_BUS, M_WAITOK | M_ZERO);
+	TAILQ_INIT(&dcp->dlc_list);
+	return (dcp);
+}
+
+void
+dev_wired_cache_fini(device_location_cache_t *dcp)
+{
+	struct device_location_node *dln, *tdln;
+
+	TAILQ_FOREACH_SAFE(dln, &dcp->dlc_list, dln_link, tdln) {
+		/* Note: one allocation for both node and strings */
+		free(dln, M_BUS);
+	}
+	free(dcp, M_BUS);
+}
+
+static struct device_location_node *
+dev_wired_cache_lookup(device_location_cache_t *dcp, const char *locator)
+{
+	struct device_location_node *dln;
+
+	TAILQ_FOREACH(dln, &dcp->dlc_list, dln_link) {
+		if (strcmp(locator, dln->dln_locator) == 0)
+			return (dln);
+	}
+	return (NULL);
+}
+
+static struct device_location_node *
+dev_wired_cache_add(device_location_cache_t *dcp, const char *locator, const char *path)
+{
+	struct device_location_node *dln;
+	size_t len;
+	char *l, *p = NULL;
+
+	len = sizeof(*dln) + strlen(locator) + 1;
+	if (path != NULL)
+		len += strlen(path) + 1;
+	dln = malloc(len, M_BUS, M_WAITOK | M_ZERO);
+	dln->dln_locator = l = (char *)(dln + 1);
+	memcpy(l, locator, strlen(locator) + 1);
+	if (path == NULL) {
+		dln->dln_path = NULL;
+	} else {
+		dln->dln_path = p = l + strlen(locator) + 1;
+		memcpy(p, path, strlen(path) + 1);
+	}
+	TAILQ_INSERT_HEAD(&dcp->dlc_list, dln, dln_link);
+	KASSERT(len == sizeof(*dln) + strlen(dln->dln_locator) + 1 +
+	    (dln->dln_path ? (strlen(dln->dln_path) + 1) : 0),
+	    ("dev_wired_cache_add: doesn't add up"));
+	return (dln);
+}
+
+bool
+dev_wired_cache_match(device_location_cache_t *dcp, device_t dev, const char *at)
+{
+	const char *cp, *path;
+	char locator[32];
+	int len;
+	struct device_location_node *res;
+
+	cp = strchr(at, ':');
+	if (cp == NULL)
+		return (false);
+	len = cp - at;
+	if (len > sizeof(locator) - 1)	/* Skip too long locator */
+		return (false);
+	memcpy(locator, at, len);
+	locator[len] = '\0';
+	cp++;
+	/* maybe cache this inside device_t and look that up, but not yet */
+	res = dev_wired_cache_lookup(dcp, locator);
+	if (res == NULL) {
+		path = device_get_path(dev, locator);
+		res = dev_wired_cache_add(dcp, locator, path);
+		free(__DECONST(void *, path), M_BUS);
+	}
+	if (res == NULL || res->dln_path == NULL)
+		return (false);
+	return (strcmp(res->dln_path, cp) == 0);
+}
+
 /*
  * APIs to manage deprecation and obsolescence.
  */
Index: sys/sys/bus.h
===================================================================
--- sys/sys/bus.h
+++ sys/sys/bus.h
@@ -832,6 +832,13 @@
 	    device_get_nameunit(device_get_parent(dev)), e));		\
 }
 
+struct device_location_cache;
+typedef struct device_location_cache device_location_cache_t;
+device_location_cache_t *dev_wired_cache_init(void);
+void dev_wired_cache_fini(device_location_cache_t *dcp);
+bool dev_wired_cache_match(device_location_cache_t *dcp, device_t dev, const char *at);
+
+
 /**
  * Shorthand macros, taking resource argument
  * Generated with sys/tools/bus_macro.sh