Index: head/usr.sbin/config/config.h
===================================================================
--- head/usr.sbin/config/config.h
+++ head/usr.sbin/config/config.h
@@ -86,6 +86,7 @@
 struct device {
 	int	d_done;			/* processed */
 	char	*d_name;		/* name of device (e.g. rk11) */
+	char	*yyfile;		/* name of the file that first include the device */
 #define	UNKNOWN -2	/* -2 means not set yet */
 	STAILQ_ENTRY(device) d_next;	/* Next one in list */
 };
@@ -125,6 +126,7 @@
 	char	*op_name;
 	char	*op_value;
 	int	op_ownfile;	/* true = own file, false = makefile */
+	char	*yyfile;	/* name of the file that first include the option */
 	SLIST_ENTRY(opt) op_next;
 	SLIST_ENTRY(opt) op_append;
 };
Index: head/usr.sbin/config/config.y
===================================================================
--- head/usr.sbin/config/config.y
+++ head/usr.sbin/config/config.y
@@ -382,11 +382,13 @@
 static void
 newdev(char *name)
 {
-	struct device *np;
+	struct device *np, *dp;
 
-	if (finddev(&dtab, name)) {
-		fprintf(stderr,
-		    "WARNING: duplicate device `%s' encountered.\n", name);
+	if ((dp = finddev(&dtab, name)) != NULL) {
+		if (strcmp(dp->yyfile, yyfile) == 0)
+			fprintf(stderr,
+			    "WARNING: duplicate device `%s' encountered in %s\n",
+			    name, yyfile);
 		return;
 	}
 
@@ -394,6 +396,7 @@
 	if (np == NULL)
 		err(EXIT_FAILURE, "calloc");
 	np->d_name = name;
+	np->yyfile = strdup(yyfile);
 	STAILQ_INSERT_TAIL(&dtab, np, d_next);
 }
 
@@ -408,6 +411,7 @@
 	dp = finddev(dh, name);
 	if (dp != NULL) {
 		STAILQ_REMOVE(dh, dp, device, d_next);
+		free(dp->yyfile);
 		free(dp->d_name);
 		free(dp);
 	}
@@ -446,8 +450,9 @@
 
 	op2 = findopt(list, name);
 	if (op2 != NULL && !append && !dupe) {
-		fprintf(stderr,
-		    "WARNING: duplicate option `%s' encountered.\n", name);
+		if (strcmp(op2->yyfile, yyfile) == 0)
+			fprintf(stderr,
+			    "WARNING: duplicate option `%s' encountered.\n", name);
 		return;
 	}
 
@@ -457,6 +462,7 @@
 	op->op_name = name;
 	op->op_ownfile = 0;
 	op->op_value = value;
+	op->yyfile = strdup(yyfile);
 	if (op2 != NULL) {
 		if (append) {
 			while (SLIST_NEXT(op2, op_append) != NULL)
@@ -481,6 +487,7 @@
 
 	while ((op = findopt(list, name)) != NULL) {
 		SLIST_REMOVE(list, op, opt, op_next);
+		free(op->yyfile);
 		free(op->op_name);
 		free(op);
 	}