Index: pci.c
===================================================================
RCS file: /usr/cvs/src/sys/dev/pci/pci.c,v
retrieving revision 1.357
diff -u -r1.357 pci.c
--- pci.c	1 Feb 2008 20:31:09 -0000	1.357
+++ pci.c	4 Aug 2008 16:03:04 -0000
@@ -2319,6 +2319,8 @@
 	 * respond oddly to having these bits enabled.  Let the user
 	 * be able to turn them off (since pci_enable_io_modes is 1 by
 	 * default).
+	 *
+	 * XXX: We probably shouldn't do this until after programming the BAR.
 	 */
 	if (pci_enable_io_modes) {
 		/* Turn on resources that have been left off by a lazy BIOS */
@@ -2355,16 +2357,32 @@
 	 */
 	res = resource_list_alloc(rl, bus, dev, type, &reg, start, end, count,
 	    prefetch ? RF_PREFETCHABLE : 0);
-	if (res == NULL)
-		return (barlen);
-	start = rman_get_start(res);
-	if ((u_long)start != start) {
-		/* Wait a minute!  this platform can't do this address. */
-		device_printf(bus,
-		    "pci%d:%d.%d.%x bar %#x start %#jx, too many bits.",
-		    pci_get_domain(dev), b, s, f, reg, (uintmax_t)start);
-		resource_list_release(rl, bus, dev, type, reg, res);
-		return (barlen);
+	if (res == NULL) {
+		/*
+		 * If this fails, clear the BAR and delete the
+		 * resource list entry to force pci_alloc_resource()
+		 * to allocate resources from the parent.
+		 */
+		resource_list_delete(rl, type, reg);
+		start = 0;
+	} else {
+		start = rman_get_start(res);
+		if ((u_long)start != start) {
+			/*
+			 * Wait a minute!  This platform can't do this
+			 * address.
+			 */
+			device_printf(bus,
+			    "pci%d:%d.%d.%x bar %#x start %#jx, too many bits.",
+			    pci_get_domain(dev), b, s, f, reg,
+			    (uintmax_t)start);
+			resource_list_release(rl, bus, dev, type, reg, res);
+
+			/*
+			 * XXX: Should this delete the resource list entry?
+			 */
+			return (barlen);
+		}
 	}
 	pci_write_config(dev, reg, start, 4);
 	if (ln2range == 64)