PCI: Look for unassigned resources on per-bus basis

When CONFIG_PCI_REALLOC_ENABLE_AUTO=y, pci_realloc_detect() looks at PCI
devices to see if any have SR-IOV resources that need to be assigned.  If
it finds any, it turns on automatic resource reallocation.

This patch changes pci_realloc_detect() so it uses pci_walk_bus() on
each root bus instead of using for_each_pci_dev().  This is a step
toward doing reallocation on a per-bus basis, so we can do it for
a hot-added host bridge.

[bhelgaas: changelog, rename callback to iov_resources_unassigned(), use
boolean for "unassigned"]
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/setup-bus.c

@@ -1359,30 +1359,44 @@ static bool __init pci_realloc_enabled(void)
 	return pci_realloc_enable >= user_enabled;
 }
 
-static void __init pci_realloc_detect(void)
-{
 #if defined(CONFIG_PCI_IOV) && defined(CONFIG_PCI_REALLOC_ENABLE_AUTO)
-	struct pci_dev *dev = NULL;
+static int __init iov_resources_unassigned(struct pci_dev *dev, void *data)
+{
+	int i;
+	bool *unassigned = data;
 
-	if (pci_realloc_enable != undefined)
-		return;
+	for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
+		struct resource *r = &dev->resource[i];
 
-	for_each_pci_dev(dev) {
-		int i;
+		/* Not assigned or rejected by kernel? */
+		if (r->flags && !r->start) {
+			*unassigned = true;
+			return 1; /* return early from pci_walk_bus() */
+		}
+	}
 
-		for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
-			struct resource *r = &dev->resource[i];
+	return 0;
+}
 
-			/* Not assigned, or rejected by kernel ? */
-			if (r->flags && !r->start) {
-				pci_realloc_enable = auto_enabled;
+static void  __init pci_realloc_detect(void)
+{
+	bool unassigned = false;
+	struct pci_bus *bus;
 
-				return;
-			}
+	if (pci_realloc_enable != undefined)
+		return;
+
+	list_for_each_entry(bus, &pci_root_buses, node) {
+		pci_walk_bus(bus, iov_resources_unassigned, &unassigned);
+		if (unassigned) {
+			pci_realloc_enable = auto_enabled;
+			return;
 		}
 	}
-#endif
 }
+#else
+static void __init pci_realloc_detect(void) { }
+#endif
 
 /*
  * first try will not touch pci bridge res