[PATCH 1/4] PCI: optimize pci_bus_get_depth() by enumerating on pci bus hierachy

[Wei Yang <weiyang@linux.vnet.ibm.com>]

Normally, on one pci bus there would be more devices than pci buses. When
calculating the depth of pci bus, it would be more time efficient by
enumerating through the child buses instead of the child devices.

Also by doing so, the code seems more self explaining. Previously, it go
through the pci devices and check whether a bridge introduce a child bus or
not, which needs more background knowledge to understand it.

This patch caculating the depth by enumerating on pci bus hierachy.

Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
---
 drivers/pci/setup-bus.c |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index d254e23..6dbe562 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1300,15 +1300,12 @@ static void pci_bus_dump_resources(struct pci_bus *bus)
 static int __init pci_bus_get_depth(struct pci_bus *bus)
 {
 	int depth = 0;
-	struct pci_dev *dev;
+	struct pci_bus *child_bus;
 
-	list_for_each_entry(dev, &bus->devices, bus_list) {
+	list_for_each_entry(child_bus, &bus->children, node){
 		int ret;
-		struct pci_bus *b = dev->subordinate;
-		if (!b)
-			continue;
 
-		ret = pci_bus_get_depth(b);
+		ret = pci_bus_get_depth(child_bus);
 		if (ret + 1 > depth)
 			depth = ret + 1;
 	}
-- 
1.7.5.4