pci_scan_root_bus
bus = pci_scan_root_bus(NULL, busnum, &pci_root_ops, sd, &resources);
EXPORT_SYMBOL(pci_scan_root_bus);
b = pci_scan_root_bus(&pdev->xdev->dev, bus,
struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,