PCI: Introduce /sys/bus/pci/rescan

This interface allows the user to force a rescan of all PCI buses
in system, and rediscover devices that have been removed earlier.

pci_bus_attrs implementation from Trent Piepho.

Thanks to Vegard Nossum for discovering locking issues with the
sysfs interface.

Cc: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 22dcfdb..45833a5 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -138,6 +138,12 @@
 extern struct device_attribute pci_dev_attrs[];
 extern struct device_attribute dev_attr_cpuaffinity;
 extern struct device_attribute dev_attr_cpulistaffinity;
+#ifdef CONFIG_HOTPLUG
+extern struct bus_attribute pci_bus_attrs[];
+#else
+#define pci_bus_attrs	NULL
+#endif
+
 
 /**
  * pci_match_one_device - Tell if a PCI device structure has a matching