vgaarb: a NULL bridge is acceptable for root devices.
Dave Airlie [Mon, 10 Oct 2011 08:29:18 +0000 (09:29 +0100)]
I assumed all PCI buses had a bridge, but playing with qemu recently, I
discovered vgaarb bug where it wasn't detecting both devices shared a bridge
at the root level.

Don't check for NULL, if two buses have a NULL bridge, assume they share the
root bus.

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/vga/vgaarb.c

index c72f1c0..bdde899 100644 (file)
@@ -465,31 +465,29 @@ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev)
        while (new_bus) {
                new_bridge = new_bus->self;
 
-               if (new_bridge) {
-                       /* go through list of devices already registered */
-                       list_for_each_entry(same_bridge_vgadev, &vga_list, list) {
-                               bus = same_bridge_vgadev->pdev->bus;
-                               bridge = bus->self;
-
-                               /* see if the share a bridge with this device */
-                               if (new_bridge == bridge) {
-                                       /* if their direct parent bridge is the same
-                                          as any bridge of this device then it can't be used
-                                          for that device */
-                                       same_bridge_vgadev->bridge_has_one_vga = false;
-                               }
+               /* go through list of devices already registered */
+               list_for_each_entry(same_bridge_vgadev, &vga_list, list) {
+                       bus = same_bridge_vgadev->pdev->bus;
+                       bridge = bus->self;
+
+                       /* see if the share a bridge with this device */
+                       if (new_bridge == bridge) {
+                               /* if their direct parent bridge is the same
+                                  as any bridge of this device then it can't be used
+                                  for that device */
+                               same_bridge_vgadev->bridge_has_one_vga = false;
+                       }
 
-                               /* now iterate the previous devices bridge hierarchy */
-                               /* if the new devices parent bridge is in the other devices
-                                  hierarchy then we can't use it to control this device */
-                               while (bus) {
-                                       bridge = bus->self;
-                                       if (bridge) {
-                                               if (bridge == vgadev->pdev->bus->self)
-                                                       vgadev->bridge_has_one_vga = false;
-                                       }
-                                       bus = bus->parent;
+                       /* now iterate the previous devices bridge hierarchy */
+                       /* if the new devices parent bridge is in the other devices
+                          hierarchy then we can't use it to control this device */
+                       while (bus) {
+                               bridge = bus->self;
+                               if (bridge) {
+                                       if (bridge == vgadev->pdev->bus->self)
+                                               vgadev->bridge_has_one_vga = false;
                                }
+                               bus = bus->parent;
                        }
                }
                new_bus = new_bus->parent;