vgaarb: a NULL bridge is acceptable for root devices.

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>

1 files changed, 21 insertions, 23 deletions

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index c72f1c0b5e63..bdde899af72e 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -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;