Merge branch 'bugzilla-13577-video' into release

diff --combined drivers/acpi/video.c
index 72e76b4b6538f2da73ca4b9060e3cf12ce1808fc,45e6a29c8177e573442380a79a80f44e0952659e..b765790b32be1841d652d3e834c6013950700efc
--- 1/drivers/acpi/video.c
--- 2/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@@ -78,6 -78,13 +78,13 @@@ MODULE_LICENSE("GPL")
  static int brightness_switch_enabled = 1;
  module_param(brightness_switch_enabled, bool, 0644);
  
+ /*
+  * By default, we don't allow duplicate ACPI video bus devices
+  * under the same VGA controller
+  */
+ static int allow_duplicates;
+ module_param(allow_duplicates, bool, 0644);
+ 
  static int register_count = 0;
  static int acpi_video_bus_add(struct acpi_device *device);
  static int acpi_video_bus_remove(struct acpi_device *device, int type);
@@@ -999,10 -1006,8 +1006,10 @@@ static void acpi_video_device_find_cap(
                sprintf(name, "acpi_video%d", count++);
                device->backlight = backlight_device_register(name,
                        NULL, device, &acpi_backlight_ops);
 -              device->backlight->props.max_brightness = device->brightness->count-3;
                kfree(name);
 +              if (IS_ERR(device->backlight))
 +                      return;
 +              device->backlight->props.max_brightness = device->brightness->count-3;
  
                result = sysfs_create_link(&device->backlight->dev.kobj,
                                           &device->dev->dev.kobj, "device");
@@@ -1981,10 -1986,6 +1988,10 @@@ acpi_video_switch_brightness(struct acp
        unsigned long long level_current, level_next;
        int result = -EINVAL;
  
 +      /* no warning message if acpi_backlight=vendor is used */
 +      if (!acpi_video_backlight_support())
 +              return 0;
 +
        if (!device->brightness)
                goto out;
  
@@@ -2239,11 -2240,47 +2246,47 @@@ static int acpi_video_resume(struct acp
        return AE_OK;
  }
  
+ static acpi_status
+ acpi_video_bus_match(acpi_handle handle, u32 level, void *context,
+                       void **return_value)
+ {
+       struct acpi_device *device = context;
+       struct acpi_device *sibling;
+       int result;
+ 
+       if (handle == device->handle)
+               return AE_CTRL_TERMINATE;
+ 
+       result = acpi_bus_get_device(handle, &sibling);
+       if (result)
+               return AE_OK;
+ 
+       if (!strcmp(acpi_device_name(sibling), ACPI_VIDEO_BUS_NAME))
+                       return AE_ALREADY_EXISTS;
+ 
+       return AE_OK;
+ }
+ 
  static int acpi_video_bus_add(struct acpi_device *device)
  {
        struct acpi_video_bus *video;
        struct input_dev *input;
        int error;
+       acpi_status status;
+ 
+       status = acpi_walk_namespace(ACPI_TYPE_DEVICE,
+                               device->parent->handle, 1,
+                               acpi_video_bus_match, NULL,
+                               device, NULL);
+       if (status == AE_ALREADY_EXISTS) {
+               printk(KERN_WARNING FW_BUG
+                       "Duplicate ACPI video bus devices for the"
+                       " same VGA controller, please try module "
+                       "parameter \"video.allow_duplicates=1\""
+                       "if the current driver doesn't work.\n");
+               if (!allow_duplicates)
+                       return -ENODEV;
+       }
  
        video = kzalloc(sizeof(struct acpi_video_bus), GFP_KERNEL);
        if (!video)