ACPI video: Prune dupe video devices, unless "video.allow_duplicates"
Some buggy BIOS exports multiple ACPI video bus devices for the same
VGA controller, and multiple backlight control methods as well.
This messes up the ACPI video backlight control.
http://bugzilla.kernel.org/show_bug.cgi?id=13577
With this patch applied, only the FIRST ACPI video bus device
under a PCI device node is bind to ACPI video driver by default.
If the first ACPI video bus device doesn't work well, we can use
video.allow_duplicates=1 to go back to the old behavior.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 05dff63..45e6a29 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -78,6 +78,13 @@
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);
@@ -2233,11 +2240,47 @@
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)
