Introduce module parameter 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@xxxxxxxxx> --- drivers/acpi/video.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) Index: linux-2.6/drivers/acpi/video.c =================================================================== --- linux-2.6.orig/drivers/acpi/video.c +++ linux-2.6/drivers/acpi/video.c @@ -78,6 +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); @@ -2233,11 +2240,47 @@ static int acpi_video_resume(struct acpi 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) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
