[PATCH 3/3] i915: Don't provide ACPI backlight interface if firmware expects Windows 8

[Daniel Vetter]

On Sun, Jun 09, 2013 at 07:01:39PM -0400, Matthew Garrett wrote:
> Windows 8 leaves backlight control up to individual graphics drivers rather
> than making ACPI calls itself. There's plenty of evidence to suggest that
> the Intel driver for Windows doesn't use the ACPI interface, including the
> fact that it's broken on a bunch of machines when the OS claims to support
> Windows 8. The simplest thing to do appears to be to disable the ACPI
> backlight interface on these systems.
> 
> Signed-off-by: Matthew Garrett <matthew.garrett at nebula.com>

Make sense and I guess it's easier to merge this all through the acpi
tree. So

Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/i915/i915_dma.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 3b315ba..23b6292 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1661,6 +1661,9 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
>  		/* Must be done after probing outputs */
>  		intel_opregion_init(dev);
>  		acpi_video_register();
> +		/* Don't use ACPI backlight functions on Windows 8 platforms */
> +		if (acpi_osi_version() >= ACPI_OSI_WIN_8)
> +			acpi_video_backlight_unregister();
>  	}
>  
>  	if (IS_GEN5(dev))
> -- 
> 1.8.2.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch