WDDM driver DDI brightness control interface

Windows interfaces with the Windows Display Driver Model (WDDM) graphics driver to determine the presence of an integrated display. If an integrated display is detected, Windows will query the WDDM driver for the DXGK_BRIGHTNESS_INTERFACE_2 interface. This interface is mandatory for all WDDM 1.2 drivers. The presence of this interface indicates that the driver supports brightness control of the integrated display.

The WDDM driver must implement this interface as defined by the Windows Hardware Certification Requirement System.Client.BrightnessControls. A key new requirement for the driver is to support 101 brightness levels.

For backward compatibility with Windows 7 systems, Windows 8 still supports brightness control using the Advanced Configuration and Power Interface (ACPI). However, new features like smooth brightness will not be available on such systems.

To avoid problems that might occur if the system basic input/output system (BIOS) and the monitor driver both control display panel brightness, the display miniport driver should set bit 2 of the argument to the _DOS ACPI control method. With the setting of bit 2, the system BIOS is informed that it should not perform any automatic brightness changes. The WDDM driver must set this particular bit because it controls the _DOS method. The other bits in the _DOS methods are used to control the BIOS behavior for display switch shortcut keys.

For more information about the _DOS method and its arguments, see Appendix B of the Advanced Configuration and Power Interface Specification.

 

 

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