Unfortunately this was not something we could do with standalone Windows machines due the vast array of video cards and display devices out there.
Backlight Control Interface
The first step is to query the device for the supported brightness using the IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS control code. This operation returns a buffer that specifies the available brightness levels. Next, you can query the device for the current display brightness using the IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS control code. This operation returns the current settings for alternating current (AC) brightness, direct current (DC) brightness, and the power state. To change the display brightness, use the IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS control code. You can set the AC brightness, the DC brightness, or both.
Windows 7 Brightness Control for Integrated Displays
Brightness controls are implemented in the monitor driver—Monitor.sys—that is included with Windows. The Windows monitor driver calls the display miniport driver's DxgkDdiQueryInterface function for the first video target in the system that is identified as having output technology that connects to an internal display device. This video target has the InterfaceTechnology member of the DXGK_VIDEO_OUTPUT_CAPABILITIES structure set to D3DKMDT_VOT_INTERNAL. This call queries for the brightness control interface that is identified by GUID_DEVINTERFACE_BRIGHTNESS and DXGK_BRIGHTNESS_INTERFACE_VERSION_1.
Unfortunately this was not something we could do with standalone Windows machines due the vast array of video cards and display devices out there.
Backlight Control Interface
The first step is to query the device for the supported brightness using the IOCTL_VIDEO_QUERY_SUPPORTED_BRIGHTNESS control code. This operation returns a buffer that specifies the available brightness levels. Next, you can query the device for the current display brightness using the IOCTL_VIDEO_QUERY_DISPLAY_BRIGHTNESS control code. This operation returns the current settings for alternating current (AC) brightness, direct current (DC) brightness, and the power state. To change the display brightness, use the IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS control code. You can set the AC brightness, the DC brightness, or both.
Windows 7 Brightness Control for Integrated Displays
Brightness controls are implemented in the monitor driver—Monitor.sys—that is included with Windows. The Windows monitor driver calls the display miniport driver's DxgkDdiQueryInterface function for the first video target in the system that is identified as having output technology that connects to an internal display device. This video target has the InterfaceTechnology member of the DXGK_VIDEO_OUTPUT_CAPABILITIES structure set to D3DKMDT_VOT_INTERNAL. This call queries for the brightness control interface that is identified by GUID_DEVINTERFACE_BRIGHTNESS and DXGK_BRIGHTNESS_INTERFACE_VERSION_1.
