Unloading Video Hardware
When a surface is no longer required, a GDI call to DrvDisableSurface informs the display driver that the surface created for the current hardware device by DrvEnableSurface can be disabled. The driver must also free any resources the surface was using.
After the surface is disabled, GDI calls DrvDisablePDEV to inform the driver that the hardware device is no longer needed. The driver then frees any memory and resources that were allocated during the processing of DrvEnablePDEV.
Finally, GDI disables the display driver by calling DrvDisableDriver. The driver must free any resources allocated during DrvEnableDriver and restore the video hardware to its default state. After the driver returns from the DrvDisableDriver function, GDI frees the memory it has allocated for the driver and removes driver code and data from memory.
The following figure shows GDI's calling sequence for disabling the video hardware.