DRM_VMW_CONTROL_STREAM - Control overlays, aka streams.
This IOCTL controls the overlay units of the svga device. The SVGA overlay units does not work like regular hardware units in that they do not automaticaly read back the contents of the given dma buffer. But instead only read back for each call to this ioctl, and at any point between this call being made and a following call that either changes the buffer or disables the stream. struct drm_vmw_rect
Defines a rectangle. Used in the overlay ioctl to define source and destination rectangle.
