Mechanism allowing asynchronous access to graphics adapter frame buffer physical memory linear aperture in a multi-tasking environment

摘要

A module is interposed between a multitasking operating system and the device driver for a graphics adapter including a frame buffer with a linear aperture for continuous, asynchronous data transfers. The interposed module may selectively intercept all graphics device driver function requests or simply pass such requests to the device driver, and provides a mechanism for generating graphics output in the frame buffer without utilizing graphics accelerator hardware on the graphics adapter. The interposed module is aware of the start and stop of asynchronous data transfers to the frame buffer. When asynchronous data transfers are started, the interposed module invokes the graphics adapter device driver to obtain access to the frame buffer linear aperture and sets its own internal state to active. While active, the interposed module intercepts all graphics device driver requests and employs its own mechanism to generate graphics output in the frame buffer responsive to such requests, without utilizing the graphics accelerator hardware. Since the graphics accelerator hardware is not utilized, the frame buffer linear aperture always remains enabled. While inactive, the interposed module simply passes all graphics device driver requests to the device driver. The interposed module is preferably implemented in accordance with the GRADD architecture model, with the mechanism for generating graphics output being provided by the VMAN and SOFTDRAW libraries.