Re: OpenGL-based framebuffer concepts

From: Kyle Moffett
Date: Tue May 23 2006 - 20:09:53 EST

On May 23, 2006, at 13:17:18, Jon Smirl wrote:
By implementing a framework where userspace doesn't have to know - or care - about the hardware, which, IMNSHO, is the way things should be, then userspace applications can take advantage of such a system and be even more stable.

A true monolithic design doesn't really work for video hardware. In the monolithic model all devices in a class present a uniform API. The better design for GPUs is the exo-kernel model. DRM already uses the exo-kernel model. With exokernels each driver presents a unique API and userspace libraries are used to provide a uniform API.

The one really significant potential problem with the exo-kernel model for graphics is that the kernel *must* have a stable way to display kernel panics regardless of current video mode, framebuffer settings, 3D rendering, etc. The kernel driver should be able to provide some fundamental operations for compositing text on top of the framebuffer at the primary viewport regardless of whatever changes userspace makes to the GPU configuration. We don't have this now, but I see it as an absolute requirement for any replacement graphics system. This means that the kernel driver should be able to understand and modify the entire GPU state to the extent necessary for such a text console.

Kyle Moffett

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