[Xorg] Non-fb video driver

Alan Cox alan at lxorguk.ukuu.org.uk
Thu Aug 19 04:06:43 PDT 2004

On Iau, 2004-08-19 at 07:10, Stanislaw Skowronek wrote:
> Accessing the framebuffer is a rather intricate process involving setup of
> about 20 registers and DMA, so "just copy a virtual fb to screen" would be
> too slow.

To just get you going you can still use shadowfb. That will tell you
which rectangles changed so you can just blit those to screen. That
is how things like the vesa driver are working
> However, I can draw accelerated rectangles, pixmaps, lines, polygons (I
> haven't quite worked the stipple out as yet), alpha blending, gradients
> et al. And acceleration on this card is, well, SGI standard :)
> How does one write a driver for a monster like this: no fb, good accel?

Pull XFree 3.3.x and take a look at the IBM 8514 driver. This doesn't
use XAA but uses the layer above which simply requires set/get pixel but
allows you to implement higher level functions accelerated.

This driver rotted by XFree 4 as it was for old MCA bus PC hardware
which mostly doesn't exist, and certainly isn't used nowdays.


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