FB model basic issues (WAS: radeon, apertures & memory mapping)

[Michel Dänzer]

On Tue, 2005-03-15 at 12:30 +0100, Roland Scheidegger wrote:
> Ville Syrjälä wrote:
>   > I think that making the assumption that all memory is preserved when 
> the
> > memory layout (virtual resolution and depth) doesn't change is perfectly 
> > valid too. That would allow X to do it's Ctrl-Alt-+ and - things without 
> > repainting the whole screen.
> I'm not sure I agree here, as it's not always true. For instance, the 
> radeon has some restrictions whether it can use tiling or not with a 
> certain mode (interlace/double scan) thus you need to redraw everything 
> anyway (which is exactly why I implemented a driver workaround to 
> repaint everything when that happens - in fact the workaround also gets 
> rid of the offscreen contents, which is not necessary, but was much 
> easier to implement, since I couldn't find an easy way to "invalidate 
> the framebuffer"). What's the big deal with repainting everything? It's 
> not like you would do 100 mode changes per second so it would be 
> performance-critical...

It's ugly, but that's not the point. The point is that all deployed
versions of X (and even current X.org CVS head still, in fact) make this
assumption.


-- 
Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer