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

[Ville Syrjälä]

On Tue, Mar 15, 2005 at 12:30:56PM +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

I didn't know about that. My first thought would be to disallow such modes 
but knowing that X lacks a proper fullscreen API that might not be a 
realistic option.

> (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...

I don't really have a big deal with invalidating the visible part of the 
memory.

-- 
Ville Syrjälä
syrjala at sci.fi
http://www.sci.fi/~syrjala/