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

[Ville Syrjälä]

On Wed, Mar 16, 2005 at 02:09:18PM +1100, Benjamin Herrenschmidt wrote:
> 
> > 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.
> 
> Oh, that's fine and that's not a problem. I will only repaint the
> framebuffer on bit depth or line lenght changes. I'm trying to talk
> about the _future_ here. That is support for dual head at the fbdev
> level and other niceties.

I don't see the current system slowly evolving into some superb future 
system with an in kernel memory manager. The current APIs just have too 
many limitations. I think the memory manager must be the foundation of 
everything and after it's in place the fbdev API should be able to use it. 
The only change to simple fbdev apps would be that they can't get access 
to any offscreen memory as they do now. Something like DirectFB would need 
to change to accomodate the new system but I don't see that as a problem.

I think the best short term option for radeonfb is to simply follow 
matroxfb's example and cut the memory into two parts. The cutoff point 
should probably be configurable via a module option.

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