Re: vesafb problem with 1GB Ram and possible fix

[Antonino Daplas <adaplas@pol.net>]

On Sun, 2003-03-30 at 04:24, Walt H wrote:
> > 
> <Patch snipped>
> 
> One question I've been wondering about with either one of these 
> approaches has to do with mode changes. I might be mistaken, but if I 
> remember correctly, video mode changes aren't supported for vesa 
> framebuffers. Would you ever need to allocate additional memory other 
> than that allocated at startup? I'm thinking that in the small tweak 
> that I did, you can perhaps not allocate enough memory for some 
> unforseen future event, although I can't think of any off hand. Then 
> again, I'm not a kernel programmer, I could be way off base here.
> 

True, vesafb does not support mode changes.  However, the extra graphics
memory is useful for some framebuffer-based applications that implement
multi-buffering. DirectFB, for instance, takes advantage of this since
it uses a frontbuffer and a backbuffer (display the frontbuffer, render
to the backbuffer, swap the front and backbuffer pointers, then display
the new frontbuffer).  Xine and mplayer using the framebuffer backend
are probably using similar setups. 

Tony  



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