locking memory ranges with the exa memory manager

Jesse Barnes jbarnes at virtuousgeek.org
Thu Aug 11 09:40:46 PDT 2005

On Thursday, August 11, 2005 8:56 am, Eric Anholt wrote:
> Currently, the offscreen allocator allocates within memory ranges
> from (memoryBase + offScreenBase) to (memoryBase + memorySize).  Your
> memoryBase should point to the beginning of framebuffer memory. 
> Adjust your offScreenBase and memorySize to get the allocator to
> point to whatever region you want it to, probably the largest one. 
> I'm actually wondering if there is any case where the driver doesn't
> stick its static things at the start and end of framebuffer memory,
> i.e. why people are so worried about this simple system for now.

Now that you've cleared it up, I'm no longer worried/confused. :)  But 
given what you've stated above, the variables aren't named very well.  
If offscreenBase is really an offset, it should probably be called 
offscreenOffset, either that or EXA should actually use it as a real 
base pointer.  In the latter case, we should have an offscreenSize or 
offscreenEnd that EXA can use as an upper bound for the allocation 

Anyway, I've updated http://www.virtuousgeek.org/exa-driver.txt with 
this new info, I'll try it in i830 when I get home today.

> It would be nice to support multiple ranges, though, since a lot of
> cards can probably treat agp space basically the same as framebuffer.
> However, that gets into more complicated migration questions that we
> haven't dealt with in exa yet.



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