Mapping large framebuffers into kernel space

[Jon Smirl]

I just got a new P4 machine with 1GB memory and I'm trying to make radeonfb
work on it.  I am compiled with HIGHMEM4G. The motherboard is i875P based which
supports 64b DMA.

When I first loaded radeonfb it would fail because ioremap was failing. I
tracked the problem down to not having any free kernel address space below 1GB.
I created some by adding reserve=FE000000-100000000 to the kernel command line.
 This allowed radeonfb to load.

I'm beginning to wonder if framebuffers should be mapped into kernel space. 
What's going to happen when I get a 512MB video card? Does the framebuffer have
to be mapped in the first 1GB of kernel address space?

If the framebuffer is mapped, it's a perfect candidate for a large page table
entry because it is a very large piece of linear memory that not's going to be paged.

=====
Jon Smirl
jonsmirl@xxxxxxxxx

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