Re: Adding kmap_atomic_prot_pfn (was: [git pull] drm patches for2.6.27-rc1)

[Benjamin Herrenschmidt]

On Thu, 2008-10-23 at 14:24 -0700, Linus Torvalds wrote:
> The whole point of that function has absolutely nothing to do with 
> highmem, and it *must* be useful on non-highmem configurations to be 
> appropriate.
> 
> So I'd much rather create a new <linux/kmap.h> or something. Or just 
> expose this from to <asm/fixmap.h> or something. Let's not confuse
> this 
> with highmem, even if the implementation _historically_ was due to
> that.

Well, on powerpc, we just went (or rather, Kumar just went) through the
oops of implementing fixmap and then kmap on top of it... just because
we wanted kmap_atomic functionality on non-highmem platforms :-) (and
the fixmap approach has some other interesting features).

So yes, I agree. Typically very useful for any 32-bit processor with a
memory mapped PCI Express config space since it's something like 256M of
virtual space to map it all iirc.

Cheers,
Ben.

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