Re: RFC: Deprecating io_block_mapping

quoted

Somewhere, at some point, prior to VM setup, we need to forcibly map
virtual to physical addresses.  These are going to be "hard coded"
mappings, that's exactly how ioremap_bot is set.  This is why
io_block_mapping was created in the first place.  Somehow you have
to specify this mapping before you have a VM allocator to give it to
you. :-)

No, you just need to have ioremap_bot (which is in fact "top" not
"bottom", bad naming) initialized to something sane. This is currently
done in MMU_init() but could probably be initialized statically instead.
I do just that on ppc64 and thus can ioremap at any time without needing
to allocate vmalloc space. The vmalloc space is automatically "cap'd" by
ioremap_bot anyway.

Can one of you explain why this is necessary.  I believe it I just dont understand.  I think this is one of the abuses of io_block_mapping().  People, myself included, realize some of the caveats implied by calling io_block_mapping().

- kumar