RFC: Deprecating io_block_mapping
kumar.gala at freescale.com
Wed May 25 16:08:06 EST 2005
>> 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
> I do just that on ppc64 and thus can ioremap at any time without
> to allocate vmalloc space. The vmalloc space is automatically "cap'd"
> 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
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