Re: [patch 4/6] xip: support non-struct page backed memory

["Jared Hulbert" <jaredeh@gmail.com>]

>  OK right... one problem is that we need an address for the kernel to
>  manipulate the memory with, but we also need a pfn to insert into user
>  page tables. So I like your last suggestion, but I think we always
>  need both address and pfn.

Right I forgot about the xip_file_read() path.

I like to use UML kernels with the file-to-iomem interface for
testing.  I forget how UML kernels deal with physical address like
this.  I remember there are some caveats.  I'll look into it.  But I
think I can do for UML:

*kaddr = (void *)(start_virt_addr + offset);
*pfn = virt_to_phys(*kaddr) >> PAGE_SHIFT;

And the ARM + MTD I can do:

*kaddr = (void *)(start_virt_addr + offset);
*pfn = (start_phys_addr + offset) >> PAGE_SHIFT;

>  This should work for you too?

I think so.  But like Carsten I'd prefer a virtual only solution.

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