RE: [openib-general] Re: [PATCH] arch/xx/pci: remap_pfn_range -> io_remap_pfn_range

["Ian Pratt" <m+Ian.Pratt@cl.cam.ac.uk>]

> >     Greg> Hm, you do realize that io_remap_pfn_range() is the same
> >     Greg> thing as remap_pfn_range() on i386, right?
> > 
> >     Greg> So, why would this patch change anything?
> > 
> > It's not the same thing under Xen.  I think this patch 
> fixes userspace 
> > access to PCI memory for XenLinux.
> 
> But Xen is a separate arch, and hence, will get different pci 
> arch specific functions, right?
> 
> In short, what is this patch trying to fix?  What is the 
> problem anyone is seeing with the existing code?

As I understand it, remap_pfn_range should be used for mapping pages
that are backed by memory, and io_remap_pfn_range should be used for
mapping MMIO regions.
There's a distinciton between the two for architectures like Sparc and
xen/x86. 

For example, drivers/char/mem.c uses io_remap_pfn_range for mmap'ing
/dev/mem

Ian
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