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

[Randy.Dunlap]

On Thu, 28 Jul 2005 12:57:51 +0100 Ian Pratt wrote:

> > >     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

That is my (limited) understanding also, but when I built
io_remap_pfn_range(), I didn't search all callers of
remap_pfn_range() to see which ones that I could fix (or break)
by changing them.  Mostly due to the possible breakage part.

---
~Randy
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