Xserver device I/O on Linux

[John Dennis]

Both xfree86 and xorg on which it is based has code for using
/proc/bus/pci on linux, in fact when building for ia64 this is exactly
what happens so I'm a bit confused as to why you're having an issue with
ia64. We've been building and shipping X for ia64 for a while using this
code base. One change we recently made was to always use the linux
version of the pci routines on all architectures, it had been the case
that on x86 the pci code was accessing pci config space via the IO ports
and soon this won't be supported (pci express does not support it and
there are issues with concurrency on mp machines). This was a trival one
line change to an ifdef to use the linux code.

I'm not sure what you mean by port I/O and mapping not being provided in
a way the server expects could you elaborate? A lot of these issues have
been addressed. But you're certainly right, port I/O on non-x86
architectures has been a nasty area.

On Thu, 2004-04-29 at 18:02, Jesse Barnes wrote:
> In trying to port the X server to SGI ia64-based sn2 machines, I ran into a 
> few problems, and I'm wondering what people think (if this discussion has 
> happened before, please point it out to me--I've looked around a bit but 
> haven't found much).
> 
> Device discovery:  all Linux ports that I'm aware of provide a PCI API that's 
> accessable via /proc/bus/pci.  It seems like it would make sense to simplify 
> some of the Linux code by assuming this was true.
> 
> Device I/O: some platforms (like sn2 and ppc) don't provide a way to do port 
> I/O and mapping in the way that the server expects.  Would it make sense to 
> have a per-device IO base address so that these platforms (and others like 
> them) could simply use loads and stores to access the I/O ports they need?  
> Mapping could also be done relatively simply if we assumed the presence of 
> the /proc/bus/pci API.
> 
> Ideally, all of the Linux device access code would be unified, but I'm not 
> sure if that's possible, so I'm willing to do this just for ia64 as long as 
> people are ok with the non-platform specific bits.
> 
> Any thoughts?
> 
> Thanks,
> Jesse
> 
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-- 
John Dennis <jdennis at redhat.com>