Re: The IO problem on multiple PCI busses

David S. Miller
2001-03-01T19:14:32Z

Benjamin Herrenschmidt writes:
> I'm, of course open to any comments about this (in fact, I'd really like
> some feedback). One thing is that we also need to find a way to pass
> those infos to userland. Currently, we implement an arch-specific syscall
> that allow to retreive the IO physical base of a given PCI bus. That may
> be enough, but we may also want something that match more closely what we
> do in the kernel.

Same problem on sparc64. Using a special PCI syscall is fine, _if_ we
all end up using the same one. However, I would prefer another
mechanism...

I think a cleaner scheme is to allow mmap() on
/proc/bus/pci/${BUS}/${DEVICE} nodes, that is much cleaner and solves
transparently any "different word size between userland and kernel"
issues (specifically 32-bit userlands executing on 64-bit kernels).

I played around with something akin to this, and some of the necessary
Xfree86-4.0.x hackery needed, some time ago. But I never finished
this.

Later,
David S. Miller
davem@redhat.com