Re: pci segments/domains

[Ivan Kokshaysky]

On Fri, May 17, 2002 at 04:41:57AM -0700, David S. Miller wrote:
> So, as a (real life) example, suppose you wanted to portably point
> your BTTV card at the framebuffer of a video card, you'd do
> something like:
> 
> 	res = fb_pdev->resource[1];
> 	res_off = OFFSET_INTO_FRAMEBUFFER;
> 	bttv_dma_addr = pci_to_pci_map_single(struct pci_dev *bttv_pdev,
> 					      struct pci_dev *fb_pdev,
> 					      res, res_off, size,
> 					      PCI_DMA_FROMDEVICE);

Exactly. And this function will look like this

	if (domain(bttv_pdev) == domain(fb_pdev))
		return arch_res_to_bus(res->start) + res_off;
	else if (!interdomain_dma_supported)
		return 0;
	else
		return some_iommu_magic(...);

BTW, I don't see anymore why pci domain info should be exposed to
users at all. :-)

Ivan.