Re: pci_dma64_available() and Xen

[Martin Husemann <martin%duskware.de@localhost>]

On Sat, Oct 11, 2008 at 10:58:54PM +0200, Manuel Bouyer wrote:
> Hi,
> I just noticed that pci_dma64_available() does the following:
> int
> pci_dma64_available(struct pci_attach_args *pa)
> {
> #ifdef _PCI_HAVE_DMA64
>         if (BUS_DMA_TAG_VALID(pa->pa_dmat64) &&
>               ((uint64_t)physmem << PAGE_SHIFT) > 0xffffffffULL)
>                       return 1;
> #endif
>       return 0;
> }

Just a note in passing: this function seems underdocumented, as well as
_PCI_HAVE_DMA64.

Probably as a consequence of this, only amd64 and xen define _PCI_HAVE_DMA64.

Can someone summarize the 64 bit PCI operation?

Martin