Re: A simple question about readw, readw and the like

From: Andreas Bombe (
Date: Wed Aug 02 2000 - 11:12:24 EST

On Sat, Jul 29, 2000 at 04:53:23PM -0700, David S. Miller wrote:
> Date: Sun, 30 Jul 2000 00:55:29 +0200
> From: Andreas Bombe <>
> Sometimes it is needed to let one PCI device do DMA to another part
> of itself or another PCI device. For this, you need the bus
> addresses of the PCI memory resources. If
> pci_resource_start(dev,x) doesn't give you that, where else could
> it be found? By doing configure space reads I guess, but is that
> really necessary?
> I just remembered that there is a problem with this, not all PCI
> implementations can DMA across different bus segments. For example,
> if the two busses are behind different PCI controllers on sparc64,
> you cannot do peer-to-peer DMA between them.
> So besides putting the resource->pci_bus_address translation interface
> into asm/pci.h, we'd need to provide an interface which a driver can
> use to ask "pci_peer_to_peer_possible(pci_dev1, pci_dev2)".

Not an issue for me, I just need to tell a PCI device to DMA to/from a
memory resource of itself. But I think TV cards do DMA to graphics
cards, don't they?

 Andreas E. Bombe <>    DSA key 0x04880A44

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