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SubjectRe: [PATCH] Introduce PCI <-> CPU address conversion [1/2]
On Thu, Oct 14, 2004 at 06:27:04PM +0400, Ivan Kokshaysky wrote:
> On Thu, Oct 14, 2004 at 01:47:37PM +0100, Matthew Wilcox wrote:
> > Some machines have a different address space on the PCI bus from the
> > CPU's bus. This is currently fixed up in pcibios_fixup_bus(). However,
> > this is not called for hotplug devices. Calling pcibios_fixup_bus() when
> > a device is hotplugged onto a bus is also wrong as it would attempt to
> > fixup devices that have already been fixed up with potentially horrific
> > consequences.
> This logic makes sense only if you have sort of firmware which
> properly initializes the hotplug devices

Yes, this is the case for the ACPI hotplug driver, for example.

> so I think that the fixup
> should belong in that particular hotplug driver (or architecture).

*sigh*. Greg rejected a patch that did that. He wanted it fixed
more generally.

> > This patch teaches the generic PCI layer that there may be different
> > address spaces, and converts from bus views to cpu views when reading
> > from BARs. Some drivers (eg sym2, acpiphp) need to go back the other
> > way, so it also introduces the inverse operation.
> This one already exists - pcibios_resource_to_bus().

I can't use it in the symbios driver because it only exists on alpha,
arm, mips, parisc, ppc, ppc64, sparc64 and v850. It doesn't exist on
i386, ia64, x86_64, arm26, cris, h8300, m32r, sh, sh64 or sparc.

Perhaps from your point of view this patch makes more sense as a cleanup.
Rather than having all the duplicate code in all the architecture
pcibios_fixup_device and pcibios_resource_to_bus, they can implement
pci_bus_to_phys and pci_phys_to_bus.

"Next the statesmen will invent cheap lies, putting the blame upon
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince
himself that the war is just, and will thank God for the better sleep
he enjoys after this process of grotesque self-deception." -- Mark Twain
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