On Wed, Nov 12, 2014 at 1:58 AM, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote: > On Wed, Nov 12, 2014 at 10:47 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: >> On Tue, Nov 11, 2014 at 7:12 PM, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote: >>> ... >>> Do you think it is doable to introduce a option(from module >>> parameter, or device tree, ...) to let the driver and PCI core >>> ignore/bypass all pcibios handling for the generic bus? >> >> No, I don't think so. > > Could you explain a bit? In VM world, it might be reasonable to > claim that there is no pcibios service or pcibios service needn't. > > IMO it isn't easy to make a cross-arch PCI generic controller > driver if pcibios handling has to be involved. I'm not going to add kernel or module parameters to change the way the basic code works. We need a way to factor the differences so the PCI core code is the same for all arches, and the differences are hidden in the arch-specific code. That's basically what the pcibios interfaces do. I suspect they were originally named "pcibios" because there's a "PCI BIOS" spec that tells you how to make BIOS calls to enumerate devices, access config space, manage interrupts, etc. But "pcibios" is now just the name of interfaces to arch-specific functionality. Most arches don't have a BIOS, and most pcibios_*() functions don't make BIOS calls. If you have a new arch that has no "pcibios service" (I don't know exactly what you mean by that), you can still implement the pcibios_*() interfaces used by the PCI core. If some of these interfaces don't actually do anything on your arch, that's fine; they can be no-ops. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
