On Mon, Feb 01, 2016 at 04:28:38PM +0000, Lorenzo Pieralisi wrote: > On Fri, Jan 29, 2016 at 05:25:38PM -0600, Bjorn Helgaas wrote: > > On Wed, Jan 20, 2016 at 06:10:03PM +0000, Lorenzo Pieralisi wrote: > > > > > To do that, we must claim resources on PCI_PROBE_ONLY systems, but > > > I know for certain Bjorn does not like the idea (I let you trawl > > > the archives - at least he does not accept the idea of claiming > > > resources ONLY on PCI_PROBE_ONLY systems, he thinks we should > > > always claim resources regardless of that flag and fall-back to > > > reassigning them in case claiming fails. That's perfectly reasonable, > > > at least on systems with FW initializing PCI). The problem is dealing > > > with legacy, so switching to resources claiming by default is a tad > > > complicated, at least for testing (code is easy to implement). > > > > I'd like to think of PCI_PROBE_ONLY basically as "setting > > IORESOURCE_PCI_FIXED for every BAR", i.e., we can do everything we > > normally do *except* write to the BAR (of course we have to write to > > it to size the BAR during enumeration, but we have to restore the > > original value). > > I am honestly a bit confused about the distinction between > PCI_PROBE_ONLY and "IORESOURCE_PCI_FIXED for every BAR", the more > so if I read the resources assignment code, in particular: > > pci_assign_resource() > > in drivers/pci/setup-res.c > > That function assigns the resource but does not update the BAR > if IORESOURCE_PCI_FIXED is set. I wonder why the resource is > assigned at all if IORESOURCE_PCI_FIXED is set, probably to > initialize its parent pointer and set it, still, the value in > the struct resource may differ from what's in the BAR, I am not sure > I understand why we are happy with that or I am reading code the > wrong way (does not this give a view of resource tree disconnected > from how HW is actually programmed ?) I'm not happy with that -- it's just one of our many problems. The assignment code doesn't doesn't really pay attention to IORESOURCE_PCI_FIXED. I don't think it pays attention to PCI_PROBE_ONLY either, except that some arches don't even call the assignment code if it is set. 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
