On Wed, 18 May 2011, Sarah Sharp wrote: > On Tue, May 17, 2011 at 03:12:36PM -0700, Greg KH wrote: > > On Tue, May 17, 2011 at 02:46:26PM -0700, Sarah Sharp wrote: > > > I see that ehci-hcd.c has a warning in when either the UHCI or OHCI > > > driver is loaded before the EHCI driver: > > > > > > set_bit(USB_EHCI_LOADED, &usb_hcds_loaded); > > > if (test_bit(USB_UHCI_LOADED, &usb_hcds_loaded) || > > > test_bit(USB_OHCI_LOADED, &usb_hcds_loaded)) > > > printk(KERN_WARNING "Warning! ehci_hcd should always be loaded" > > > " before uhci_hcd and ohci_hcd, not after\n"); > > > > > > What actually prevents the UHCI or OHCI driver from being loaded before > > > the EHCI driver? Is it left up to userspace? > > > > Yes. Hopefully all of the distros now have properly modprobe rules to > > load these before the ehci driver, otherwise we would be getting the > > kernel warnings sent to us :) > > Great. Tony Luck had mentioned he saw this warning on boot on some box > of his, but hasn't been able to reproduce it. Where can I find these > modprobe rules files? Is it the same for every distro, or do different > distros store them in different places? Often they aren't in the form of udev rules at all. The script files in an initramfs image may be set up to explicitly load the drivers in the proper order. > > > Since PCI devices can be initialized in parallel, even if the EHCI > > > driver is loaded first, that doesn't guarantee that the PCI probe for > > > the EHCI controller actually finishes before the UHCI/OHCI PCI probe, > > > right? > > > > I didn't think that PCI devices were initialized in parallel all that > > often, so this might be pretty rare. > > Hmm, ok, HPA was muttering something on IRC about some PCI core rework > to make it possible to initialize PCI devices in parallel, so it might > be new. I asked about parallel probing of PCI devices at one point. Linus said he wasn't in favor of it because of the potential for problems like this one. > If it were possible that (even though the EHCI driver is loaded > first), the UHCI/OHCI driver could complete PCI probe first, would we > have an issue with the current companion system? We could. Probably only in a small number of obscure cases, though. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
