On Fri, 12 Aug 2016, Lukas Wunner wrote: > Thank you for explaining the motivation to carry out ->prepare top-down. > However my problem is really that ->complete is carried out bottom-up. > What's the motivation for that? Merely to mirror the behaviour of > ->prepare? Would it be possible to change it to top-down? Note that > re-enablement of device addition is already allowed in ->resume, > which is called top-down. I'm not aware of any particular reason why making ->complete run top-down wouldn't work. Of course, if you did then the environment at the start of the ->complete callback wouldn't be the same as it was at the end of the ->prepare callback. I think originally the idea was just to mirror ->prepare. Perhaps Rafael will remember something that has escaped me. > By the way, neither the PCI nor USB bus-level ->prepare callbacks perform > any action that would stop device addition. Same for the pciehp driver > (we don't even have a ->prepare callback defined for PCIe port services. > So it *is* possible to hotplug PCI devices after ->prepare. I don't know about PCI (although what you describe sounds like a bug). USB relies on a freezable workqueue for adding child devices, so it stops adding children even before the prepare phase begins. Alan Stern -- 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
