On Wed, Dec 09, 2015 at 08:43:05AM +0200, Panu Matilainen wrote: > On 12/08/2015 01:47 PM, Greg KH wrote: > >On Tue, Dec 08, 2015 at 11:34:36AM +0200, Panu Matilainen wrote: > >>>As was mentioned recently PCI bus numbers may change between reboots, so > >> > >>Hmm, got a pointer? I dont think PCI slots change between reboots without > >>physically swapping hardware, the "ethX-problem" comes from the order of > >>device discovery being unstable across boots, which is a different issue and > >>not relevant for this case. > > > >PCI can renumber the bus ids any time it wants to between reboots, it's > >not only if you add/remove new hardware. Now luckily most BIOSes aren't > >that broken and do keep keep things stable if the hardware doesn't > >change, but not all do, so be careful about this. I had a broken BIOS > >that would renumber things about every 10 reboots just "for fun" that > >was very good at using for testing system assumptions about static PCI > >device ids. > > Ugh :-/ I've clearly only seen well-behaved BIOSes. But even if the news is > bad its good to know, thanks.
See the other messages in this thread about how Qemu will also give you semi-random PCI addresses every other boot, that's a much more common problem and something easy to test with. > >>>you may want to start with something more stable from the very beginning. > >> > >>Such as? I dont see any other data that is there for all PCI (and USB) > >>devices that allows differentiating between two otherwise identical devices. > > > >Again, it all depends on the device itself, they should provide > >something that makes them unique (MAC address, serial number, topology > >at the moment, etc.) There is no one-thing-fits-all, which is why udev > >provides so many different ways to name things (look at /dev/disk/* and > >/dev/serial/* as examples of this.) > > At the time driverctl runs, things like MAC address are not available since > the normal driver is not loaded, its just a "raw" device on a bus. It's a PCI device on the bus, not a network device. When you create the network device, then you have a MAC address. You never need to rename a PCI device. > So I guess it'll need to grow an alternative mode that allows override by > PCI ID and operates on all devices by that ID, which loses a bit of control > vs the slot number but for the cases where slot number isn't reliable... What? What are you trying to "rename" here? I thought we were talking about network devices, or something else that a user actually interacts with. Userspace never deals with a "raw" PCI device, you should never care about those ids for anything "real". thanks, greg k-h _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
