On Tue, Apr 13, 2021 at 08:57:19AM +0200, Niklas Schnelle wrote: > On Tue, 2021-04-13 at 08:39 +0300, Leon Romanovsky wrote: > > On Mon, Apr 12, 2021 at 03:59:04PM +0200, Niklas Schnelle wrote: > > > Hi Narendra, Hi All, > > > > > > According to Documentation/ABI/testing/sysfs-bus-pci you are responsible > > > for the index device attribute that is used by systemd to create network > > > interface names. > > > > > > Now we would like to reuse this attribute for firmware provided PCI > > > device index numbers on the s390 architecture which doesn't have > > > SMBIOS/DMI nor ACPI. All code changes are within our architecture > > > specific code but I'd like to get some Acks for this reuse. I've sent an > > > RFC version of this patch on 15th of March with the subject: > > > > > > s390/pci: expose a PCI device's UID as its index > > > > > > but got no response. Would it be okay to re-use this attribute for > > > essentially the same purpose but with index numbers provided by > > > a different platform mechanism? I think this would be cleaner than > > > further proliferation of /sys/bus/pci/devices/<dev>/xyz_index > > > attributes and allows re-use of the existing userspace infrastructure. > > > > I'm missing an explanation that this change is safe for systemd and > > they don't have some hard-coded assumption about the meaning of existing > > index on s390. > > > > Thanks > > > Sure, good point. So first off yes this change does create new index > based names also on existing systemd versions, this is known and > intended and we'll certainly closely collaborate with any distributions > wishing to backport this change. > > As for being otherwise safe or having unintended consequences, Viktor > (see R-b) and I recently got the following PR merged in that exact area > of systemd to fix how hotplug slot derived interface names are > generated: > https://github.com/systemd/systemd/pull/19017 > In working on that we did also analyse the use of the index attribute > for hidden assumptions and tested with this attribute added. Arguably, > as the nature of that PR shows we haven't had a perfect track record of > keeping this monitored but will in the future as PCI based NICs become > increasingly important for our platform. We also have special NIC > naming logic in the same area for our channel based platform specific > NICs which was also contributed by Viktor. Thanks, this PR is exciting to read, very warm words were said about kernel developers :). Can you please summarize that will be the breakage in old systemd if this index will be overloaded? Thanks > > Thanks, > Niklas >
