On Mon, 18 Jan 2021 14:00:09 +0100 Jiri Pirko wrote: > >> >Or to put it differently IMO the netdev should be provisioned if the > >> >system has a port into which user can plug in a cable. When there is > >> > >> Not really. For slit cables, the ports are provisioned not matter which > >> cable is connected, slitter 1->2/1->4 or 1->1 cable. > >> > >> > >> >a line card-sized hole in the chassis, I'd be surprised to see ports. > >> > > >> >That said I never worked with real world routers so maybe that's what > >> >they do. Maybe some with a Cisco router in the basement can tell us? :) > >> > > >> > >> The need for provision/pre-configure splitter/linecard is that the > >> ports/netdevices do not disapper/reappear when you replace > >> splitter/linecard. Consider a faulty linecard with one port burned. You > >> just want to replace it with new one. And in that case, you really don't > >> want kernel to remove netdevices and possibly mess up routing for > >> example. > > > >Having a single burned port sounds like a relatively rare scenario. > > Hmm, rare in scale is common...
Sure but at a scale of million switches it doesn't matter if a couple are re-configuring their routing. > >Reconfiguring routing is not the end of the world. > > Well, yes, but you don't really want netdevices to come and go then you > plug in/out cables/modules. That's why we have split implemented as we > do. I don't understand why do you think linecards are different. If I have an unused port it will still show up as a netdev. If I have an unused phymod slot w/ a slot cover in it, why would there be a netdev? Our definition of a physical port is something like "a socket for a networking cable on the outside of the device". With your code I can "provision" a phymod and there is no whole to plug in a cable. If we follow the same logic, if I have a server with PCIe hotplug, why can't I "provision" some netdevs for a NIC that I will plug in later? > Plus, I'm not really sure that our hw can report the type, will check. I think that's key. > One way or another, I think that both configuration flows have valid > usecase. Some user may want pre-configuration, some user may want auto. > Btw, it is possible to implement splitter cable in auto mode as well. Auto as in iterate over possible configs until link up? That's nasty. > >> >If the device really needs this configuration / can't detect things > >> >automatically, then we gotta do something like what you have. > >> >The only question is do we still want to call it a line card. > >> >Sounds more like a front panel module. At Netronome we called > >> >those phymods. > >> > >> Sure, the name is up to the discussion. We call it "linecard" > >> internally. I don't care about the name. > > > >Yeah, let's call it something more appropriate to indicate its > >breakout/retimer/gearbox nature, and we'll be good :) > > Well, it can contain much more. It can contain a smartnic/fpga/whatever > for example. Not sure we can find something that fits to all cases. > I was thinking about it in the past, I think that the linecard is quite > appropriate. It connects with lines/lanes, and it does something, > either phy/gearbox, or just interconnects the lanes using smartnic/fpga > for example. If it has a FPGA / NPU in it, it's definitely auto-discoverable. I don't understand why you think that it's okay to "provision" NICs which aren't there but only for this particular use case.
