Fri, Jan 15, 2021 at 08:26:17PM CET, k...@kernel.org wrote: >On Fri, 15 Jan 2021 15:39:06 +0100 Jiri Pirko wrote: >> >I'm not a SFP experts so maybe someone will correct me but AFAIU >> >the QSFP (for optics) is the same regardless of breakout. It's the >> >passive optical strands that are either bundled or not. So there is >> >no way for the system to detect the cable type (AFAIK). >> >> For SFP module, you are able to detect those. > >Not sure you understand what I'm saying. Maybe you're thinking about >DACs? This is a optical cable for breakout: > >https://www.fs.com/products/68048.html > >There is no electronics in it to "detect" things AFAIU. Same QSFP can >be used with this cable or a non-breakout.
Ah, got you. > >> >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... >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. Plus, I'm not really sure that our hw can report the type, will check. 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. > >> >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.
