On Wed, 2016-11-30 at 10:10 -0800, Florian Fainelli wrote: > On 11/30/2016 09:44 AM, Joakim Tjernlund wrote: > > On Wed, 2016-11-30 at 17:55 +0100, Andrew Lunn wrote: > > > > This is an embedded system with several boards in a subrack. > > > > Each board has eth I/F connected to a switch to communicate with each > > > > other. > > > > One of the board will also house the actual switch device and manage > > > > the switch. > > > > Then the normal app just communicates over the physical eth I/F like > > > > any other board > > > > in the system. There is a "manage switch app" which brings the switch > > > > up and partition > > > > phys VLANs etc. (each phys I/F would be a a separate domain so no loop) > > > > > > So you are planning on throwing away the "manage switch app", and just > > > use standard linux networking commands? That is what switchdev is all > > > about really, throwing away the vendor SDK for the switch, making a > > > switch just a bunch on interfaces on the host which you manage as > > > normal interfaces. > > > > Something like that. I need to run routing protocols on the switch I/Fs and > > egress > > pkgs on selected switch I/Fs bypassing ARP, just like DSA does with its > > vendor > > tags. > > > > > > > > > I guess I could skip the phys I/F and have the switch app create a > > > > virtual eth0 I/F over PCIe > > > > > > No need to create this interface. It will exist if you go the > > > switchdev route. > > > > > > > > > And switchdev can do all this over PCIe instead? Can you have a > > > > > > switch tree in switchdev too? > > > > > > > > > > Mellonex says so, but i don't think they have actually implemented it. > > > > > > > > Not impl. any of DSAs features? What can you do with a Mellonex switch > > > > then? > > > > > > They don't have a tree of switches, as far as i know. Just a single > > > switch. But DSA does support a tree of switches, that is what the D in > > > DSA means, distributed. And there are a couple of boards which have 2 > > > to 4 switches in a tree. > > > > We might have a tree as well so now I really wonder: Given we write a > > proper switchdev driver, can it support switchtrees without touching > > switchdev infra structure? If not I guess we will attach a physical > > eth I/F to the switch and use both DSA and switchdev to support both trees > > and HW offload. > > switchdev in itself really is the glue layer between the networking > stack and how to push specific objects down to the Ethernet switch > driver, and that Ethernet switch driver. Switchdev does not enforce a > specific network device driver model object, and just provides standard > hooks for your network devices to register with switchdev in order to > push/receive offloads. DSA on the other hand, utilizes switchdev to get > notifications about offloads from the networking stack, but also exposes > a clearly and well defined Ethernet switch device driver model, as > Andrew described, it creates per-port network devices, binds the ports > to their PHYs (built-in, or external), and also takes care of > encapsulating/decapsulating the switch specific tagging protocol.
Lets see, switchdev is mainly for offloading L2/L3 into HW and does NOT create virtual I/F(one for each phys sw port) so if my only goal is to offload I don't need DSA? (How do one create routes if no virtual I/Fs I wonder ..) DSA then does create virt. I/Fs and manages switch trees, to actually tx pkg it needs a phys I/F using vendor specific tags(for PCIe connected switches I can envision using the PCIe connection instead). Who is the master when using both DSA and switchdev w.r.t initil conf/bring up of switch? configuring VLANs? > > We should probably put that in some crystal clear sentence somewhere in > Documentation/networking/ but switchdev and DSA are complementary and > not competitors, they just do not tackle the problems from the same angle. Yes :) > > > > > > > > > I think this is partially down to market segments. Mellonex market is > > > top of rack switches. High port count, very high bandwidth. DSA is > > > more wireless access points, set top boxes, generally up to 7 ports of > > > 1Gbps and a few custom embedded products which need more ports, so > > > build a tree of switches. > > > > We have on an existing board with a BCM ROBO switch with lots of ports(>24), > > managed over SPI. Looking at BCM DSA tag code it looks like it only supports > > some 8 ports or so. I still have to find out if this is a limitation in BCM > > tagging > > protocol or if just not impl. in DSA yet. > > Oh cool, can you share the model by chance? I suspect the tagging format I think it is an BCM5322 > of that switch is going to be different than what net/dsa/tag_brcm.c, so > feel free to add something NET_DSA_TAG_BRCM8B (for 8 bytes) or something > like that. I will have to look at that, don't have an docs handy. > > Note that DSA currently hardcodes the maximum number of ports to 14 > (DSA_MAX_PORTS), but this should obviously be something dynamically > determined based on probing the switch device. > > Can you also evaluate if using drivers/net/dsa/b53/ would work for you? > My hope would be that they preserved the register compatibility here, > but since this has a large number of ports, it may have completely > offset most registers. I will have a look, I sure want to try out DSA/switchdev on existing boards if I can :) > > BTW, there is #linuxswitch on Freenode if you want to chat!
