On Wed, Feb 06, 2019 at 04:17:24PM +0300, Mika Westerberg wrote: > Now that we can allocate hop IDs per port on a path, we can take > advantage of this and create tunnels covering longer paths than just > between two adjacent switches. PCIe actually does not need this as it is > always a daisy chain between two adjacent switches but this way we do > not need to hard-code creation of the tunnel.
That doesn't seem to be correct, at the bottom of this page there's a figure showing a PCI tunnel between non-adjacent switches (blue line): https://developer.apple.com/library/archive/documentation/HardwareDrivers/Conceptual/ThunderboltDevGuide/Basics/Basics.html I'm not sure if there are advantages to such tunnels: Reduced latency perhaps because packets need not pass through PCIe adapters on the in-between device? Or maybe this allows for more fine-grained traffic prioritization? > + i = 0; > + tb_for_each_port(in_port, src, dst) > + i++; This looks more complicated than necessary. Isn't the path length always the length of the route string from in_port switch to out_port switch, plus 2 for the adapter on each end? Or do paths without adapters exist? > + for (i = 0; i < num_hops; i++) { > + in_port = tb_port_get_next(src, dst, out_port); > + > + if (in_port->dual_link_port && in_port->link_nr != link_nr) > + in_port = in_port->dual_link_port; > + > + ret = tb_port_alloc_in_hopid(in_port, in_hopid, -1); > + if (ret < 0) > + goto err; > + in_hopid = ret; > + > + out_port = tb_port_get_next(src, dst, in_port); > + if (!out_port) > + goto err; There's a NULL pointer check here, but the invocation of tb_port_get_next() further up to assign in_port lacks such a check. Is it guaranteed to never be NULL? Thanks, Lukas
