On Sat, 1 Jun 2019 at 13:31, Vladimir Oltean <olte...@gmail.com> wrote: > > On Sat, 1 Jun 2019 at 08:07, Richard Cochran <richardcoch...@gmail.com> wrote: > > > > On Fri, May 31, 2019 at 09:12:03PM +0300, Vladimir Oltean wrote: > > > It won't work unless I make changes to dsa_switch_rcv. > > > > Or to the tagging code. > > > > > Right now taggers can only return a pointer to the skb, or NULL, case > > > in which DSA will free it. > > > > The tagger can re-write the skb. Why not reform it into a PTP frame? > > This clever trick is what the phyter does in hardware. See dp83640.c. > > > > I think you're missing the point here. > If I dress the meta frame into a PTP frame (btw is there any > preferable event message for this purpose?) then sure, I'll make > dsa_skb_defer_rx_timestamp call my .port_rxtstamp and I can e.g. move > my state machine there. > The problem is that in the current DSA structure, I'll still have less > timestampable frames waiting for a meta frame than meta frames > themselves. This is because not all frames that the switch takes an RX > timestamp for will make it to my .port_rxtstamp (in fact that is what > my .can_timestamp patch changes). I can put the timestampable frame in > a 1-entry wait queue which I'll deplete upon arrival of the first meta > frame, but when I get meta frames and the wait queue is empty, it can > mean multiple things: either DSA didn't care about this timestamp > (ok), or the timestampable frame got reordered or dropped by the MAC, > or what have you (not ok). So I can't exclude the possibility that the > meta frame was holding a relevant timestamp. > Sure, I can dress the meta frame into whatever the previous > MAC-trapped frame was (PTP or not) and then I'll have .port_rxtstamp > function see a 1-to-1 correspondence with meta frames in case > everything works fine. But then I'll have non-PTP meta frames leaking > up the stack... >
Actually maybe this is exactly what you meant and I didn't think it through. If RX timestamping is enabled, then I can just copy all MAC-trapped frames to a private skb in a per-driver data structure, and have DSA drop them. Then when their meta frame arrives, I can just morph them into what the previous frame was, just that now I'm also holding the partial timestamp in skb->cb. PTP frames will reconstruct the full timestamp without waiting for any meta (they are the meta), while other MAC-trapped frames (STP etc) will just carry a meaningless skb->cb when passed up the stack. In retrospect, it would have been amazing if the switch gave me the meta frames *before* the actual link-local frames that needed the timestamp. Thanks! -Vladimir > Regards, > -Vladimir > > > Thanks, > > Richard
