Hi all, On Tue, Jul 23, 2019 at 10:59:07AM +0200, Marc Kleine-Budde wrote: > On 7/22/19 3:37 PM, Oleksij Rempel wrote: > > We just noticed, in current implementation J1939_SOCK_RECV_OWN doesn't > > work anymore (for ETP). And ...naively thinking it probably makes no > > sense to support it for different reasons: > > > > - we have a better feedback mechanism via the error queue feature > > - with RECV_OWN the socket receives the complete payload back into user > > space, where the error queue will give back message number at state of > > the message/transfer. > > - the error queue mechanism is extendable with more information and even > > backwards compatible. > > > > However in the current implementation you'll receive an ACK via error > > queue if the (E)TP transfer is completed, but for simple messages, the > > ACK is received as soon as the packet has been put into the packet > > scheduler. It would be better to wait and send the ACK only after the > > simple message has been send onto the wire (i.e.: after the CAN > > controller's TX-complete interrupt). > > > > We'll remove J1939_SOCK_RECV_OWN for now. > > > > But we already noticed that this will break jacd, however we think we > > can fix it, by using a separate socket to receive. Are there any other > > use cases or existing applications relying on this feature? > > I think in AGL they switch on self reception of j1939 sockets by default. I have implemented missing functionality to monitor and "ACK" simple (<9 byte) packages. Users space will get same kind of notifications over the error queue: - SCHED - means, the packages was scheduled and will be soon taken over by hardware for transmission to the CAN bus. - ACK - CAN HW transmitted the package and send the echo signal back to the J1939 stack. - ABORT - we was no able to schedule the package or receive the transmit confirmation. In current kernel implementation, ABORT can be not 100% true. In case CAN bus is open and get "fixed"/closed after some time, ABORTed packages still may be transmitted to the bus. With current J1939 implementation we are able to detect it. In kernel log you will see: flexcan 2090000.flexcan can0: j1939_simple_recv: Received already invalidated message This issue can be fixed, at least for some drivers or hardware, in the CAN framework (not in J1939 stack). Since this problem was present with previous J1939 stack version and no good way to track transmitted packages, I don't see it as a regression. The jacd needed a 3 line change to make it work without J1939_SOCK_RECV_OWN flag. So, probably other projects, we be able to fix it as well. Oleksij & Marc -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
