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Date: Thu, 03 Nov 2011 15:54:50 +0100 From: Oliver Hartkopp <socketcan@...tkopp.net> To: Reuben Dowle <Reuben.Dowle@...ico.com> CC: netdev@...r.kernel.org, linux-can@...r.kernel.org Subject: Re: [PATCH] flexcan: Fix CAN_RAW_RECV_OWN_MSGS and CAN_RAW_LOOPBACK On 02.11.2011 22:31, Reuben Dowle wrote: >>> >>> If we change the behaviour of flexcan, I think at91 and slcan should >> be changed too, because this should be handled consistently across all >> drivers I would think. >> >> >> At least the slcan driver does not support the correct echo of CAN >> frames on >> driver level at all. The slcan driver adapts CAN frames to a serial >> line CAN >> adapter where the feedback of successful transmission is not >> guaranteed/checked within the serial data stream. Therefore the >> interface flag >> IFF_ECHO is not set in the slcan driver and the local echo is performed >> in >> af_can.c (as a workaround). >> >> Regards, >> Oliver > > Thats fine for the echo behaviour, but does not really answer why the slcan > (and flexcan) driver is setting the stats for tx_packets and tx_bytes at > different points in the transmission logic. To my mind, either we think the > packet has transmitted (along with its bytes) so we should increment both, > or we should increment neither. In slcan.c the points of incrementing tx_bytes and tx_packets have been adopted from slip.c where slcan.c heavily bases on. Indeed one could argument that tx_packets could be incremented in slc_encaps together with tx_bytes. This means that the packet is sent. But the packet is surely sent in slcan_write_wakeup(), when tx_packets is incremented. Unfortunately we do not have the can_dlc available at this point anymore. If you think it's worth the effort tx_packets++ could be integrated into slc_encaps() to have a consistent statistic update (but you don't know whether the packet hit the serial line entirely). Additionally slip.c does it the same (inconsistent) way for the reasons above and therefore i tend not to change it to stay on the current serial netdevices behaviour (for slcan as only CAN netdevice). Regards, Oliver -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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