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Date: Mon, 14 Jul 2008 19:57:42 +0200 From: Oliver Hartkopp <oliver@...tkopp.net> To: Andi Kleen <andi@...stfloor.org> CC: Octavian Purdila <opurdila@...acom.com>, netdev@...r.kernel.org Subject: Re: [rfc] new sk_buff member: hwstamp Andi Kleen wrote: > Octavian Purdila <opurdila@...acom.com> writes: > > >> So, would such a patch be considered for inclusion? Or maybe there is a >> better way of doing the above? >> > > You only need this between the driver and the socket recvmsg(), don't you? > > One possible alternative (I admit I haven't thought all the implications > through) would be to use a second magic internal skb for this which has the > same UDP header, but as only payload the time stamp. Disadvantage would > be the requirement to do header parsing in the driver, but often > hardware does that already. > > The additional hardware timestamp would not only be interesting for people using UDP. There had been several discussions for CAN controllers (controller area network) in the past, as some of these controllers also provide HW timestamps that are important for high quality logging tools. However i feel, that *one* nanosec resolution timestamp (as it already exists inside the skbuff) is enough. AFAIK the timestamp is only set in the netif_rx(), when it is not already set by the driver itself. For that reason i would suggest to create some semi-intelligent offset calculation inside the driver that makes the skb->tstamp value correspond with the hw timestamp and therefore transports the high resolution timestamp requirement into the userspace. 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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