netdev - Re: [RFC][PATCH 1/1] net: support for hardware timestamping

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Date:	Tue, 29 Jul 2008 21:10:44 +0300
From:	Octavian Purdila <opurdila@...acom.com>
To:	Ingo Oeser <netdev@...eo.de>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	Patrick Ohly <patrick.ohly@...el.com>, netdev@...r.kernel.org
Subject: Re: [RFC][PATCH 1/1] net: support for hardware timestamping

On Tuesday 29 July 2008, Ingo Oeser wrote:
> Hi Octavian,
>

Hi Ingo,

> Just convert your hardware specific cookie you have into the nanoseconds
> resolution timstamp in skb->tstamp just before calling netif_rx()
> or net_receive_skb().
>
> These functions will not touch it, as long as they never see a ZERO
> value there. A ZERO value in tstamp.tv64 means, we have no timestamp.
>
> The difference to CPU clock doesn't matter.
> That compensation can be done by your driver or application at will.
> For mainline, compensation in driver might be preferred.
>
> As long as it is montonic increasing and related to time in any way,
> you could put anything there, I think :-)
>

In here:

net/netfilter/xt_time.c

it seems that the skb->tstamp needs to be CPU time. 

Frankly I don't care about that, but the tstamp is also used in other places 
like the IP and TCP code paths and I can't say that I barely understand that 
part :) 

But if it is ok to use any kind of monotonic increasing timestamp, that will 
solve my problem, indeed.

Thanks,
tavi
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