netdev - Re: [PATCH net-next-2.6] net: Consistent skb timestamping

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Message-ID: <4BF039DA.3020207@chelsio.com>
Date:	Sun, 16 May 2010 11:30:50 -0700
From:	Dimitris Michailidis <dm@...lsio.com>
To:	David Miller <davem@...emloft.net>
CC:	therbert@...gle.com, eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next-2.6] net: Consistent skb timestamping

David Miller wrote:

> The real fix is to make the devices less stupid and give us timestamps
> directly, and thanks to things like PTP support in hardware that's
> actually more and more of a reality these days.

For cxgb4 a timestamp is written into Rx descriptors for each received 
packet.  The value comes from a TSC-like cycle counter.  The raw timestamp 
is very cheap to get, its value converted to system ktime a bit less so 
though not too bad.  It would be nicer though if the stack could hint the 
driver whether it should do the conversion at all.  Maybe export 
netstamp_needed and add an inline wrapper to read it?

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