netdev - Re: [RFC] net : add tx timestamp to packet mmap.

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Date:	Tue, 09 Apr 2013 12:42:57 +0200
From:	Paul Chavent <Paul.Chavent@...ra.fr>
To:	Richard Cochran <richardcochran@...il.com>
CC:	davem@...emloft.net, edumazet@...gle.com,
	daniel.borkmann@....ee.ethz.ch, xemul@...allels.com,
	ebiederm@...ssion.com, netdev@...r.kernel.org
Subject: Re: [RFC] net : add tx timestamp to packet mmap.



On 12/13/2012 07:17 PM, Richard Cochran wrote:
> On Thu, Dec 13, 2012 at 05:13:56PM +0100, Paul Chavent wrote:
>>>
>>> In order for time stamps to appear, somebody has to call
>>> skb_tx_timestamp() ...
>> Yes. "Somebody" means "the hardware driver" after completing xmit.
>> That's true ?
>
> Yes, the MAC driver must call this helper function, but not many
> drivers do this yet. You didn't say which MAC driver you are using and
> whether it supports Tx SO_TIMESTAMPING or not.
>
>> Yes, it only sets some flags. I thought that those flags was
>> required by the skb_tx_timestamp() in order to make the appropriate
>> timestamping (hardware, software, etc).
>>
>> So in order to have tx timestamp that work, both calls are needed ?
>
> Yes.
>
>> Why sock_tx_timestamp is called in packet_fill_skb and
>> packet_sendmsg_spkt and not in tpacket_fill_skb ?
>> Why i can retrieve timestamps when i add this call ?
>
> Sorry, I don't know much about packet mmap. Last time I tried it, some
> years ago, it wasn't really working.
>
> Richard
>
Hi.

Would it be possible that the packet mmap maintainers give their opinion 
on this thread please ?

Regards.

Paul.
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