netdev - Re: [PATCH net-next v2 1/8] net-timestamp: explicit SO

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Date:	Mon, 7 Jul 2014 11:34:05 -0400
From:	Willem de Bruijn <willemb@...gle.com>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	richardcochran@...ail.com,
	Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH net-next v2 1/8] net-timestamp: explicit SO_TIMESTAMPING
 ancillary data struct

On Sat, Jul 5, 2014 at 4:18 PM, Richard Cochran
<richardcochran@...il.com> wrote:
> On Thu, Jul 03, 2014 at 03:39:33PM -0400, Willem de Bruijn wrote:
>
>> +#define SCM_TSTAMP_SND               0x1     /* driver passed skb to NIC */
>> +#define SCM_TSTAMP_ACK               0x2     /* transport layer saw ACK */
>> +#define SCM_TSTAMP_ENQ               0x4     /* stack passed skb to TC layer */
>> +#define SCM_TSTAMP_RCV               0x8     /* stack received skb */
>> +#define SCM_TSTAMP_HWSYS     0x10    /* NIC tstamp in system format */
>
> We don't need this flag. Better to omit it, because we are not going
> to allow this kind of time stamp ever again.

The hardware timestamp converted to system time is deprecated? I did
not know that. Because it is largely unused, or for a more fundamental
reason?

If so, the documentation could indeed use an explicit comment. The
definition of skb_shared_hwtstamps.syststamp too. I can write a small
patch independent of this patchset.

Better, that field in could be removed completely if there are no
users.That would be self documenting, would simplify plumbing
boilerplate and shrink sbk_shared_info.

Unfortunately, a cursory inspection shows one, octeon. While that user
exists and generates such timestamps, I think that the above new flag
should be passed, as well, for API consistency.

>> +#define SCM_TSTAMP_HWRAW     0x20    /* NIC tstamp in native format */
>
> Thanks,
> Richard
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