netdev - RE: [net-next 10/13] igb: Tidy up wrapping for CONFIG_IGB

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Date:	Sun, 26 Aug 2012 01:33:42 +0000
From:	"Keller, Jacob E" <jacob.e.keller@...el.com>
To:	Richard Cochran <richardcochran@...il.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>,
	"Vick, Matthew" <matthew.vick@...el.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"sassmann@...hat.com" <sassmann@...hat.com>
Subject: RE: [net-next 10/13] igb: Tidy up wrapping for CONFIG_IGB_PTP.



> -----Original Message-----
> From: Richard Cochran [mailto:richardcochran@...il.com]
> Sent: Friday, August 24, 2012 11:20 PM
> To: Keller, Jacob E
> Cc: Ben Hutchings; Vick, Matthew; Kirsher, Jeffrey T; davem@...emloft.net;
> netdev@...r.kernel.org; gospo@...hat.com; sassmann@...hat.com
> Subject: Re: [net-next 10/13] igb: Tidy up wrapping for CONFIG_IGB_PTP.
> 
> On Fri, Aug 24, 2012 at 07:38:38PM +0000, Keller, Jacob E wrote:
> 
> > The IGP_PTP is necessary otherwise you have to do something like #if
> > defined(CONFIG_PTP_1588_CLOCK), or #ifdef CONFIG_PTP_1588_CLOCK \
> > #ifdef CONFIG_PTP_1588_CLOCK_MODULE
> 
> Yes, but maybe use IGP_PTP as Ben described?

That's exactly what I was saying :) That's the reason why IGP_PTP is necessary.

> 
> > The main reason that I wouldn't want to un-wrap the timestamping is
> > because the hwtstamp ioctl is somewhat problematic because it is
> > almost all ptp only. Also, some of the parts for igb driver don't
> > support timestamp all, they only support ptp only packets, and this
> > would be a lot more confusing since I would say still only allow that
> > if ptp is on.. (since those values are useless except with the PHC
> > clock)
> 
> I keep trying to explain that receive time stamping (HWTSTAMP_FILTER_ALL)
> is useful all by itself. It has nothing to do with PTP, and the 82580 can
> do this with very little ** overhead.
> 
> I myself have used this feature when debugging and profiling quasi real
> time Ethernet protocols like EtherCAT and IEC61850-9-2. The other drivers
> that offer this (gianfar and vxge) do so without any CONFIG conditionals.
> 
> IMHO, the Rx time stamping feature should always be available. It is
> really not much different than the vlan feature.

IMO it should be but only for parts with HWTSTAMP_FILTER_ALL, and only for that mode (other modes should be ignored) because timestamping only PTP packets is a PTP feature, so this change should still disable other modes if they exist.

> 
> Thanks,
> Richard
> 
> ** Both igb_rx_hwtstamp and igb_tx_hwtstamp only add a single test
>    when time stamping is not enabled.

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