netdev - Re: [PATCH] ptp: Set lookup cookie when creating a PTP PPS source.

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Date:   Mon, 28 Jun 2021 17:08:30 -0700
From:   Jonathan Lemon <jonathan.lemon@...il.com>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH] ptp: Set lookup cookie when creating a PTP PPS source.

On Mon, Jun 28, 2021 at 04:38:35PM -0700, Richard Cochran wrote:
> On Mon, Jun 28, 2021 at 11:25:33AM -0700, Jonathan Lemon wrote:
> > When creating a PTP device, the configuration block allows
> > creation of an associated PPS device.  However, there isn't
> > any way to associate the two devices after creation.
> > 
> > Set the PPS cookie, so pps_lookup_dev(ptp) performs correctly.
> 
> Setting lookup_cookie is harmless, AFAICT, but I wonder about the use
> case.  The doc for pps_lookup_dev() says,
> 
>  * This is a bit of a kludge that is currently used only by the PPS                                                                      
>  * serial line discipline.
> 
> and indeed that is the case.
> 
> The PHC devices are never serial ports, so how does this help?

This is for the ptp_ocp driver, I have an update coming.

The systems I'm using have the OpenCompute time card and 
several nics, all of which publish PTP/PPS devices.

When there are several PPS devices, this patch allows
selecting the correct one.
-- 
Joanthan