Re: [PATCH RFC V1 net-next 3/4] net: Let the active time stamping layer be selectable.

[Vladimir Oltean]

On Thu, Jan 20, 2022 at 08:05:08PM -0800, Richard Cochran wrote:
> On Fri, Jan 21, 2022 at 04:38:09AM +0100, Andrew Lunn wrote:
> 
> > So in the extreme case, you have 7 time stamps, 3 from MACs and 4 from
> > PHYs!
> 
> :^)
>  
> > I doubt we want to support this, is there a valid use case for it?
> 
> Someday, someone will surely say it is important, but with any luck
> I'll be dead by then...

So as I mentioned earlier, the use case would be hardware performance
testing and diagnosing. You may consider that as not that important, but
this is basically what I had to do for several months, and even wrote
a program for that, that collects packet timestamps at all possible points.
And to your point, the more complex a system is, the more important it
becomes to be able to diagnose it precisely.