netdev - Re: [PATCH net-next] ptp: add vclock timestamp conversion IOCTL

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Message-ID: <98a91f5889b346f7a3b347bebb9aab56bddfd6dc.camel@oss.nxp.com>
Date:   Tue, 28 Sep 2021 13:50:23 +0200
From:   Sebastien Laveze <sebastien.laveze@....nxp.com>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        yangbo.lu@....com, yannick.vignon@....nxp.com,
        rui.sousa@....nxp.com
Subject: Re: [PATCH net-next] ptp: add vclock timestamp conversion IOCTL

On Mon, 2021-09-27 at 13:23 -0700, Richard Cochran wrote:
> What you really want is the socket to return more than one time stamp.
> So why not do that instead?
> 
> Right now, the SO_TIMESTAMPING has an array of
> 
>    struct timespec ts[3] = 
>    [0] SOFTWARE
>    [1] LEGACY (unused)
>    [2] HARDWARE
> 
> You can extend that to have
> 
>    [0] SOFTWARE
>    [1] LEGACY (unused)
>    [2] HARDWARE (vclock 0)
>    [3] HARDWARE (vclock 1)
>    [4] HARDWARE (vclock 2)
>    ...
>    [N] HARDWARE (vclock N-2)
> 
> You could store the selected vclocks in a bit mask associated with the socket.
> 
> Hm?

Yes that would do it. Only drawback is that ALL rx and tx timestamps
are converted to the N domains instead of a few as needed.

Before going in this direction, is this a change that you really see as
worthwile for virtual clocks and timetamping support ?

What approach do you have in mind for multi-domain support with the
common CMLDS layer ?

Thanks,
Seb