netdev - Re: [net-next, v5, 02/11] ptp: support ptp physical/virtual clocks conversion

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Date:   Sat, 7 Aug 2021 13:56:44 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Yangbo Lu <yangbo.lu@....com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        mptcp@...ts.linux.dev, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        Shuah Khan <shuah@...nel.org>,
        Michal Kubecek <mkubecek@...e.cz>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>, Rui Sousa <rui.sousa@....com>,
        Sebastien Laveze <sebastien.laveze@....com>
Subject: Re: [net-next, v5, 02/11] ptp: support ptp physical/virtual clocks
 conversion

On Sat, Aug 07, 2021 at 05:43:32PM +0300, Vladimir Oltean wrote:
> >  3. Let the vclocks hold a reference to the underlying posix dynamic clock.
> 
> So even if the vclock holds a reference to the underlying POSIX clock,
> that won't prevent the hardware driver from unbinding, and further
> gettime() calls on the vclock from faulting, will it?

Oh, your are right.  The vclocks call the real PHC clock's methods
directly, not through the posix dynamic clock layer.

> What about:
> 
> 4. Create a device link with the vclock being a consumer and the parent
>    clock being a supplier? This way, ptp_vclock_unregister() is
>    automatically called whenever (and before) ptp_clock_unregister() is.
> 
> https://www.kernel.org/doc/html/latest/driver-api/device_link.html

Sounds promising.

Thanks,
Richard