linux-kernel - RE: [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks conversion

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Date:   Tue, 22 Jun 2021 10:35:13 +0000
From:   "Y.b. Lu" <yangbo.lu@....com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "mptcp@...ts.linux.dev" <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, v3, 02/10] ptp: support ptp physical/virtual clocks
 conversion

Hi Richard,

> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: 2021年6月18日 2:28
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: 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, v3, 02/10] ptp: support ptp physical/virtual clocks
> conversion
> 
> On Tue, Jun 15, 2021 at 05:45:09PM +0800, Yangbo Lu wrote:
> 
> > diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
> > index 3f388d63904c..6949afc9d733 100644
> > --- a/drivers/ptp/ptp_private.h
> > +++ b/drivers/ptp/ptp_private.h
> > @@ -46,6 +46,9 @@ struct ptp_clock {
> >  	const struct attribute_group *pin_attr_groups[2];
> >  	struct kthread_worker *kworker;
> >  	struct kthread_delayed_work aux_work;
> > +	u8 n_vclocks;
> 
> Hm, type is u8, but ...
> 
> > +	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
> > +	bool vclock_flag;
> >  };
> >
> 
> >  #define info_to_vclock(d) container_of((d), struct ptp_vclock, info)
> > diff --git a/include/uapi/linux/ptp_clock.h
> > b/include/uapi/linux/ptp_clock.h index 1d108d597f66..4b933dc1b81b
> > 100644
> > --- a/include/uapi/linux/ptp_clock.h
> > +++ b/include/uapi/linux/ptp_clock.h
> > @@ -69,6 +69,11 @@
> >   */
> >  #define PTP_PEROUT_V1_VALID_FLAGS	(0)
> >
> > +/*
> > + * Max number of PTP virtual clocks per PTP physical clock  */
> > +#define PTP_MAX_VCLOCKS			20
> 
> Only 20 clocks are allowed?  Why?

Initially I think vclock can be used for ptp multiple domains synchronization. Since the PTP domainValue is u8, u8 vclock number is large enough.
This is not a good idea to hard-code a PTP_MAX_VCLOCKS value. But it looks a little crazy to create numbers of vclocks via one command (echo n > /sys/class/ptp/ptp0/n_vclocks).
Maybe a typo creates hundreds of vclocks we don’t need. 
Do you think we should be care about setting a limitation of vclock number? Any suggestion for implementation?
Thanks.

> 
> Thanks,
> Richard