netdev - RE: [net-next, v2, 7/7] enetc: support PTP domain timestamp conversion

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Message-ID: <DB7PR04MB5017604C9B3AE7C499B413D3F83F9@DB7PR04MB5017.eurprd04.prod.outlook.com>
Date:   Mon, 31 May 2021 10:51:36 +0000
From:   "Y.b. Lu" <yangbo.lu@....com>
To:     Richard Cochran <richardcochran@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: RE: [net-next, v2, 7/7] enetc: support PTP domain timestamp
 conversion

Hi Claudiu and Richard,

> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: 2021年5月25日 20:37
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: netdev@...r.kernel.org; David S . Miller <davem@...emloft.net>; Claudiu
> Manoil <claudiu.manoil@....com>; Jakub Kicinski <kuba@...nel.org>
> Subject: Re: [net-next, v2, 7/7] enetc: support PTP domain timestamp
> conversion
> 
> On Fri, May 21, 2021 at 12:36:19PM +0800, Yangbo Lu wrote:
> 
> > @@ -472,13 +473,36 @@ static void enetc_get_tx_tstamp(struct enetc_hw
> *hw, union enetc_tx_bd *txbd,
> >  	*tstamp = (u64)hi << 32 | tstamp_lo;  }
> >
> > -static void enetc_tstamp_tx(struct sk_buff *skb, u64 tstamp)
> > +static int enetc_ptp_parse_domain(struct sk_buff *skb, u8 *domain) {
> > +	unsigned int ptp_class;
> > +	struct ptp_header *hdr;
> > +
> > +	ptp_class = ptp_classify_raw(skb);
> > +	if (ptp_class == PTP_CLASS_NONE)
> > +		return -EINVAL;
> > +
> > +	hdr = ptp_parse_header(skb, ptp_class);
> > +	if (!hdr)
> > +		return -EINVAL;
> > +
> > +	*domain = hdr->domain_number;
> 
> This is really clunky.  We do NOT want to have drivers starting to handle the
> PTP.  That is the job of the user space stack.
> 
> Instead, the conversion from raw time stamp to vclock time stamp should
> happen in the core infrastructure.  That way, no driver hacks will be needed,
> and it will "just work" everywhere.

That's perfect way.

> 
> We need a way to associate a given socket with a particular vclock.
> Perhaps we can extend the SO_TIMESTAMPING API to allow that.

How about adding a flag SOF_TIMESTAMPING_BIND_PHC, and redefining the data passing by setsockopt like,

struct timestamping {
       int flags;
       u8 hwtstamp_phc; /*phc index */
};

The sock could have a new member sk_hwtstamp_phc to record it.

> 
> > +	return 0;
> > +}
> 
> Thanks,
> Richard