netdev - Re: [PATCH net-next v2 10/11] net: dsa: microchip: ksz9477: add Pulse Per Second (PPS) support

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Message-ID: <20201113035001.GD32138@hoboy.vegasvil.org>
Date:   Thu, 12 Nov 2020 19:50:01 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Christian Eggers <ceggers@...i.de>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>,
        George McCollister <george.mccollister@...il.com>,
        Marek Vasut <marex@...x.de>,
        Helmut Grohne <helmut.grohne@...enta.de>,
        Paul Barker <pbarker@...sulko.com>,
        Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>,
        Tristram Ha <Tristram.Ha@...rochip.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 10/11] net: dsa: microchip: ksz9477: add
 Pulse Per Second (PPS) support

On Fri, Nov 13, 2020 at 04:53:11AM +0200, Vladimir Oltean wrote:

> Richard, do you think we can clarify the intended usage of PTP_CLK_REQ_PPS
> in the documentation? It doesn't appear to be written anywhere that
> PTP_ENABLE_PPS is supposed to enable event generation for the drivers/pps
> subsystem. You would sort of have to know before you could find out...

Yes, please!

The poor naming is a source of eternal confusion.  I think that the
"hard pps" thing from NTP is not used very often, maybe never, but I
didn't know that when I first drafted the whole PHC subsystem.

Naturally developers of PHC device drivers think that this the PPS
that they need to implement.  After all, the name matches!

(Actually, at the time I thought that this would be the way to
synchronize the system clock to the PHC, but it turned out that
Miroslav's generic method in phc2sys worked very well, and so the hard
pps thing has little, if any, practical value.)

The documentation is vague, yes, but I think even more important
would be to remove the word PPS from the C-language identifiers.

I'm open to suggestions/patches on this...

Thanks,
Richard