linux-kernel - Re: [PATCH 4/4] net: dsa: mv88e6xxx: add PTP support for MV88E6250 family

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Message-ID: <20190731043056.GA1482@localhost>
Date:   Tue, 30 Jul 2019 21:30:56 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Hubert Feurstein <h.feurstein@...il.com>,
        netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Subject: Re: [PATCH 4/4] net: dsa: mv88e6xxx: add PTP support for MV88E6250
 family

On Tue, Jul 30, 2019 at 11:46:51PM +0300, Vladimir Oltean wrote:

> Technically it is not "not true".

[Sigh]  The statement was:

    The adjfine API clamps ppb between [-32,768,000, 32,768,000]

The adjfine API does NOT clamp to that range.  That statement is
simply false.

> And what is the reason for the neg_adj thing? Can you give an example
> of when does the "normal way" of doing signed arithmetics not work?

The detail from years ago escape me ATM, but I needed to use div_u64.
Maybe div_s64 was broken.

But that is not the point.  Changing the adjfine() logic for this
driver is out of scope for this series.  If someone thinks the logic
needs changing, then that must carefully explained and justified in
the changelog of a patch implementing that _one_ change.

Thanks,
Richard