netdev - Re: [PATCH net-next v1 1/9] ethtool: Add support for configuring frame preemption

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Message-ID: <20201208002730.kftox7xvr7d475rp@skbuf>
Date:   Tue, 8 Dec 2020 00:27:31 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "m-karicheri2@...com" <m-karicheri2@...com>,
        "Jose.Abreu@...opsys.com" <Jose.Abreu@...opsys.com>,
        Po Liu <po.liu@....com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "anthony.l.nguyen@...el.com" <anthony.l.nguyen@...el.com>
Subject: Re: [PATCH net-next v1 1/9] ethtool: Add support for configuring
 frame preemption

On Mon, Dec 07, 2020 at 04:24:02PM -0800, Vinicius Costa Gomes wrote:
> Jakub Kicinski <kuba@...nel.org> writes:
>
> > On Mon, 07 Dec 2020 14:11:48 -0800 Vinicius Costa Gomes wrote:
> >> Jakub Kicinski <kuba@...nel.org> writes:
> >> >> + * @min_frag_size_mult: Minimum size for all non-final fragment size,
> >> >> + * expressed in terms of X in '(1 + X)*64 + 4'
> >> >
> >> > Is this way of expressing the min frag size from the standard?
> >> >
> >>
> >> The standard has this: "A 2-bit integer value indicating, in units of 64
> >> octets, the minimum number of octets over 64 octets required in
> >> non-final fragments by the receiver" from IEEE 802.3br-2016, Table
> >> 79-7a.
> >
> > Thanks! Let's drop the _mult suffix and add a mention of this
> > controlling the addFragSize variable from the standard. Perhaps
> > it should in fact be called add_frag_size (with an explanation
> > that the "additional" means "above the 64B" which are required in
> > Ethernet, and which are accounted for by the "1" in the 1 + X
> > formula)?
>
> Sounds good :-) Will add a comment with the standard reference and
> change the name to 'add_frag_size'.

I think you should be making references to the IEEE 802.3-2018, that
will age better, and a lot more people have that handy.
I believe the go-to definition for the additional fragment size can be
found in clause 30.12.2.1.37 aLldpXdot3LocAddFragSize.