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

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Message-ID: <20201207164853.3a9e6024@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
Date:   Mon, 7 Dec 2020 16:48:53 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        "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 Tue, 8 Dec 2020 00:27:31 +0000 Vladimir Oltean wrote:
> 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.

That's the LLDP incarnation of it. The variable is defined in:

99.4.7.3 Variables

Probably better mention 30.14.1.7 aMACMergeAddFragSize if we want a MIB
reference.