netdev - Re: [PATCH net 2/2] docs: networking: packet_mmap: don't mention PACKET

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Date:   Sun, 20 Dec 2020 09:52:40 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Baruch Siach <baruch@...s.co.il>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        Network Development <netdev@...r.kernel.org>,
        linux-doc@...r.kernel.org,
        Ulisses Alonso Camaró <uaca@...mni.uv.es>
Subject: Re: [PATCH net 2/2] docs: networking: packet_mmap: don't mention PACKET_MMAP

On Sun, Dec 20, 2020 at 3:00 AM Baruch Siach <baruch@...s.co.il> wrote:
>
> Hi Willem,
>
> On Thu, Dec 17 2020, Willem de Bruijn wrote:
> > On Thu, Dec 17, 2020 at 2:48 PM Jakub Kicinski <kuba@...nel.org> wrote:
> >>
> >> On Tue, 15 Dec 2020 18:51:17 +0200 Baruch Siach wrote:
> >> > Before commit 889b8f964f2f ("packet: Kill CONFIG_PACKET_MMAP.") there
> >> > used to be a CONFIG_PACKET_MMAP config symbol that depended on
> >> > CONFIG_PACKET. The text still refers to PACKET_MMAP as the name of this
> >> > feature, implying that it can be disabled. Another naming variant is
> >> > "Packet MMAP".
> >> >
> >> > Use "PACKET mmap()" everywhere to unify the terminology. Rephrase the
> >> > text the implied mmap() feature disable option.
> >>
> >> Should we maybe say AF_PACKET mmap() ?
> >
> > I don't think that the feature name PACKET_MMAP implies
> > CONFIG_PACKET_MMAP, or thus that the name is obsolete now that the
> > latter is.
>
> Current text says "if PACKET_MMAP is not enabled ...". This clearly
> implies a CONFIG_ symbol. Besides, the PACKET_MMAP term is mentioned
> nowhere else in the source tree. At the very least we need to clarify
> what it means.

At this point I don't think renaming will simplify anything. It is by
now referred to by that name outside the kernel, a google search
shows. It is also even the name of the documentation file
(packet_mmap.rst).

The file starts with

  PACKET_MMAP

  Abstract

  This file documents the mmap() facility available with the PACKET
  socket interface on 2.4/2.6/3.x kernels. This type of sockets is used for

That introduces the term well enough, I think.

Agreed that references to old kernel versions and the previous compile
time configurability of the feature are no longer relevant.

> > If it needs a rename, the setsockopt is PACKET_[RT]X_RING. So, if this
> > needs updating, perhaps PACKET_RING would be suitable. Or TPACKET,
> > based on the version definitions.
>
> So how would you rephrase text like "PACKET_MMAP provides a size
> configurable circular buffer ..."?

PACKET_RING provides a size configurable circular buffer would work,
but see previous comment.