netdev - Re: [PATCH net-next] net: appletalk: remove Apple/Farallon LocalTalk PC support

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Message-ID: <CAK8P3a1AA181LqQSxnToSVx0e5wmneUsOKfmnxVMsUNh465C_Q@mail.gmail.com>
Date:   Tue, 10 May 2022 08:48:17 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Doug Brown <doug@...morgal.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        David Miller <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH net-next] net: appletalk: remove Apple/Farallon LocalTalk
 PC support

On Tue, May 10, 2022 at 4:34 AM Doug Brown <doug@...morgal.com> wrote:
>
> On 5/9/2022 10:32 AM, Jakub Kicinski wrote:
> > On Mon, 9 May 2022 19:14:42 +0200 Arnd Bergmann wrote:
> >> I think however, if we remove this driver, we need to discuss removing the
> >> last remaining localtalk driver (CONFIG_COPS) and possibly the localtalk
> >> bits in net/appletalk along with it.
> > Removing COPS and appletalk makes perfect sense to me (minus what Doug
> > has plans to use, obviously).
>
> I also think removing the COPS driver is a great idea. I actually ended
> up buying a compatible card in the hopes of working on that driver to
> change it to load the firmware through the firmware API, but the
> licensing situation with the firmware blobs kind of brought that idea to
> a standstill. I would be very surprised if anybody is actually using
> LocalTalk ISA cards these days anyway, so it's probably not worth the
> effort to maintain it.
>
> There have been a few "modern" LocalTalk interface projects. One is
> mine, which I haven't found time to finish, but I was able to get
> working in the kernel with a lt0 network interface. I suspect I was the
> only one in the last decade to actually use the LocalTalk code in modern
> kernel versions, because it was crashing until I fixed a bug involving
> too short of a header length being allocated. There's another more
> recent LocalTalk project called TashTalk [1]. A kernel driver could be
> developed for it using serdev or a tty ldisc, but all of the current
> development seems focused on the userspace side.
>
> With that in mind, I personally wouldn't be sad to see the entire
> LocalTalk interface support stripped from the kernel, as long as
> EtherTalk support can remain. There is still a decent sized community of
> users who are using it to talk with classic Macs using netatalk 2.x.
> So most of the stuff in net/appletalk is still relevant today for us.
>
> Might as well remove CONFIG_IPDDP too. It actually -interferes- with the
> current way that people do MacIP gateways through userspace with macipgw
> [2]. I'm not aware of anyone actually using the kernel's implementation.

Thanks for all the background information!

If I understand this correct, this means we could remove all of
drivers/net/appletalk/ except for the CONFIG_ATALK Kconfig entry,
and also remove net/appletalk/dev.c and a few bits of net/appletalk
that reference localtalk device structures and their ioctls, right?

What about appletalk over PPP (phase1 probing in aarp.c) and
ARPHRD_LOCALTLK support in drivers/net/tun.c? Are these still
useful without localtalk device support?

         Arnd