Il giorno 9 ott 2023, alle ore 19:29, Arnd Bergmann [off-list ref] ha scritto:

On Mon, Oct 9, 2023, at 18:49, Rodolfo Zitellini wrote:

quoted

quoted

From: Arnd Bergmann <arnd@arndb.de>

The last localtalk driver is gone now, and ppp support was never fully
merged, so clean up the appletalk code by removing the obvious dead
code paths.

Notably, this removes one of the two callers of the old .ndo_do_ioctl()
callback that was abused for getting device addresses and is now
only used in the ieee802154 subsystem, which still uses the same trick.

The include/uapi/linux/if_ltalk.h header might still be required
for building userspace programs, but I made sure that debian code
search and the netatalk upstream have no references it it, so it
should be fine to remove.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Hi!
I’ve been working on a new LocalTalk interface driver for the last 
couple months, do you think it would be possible to at least postpone 
the removal of LT a bit?

It is a driver for an open source device called TashTalk 
(https://github.com/lampmerchant/tashtalk), which runs on a PIC micro 
that does all the LT interfacing, and communicates back via serial to 
the host system. My driver is relatively simple and works very well 
with netatalk 2.2 (which is still maintained and still has support for 
AppleTalk). The driver is basically complete and trsted and I was 
preparing to submit a patch.

Still having LocalTalk in my view has many advantages for us 
enthusiasts that still want to bridge old machines to the current world 
without modifications, for example for printing on modern printers, 
netbooting, sharing files and even tcp/ip. All this basically works out 
of the box via the driver, Linux and available userspace tools 
(netatalk, macipgw).

The old ISA cards supported by COPS were basically unobtanium even 20 
years ago, but the solution of using a PIC and a serial port is very 
robust and much more furure-proof. We also already have a device that 
can interface a modern machine directly via USB to LocalTalk.

The development of the TashTalk has been also extensively discussed on 
thr 68KMLA forum 
(https://68kmla.org/bb/index.php?threads/modtashtalk-lt0-driver-for-linux.45031/)

I hope the decision to remove LocalTalk can be reconsidered at least 
for the time being so there is a chance to submit a new, modern device 
making use of this stack.

Nothing is decided, I'm just proposing my patch as a cleanup
for now. It would be nice to still drop the ndo_do_ioctl function
though, at least in some form. When your driver actually makes
it into the kernel, you can find a different method of communicating
the address between the socket interface and the device driver.

Yes I too think it is good to remove ndo_do_ioctl, I designed the TashTalk driver to be a drop-in replacement for COPS mostly for compatibility with netatalk 2.2. My plan was to propose it like this (so nothing else needed to be changed) and the propose some patches in the kernel part and userspace part (netatalk).

I can see a few ways this could work out:

- add a custom callback pointer to struct atalk_iface to
 get and set the address for phase1 probing instead of going
 through the ioctl

This was my initial thought, at least for the moment, mostly to keep netatalk happy and make sure I don’t break other stuff that makes assumptions on how the address probing worked. There are other bits I would like to improve, for example tcpdump (which parses correctly appetalk packets!) is broken in the current implementation.

- rewrite the probing logic in aarp.c more widely, and improve
 the userspace interface in the process by introducing a netlink
 interface

This is sorta the “second step” I was planning, I think the logic for probing could be redesigned and simplified (it also does not work 100% correctly), and it could be a good chance to improve the interface with netatalk too.

- Move your entire driver into userspace and go to the kernel
 using tun/tap. This has the added benefit of avoiding a lot
 of the complexity of the tty line discipline code you have.

We had some discussion too if to just make the lt an userspace stack, I personally like how it is currently implemented because existing code can run basically without modification.

I would propose at this stage to change the TashTalk driver to remove ndo_do_ioctl and to use a custom callback, if this ok.

Many thanks,
Rodolfo