Jakub Kicinski [off-list ref] writes:

quoted

For the wireless drivers, removing the old drivers
instead of just the dead code might be an alternative, depending
on whether anyone thinks there might still be users.

Dunno if you want to dig into removal with a series like this, 
anything using ioctls will be pretty old (with the exception 
of what you separated into ndo_eth_ioctl). You may get bogged 
down.

I would very much like to get rid of unused ancient wireless drivers but
the problem is that it's next to impossible to know if someone still
uses a driver, or if the driver is even working. For example, few months
back I suggested removing one driver which I thought to be completely
unused (forgot already the name of the driver) and to my big surprise
there was still a user, and he reported it working with a recent kernel
release.

So I don't know what to do. Should we try adding a warning like below? :)

  "This ancient driver will be removed from the kernel in 2022, but if
   it still works send report to <...@...> to avoid the removal."

How do other subsystems handle ancient drivers?

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches