Re: [PATCH v3 1/4] mac80211-hwsim: notify user-space about channel change.

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2017-03-31 at 06:33 -0700, Ben Greear wrote:
> 
> In my experience, the big problem with netlink is that if you write
> a patch that cannot make it upstream (or takes forever), then the
> netlink IDs conflict as upstream adds more stuff.

Sure, that's a common problem we all run into :)

> Other than that, it is easy to add new members, or completely new
> commands.
> 
> User-space can drop old API and simply not fully work against older
> kernels if it wants, especially for something as specialized as a
> simulated wifi radio.

Yeah, but the kernel will have to maintain both versions, and strictly
speaking shouldn't be breaking old userspace - but that would be
impossible as one moves to chanctx, perhaps even by default.

This is the problem I have with it - chanctx code already exists and is
used, so there's no technical reason not to support both now.

> So, if my patch can go in as is or with small tweaks, then I'm happy
> to keep working on it.  If it needs a complete re-write, then it will
> have to wait for someone else or some later date.

Ok, that's fair. I think I'll leave it out then though, because I
really do think that we should aim to support chanctx from the start
with this, it's well-established by now.

johannes