Re: [PATCH 5/7] mac80211: improve CSA locking

[Luca Coelho <luca@coelho.fi>]

On Thu, 2014-01-23 at 13:41 +0100, Michal Kazior wrote:
> On 23 January 2014 13:09, Johannes Berg <johannes@sipsolutions.net> wrote:
> > On Thu, 2014-01-23 at 08:57 +0100, Michal Kazior wrote:
> >
> >> This is actually the tricky part. How do you automatically switch an
> >> AP interface? You should be able to at least generate CSA IE - true -
> >> but what about beacon after CSA? You need to update HT IE and VHT IE
> >> at least.
> >>
> >> Perhaps we could split CSA into two parts somehow and make it more
> >> userspace coordinated. The first part of CSA - announcing it, is
> >> trivial and can actually be done entirely within mac80211 if I'm not
> >> mistaken. What needs userspace input is what happens after the
> >> announcement. This would mean that there is a possible time gap
> >> between announcement being completed and the actual channel switch &
> >> operation resuming.
> >
> > I believe that even announcing it isn't necessarily possible without
> > userspace involvement, particularly for things like 11ac's channel
> > switch wrapper IE and/or operating class changes.
> 
> Aww, too bad then.
> 
> But splitting would still be useful (at least in some sense) if you
> consider CSA to "usable" DFS channels.

I don't like the split idea that much.  If we send the CS announcement
automatically but the userspace never reacts to our indication, we will
be stuck in the middle of the channel switch...

--
Luca.