Re: [RFC 0/4] add master channel switch announcement support

[Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>]

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> > > >  * could other drivers (next to ath9k) work with this API?
> > > 
> > > Probably not easily. Any TI folks reading this?
> > 
> > I was thinking about adding another callback function or option for that for drivers
> > who do the channel switch internally. Then we would only need mac80211 to adapt.
> > 
> > Would that help, or what would be problematic?
> 
> I don't really know. If you look at what we do in managed mode now, some
> drivers will do the switching and report back when done.
> 

OK, maybe we should leave that open to people who implement that feature for
their respective drivers.

> > Yeah, that would be an alternative. I've been inspired by IEEE 802.11-2012/6.3.17
> > (MLME-CHANNELSWITCH) originally. :)
> > I think your suggestion is good for AP where we control the beacon. For IBSS it
> > would be a little different: when a channel switch is triggered, userspace does
> > not know the beacon (and will not set it). Therefore, we could only accept the
> > change IEs and skip the "after-switch-beacon" IEs (these would be re-generated
> > internally) in IBSS mode. I guess it would be similar for mesh.
> 
> Yeah, agree, IBSS/mesh modes are somewhat different here, userspace
> doesn't really know the channel is switching at all, does it?

IBSS/Mesh does not process CSA so far. When we do, we should switch the channel
and inform userspace by using an event (the same way it is done for station, I think).

What I'm concered about is to initiate a channel switch from userspace. This will be
required for IBSS-DFS: when a radar is detected and this event is sent to userspace, it
must react by initiating a channel switch.

My plan was to use the same "channel switch" command, just without the CSA-IE and
after-change IEs (see the new PATCH series). The rest would be pretty similar to the
AP-operation: add CSA IEs, switch channel, create a new beacon for the new channel and
set it. Only that this would be done in kernel space instead of userspace.

Cheers,
	Simon

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