Re: [PATCH] cfg80211: fix regression on beacon world roaming feature

Johannes Berg
2009-07-31T16:43:37Z

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On Fri, 2009-07-31 at 09:32 -0700, Luis R. Rodriguez wrote:

> Its not that simple. Consider the fact we build our own custom
> regulatory domain and stuff what is intended for each one of them. The
> _orig stuff is set upon channel registration so it is correct that
> we'd have to avoid setting the channel flags prior to wiphy
> registration. How you do that is left up to implementation. Since
> cfg80211 will set the channel *_orig params based on
> wiphy_registration() you're only option is to either prevent your
> wiphy being registered with the flags set or to reset the channel
> flags on the reg_notifier(). The later seems like the way to go but we
> currently do not call the reg_notifier() upon beacon hints -- we
> currently only call the reg_notifier() upon regulatory domain changes
> and upon wiphy registration. My point is both of these options require
> considerable changes for 2.6.31.

Aha. So the problem really is that we don't have a reg notifier on
updates due to beacons.

> > and set them in ath_reg_apply_beaconing_flags and
> > ath_reg_apply_active_scan_flags, changing the polarity?
> >
> > I mean, right now you tell cfg80211 you don't support it,
> > and then try
> > to support it anyhow.
>
> Not sure I follow, support what? The reg_notifier() is there for
> regulatory domain changes, we didn't call it upon beacon hints. We
> can, and I agree its the right approach, but not for 2.6.31.

I'm thinking more in terms of iwlwifi here, for all intents and purposes
it doesn't support beaconing on channel N, so it only supports NO_IBSS
on that channel. Which is what it puts into flags before registration.

> > Instead, you could tell cfg80211 you _do_ support
> > it, and then not support them depending on the notifier? It seems like
> > that should work and not break cfg80211's assumption that you can never
> > ever support _more_ than registration flags (orig_flags).
>
> I'm not following at all, orig_flags do not tell cfg80211 the channel
> flags the device supports. Most devices set flag to 0 upon wiphy
> registration and therefore cfg80211 sets orig_flags to 0 as well
> during wiphy registration.

Well ok, "supports" is a bad word since we're talking about
restrictions. But for iwlwifi the orig_flags _do_ tell cfg80211 the
channel restrictions that the device _requires_.

Your devices, however, do not _strictly_ _require_ those channel flags,
they just require them for compliance. Unlike iwlwifi which crashes when
you don't do it right :)

So I think we're in agreement -- the proper solution would be to call
the reg notifier on beacon hints too. What we do for .31 I can't say I
really care, how much work do you think this would be? It doesn't seem
all _that_ bad, at least for core changes?

johannes

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