Re: [PATCH] nl/cfg80211: advertise OBSS scan offload capability

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2012-11-09 at 12:18 -0800, Bing Zhao wrote:

> > > New flag is added to inform userspace that this driver doesn't
> > > internally perform OBSS scan. It can use this feature available
> > > in userspace application.
> > 
> > Shouldn't that be a little more precisely worded? Most drivers already
> > expect wpa_s to do this, but apparently the assumption was that without
> > the flag, full-MAC drivers, i.e. drivers implementing the nl80211
> > connect API (rather than auth/assoc) do it themselves?
> 
> That's right.
> 
> > 
> > Or maybe mac80211 should just set the flag?
> 
> Currently wpa_s checks WPA_DRIVER_FLAGS_SME flag for OBSS scan.
> Since WPA_DRIVER_FLAGS_SME bit is set for mac80211, it's unnecessary to set this new flag.
> 
> Or, are you suggesting that we should set the new flag in mac80211
> (and all drivers that need OBSS scan feature in wpa_s) and replace
> WPA_DRIVER_FLAGS_SME check with the new flag?

I don't think that can be done, for the simple reason that wpa_s should
continue to work on older kernels.

Thus, I guess that wpa_s is going to continue with the assumption that
auth/assoc API implies also doing OBSS in wpa_s (which is a fair
assumption), but then I think we should simply change the documentation
of this new feature flag to indicate that it's interesting only in the
case of a driver that has connect API.

johannes