Return-path: Received: from mail-bk0-f49.google.com ([209.85.214.49]:33274 "EHLO mail-bk0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753940AbaBDM1A convert rfc822-to-8bit (ORCPT ); Tue, 4 Feb 2014 07:27:00 -0500 Received: by mail-bk0-f49.google.com with SMTP id v15so3172007bkz.8 for ; Tue, 04 Feb 2014 04:26:59 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1391509638.26522.72.camel@porter.coelho.fi> References: <1391421529-6067-1-git-send-email-michal.kazior@tieto.com> <1391431407.4488.9.camel@jlt4.sipsolutions.net> <1391509638.26522.72.camel@porter.coelho.fi> Date: Tue, 4 Feb 2014 13:26:58 +0100 Message-ID: (sfid-20140204_132704_661014_6C2EE428) Subject: Re: [RFC 0/2] cfg80211: add channel switching awareness From: Michal Kazior To: Luca Coelho Cc: Johannes Berg , linux-wireless Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 4 February 2014 11:27, Luca Coelho wrote: > On Mon, 2014-02-03 at 13:43 +0100, Johannes Berg wrote: >> On Mon, 2014-02-03 at 10:58 +0100, Michal Kazior wrote: >> > This makes it possible for more elegant channel >> > switching behavior by moving the decision up to >> > cfg80211. >> > >> > Until now mac80211 could start channel switching >> > internally for STA, mesh and IBSS interfaces >> > without userspace interaction. This bypassed >> > interface combination checks at the very least. >> > >> > Now mac80211 requests cfg80211 to channel switch >> > an interface, in a similar manner as userspace >> > asks cfg80211 for a channel switch. This makes it >> > possible to perform interface combination checks >> > (albeit it is not implemented yet). >> >> Couldn't you just return the decision to mac80211? It would also have to >> keep track of start/end of the CSA period, I guess, since a few things >> that Ilan is working on shouldn't be allowed while the AP announces CSA. > > mac80211 could keep track of the start/finalize callbacks. But I don't > think that's a good idea, as I mentioned in the other email. > > I think mac80211 should keep the client CSA control and the userspace > should control the host interfaces. cfg80211 should keep track of the > channel switches and be asked if the switch is okay (so it can take the > interface combinations and regulatory into consideration). Why does mac80211 need to keep CSA control? Does it solve anything? > Maybe mac80211 could call a cfg80211_reserve_channel() function? If that > call fails, it means the switch cannot be done. If it succeeds, > cfg80211 keeps the reservation. Same thing if the switch is coming from > userspace, nl80211 could call cfg80211_reserve_channel() in the same > way. The problem is you need RTNL for this to make any sense (interface combinations need it). You can't make a directly callable cfg80211 function available in mac80211 that takes RTNL. It just won't work. The only way I see it, is you need an asynchronous call with a callback. Michał