Return-path: Received: from arroyo.ext.ti.com ([192.94.94.40]:54264 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753569Ab2KTPRS (ORCPT ); Tue, 20 Nov 2012 10:17:18 -0500 Message-ID: <50AB9E9D.2090801@ti.com> (sfid-20121120_161834_106599_BC197B71) Date: Tue, 20 Nov 2012 17:15:41 +0200 From: Victor Goldenshtein MIME-Version: 1.0 To: Johannes Berg CC: Michal Kazior , "linux-wireless@vger.kernel.org" , "kgiori@qca.qualcomm.com" , "mcgrof@frijolero.org" , "zefir.kurtisi@neratec.com" , "adrian.chadd@gmail.com" , "j@w1.fi" , "coelho@ti.com" , "igalc@ti.com" , "adrian@freebsd.org" , "nbd@nbd.name" , "simon.wunderlich@s2003.tu-chemnitz.de" , Subject: Re: [PATCH v4 6/6] mac80211: add ap channel switch command/event References: <1350226137-13704-1-git-send-email-victorg@ti.com> <1350226137-13704-7-git-send-email-victorg@ti.com> <1350414472.10177.17.camel@jlt4.sipsolutions.net> <50842563.4010201@ti.com> <1350910599.10166.4.camel@jlt4.sipsolutions.net> <50922AA9.4030509@ti.com> <1352128994.9466.19.camel@jlt4.sipsolutions.net> <50A2617B.3060807@ti.com> <1352892233.9510.26.camel@jlt4.sipsolutions.net> <50A38C3A.20908@tieto.com> <1352896680.9510.28.camel@jlt4.sipsolutions.net> In-Reply-To: <1352896680.9510.28.camel@jlt4.sipsolutions.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 14/11/2012 14:38, Johannes Berg wrote: > On Wed, 2012-11-14 at 13:19 +0100, Michal Kazior wrote: > >>> However, then I realised that that still doesn't work -- once initial >>> radar detection is done, it needs to continue while the AP is active. If >>> the channel context was going to be relinquished, or even just the >>> channel changed for a few seconds, it would be unsafe. So as a result, >>> the radar detect operation has to somehow be coupled to the start AP >>> operation and prohibit channel changes and additional channel contexts >>> during the entire operation time. >> >> Hmm.. cfg80211 doesn't really know about channel contexts. >> >> The problem I see is that cfg80211 may be in a combination with >> `num_different_channels = 1` and mac80211 can have 2 channel contexts >> due to channel type incompatibilities. > > Yes, this is a concern, we need to fix that anyway though, otherwise it > may assume that some operations are possible when they really aren't > (e.g. starting an HT40+ and HT40- AP on the same channel, which > shouldn't be done anyway, but still) > not sure how it can happen if have this check: if ((cac_type != NL80211_CHAN_HT20) && (cac_type != NL80211_CHAN_NO_HT)) return -EOPNOTSUPP; in both start_radar_detection() & enable_tx() ? >> We'd need to tell cfg80211 that multi-interface is not possible when DFS >> is active if we want to at least consider single-channel only DFS. > > Not sure about multi-interface, but multi-channel at least. > Agree, maybe you have an idea how we should do this ? -- Thanks, Victor.