From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from s3.sipsolutions.net ([144.76.43.152]:38009 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965054AbaCSOWS (ORCPT ); Wed, 19 Mar 2014 10:22:18 -0400 Message-ID: <1395238934.4142.22.camel@jlt4.sipsolutions.net> (sfid-20140319_152221_926466_2421DAED) Subject: Re: [PATCH] mac80211: don't downgrade VHT20 to HT20 From: Johannes Berg To: Michal Kazior Cc: linux-wireless Date: Wed, 19 Mar 2014 15:22:14 +0100 In-Reply-To: (sfid-20140225_141121_872159_6A96AC3B) References: <1393327628-1078-1-git-send-email-michal.kazior@tieto.com> <1393330040.4170.0.camel@jlt4.sipsolutions.net> <1393330210.4170.1.camel@jlt4.sipsolutions.net> (sfid-20140225_141121_872159_6A96AC3B) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: Sorry for the delay. Somehow I thought this was addressed, but I'm confused. I think we all agree that the spec says: > > A VHT STA shall set the Supported Channel Width Set subfield in its HT > > Capabilities element HT Capabilities Info field to 1, indicating that > > both 20 MHz operation and 40 MHz operation are supported. and that the station should therefore set the 20_40 capability bit in the association response? > The spec also defines VHT BSS operating channel width is derived from > HT Operation Element: STA Channel Width field (Table 10-19) and 20 MHz > is not forbidden for AP/mesh. hostapd seems to go in line with this > and allows VHT20 and VHT40. Yes but how is that related to the *capability* bit? You're talking about the HT/VHT operation information. > Without my patch (i.e. with the 20/40 check left intact): > > * If a station connects to VHT20 BSS, hostapd tries to add a VHT20 > station, but mac80211 downgrades it to HT20, > * If mac80211 station connects to a VHT20 BSS it gets downgraded to HT20 too. > > This means mac80211 is unable to setup VHT20 pairing properly even > though VHT20 BSS is defined in the spec. > > My take is 10.39.1 means VHT STA AssocReq must contain > IEEE80211_HT_CAP_SUP_WIDTH_20_40. > I suppose AP (hostapd) should deny STA association in that case. So are you saying the station isn't setting 20_40 capability? Or is something else unsetting the bit in case it's a 20MHz network? johannes