Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:50331 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752273AbaKYLEQ (ORCPT ); Tue, 25 Nov 2014 06:04:16 -0500 Message-ID: <1416913453.2045.4.camel@sipsolutions.net> (sfid-20141125_120423_547649_CDE1F37B) Subject: Re: [PATCH] mac80211: check if channels allow 80 MHz for VHT probe requests From: Johannes Berg To: YanBo Cc: linux-wireless Date: Tue, 25 Nov 2014 12:04:13 +0100 In-Reply-To: (sfid-20141125_120059_502403_E712C430) References: <1416911009-22405-1-git-send-email-johannes@sipsolutions.net> (sfid-20141125_120059_502403_E712C430) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Tue, 2014-11-25 at 19:00 +0800, YanBo wrote: > On Tue, Nov 25, 2014 at 6:23 PM, Johannes Berg > wrote: > > From: Johannes Berg > > > > If there are no channels allowing 80 MHz to be used, then the > > station isn't really VHT capable even if the driver and device > > support it in general. In this case, exclude the VHT capability > > IE from probe request frames. > > > > FYI, there are some new devices could support the VHT even at 20Mhz > band 2.4G mode. So in 2.4 GHz we typically don't have VHT anyway - and realistically you can't support real "VHT" there, you can only support the new modulations. I think this will require some custom (vendor-specific) advertisement though, since VHT advertisement implies 80 MHz support. IOW, I think at this point this patch isn't a problem. If we really need to support VHT modulations in 2.4 GHz (or even have devices that have VHT modulation support, but no 80 MHz support in 5 GHz) then some new advertisement will have to be done. OTOH, you could argue for that advertisement that on 2.4 GHz you can never do 80 MHz anyway - but can't you? In theory there's enough spectrum for exactly one 80 MHz channel ... johannes