Return-path: Received: from MAIL.IHTFP.ORG ([204.107.200.6]:37299 "EHLO mail.ihtfp.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755885AbXHBQWV (ORCPT ); Thu, 2 Aug 2007 12:22:21 -0400 To: dragoran Cc: "Johannes Berg" , "Winkler\, Tomas" , linux-wireless@vger.kernel.org, network manager , ipw3945-devel@lists.sourceforge.net Subject: Re: [ipw3945-devel] chaning mode only when interface down? References: <1186058047.24230.38.camel@johannes.berg> <46B1D28F.1080006@gmail.com> <1186059192.24230.44.camel@johannes.berg> From: Derek Atkins Date: Thu, 02 Aug 2007 11:52:26 -0400 In-Reply-To: (dragoran's message of "Thu\, 2 Aug 2007 15\:43\:24 +0200") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: dragoran writes: > On 8/2/07, Johannes Berg wrote: > > On Thu, 2007-08-02 at 14:48 +0200, dragoran wrote: > > > > Nono, you cannot solve it in the driver. The whole design of mac80211 > > > mandates that assumption and I think it is a valid one to make. > > why? did the old way (allow mode changing while up) caused any problems? > > Why should it be allowed? Can you come up with a good reason for that > since you lose all state anyway when doing mode transitions? > > Until then (and I guess somebody *really* wants it) it's just a lot > easier to not even try to change these low-level things while the > interface is operating. > > ok fair enough Well, for one thing in many cases the interface needs to be "up" in order to scan. Also, many times the driver itself will incorrectly associate on insert before NetworkManager gets a chance to chime in and then you're stuck in a situation where you never get to the band you want. Regardless, you should NEVER require a driver reload to switch bands and if you do that's a bug. If mac80211 requires a driver reload then that's a MAJOR flaw in that layer. Still, NM keeps the interface "up" even when there's no packets, because it's required to scan. So that may be why I've had trouble going between 802.11(a) and 802.11(b/g) networks at times. It's quite frustrating. -derek -- Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory Member, MIT Student Information Processing Board (SIPB) URL: http://web.mit.edu/warlord/ PP-ASEL-IA N1NWH warlord@MIT.EDU PGP key available