From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:38132 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379AbbBXKL5 (ORCPT ); Tue, 24 Feb 2015 05:11:57 -0500 Message-ID: <1424772714.2192.16.camel@sipsolutions.net> (sfid-20150224_111201_937551_8C3B71CC) Subject: Re: [RFC] mac80211_hwsim: notify user-space about channel change. From: Johannes Berg To: Ben Greear Cc: linux-wireless@vger.kernel.org Date: Tue, 24 Feb 2015 11:11:54 +0100 In-Reply-To: <54EB66CC.1030800@candelatech.com> References: <1424217588-29558-1-git-send-email-greearb@candelatech.com> (sfid-20150218_005956_617537_D2A9B91F) <1424692155.2782.6.camel@sipsolutions.net> <54EB66CC.1030800@candelatech.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, 2015-02-23 at 09:43 -0800, Ben Greear wrote: > > This seems a bit strange - don't we already tag packets with the > > frequency? Why would you need the channel change separately? What does > > that even mean? Depending on how you use this it could entirely break > > off-channel operation, for example. > > I was thinking about passive scans. In that case, we would not always get a packet transmitted > when the channel changes? Ah, well, ok. However, hwsim doesn't actually really have a concept of the 'current channel', for example in the offchannel code it just temporarily listens on two channels ... so that's not very good for a more realistic implementation :) > I was thinking user-space would mimic a real radio that can only listen on > one channel at once (can any real radios actually listen on two channels at once?) No, real radios cannot do that (not really anyway - I guess if it was VHT80 it's really already listening on 4 channels but ...) > So, if we are off-channel, and pkt arrives for the 'main' channel, then > a real radio should drop it, right? Yes. > Of course, if user-space does not care, then it can simply ignore the channel-change > logic so I think this would be backwards compat with existing hwsim user-space apps. Sure. But given the murky concept of channel change, and not going to PS for off-channel in hwsim etc. I think this would need a bit more design rather than just exposing the mac80211 channel change. Additionally, with chanctx support that won't even be invoked for example. johannes