Return-path: Received: from mail.candelatech.com ([208.74.158.172]:39461 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752948Ab0IPALN (ORCPT ); Wed, 15 Sep 2010 20:11:13 -0400 Message-ID: <4C91609B.5090501@candelatech.com> Date: Wed, 15 Sep 2010 17:11:07 -0700 From: Ben Greear MIME-Version: 1.0 To: "Luis R. Rodriguez" CC: Jouni Malinen , "linux-wireless@vger.kernel.org" Subject: Re: RFC: mac80211/ath9k: allow scanning single channel if other VIF is associated. References: <4C8EB03D.7070808@candelatech.com> <20100915030316.GB30253@jm.kir.nu> <4C9059DC.7060009@candelatech.com> <20100915203133.GA14541@jm.kir.nu> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 09/15/2010 02:04 PM, Luis R. Rodriguez wrote: > On Wed, Sep 15, 2010 at 1:31 PM, Jouni Malinen wrote: >> On Tue, Sep 14, 2010 at 10:30:04PM -0700, Ben Greear wrote: >>> I think for the multi-VIF scenario, it should scan the single associated >>> channel by default, but it would be nice to allow full scans on demand. >>> (I would very much like to work with standard wpa_supplicant, but if hacking it >>> is the only way, then I can attempt that.) >> >> "Standard wpa_supplicant" needs to become more aware of multiple users >> of the same radio, so it is certainly fine to add changes there. For >> example, a mechanism for noticing that interfaces are sharing a radio >> would be useful. With that, it should also be possible to share the BSS >> table and scan results (and requests!) within wpa_supplicant. > > Depending on how this is implementing, sharing of the physical radio > may require some kernel synchronization between the different > interfaces using the same radio. It may also be possible to share the > same radio between an 802.11 device and a wimax device, for example. > Long ago we thought up of a frequency broker [1] but never really > wrote it as we have had no usage case for it yet. If we implement the > frequency broker we could also technically add a scheduler to sharing > the same radio between separate interfaces / technologies, this could > just be done in userspace as well, although I am not sure if the > timing considerations for doing it in userspace would suffice. At least for my use, I hope to be able to fully utilize the bandwidth for a particular channel, and emulate as close as possible a bunch of wireless devices sharing an AP or set of APs. So, I don't want to be switching off the main channel for any significant amount of time. I think as long as you stick to the main channel, there are no significant scheduling issues with the hardware, but I could be wrong about that. Also, I want to be able to run one supplicant per interface, so while wpa_supplicant could become clever if it manages multiple devices, I want them to be able to run independently as well. As for figuring out what hardware a VIF belongs to, you can deduce this by following links in sysfs to find it's phyX device. It is a pain when the phyX changes name due to module reload or something, but it can still be dealt with. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com