From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Re: [patch net-next-2.6 1/2] net: allow to change carrier via sysfs Date: Wed, 31 Aug 2011 13:48:22 -0700 Message-ID: <4E5E9E16.6060502@candelatech.com> References: <1314715608-978-1-git-send-email-jpirko@redhat.com> <1314715608-978-2-git-send-email-jpirko@redhat.com> <20110831082655.GB2010@minipsycho.brq.redhat.com> <20110831084511.GD2010@minipsycho.brq.redhat.com> <4E5E939C.5000009@gmail.com> <1314821537.3274.24.camel@bwh-desktop> <4E5E9A30.1040105@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ben Hutchings , Jiri Pirko , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , netdev@vger.kernel.org, davem@davemloft.net, eric.dumazet@gmail.com, shemminger@vyatta.com To: =?UTF-8?B?Tmljb2xhcyBkZSBQZXNsb8O8YW4=?= Return-path: Received: from mail.candelatech.com ([208.74.158.172]:40446 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754673Ab1HaUsi (ORCPT ); Wed, 31 Aug 2011 16:48:38 -0400 In-Reply-To: <4E5E9A30.1040105@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On 08/31/2011 01:31 PM, Nicolas de Peslo=C3=BCan wrote: > Le 31/08/2011 22:12, Ben Hutchings a =C3=A9crit : >> On Wed, 2011-08-31 at 22:03 +0200, Nicolas de Peslo=C3=BCan wrote: >>> Le 31/08/2011 10:45, Jiri Pirko a =C3=A9crit : >>> >>>>>>> Do you expect drivers using implementation different than just = calling >>>>>>> netif_carrier_on/off? Or is it supposed to also e.g. power down= PHYs? >>>>>> Yes, generally it can be used also for en/disable phy, for testi= ng >>>>>> purposes if hw and driver would support it. >>>>> >>>>> I'd like to see this working for GRE tunnel devices (for keepaliv= e >>>>> daemon to be able to indicate to routing daemons whether tunnel i= s >>>>> really working) - implementation would be identical to dummy's ca= se. >>>>> Should I prepare a patch or can I leave it to you? >>>> >>>> Ok, I can include it to this patchset (I'm going to repost first p= atch >>>> anyway) >>> >>> Can't we assume that the dummy's case is the default behavior and >>> register this default >>> ndo_change_carrier callback for every device ? >> >> You have got to be joking. No device driver that has real link >> monitoring should use this implementation. > > Well, why not? Arguably, this is probably not the feature one would u= se every day, but... > > Testing a cluster reaction to a link down event would be easier if on= e doesn't need to unplug the cable for the test. I understand that one = can turn off the > switch port (physical or virtual), but echo 0 > /sys/class/net/eth0/c= arrier would be nice too. There is special hardware out there that can do bypass, and often it al= so has a mode that will programatically cut link by throwing some relays. We use thi= s for our testing equipment... If there is some way to twiddle standard-ish hardware to actually drop = link, that would be neat. I'd think it should be an ethtool type of thing, howeve= r. Actually dropping link, and letting that naturally propagate up the sta= ck seems more reasonable than lying about the status half way up the stack. Thanks, Ben --=20 Ben Greear Candela Technologies Inc http://www.candelatech.com