From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: [PATCH 1/2] usbnet: allow status interrupt URB to always be active Date: Sat, 05 Jan 2013 12:01:55 +0100 Message-ID: <3476529.YzSzbMTfeu@linux-5eaq.site> References: <20110727141246.GC29616@orbit.nwl.cc> <2212516.GkG3xP33yG@linux-5eaq.site> <1357349193.19684.3.camel@dcbw.foobar.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Elina Pasheva , netdev@vger.kernel.org, linux-usb@vger.kernel.org, Rory Filer , Phil Sutter To: Dan Williams Return-path: Received: from smtp-out002.kontent.com ([81.88.40.216]:57162 "EHLO smtp-out002.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755470Ab3AELBy (ORCPT ); Sat, 5 Jan 2013 06:01:54 -0500 In-Reply-To: <1357349193.19684.3.camel@dcbw.foobar.com> Sender: netdev-owner@vger.kernel.org List-ID: On Friday 04 January 2013 19:26:33 Dan Williams wrote: > On Fri, 2013-01-04 at 23:16 +0100, Oliver Neukum wrote: > > On Friday 04 January 2013 10:48:16 Dan Williams wrote: > > > Some drivers (ex sierra_net) need the status interrupt URB > > > active even when the device is closed, because they receive > > > custom indications from firmware. Allow sub-drivers to set > > > a flag that submits the status interrupt URB on probe and > > > keeps the URB alive over device open/close. The URB is still > > > killed/re-submitted for suspend/resume, as before. > > > > > > Signed-off-by: Dan Williams > > > --- > > > Oliver: alternatively, is there a problem with *always* > > > submitting the interrupt URB, and then simply not calling > > > the subdriver's .status function when the netdev is > > > closed? That would be a much simpler patch. > > > > That is quite radical. We have no idea what a device > > does when we do not react to a status update. I would > > much prefer to not take the risk. > > Besides, we don't use bandwidth if we don't have to. > > Ok, so scratch the alternative. Thus, does the posted patch look like > the right course of action? In principle yes. > If I wasn't clear enough before, sierra_net needs to listen to the > status interrupt URB to receive the custom Restart indication as part of > the driver's device setup. Thus for sierra_net at least, tying the > status interrupt URB submission to device open/close isn't right. So, there seems to be an inevitable race before probe() is called. Have you looked at FLAG_AVOID_UNLINK_URBS ? > I'd previously done a patch to handle this all in sierra_net, but the > problem there is suspend/resume: without directly accessing the usbnet > structure's ->suspend_count member (icky!) sierra_net can't correctly > kill/submit the URB itself. So I went with a flag to usbnet that Sierra > can set. That is absolutely the right way to do it. Regards Oliver