From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754214AbbG2XeW (ORCPT ); Wed, 29 Jul 2015 19:34:22 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45763 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753849AbbG2XeV (ORCPT ); Wed, 29 Jul 2015 19:34:21 -0400 Date: Wed, 29 Jul 2015 16:34:20 -0700 From: Greg KH To: "Rafael J. Wysocki" Cc: Viresh Kumar , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, pi-cheng.chen@linaro.org Subject: Re: [PATCH] bus: subsys: propagate errors from subsys interface's ->add_dev() Message-ID: <20150729233420.GA18070@kroah.com> References: <2867166.mZBGleMS1o@vostro.rjw.lan> <20150729223743.GA17250@kroah.com> <2113628.vmLC8GdsGl@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2113628.vmLC8GdsGl@vostro.rjw.lan> User-Agent: Mutt/1.5.23+102 (2ca89bed6448) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 30, 2015 at 01:29:01AM +0200, Rafael J. Wysocki wrote: > On Wednesday, July 29, 2015 03:37:43 PM Greg KH wrote: > > On Thu, Jul 30, 2015 at 01:01:21AM +0200, Rafael J. Wysocki wrote: > > > On Wednesday, July 29, 2015 02:19:16 PM Greg KH wrote: > > > > On Fri, Jun 26, 2015 at 02:32:47PM +0530, Viresh Kumar wrote: > > > > > ->add_dev() may fail and the error returned from it can be useful for > > > > > the caller. > > > > > > > > > > For example, if some of the resources aren't ready yet and -EPROBE_DEFER > > > > > is returned from ->add_dev(), then the owner of 'struct > > > > > subsys_interface' may want to try probing again at a later point of > > > > > time. And that requires a proper return value from ->add_dev(). > > > > > > > > > > Also, if we hit an error while registering subsys_interface, then we > > > > > should stop proceeding further and rollback whatever has been done until > > > > > then. Break part of subsys_interface_unregister() into another routine, > > > > > which lets us call ->remove_dev() for all devices for which ->add_dev() > > > > > is already called. > > > > > > > > > > Cc: 3.3+ # 3.3+ > > > > > Fixes: ca22e56debc5 ("driver-core: implement 'sysdev' functionality for regular devices and buses") > > > > > > > > I don't see how this is a stable bug fix, what is resolved by it that > > > > doesn't work today? Is there some code that is expecting this > > > > functionality that has never been present? > > > > > > > > I'll go queue it up, but I don't think it is -stable material, but feel > > > > free to change my mind. > > > > > > There is a small problem with it that I've already pointed out to Viresh. > > > > > > Namely, while changing subsys_interface_(un)register() to handle return > > > values from ->add_dev(), it doesn't do the same thing in bus_probe_device() > > > which I believe it should for consistency at least. > > > > Oops, sorry, missed that response. I'll go drop this patch then, thanks > > for letting me know. > > > > > But then, the question is whether or not the probing should fail and > > > what if device_attach() returns 0 and one of the ->add_dev() callbacks > > > returns an error. > > > > That's a total mess... > > > > Given that there are almost no uses of this api, I think people should > > work it out before any more start to pop up :) > > cpufreq is one of the users and that's where the problem is, but in my opinion > it should be addressed in a different way. > > But while we are at it, should the ->add_dev and ->remove_dev callbacks in > struct subsys_interface return an int if their return values are always > ignored? Maybe it would be better to redefine them to be void to make it clear > that they can't fail? void makes sense to me.