From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751723AbaDCK6M (ORCPT ); Thu, 3 Apr 2014 06:58:12 -0400 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:50200 "EHLO opensource.wolfsonmicro.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751450AbaDCK6I (ORCPT ); Thu, 3 Apr 2014 06:58:08 -0400 Date: Thu, 3 Apr 2014 11:58:04 +0100 From: Charles Keepax To: Mark Brown Cc: lgirdwood@gmail.com, linux-kernel@vger.kernel.org, patches@opensource.wolfsonmicro.com Subject: Re: [PATCH] regulator: core: Get and put regulator of_node Message-ID: <20140403105804.GP1665@opensource.wolfsonmicro.com> References: <1396447614-3048-1-git-send-email-ckeepax@opensource.wolfsonmicro.com> <20140402142356.GE2269@sirena.org.uk> <20140402160438.GO1665@opensource.wolfsonmicro.com> <20140402165354.GG2269@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140402165354.GG2269@sirena.org.uk> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 02, 2014 at 05:53:54PM +0100, Mark Brown wrote: > To make this correct we need to at least ensure that the node passed > into the regulator API is valid and referenced at that time so there > should only be an issue for the core if the reference is dropped after > that. In the above case the device model is holding a reference since > this is the of_node for the device itself so taking the reference won't > hurt but is redundant. In cases where we have more than one regulator > and are using of_regulator_match() then things are more tricky. > Something needs to drop the references it returns (which isn't happening > at all at the minute). >>From what I can see of_regulator_match isn't taking any references at the minute? for_each_child_of_node will get a reference but it will also put that when we process the next child. We copy the pointer to the child into match->of_node but don't manually increment the reference at all. So of_regulator_match has no effect on the reference count of the of_node. > Doing it while doing the match and register > seems simple and neat from an error handling point of view so having the > core take an additional reference during the registration would join up > with that. The main issue I have is that devm_regualtor_register is a bit awkward. With regulator_register you will always be calling regulator_unregister so you can put the of_node there but with devm there isn't really a good place to put the of_node. Would perhaps a sensible thing here be to add an of_node_get to of_regulator_match, since we seem to be expecting that to increase the ref count. And then just add an of_node_put to regulator_unregister. And for anything directly using regulator_register/devm_regulator_register they should add a manual of_node_get? Thanks, Charles