From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68D56C433E6 for ; Wed, 13 Jan 2021 15:58:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EDF32339F for ; Wed, 13 Jan 2021 15:58:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726775AbhAMP66 (ORCPT ); Wed, 13 Jan 2021 10:58:58 -0500 Received: from mga04.intel.com ([192.55.52.120]:33998 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726238AbhAMP65 (ORCPT ); Wed, 13 Jan 2021 10:58:57 -0500 IronPort-SDR: +t8qwMsc5xqYIPUVp0Hj1ZxPGExmQyF8zgd9LhIPppku6i5Y6IuFVg01fZgZ7UnPBlKzqT3+3B cWuRF+QBe0Pw== X-IronPort-AV: E=McAfee;i="6000,8403,9863"; a="175644305" X-IronPort-AV: E=Sophos;i="5.79,344,1602572400"; d="scan'208";a="175644305" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 07:57:12 -0800 IronPort-SDR: lbQWPZXLqGsSDf80WJjQnGlG4PZX+1GPvq2xE5EDCSui6aPj6gTkiWSREJWdBaFpKfFLLXOeuc BEPmhtzGcZqw== X-IronPort-AV: E=Sophos;i="5.79,344,1602572400"; d="scan'208";a="499305220" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 07:57:10 -0800 Received: from andy by smile with local (Exim 4.94) (envelope-from ) id 1kziXE-00DFLl-9v; Wed, 13 Jan 2021 17:58:12 +0200 Date: Wed, 13 Jan 2021 17:58:12 +0200 From: Andy Shevchenko To: Daniel Scally Cc: Heikki Krogerus , Felipe Balbi , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 1/3] software node: Introduce device_add_software_node() Message-ID: <20210113155812.GT4077@smile.fi.intel.com> References: <20210111141045.14027-1-heikki.krogerus@linux.intel.com> <20210111141045.14027-2-heikki.krogerus@linux.intel.com> <2f552de5-4839-a1e5-3012-c56f9fa3bdd5@gmail.com> <20210113155504.GS4077@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210113155504.GS4077@smile.fi.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 05:55:04PM +0200, Andy Shevchenko wrote: > On Wed, Jan 13, 2021 at 12:40:03AM +0000, Daniel Scally wrote: > > On 11/01/2021 14:10, Heikki Krogerus wrote: > > ... > > > > +/** > > > + * device_remove_software_node - Remove device's software node > > > + * @dev: The device with the software node. > > > + * > > > + * This function will unregister the software node of @dev. > > > + */ > > > +void device_remove_software_node(struct device *dev) > > > +{ > > > + struct swnode *swnode; > > > + > > > + swnode = dev_to_swnode(dev); > > > + if (!swnode) > > > + return; > > > + > > > + kobject_put(&swnode->kobj); > > > +} > > > +EXPORT_SYMBOL_GPL(device_remove_software_node); > > > > I wonder if this also ought to set dev_fwnode(dev)->secondary back to > > ERR_PTR(-ENODEV)? > > Looking more into this code I think we need to call > > set_secondary_fwnode(dev, NULL); > > among these lines. > > The real problem is that set_primary_fwnode() and set_secondary_fwnode() have > no reference counting. If we have a chain ->primary->secondary->-ENODEV is > being used somewhere we can't tell from here. > > So, in practice it means that we lack of some kind of primary node to increment > reference count of the secondary node when the latter is chained to the given > primary. But it makes things too complicated. Any other options for shared > primary-secondary chain? Standalone primary along with standalone (exclusive) > secondary doesn't need this AFAICS. Perhaps a flag to primary like shared / > exclusive that will prevent breaking the chain in set_secondary_fwnode()? Or maybe I imagined only theoretical cases and we have no such issue? -- With Best Regards, Andy Shevchenko