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 ACB05C433DB for ; Wed, 13 Jan 2021 15:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 67AC523120 for ; Wed, 13 Jan 2021 15:55:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727380AbhAMPzu (ORCPT ); Wed, 13 Jan 2021 10:55:50 -0500 Received: from mga05.intel.com ([192.55.52.43]:9961 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726523AbhAMPzt (ORCPT ); Wed, 13 Jan 2021 10:55:49 -0500 IronPort-SDR: BzopvCSuqR2jlMbSyzpwt+fRD6u3HMHPr/V1DbyqMNsDZ+wskKz0xqf62YZLkqE6m16ngEZPTI 6FJI4zIVtyGw== X-IronPort-AV: E=McAfee;i="6000,8403,9863"; a="263010353" X-IronPort-AV: E=Sophos;i="5.79,344,1602572400"; d="scan'208";a="263010353" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 07:54:04 -0800 IronPort-SDR: 1rzca7Kk7wvv6I7yM/uzJhVuvdBNIiGuOrg55KJI6KKD/Zop4q5DlhD6+mH3f3F4iqkLwogQMU Of6bdw9/LXHA== X-IronPort-AV: E=Sophos;i="5.79,344,1602572400"; d="scan'208";a="464946026" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2021 07:54:02 -0800 Received: from andy by smile with local (Exim 4.94) (envelope-from ) id 1kziUC-00DF9Y-JU; Wed, 13 Jan 2021 17:55:04 +0200 Date: Wed, 13 Jan 2021 17:55:04 +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: <20210113155504.GS4077@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2f552de5-4839-a1e5-3012-c56f9fa3bdd5@gmail.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 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()? -- With Best Regards, Andy Shevchenko