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 CBD64C43381 for ; Thu, 14 Jan 2021 14:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A368823A7E for ; Thu, 14 Jan 2021 14:02:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729083AbhANOCb (ORCPT ); Thu, 14 Jan 2021 09:02:31 -0500 Received: from mga14.intel.com ([192.55.52.115]:64257 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726236AbhANOCa (ORCPT ); Thu, 14 Jan 2021 09:02:30 -0500 IronPort-SDR: yxBeRgV46G0OXxt2EuNS1dTJReuZT8BLLDfNU1FQUQ/GgWMn6BxM2/7+chHw1FE/w+CeWZXVw3 MFxACtLtk8Pg== X-IronPort-AV: E=McAfee;i="6000,8403,9863"; a="177587528" X-IronPort-AV: E=Sophos;i="5.79,347,1602572400"; d="scan'208";a="177587528" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2021 06:00:44 -0800 IronPort-SDR: YQM+ZwmYxir5mt/GQNL8nFQW8fJzbU/DuBxHPNjaVxDkdqEiwiPFJU8LBRidzr36y7wXpAl3Xn YkE//FKZrrEA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,347,1602572400"; d="scan'208";a="465258899" Received: from kuha.fi.intel.com ([10.237.72.162]) by fmsmga001.fm.intel.com with SMTP; 14 Jan 2021 06:00:41 -0800 Received: by kuha.fi.intel.com (sSMTP sendmail emulation); Thu, 14 Jan 2021 16:00:40 +0200 Date: Thu, 14 Jan 2021 16:00:40 +0200 From: Heikki Krogerus To: Andy Shevchenko Cc: Daniel Scally , 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: <20210114140040.GB2864731@kuha.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> <20210113155812.GT4077@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210113155812.GT4077@smile.fi.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 05:58:12PM +0200, Andy Shevchenko wrote: > 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? I think we should really start looking into the possibility of removing the whole secondary coupling, because that is the thing that is crippling us. Br, -- heikki