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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4894EC43334 for ; Mon, 18 Jul 2022 19:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235841AbiGRTYY (ORCPT ); Mon, 18 Jul 2022 15:24:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235833AbiGRTYX (ORCPT ); Mon, 18 Jul 2022 15:24:23 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AC152CE2B; Mon, 18 Jul 2022 12:24:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1658172262; x=1689708262; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=OXqejUTzX+fvce7JjUJhsn70C74RWhXrDYrBi19HgoQ=; b=KSRQpvKqGXqvNMZ12mObsPF1RfOKHQG+fR6jp8O88nFOsUvVG3qNr0Tb S6Zj3k1aKWaIHfqzxMtVxZivViJt/zGOaXdPKl+FIwkvurs6yecSiufVb xey/AVkIhjedsCyeagD+dvVYZ8jRWiTTknOeoypQRB/zgAueohdhm3g0/ Xlfr8Su4t2rGLPOrPgiMGyfeSCF0V7C3L56SXB3j9lbFHK98pCCKJcMAa 7/Qp7UgEzciM4StZ7r4ZAwhX50YuqWwWyjFD5AvUfb8SQ7Km2A0WXNmF5 6IAm4BWaJ5n7s6fSxXAOLbm47cdheJKrQjh5RlvuV0xBNYaxES0T4ElaZ w==; X-IronPort-AV: E=McAfee;i="6400,9594,10412"; a="266708197" X-IronPort-AV: E=Sophos;i="5.92,281,1650956400"; d="scan'208";a="266708197" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 12:24:22 -0700 X-IronPort-AV: E=Sophos;i="5.92,281,1650956400"; d="scan'208";a="624860660" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2022 12:24:14 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1oDWLh-001OQH-3C; Mon, 18 Jul 2022 22:24:09 +0300 Date: Mon, 18 Jul 2022 22:24:09 +0300 From: Andy Shevchenko To: "Russell King (Oracle)" Cc: Vladimir Oltean , Andrew Lunn , Heiner Kallweit , Alexandre Belloni , Alvin __ipraga , Claudiu Manoil , Daniel Scally , "David S. Miller" , DENG Qingfang , Eric Dumazet , Florian Fainelli , George McCollister , Greg Kroah-Hartman , Hauke Mehrtens , Heikki Krogerus , Jakub Kicinski , Kurt Kanzenbach , Landen Chao , Linus Walleij , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Matthias Brugger , netdev@vger.kernel.org, Paolo Abeni , "Rafael J. Wysocki" , Sakari Ailus , Sean Wang , UNGLinuxDriver@microchip.com, Vivien Didelot , Woojung Huh , Marek =?iso-8859-1?Q?Beh=FAn?= Subject: Re: [PATCH net-next 2/6] software node: allow named software node to be created Message-ID: References: <20220715201715.foea4rifegmnti46@skbuf> <20220715204841.pwhvnue2atrkc2fx@skbuf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jul 18, 2022 at 08:14:58PM +0100, Russell King (Oracle) wrote: > On Mon, Jul 18, 2022 at 09:53:39PM +0300, Andy Shevchenko wrote: > > On Mon, Jul 18, 2022 at 09:43:42PM +0300, Andy Shevchenko wrote: > > > On Mon, Jul 18, 2022 at 02:27:02PM +0100, Russell King (Oracle) wrote: > > > > On Mon, Jul 18, 2022 at 03:29:52PM +0300, Andy Shevchenko wrote: > > > > > On Fri, Jul 15, 2022 at 11:48:41PM +0300, Vladimir Oltean wrote: > > > > > > So won't kobject_init_and_add() fail on namespace collision? Is it the > > > > > > problem that it's going to fail, or that it's not trivial to statically > > > > > > determine whether it'll fail? > > > > > > > > > > > > Sorry, but I don't see something actionable about this. > > > > > > > > > > I'm talking about validation before a runtime. But if you think that is fine, > > > > > let's fail it at runtime, okay, and consume more backtraces in the future. > > > > > > > > Is there any sane way to do validation of this namespace before > > > > runtime? > > > > > > For statically compiled, I think we can do it (to some extent). > > > Currently only three drivers, if I'm not mistaken, define software nodes with > > > names. It's easy to check that their node names are unique. > > > > > > When you allow such an API then we might have tracebacks (from sysfs) bout name > > > collisions. Not that is something new to kernel (we have seen many of a kind), > > > but I prefer, if possible, to validate this before sysfs issues a traceback. > > > > > > > The problem in this instance is we need a node named "fixed-link" that > > > > is attached to the parent node as that is defined in the binding doc, > > > > and we're creating swnodes to provide software generated nodes for > > > > this binding. > > > > > > And how you guarantee that it will be only a single one with unique pathname? > > > > > > For example, you have two DSA cards (or whatever it's called) in the SMP system, > > > it mean that there is non-zero probability of coexisting swnodes for them. > > > > > > > There could be several such nodes scattered around, but in this > > > > instance they are very short-lived before they are destroyed, they > > > > don't even need to be published to userspace (and its probably a waste > > > > of CPU cycles for them to be published there.) > > > > > > > > So, for this specific case, is this the best approach, or is there > > > > some better way to achieve what we need here? > > > > > > Honestly, I don't know. > > > > > > The "workaround" (but it looks to me rather a hack) is to create unique swnode > > > and make fixed-link as a child of it. > > > > > > Or entire concept of the root swnodes (when name is provided) should be > > > reconsidered, so somehow we will have a uniqueness so that the entire > > > path(s) behind it will be caller-dependent. But this I also don't like. > > > > > > Maybe Heikki, Sakari, Rafael can share their thoughts... > > > > > > Just for my learning, why PHY uses "fixed-link" instead of relying on a > > > (firmware) graph? It might be the actual solution to your problem. > > > > > > How graphs are used with swnodes, you may look into IPU3 (Intel Camera) > > > glue driver to support devices before MIPI standardisation of the > > > respective properties. > > > > Forgot to say (yes, it maybe obvious) that this API will be exported, > > anyone can use it and trap into the similar issue, because, for example, > > of testing in environment with a single instance of the caller. > > I think we're coming to the conclusion that using swnodes is not the > correct approach for this problem, correct? If I understand the possibilities of the usage in _this_ case, then it's would be problematic (it does not mean it's incorrect). It might be due to swnode design restrictions which shouldn't be made, I dunno. That' why it's better to ask the others for their opinions. By design swnode's name makes not much sense, because the payload there is a property set, where _name_ is a must. Now, telling you this, I'm questioning myself why the heck I added names to swnodes in the intel_quark_i2c_gpio driver... -- With Best Regards, Andy Shevchenko