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 E044EC433EF for ; Mon, 18 Jul 2022 19:15:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234906AbiGRTPN (ORCPT ); Mon, 18 Jul 2022 15:15:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234131AbiGRTPM (ORCPT ); Mon, 18 Jul 2022 15:15:12 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49AB62CCB6; Mon, 18 Jul 2022 12:15:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=G1YSdmImKh2l18ecQ7FfzX2zqvO0awAs2ffUiZkZuSw=; b=uTS4R1PCUCCnZ83svGKLX53ve1 C/11IYua0pNPYugrPmbYoaikCsT12yW4BX/nS2o/OIcmkTQ7YLxqjvT6DLGa7hcqDYn1CIa+6TM6V 7AsENwcdlfZnZ4c1RnhUoU2FfYom1Hqbu1cr4JDB+3UAx7XXI0FS/tX8+wBd5t2wHGqW3jfEgRVgI 7nSahUr1d3h85yXh39YKLE5eLCPi9vcmNFpG5bw805uyFH/yx+Xl1BMFHNl6AQGMiOhzgZ9kDxlhJ oZP0mArmGJuCwOsFPAa+F8EMGsEd/RKGb3+2bvQLeMiMg1HmhDsdOzsdhQok/+fEzmkU/ZBRvIYWF 2kEnXPCA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:33434) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1oDWCq-000232-Ra; Mon, 18 Jul 2022 20:15:00 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1oDWCo-0002DB-Tm; Mon, 18 Jul 2022 20:14:58 +0100 Date: Mon, 18 Jul 2022 20:14:58 +0100 From: "Russell King (Oracle)" To: Andy Shevchenko 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: Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!