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Message-ID: <YtWzWdkFVMg0Hyvf@smile.fi.intel.com> Date: Mon, 18 Jul 2022 22:24:09 +0300 From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> To: "Russell King (Oracle)" <linux@...linux.org.uk> Cc: Vladimir Oltean <olteanv@...il.com>, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, Alvin __ipraga <alsi@...g-olufsen.dk>, Claudiu Manoil <claudiu.manoil@....com>, Daniel Scally <djrscally@...il.com>, "David S. Miller" <davem@...emloft.net>, DENG Qingfang <dqfext@...il.com>, Eric Dumazet <edumazet@...gle.com>, Florian Fainelli <f.fainelli@...il.com>, George McCollister <george.mccollister@...il.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Hauke Mehrtens <hauke@...ke-m.de>, Heikki Krogerus <heikki.krogerus@...ux.intel.com>, Jakub Kicinski <kuba@...nel.org>, Kurt Kanzenbach <kurt@...utronix.de>, Landen Chao <Landen.Chao@...iatek.com>, Linus Walleij <linus.walleij@...aro.org>, linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, Matthias Brugger <matthias.bgg@...il.com>, netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>, "Rafael J. Wysocki" <rafael@...nel.org>, Sakari Ailus <sakari.ailus@...ux.intel.com>, Sean Wang <sean.wang@...iatek.com>, UNGLinuxDriver@...rochip.com, Vivien Didelot <vivien.didelot@...il.com>, Woojung Huh <woojung.huh@...rochip.com>, Marek BehĂșn <kabel@...nel.org> Subject: Re: [PATCH net-next 2/6] software node: allow named software node to be created 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
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