On Mon, Jul 18, 2022 at 10:39:42PM +0200, Marek Behún wrote: > On Mon, 18 Jul 2022 22:24:09 +0300 > Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > 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... > > 1. the way we use this new named swnode (in patch 5/6 of this series) is > that it gets destroyed immediately after being parsed, so I don't > think there will be collisions in the namespace for forseeable future > > also, we first create an unnamed swnode for port and only then > fixed-link swnode as a child. > > new_port_fwnode = fwnode_create_software_node(port_props, NULL); > ... > fixed_link_fwnode = > fwnode_create_named_software_node(fixed_link_props, > new_port_fwnode, "fixed-link"); > > so there shouldn't be a name collision, since the port node gets a > unique name, or am I misunderstanding this? This is not problem, but what I was talking about is how to guarantee this hierarchy? See what I answered to RNK. > 2. even if there was a problem with name collision, I think the place > that needs to be fixed is swnode system. What use are swnodes if > they cannot be used like this? Precisely, that's why I don't want to introduce an API that needs to be fixed. -- With Best Regards, Andy Shevchenko
