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!
