On Mon, Apr 03, 2023 at 02:02:48PM +0100, Russell King (Oracle) wrote: > On Thu, Mar 30, 2023 at 04:54:51PM +0300, Heikki Krogerus wrote: > > On Wed, Mar 29, 2023 at 03:33:48PM +0100, Russell King (Oracle) wrote: > > > On Wed, Mar 29, 2023 at 05:07:26PM +0300, Heikki Krogerus wrote: > > > > On Tue, Mar 28, 2023 at 02:23:41PM +0100, Russell King (Oracle) wrote: > > > > > On Tue, Mar 28, 2023 at 03:09:56PM +0300, Heikki Krogerus wrote: > > > > > > The problem is that the function you are proposing will be exploited > > > > > > silently - people will use NULL as the parent without anybody > > > > > > noticing. Everything will work for a while, because everybody will > > > > > > first only have a single device for that driver. But as time goes by > > > > > > and new hardware appears, suddenly there are multiple devices for > > > > > > those drivers, and the conflict start to appear. > > > > > > > > > > So, an easy solution would be to reject a call to > > > > > fwnode_create_named_software_node() when parent is NULL, thereby > > > > > preventing named nodes at the root level. > > > > > > > > > > > At that point the changes that added the function call will have > > > > > > trickled down to the stable trees, so the distros are affected. Now we > > > > > > are no longer talking about a simple cleanup that fixes the issue. In > > > > > > the unlikely, but possible case, this will turn into ABI problem if > > > > > > > > > > There is no such thing as stable APIs for internal kernel interfaces. > > > > > > > > > > Documentation/process/stable-api-nonsense.rst > > > > > > > > > > > As you pointed out, this kind of risks we have to live with kbojects, > > > > > > struct device stuff and many others, but the thing is, with the > > > > > > software node and device property APIs right now we don't. So the fact > > > > > > that a risk exists in one place just isn't justification to accept the > > > > > > same risk absolutely everywhere. > > > > > > > > > > Meanwhile, firmware descriptions explicitly permit looking up nodes by > > > > > their names, but here we are, with the software node maintainers > > > > > basically stating that they don't wish to support creating software > > > > > nodes with explicit names. > > > > > > > > If you want to name the nodes then you just go ahead and name them, > > > > nobody is preventing you and you can already do that, but if you do > > > > so, then you will take full responsibility of the entire software node > > > > - that is what you are naming here - instead of just the fwnode that > > > > it contains. The users of the node can deal with the fwnode alone, but > > > > you as the creator of the software node have to take proper ownership > > > > of it. > > > > > > > > > > Russell, if you have some good arguments for accepting your proposal, > > > > > > I assure you I will agree with you, but so far all you have given are > > > > > > attacks on a sketch details and statements like that "I think you're > > > > > > making a mountain out of a mole". Those just are not good enough. > > > > > > > > > > Basically, I think you are outright wrong for all the reasons I have > > > > > given in all my emails on this subject. > > > > > > > > > > Yes, I accept there is a *slight* risk of abuse, but I see it as no > > > > > different from the risk from incorrect usage of any other kernel > > > > > internal interface. Therefore I just do not accept your argument > > > > > that we should not have this function, and I do not accept your > > > > > reasoning. > > > > > > > > I would not be so against the function if there wasn't any other way > > > > to handle your case, but there is. > > > > > > > > You really can not claim that the existing API is in any way inferior, > > > > or even more complex, compared to your function before you actually > > > > try it. You simply can not make judgement based on a sketch that is > > > > basically just showing you the functions and structures that you need. > > > > > > > > If there are issues with the API, then we need to of course fix those > > > > issues, but please keep in mind that still does not mean we have any > > > > need for the function you are proposing. > > > > > > > > Please also note that helpers are welcome if you feel we need them. If > > > > you want to add for example an allocation routine that duplicates also > > > > the properties in one go, then that alone would reduce the complexity > > > > needed in the drivers that create the nodes. I think in most cases, > > > > possibly also in yours, that alone would allow most stuff to be > > > > handled from stack memory. > > > > > > > > fwnode_create_software_node() is there just to support the legacy > > > > device properties. You really should not be using even that. If you > > > > need to deal with software nodes then you deal with them with struct > > > > software_node. > > > > > > You forgot to explain how to free them once they're done, because > > > struct swnode will contain a pointer to the struct software_node > > > which can be a dangling stale reference - and there's no way for > > > code outside swnode.c to know when that reference has gone. > > > > > > That is another reason why I prefer my existing solution. That > > > problem is taken care of already by the existing code - and as > > > it's taken care of there, and properly, there's less possibilities > > > for users of swnode to get it wrong. > > > > We need an improved release mechanism, yes. > > > > My idea with the new dynamic allocation routine was that it could be > > introduced together with a release callback that we add to the struct > > software_node. > > > > The idea of adding the release callback to the structure was actually > > considered already some time ago - I think it was discussed at least > > shortly also on the public ACPI mailing list. The idea back then > > included a default release function that simply frees the struct > > software_node instance. That default release function we could then > > assign to the release callback in that new software node > > allocation/creation routine. That way the drivers should be able to > > continue to rely on the underlying code to take care of freeing the > > node instance. > > > > Back then there was nobody who really needed that functionality, so > > nobody even tried to implement it. Now we of course clearly do need > > something like it. > > > > I think the release callback together with the default release > > function should work. Let me know what you guys think. > > Thinking about this more, no. This is utterly vile, and I will not > create code that is vile. > > Greg, please can you take a look at this, and give your opinion on > how named software nodes (which are required to describe things in > specific ways by firmware descriptions) should be handled? Is my > proposal reasonable in your eyes? Thanks. I'm lost, sorry, this thread is crazy long and I do not have the bandwidth to try to dig through it. I think you two need to work it out together please. thanks, greg k-h > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
