On Fri, Jul 26, 2024 at 11:07:19PM +1000, Ben Skeggs wrote: > > Right, I think I took that too literally. > > > > The lifetime of the DRM device (or more precisely one of its references) is > > bound to the binding between the parent device and its corresponding driver. > > > > But the lifetime of the parent device itself is bound to the DRM device. > > > > So, yes this doesn't work, and proves the point that initializing the DRM device > > with the parent's parent is just a workaround. > > You're greatly overstating the "complexity" that's added here. It's a minor > inconvenience that doesn't require much code at all to implement, and is > essentially irrelevant outside of module load/unload. > > I agree it's not ideal, and userspace should gain auxiliary bus support > before a new driver implements a similar architecture, but it's really not > that big a deal. Ben asked me to share what other places are doing this stuff. To recap, when converting a legacy driver into an aux split we've found in several places that there is existing userspace that has hardwired certain sysfs paths. ie an assumption that an infiniband device appears under the sys/../pci/ directory. Argubaly this userspace is not in good shape, but we have to preserve it. So the approach is to make the sysfs visible elements tied to the original sysfs location (ie the pci device) and continue to use aux otherwise for discovery, probing and tying subsystems together. Obviously you have to be careful about the difference between the sysfs parent (for owning a subordinate struct device, sysfs files, etc) and the probe time parent (for owning devres, and other tasks) We've been fortunate enough that subsystems so far have had a clean enough setup that this is easy enough to do. It sounds like DRM is the same if it just requires calling a put in .remove() - that is pretty normal (though most subsystems would call that unregister, not put) Jason
