Lukas Wunner wrote: > On Sat, Apr 27, 2024 at 09:49:41AM -0700, Dan Williams wrote: > > Lukas Wunner wrote: > > > But I want to raise awareness that the inability to hide > > > empty attribute groups feels awkward. > > > > That is fair, it was definitely some gymnastics to only change user > > visible behavior for new "invisible aware" attribute groups that opt-in > > while leaving all the legacy cases alone. > > > > The concern is knowing when it is ok to call an is_visible() callback > > with a NULL @attr argument, or knowing when an empty array actually > > means "hide the group directory". > > > > We could add a sentinel value to indicate "I am an empty attribute list > > *AND* I want my directory hidden by default". However, that's almost > > identical to requiring a placeholder attribute in the list just to make > > __first_visible() happy. > > > > Other ideas? > > Perhaps an optional ->is_group_visible() callback in struct attribute_group > which gets passed only the struct kobject pointer? > > At least for PCI device authentication, that would be sufficient. > I could get from the kobject to the corresponding struct device, > then determine whether the device supports authentication or not. > > Because it's a new, optional callback, there should be no compatibility > issues. The SYSFS_GROUP_INVISIBLE return code from the ->is_visible() > call for individual attributes would not be needed then, at least in my > use case. That's where I started with this, but decided it was overkill to increase the size of that data structure globally for a small number of use cases.
