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. Thanks, Lukas
