On Fri, 27 Sep 2019, Greg Kroah-Hartman wrote: > > It turns out the reason for this error is simple: The driver > > unregisters its subdevices in the release handler instead of in the > > disconnect handler. There probably is documentation about this > > somewhere, but I don't know exactly where -- maybe Greg remembers. > > Nope, I don't remember. It should happen in the disconnect handler, odd > of it to be in release, but maybe that's the "easiest" way for v4l to > handle this? This isn't a question of "easiest". Unregistering child devices in a release handler is just _wrong_, plain and simple. That's what gives rise to the "sysfs group 'power' not found for kobject 'i2c-0'" warning in the kernel log. The group can't be found because it has already been removed; it gets destroyed when the parent USB interface device is unregistered, because unregistering a device also removes from sysfs everything below that device. Alan Stern
