Quoting Dr. Nikolaus Klepp (dr.klepp@???):

> Sure I cannot use /proc/sys/kernel/hotplug any more, but that's just
> another inconvinience. As long as hotpluging works for you, why should
> you worry? But what when it's broken?

As I believe I already clarified, I _personally_ currently have no use
for hotplugging of any description.

The answer to your implied question of 'What do I use if the older
hotplug subsystem is no longer supported by my very recent Linux kernel?'[1]
is 'Use a different utility to pick up kernel uevents from the netlink
interface and feed them to mdev or whatever you are using to process
dynamic device requirements.'

This answer was already posted a couple of times. You're welcome.

Want a automagical solution that is all-singing, all-dancing and doesn't
require you to set anything up? There's always udev and various workalikes.
Choose and be happy.

[1] Question assumes this to be the case, which is either true or not.
You might want to check whether CONFIG_HOTPLUG merely wasn't set in your
compiled kernel. Might be gone from your version, or might be
'deprecated' but buildable. You want to know which, you'll need to do
the checking yourself.