Add notification events for add/remove device definitions

[jonner]

A management app like libvirt would like to be able to monitor new or removed mediated device definitions. Currently, we have resort to something like periodically polling mdevctl list --defined to detect new or removed devices. It would be nice if we could instead listen for events indicating that a device is defined or undefined.

I envision something similar in concept to udev 'add' or 'remove' events for regular devices. Perhaps DBus could be the mechanism for announcing these events? I'm open to other ideas.

[cohuck]

I'm wondering whether we can combine this with the 'callout' interface suggested in #20 -- we need a mechanism to invoke scripts etc. for that as well.

A post-create/post-remove callout should basically cover the add/remove events. If we do not introduce a more formal message via DBus, would the ability to invoke a custom script be already enough to process state changes?

[jonner]

That's not a bad idea. It would probably work for what I need, depending on exactly how it is implemented.

[cohuck]

Looking through old issues... I'm wondering whether the callout feature as it is merged does what you need?

[collinwalling]

A notification script should hopefully suffice? :)

[cohuck]

I'm mostly asking whether we can close this issue :)

[jonner]

yep, I think we can close it.