support for GPU hotplug
On machines with "hybrid GPU" (one integrated GPU + one discrete GPU), it is possible to turn on and off again the discrete GPU (for power saving purposes) by manipulating the PCI registration knobs in /sys/bus/pci.
Other machines provide support for "USB monitors" and USB GPU; the use of USB-C connectors makes this a workable solution. IT will be desirable by end uses to plug in and out these GPU the same way they currently expect to plug an external monitor into a VGA or HDMI connector.
At this moment, mutter:
- doesn't look for additional GPU coming up
- doesn't provide a facility for requesting a rescan of available GPU
- doesn't provide a facility for user-coordinated release of a GPU
- doesn't cope with the sudden loss of a GPU