Support Plug&Play Permission updates on CGroupv2

[agners]

Describe the issue

Currently, hotplugging a USB device like /dev/ttyUSB0 or /dev/ttyACM0 (using uart: true add-on configuration) does not update the permissions correctly if CGroupsV2 is used (HAOS 9.x).

Permissions are correctly set when the device, or a device of that same major, is plugged in at boot.

From what I understand, the reason is that systemd crgroup support (which runc calls) requires an existing device with that major for it to be able to resolve the major from /proc/devices. This is at least true when using <major>:* type of rules (which Supervisor is using).

https://github.com/opencontainers/runc/blob/v1.1.4/libcontainer/cgroups/systemd/common.go#L236-L256

Possible solution: Add the <major>:* rules not at start but when the first device of that major is being plugged-in.

Steps to reproduce

1. Use add-on with uart: true
2. Start the add-on
3. Plug-in USB to UART adapter after starting the add-on

Environment details

• Operating System:: 9.0
• Supervisor version:: 2022.09.0
• Home Assistant version:

Supervisor logs

Supervisor logs

Sep 15 20:39:04 ha-fujitsu os-agent[101]: INFO: 2022/09/15 20:39:04 cgroup.go:66: Successfully called runc for '6eda7993251104ee747d13f205a8f776fd7468c0ce8bbfa3774569535547621c', output time="2022-09-15T20:39:04Z" level=warning msg="could not find device group for '99/204' in /proc/devices -- temporarily ignoring rule: {99 204 -1 rwm true}"

System Information

System Information

Paste system info here

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