Allow for udev rules without devnode

[agracey]

Is your feature request related to a problem? Please describe.

I'm trying to get Akri to detect if a display is connected or not then schedule an X11 container to it. I found the correct rule but Akri doesn't seem to like it.

Is your feature request related to a way you would like Akri extended? Please describe.

Currently, when I use the rule SUBSYSTEM=="drm", ATTR{status}=="connected" I see the below in the logs:

find_devices - ignoring device with devpath "/devices/pci0000:00/0000:00:02.0/drm/card0/card0-DP-1" due to having no devnode

I would imagine this is because the drm subsystem is at /sys/class/drm/?

Describe the solution you'd like
I would like for udev rules without devnodes to be allowed in the udev discovery handler

Describe alternatives you've considered
I don't think there are alternatives?

[agracey]

I'm looking at the traceback from

akri/discovery-handlers/udev/src/discovery_impl.rs

Line 157 in 4cad8e7

"find_devices - ignoring device with devpath {:?} due to having no devnode",

I think there might be 2 options:

• I build a custom discovery handler based on the udev handler that uses something other than devnode
• If get_devnode(&device) returns None, you could optionally return a predictable name based on the KERNEL or SUBSYSTEM and the node name

[kate-goldenring]

Hi @agracey. I think option 1 is a good route and one that we have discussed before in Slack (https://kubernetes.slack.com/archives/C01D9L7QE8Z/p1662486545856829?thread_ts=1662022333.544559&cid=C01D9L7QE8Z). It seems that using syspath rather than devnode would be more ideal which would keep device ids more deterministic too.

[agracey]

I went with option 1: https://github.com/agracey/display-discovery and it works!

An example of it's use is here: https://gist.github.com/agracey/96cfa8c150687ec43b0ca18d42c05332

Should I close this? Or rename to reflect the previously discussed syspath change that you linked (for some reason slack isn't deep-linking for me so I can't actually see the conversation ☹️)?

[kate-goldenring]

@agracey looks like you are using devpath if devnode does not exist. Should we just always use devpath/syspath? Then rather than a custom DH we could just update the current udev one? Great that you were able to create a DH to get things going in the meantime.

[agracey]

🎉 Thank you!