No hotplug auto-connect on /dev/ttyACM*?

Hey group,

we are happily running ubuntu-core and have hotplug auto-connecting our usb serial device on our snap.

Now we need to add other usb devices that usually show up as /dev/ttyACM* on normal devices. I thought, similar rules apply here, that the devices would be recognized as serial and automatically connected. This is, however not the case. After reading in the wiki:

Along with only supporting USB serial port adapters, hotplug is restricted to devices that provide a specific set of udev attributes; name, vendor identifier and/or serial number.

These attributes are needed to identify and track devices. This isn’t normally a problem for branded devices, but it may cause issues with unbranded devices. Without the required attributes, a device cannot be supported and will be ignored when connected.

So I was wondering what these “specifc udev attributes” are. Or am I missing something here? Essentially we are trying to connect multiple Digisparks which use the v-usb library to connect. This means btw. that we are also theoretically freely able to choose what vendor-id/device-id we would offer.

When does the auto-connection happen? When I stop my service and replug the FTDI, the auto-connection isn’t performed either. I have to restart. Actually, while I’m writing this, my FTDI also doesn’t auto-connect anymore… HELP! Any idea how I can debug this or how to continue?

Edit: Additional info: I’m on a raspberry pi and I can’t change a gadet snap.

Cheers,

Markus

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Ok, I have to backpaddle a bit… It’s embarrassing… I reinstalled core after I couldn’t get auto-connection back and it after that it worked smoothly for the FTDI and surprisingly for /dev/ttyACM* devices as well… The original problem I faced and tried to circumvent before was that both devices created the same /dev/serial/by-id/file and I solved this by adding a serial number to the usb device descriptor. Don’t ask me what exactly happend. But now it seems to work.

I have a few other devices for which I need to test. but I guess, I will work now. I still don’t know what originally happend, though…

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