mbimcli has trouble with MBIM device file symlinks created by udev rules, "Couldn't find udev device" and "Couldn't get descriptors file path"

[Ed Peguillan]

I created an issue on MBIM's GitLab. You can see it here: https://gitlab.freedesktop.org/mobile-broadband/libmbim/issues/6
But I will restate it:

I am working on a device that will have several MBIM devices connected. In order to guarantee persistent device file naming under /dev, I am in the process of writing a udev rule to create symbolic links to the cdc-wdm[n] interfaces--you can see it attached to this post. However, invoking mbimcli --device=/dev/SYMLINK-TO-MODEM throws a couple of errors.

Here invoking on the original device file:

# mbimcli --device-open-proxy --device=/dev/cdc-wdm0 --query-registration-state
[/dev/cdc-wdm0] Registration status:
                 Network error: 'unknown'
                Register state: 'home'
                 Register mode: 'automatic'
        Available data classes: 'lte'
        Current cellular class: 'gsm'
                   Provider ID: '311480'
                 Provider name: 'Verizon'
                  Roaming text: 'unknown'
            Registration flags: 'packet-service-automatic-attach'

and now on the symbolic link to the device file. It hangs and I send SIGINT:

$ mbimcli --device-open-proxy --device=/dev/cdc-wdm-HL7618-MBIM0 --query-registration-state
[01 Jul 2019, 20:47:42] -Warning ** [/dev/cdc-wdm-HL7618-MBIM0] Couldn't find udev device
[01 Jul 2019, 20:47:42] -Warning ** [/dev/cdc-wdm-HL7618-MBIM0] Couldn't get descriptors file path
^Ccancelling the operation...
error: couldn't open the MbimDevice: Operation was cancelled

$ ls -l /dev/cdc*
crw------- 1 root root 180, 176 Jul  1 19:03 /dev/cdc-wdm0
lrwxrwxrwx 1 root root        8 Jul  1 19:03 /dev/cdc-wdm-HL7618-MBIM0 -> cdc-wdm0

$ mbimcli --version

mbimcli 1.18.0
Copyright (C) 2013-2019 Aleksander Morgado
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl-2.0.html><http://gnu.org/licenses/gpl-2.0.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

--------------------------------

Interesting thing: I rebooted and now the symlink works, but the original device file does not. The symlink still shows the error mentioned in my OP. It times out if I try to use it.

Symlink:

$ mbimcli --device-open-proxy --device=/dev/cdc-wdm-HL7618-MBIM0 --query-registration-state
[01 Jul 2019, 21:18:07] -Warning ** [/dev/cdc-wdm-HL7618-MBIM0] Couldn't find udev device
[01 Jul 2019, 21:18:07] -Warning ** [/dev/cdc-wdm-HL7618-MBIM0] Couldn't get descriptors file path
[/dev/cdc-wdm-HL7618-MBIM0] Registration status:
                 Network error: 'unknown'
                Register state: 'home'
                 Register mode: 'automatic'
        Available data classes: 'lte'
        Current cellular class: 'gsm'
                   Provider ID: '311480'
                 Provider name: 'Verizon'
                  Roaming text: 'unknown'
            Registration flags: 'packet-service-automatic-attach'


Original:

$ mbimcli --device-open-proxy --device=/dev/cdc-wdm0 --query-registration-state
error: couldn't open the MbimDevice: Transaction timed out

Thank you,

Ed Peguillan III

Contents of udev rule (work in progress): https://gist.github.com/yankee14/f361f8b7dee211faaed0e8ea69620ac9
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