ADD whitelist to devices probed by modem manager

snap
1

Hi,

https://www.freedesktop.org/software/ModemManager/man/latest/ModemManager.8.html

From this link, i was able to add a specific usb port as whitelist and was able to reduce the wwan0 device boot up time from 1 min to 3 seconds. I want to do it through the snap too. How can i achieve that.

I tested this on ubuntu server by running "sudo /usr/sbin/ModemManager --debug --filter-policy=whitelist-only "

and adding a udev rule SUBSYSTEM==“tty”, KERNEL==“ttyUSB2”, ENV{ID_MM_DEVICE_PROCESS}=“1”

2

Hi @rahul-tt, if you mean doing the same on Ubuntu Core with the modem-manager snap, that is not possible, as

  1. You cannot change the ModemManager binary command line directly, only by using snap options, and changing the filter policy is not one of those
  2. You cannot easily add udev rules by yourself on UC systems, that is done from interfaces. For instance, the mm interface introduces these: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/modem_manager.go#L265

Note also that the changes you are doing are very specific to your use case, as basically the gains you have are because MM does not probe any port, only the one you tell it to probe. Anyway, it would not be impossible to provide ways to do such a configuration on a UC system in the future, but we do not support that oob yet.

3

Thats too bad, Will this option to whitelist a USB port be available in the future updates of modem manager snap?

4

Handling point 1) would be easy enough, but point 2) is not something that will be easily fixed in the near future, at least in the general case.

1 Like