Hi Matthew,
On Sat, Sep 5, 2020 at 10:27 AM Aleksander Morgado <aleksan...@aleksander.es> wrote: > Hey Matthew, > > > u-blox released the following guidance in June 2020 on the TOBY-L2, > TOBY-R2, and LARA-R2 to setup your APN you want to connect to as the > initial bearer at CID=1. > > > > > https://www.u-blox.com/sites/default/files/LTE-initial-default-bearer_AppNote_%28UBX-20015573%29.pdf > > > > These modems already have a default CID=1 APN setup that is generic and > ModemManager then uses another CID based on the APN you want to use and the > IP type (IPv4, IPv6, both). When I manually modified the modem's CID=1 > entry to the correct APN and IP type to match what ModemManager is trying > to use, the modem connected so much faster with ModemManager and did not > have as many issues with re-connection times. > > > > I am interested in making changes to ModemManager to implement always > using CID=1 for these modems. I know the code that handles the CID > selection and creation of new ones if there is no a match is in > src/mm-broadband-bearer.c. I also know there is a plugin for u-blox that > can detect model types. What I am not sure how to do is override the > functions in src/mm-broadband-bearer.c with ones that will be in the u-blox > plugin. The AT command u-blox uses to modify CIDs is AT+CGDCONT. > > > > Additionally I still want to use the code in src/mm-broadband-bearer.c > for all other u-blox modems that don't match these models. > > > > Another difficult part of this is the modem needs to be de-registered > from the network when changing CID=1 if the APN and IP type do not match > what the ModemManager APN and IP type are. The modems use AT+CFUN to put > the modem in airplane mode and back to full mode when changing the CID=1 > APN settings. I don't think this works with the current data connection > flow in ModemManager. > > > > I am currently using the ModemManager 1.8.X series, but could implement > the changes on the newest version and the back port them for the product I > am working on. I plan to update to the newest ModemManager eventually, but > if updating now makes this easier to implement, then I might do that sooner > than originally planned. > > > > I would really appreciate some guidance on how I would best go about > implementing these changes. Thanks. > > > > Please take a look at the recent Cinterion plugin changes, because > Giacinto has already implemented this kind of thing for Cinterion > modems, using the SetInitialEpsBearerSettings() method: > > https://www.freedesktop.org/software/ModemManager/api/latest/gdbus-org.freedesktop.ModemManager1.Modem.Modem3gpp.html#gdbus-method-org-freedesktop-ModemManager1-Modem-Modem3gpp.SetInitialEpsBearerSettings > > See > https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/e2ab49db0f5078716156c70a23f8f5d5b6d27848 > for the specific details. In the case of Cinterion modems, it was not > always CID=1, it was required some additoinal logic to guess which > would be the correct CID to use based on the operator. > > My suggestion would be to provide a u-blox specific implementation for > now, without looking at making it generic yet, and once we have > several such implementations we can simplify the logic and build up > the generic code to match all. > I would like to add one note: NM does not call this SetInitialEpsBearerSettings() method. You will need a separate supervision to set it adequately on a given trigger (when the modem is detected or when a new SIM is detected). Regards, Giacinto
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