135d484501
The "Serving System" indications reported via QMI when the device is
moving may contain LAC/TAC+CID updates or just CID updates.
E.g. this one has "CID 3GPP" (0x1e):
Mon Aug 3 11:22:42 2020 daemon.debug [1567]: [/dev/cdc-wdm0] received
generic indication (translated)... <<<<<< QMUX: <<<<<< length = 33
<<<<<< flags = 0x80 <<<<<< service = "nas" <<<<<< client = 3
<<<<<< QMI: <<<<<< flags = "indication" <<<<<< transaction =
4512 <<<<<< tlv_length = 21 <<<<<< message = "Serving System"
(0x0024) <<<<<< TLV: <<<<<< type = "Serving System" (0x01)
<<<<<< length = 6 <<<<<< value = 01:01:01:02:01:08 <<<<<<
translated = [ registration_state = 'registered' cs_attach_state =
'attached' ps_attach_state = 'attached' selected_network = '3gpp'
radio_interfaces = '{ [0] = 'lte '}' ] <<<<<< TLV: <<<<<< type
= "Data Service Capability" (0x11) <<<<<< length = 2 <<<<<<
value = 01:0B <<<<<< translated = { [0] = 'lte '} <<<<<< TLV:
<<<<<< type = "CID 3GPP" (0x1e) <<<<<< length = 4 <<<<<<
value = 14:C2:A8:00 <<<<<< translated = 11059732
And this one has both "CID 3GPP" (0x1e) and "LTE TAC" (0x25):
Mon Aug 3 11:23:05 2020 daemon.debug [1567]: [/dev/cdc-wdm0] received
generic indication (translated)... <<<<<< QMUX: <<<<<< length = 38
<<<<<< flags = 0x80 <<<<<< service = "nas" <<<<<< client = 3
<<<<<< QMI: <<<<<< flags = "indication" <<<<<< transaction =
4513 <<<<<< tlv_length = 26 <<<<<< message = "Serving System"
(0x0024) <<<<<< TLV: <<<<<< type = "Serving System" (0x01)
<<<<<< length = 6 <<<<<< value = 01:01:01:02:01:08 <<<<<<
translated = [ registration_state = 'registered' cs_attach_state =
'attached' ps_attach_state = 'attached' selected_network = '3gpp'
radio_interfaces = '{ [0] = 'lte '}' ] <<<<<< TLV: <<<<<< type
= "Data Service Capability" (0x11) <<<<<< length = 2 <<<<<<
value = 01:0B <<<<<< translated = { [0] = 'lte '} <<<<<< TLV:
<<<<<< type = "CID 3GPP" (0x1e) <<<<<< length = 4 <<<<<<
value = 32:36:BC:00 <<<<<< translated = 12334642 <<<<<< TLV:
<<<<<< type = "LTE TAC" (0x25) <<<<<< length = 2 <<<
We should therefore allow changes only in the CID, maintaining
whatever LAC/TAC value we had before.
ModemManager. ModemManager provides a unified high level API for communicating with mobile broadband modems, regardless of the protocol used to communicate with the actual device (Generic AT, vendor-specific AT, QCDM, QMI, MBIM...). Using. ModemManager is a system daemon and is not meant to be used directly from the command line. However, since it provides a DBus API, it is possible to use 'dbus-send' commands or the new 'mmcli' command line interface to control it from the terminal. The devices are queried from udev and automatically updated based on hardware events, although a manual re-scan can also be requested to look for RS232 modems. Implementation. ModemManager is a DBus system bus activated service (meaning it's started automatically when a request arrives). It is written in C, using glib and gio. Several GInterfaces specify different features that the modems support, including the generic MMIfaceModem3gpp and MMIfaceModemCdma which provide basic operations for 3GPP (GSM, UMTS, LTE) or CDMA (CDMA1x, EV-DO) modems. If a given feature is not available in the modem, the specific interface will not be exported in DBus. Plugins. Plugins are loaded on startup, and must implement the MMPlugin interface. It consists of a couple of methods which tell the daemon whether the plugin supports a port and to create custom MMBroadbandModem implementations. It most likely makes sense to derive custom modem implementations from one of the generic classes and just add (or override) operations which are not standard. There are multiple fully working plugins in the plugins/ directory that can be used as an example for writing new plugins. Writing new plugins is highly encouraged! The plugin API is open for changes, so if you're writing a plugin and need to add or change some public method, feel free to suggest it! License. The ModemManager and mmcli binaries are both GPLv2+. The libmm-glib library is LGPLv2+.