Aleksander Morgado
c2952e0adc
Sometimes the 'Mode Preference' TLV in the SSP response will have incorrect values. The following log is for a Gobi3k modem which is *only* GMS/UMTS. ModemManager[13415]: [/dev/cdc-wdm0] Received message... >>>>>> QMUX: >>>>>> length = 44 >>>>>> flags = 0x80 >>>>>> service = "nas" >>>>>> client = 2 >>>>>> QMI: >>>>>> flags = "response" >>>>>> transaction = 1 >>>>>> tlv_length = 32 >>>>>> message = "Get System Selection Preference" (0x0034) >>>>>> TLV: >>>>>> type = "Result" (0x02) >>>>>> length = 4 >>>>>> value = 00:00:00:00 >>>>>> translated = SUCCESS >>>>>> TLV: >>>>>> type = "Emergency mode" (0x10) >>>>>> length = 1 >>>>>> value = 00 >>>>>> translated = 0 >>>>>> TLV: >>>>>> type = "Mode Preference" (0x11) >>>>>> length = 2 >>>>>> value = 0F:00 >>>>>> translated = 15 >>>>>> TLV: >>>>>> type = "Band Preference" (0x12) >>>>>> length = 8 >>>>>> value = FF:FF:FF:3F:FF:FF:FF:FF >>>>>> translated = 18446744070488326143 >>>>>> TLV: >>>>>> type = "Roaming Preference" (0x14) >>>>>> length = 2 >>>>>> value = FF:00 >>>>>> translated = 255 Instead of setting to '1' only the bits related to GSM/UMTS in the "Mode Preference" TLV, the modem sets all the bits it knows of to '1', including the CDMA/EVDO ones. It is not easy to detect this properly, because the modem didn't set to '1' the bits it didn't know of (e.g. LTE or TD-SCDMA), so we *cannot* assume that 0x000F actually means 'unknown'. So, we now will pass these returned values through the "DMS Get Capabilities" filter, as we did for the Technology Preference result. The final reported current capabilities will be either: * The intersection between the capabilities loaded by "NAS Get System Selection Preference" and "DMS Get Capabilities" or, * The intersection between the capabilities loaded by "NAS Get Technology Preference" and "DMS Get Capabilities". For 'modem' (not 'current') capabilities, we still rely only on "DMS Get Capabilities".
ModemManager. The problem ModemManager tries to solve is to provide a unified high level API for communicating with (mobile broadband) modems. While the basic commands are standardized, the more advanced operations (like signal quality monitoring while connected) varies a lot. Using. ModemManager is a system daemon and is not meant to be used directly from the command line. However, since it provides DBus API, it is possible to use 'dbus-send' command to control it from the terminal. There's an example program (tests/mm-test.py) that demonstrates the basic API usage. Implementation. ModemManager is a DBus system bus activated service (meaning it's started automatically when a request arrives). It is written in C. The devices are queried from udev and automatically updated based on hardware events. There's a GInterface (MMModem) that defines the modem interface and any device specific implementation must implement it. There are two generic MMModem implementations to support the basic operations (one for GSM, one for CDMA,) which are common for all cards. 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 MMModem 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's a fully working plugin in the plugins/ directory for Huawei cards that can be used as an example for writing new plugins. Writing new plugins is highly encouraged! API. The 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!