dc89c0a42d
Long ago there were problems where certain Huawei devices would stop responding on various ports, and sometimes would crash randomly. The theory at the time was that touching the secondary ports made the device angry, thus the plugin simply opened the ports and listened for unsolicited messages. But if the device didn't send any during that 7 second period, MM would not detect and secondary ports at all. Plus, it was always a hack. Instead, the new theory is that the device crashes if unsolicited messages are enabled (^CURC=1), the secondary port gets touched, *and* then closed and left for a while. Fix that by turning unsolicited messages off at probe time, on when the device is enabled, and off again when the device is disabled like happens for other modems. Thus when MM first detects the modem, it turns off unsolicited messages and the serial buffer on the secondary port doesn't fill up and crash the modem. Second, this allows us to simplify the probing logic quite a bit so that we can probe all ports we find, but we still wait to probe the first port so we can turn off unsolicited messages and get hints about what port is the secondary.
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 HAL 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 HAL UDI 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!