On Mon, 2019-06-24 at 11:30 -0500, Alex Elder wrote: > OK I want to try to organize a little more concisely some of the > discussion on this, because there is a very large amount of volume > to date and I think we need to try to narrow the focus back down > again. > > I'm going to use a few terms here. Some of these I really don't > like, but I want to be unambiguous *and* (at least for now) I want > to avoid the very overloaded term "device". > > I have lots more to say, but let's start with a top-level picture, > to make sure we're all on the same page. > > WWAN Communication > Channel (Physical) > | ------------------------ > ------------ v | :+ Control | \ > > |-----------| :+ Data | | > > AP | | WWAN unit :+ Voice | > Functions > > |===========| :+ GPS | | > ------------ ^ | :+ ... | / > | ------------------------- > Multiplexed WWAN > Communication > Channel (Physical) > > - The *AP* is the main CPU complex that's running Linux on one or > more CPU cores. > - A *WWAN unit* is an entity that shares one or more physical > *WWAN communication channels* with the AP. You could just say "WWAN modem" here. > - A *WWAN communication channel* is a bidirectional means of > carrying data between the AP and WWAN unit. > - A WWAN communication channel carries data using a *WWAN protocol*. > - A WWAN unit implements one or more *WWAN functions*, such as > 5G data, LTE voice, GPS, and so on. Go more generic here. Not just 5G data but any WWAN IP-based data (GPRS, EDGE, CDMA, UMTS, EVDO, LTE, 5G, etc). And not just LTE voice but any voice data; plenty of devices don't support LTE but still have "WWAN logical communication channels" > - A WWAN unit shall implement a *WWAN control function*, used to > manage the use of other WWAN functions, as well as the WWAN unit > itself. > - The AP communicates with a WWAN function using a WWAN protocol. > - A WWAN physical channel can be *multiplexed*, in which case it > carries the data for one or more *WWAN logical channels*. It's unclear to me what "physical" means here. USB Interface or Endpoint or PCI Function or SMD channel? Or kernel TTY device? For example on Qualcomm-based USB dongles a given USB Interface's Endpoint represents a QMAP "IP data" channel which itself could be multiplexed into separate "IP data" channels. Or that USB Endpoint(s) could be exposed as a TTY which itself can be MUX-ed dynamically using GSM 07.10. To me "physical" usually means the bus type (PCI, USB, SMD, whatever). A Linux hardware driver (IPA, qmi_wwan, option, sierra, etc) binds to that physical entity using hardware IDs (USB or PCI VID/PID, devicetree properties) and exposes some "WWAN logical communication channels". Those logical channels might be multiplexed and another driver (rmnet) could handle exposing the de-muxed logical channels that the muxed logical channel carries. > - A multiplexed WWAN communication channel uses a *WWAN wultiplexing > protocol*, which is used to separate independent data streams > carrying other WWAN protocols. > - A WWAN logical channel carries a bidirectional stream of WWAN > protocol data between an entity on the AP and a WWAN function. It *usually* is bidirectional. For example some GPS logical communication channels just start spitting out NMEA when you give the control function a command. The NMEA ports themselves don't accept any input. > Does that adequately represent a very high-level picture of what > we're trying to manage? Yes, pretty well. Thanks for trying to specify it all. > And if I understand it right, the purpose of the generic framework > being discussed is to define a common mechanism for managing (i.e., > discovering, creating, destroying, querying, configuring, enabling, > disabling, etc.) WWAN units and the functions they implement, along > with the communication and logical channels used to communicate with > them. Yes. Dan > Comments? > > -Alex
