Mapping MBIM HighestAvailableDataClass to MM property

[Aleksander Morgado]

On Wed, Apr 16, 2014 at 5:34 AM, Ben Chan <benchan at chromium.org> wrote:
> I'm looking into the following properties of the
> org.freedesktop.ModemManger.Modem interface:
>
> * AccessTechnologies
> * CurrentModes
>
> CurrentModes and AccessTechnologies look quite similar to me. If I
> understand currently, the former indicates what technologies can be
> used to make a connection, and the latter indicates what technologies
> are being used in the currently established connection.
>

"Modes" is primarily to let the user identify which kind of technology
to use; e.g. "2G-only" or "2G,3G with 3G preferred". It doesn't have
much granularity (e.g. only 2G, 3G, 4G; not
GSM,GPRS,EDGE,UMTS,HSPA...), because that is what modems actually
allow to change. Never seen a modem which e.g. allows saying "use EDGE
but not plain GPRS".

Access Technology has much more granularity, and allows identifying
exactly which access tech being used in the radio link (e.g. GPRS vs
EDGE). And it's a mask of values because multimode devices can expose
more than one value. If a UI app needs to show the access tech as a
single value, it can always take the biggest one in order.

> ModemManager currently updates AccessTechnologies based on
> AvailableDataClasses in MBIM_REGISTRATION_STATE_INFO (i.e. the device
> is registered but not necessarily connected to the network). That
> doesn't seem to reflect the actual technology being used after the a
> packet service is attached, which is indicated by
> HighestAvailableDataClass in MBIM_PACKET_SERVICE_INFO. I wonder if
> AccessTechnologies should be updated based on
> HighestAvailableDataClass. I also wonder if AccessTechnologies should
> actually be a single value.
>
> What do you think about the mapping?

Yeah, I believe I remember about HighestAvailableDataClass... Can you
provide some examples on e.g. what the values are for
HighestAvailableDataClass and AvailableDataClasses during a
connection? My assumption, IIRC, was that AvailableDataClasses is
always the current one and HighestAvailableDataClass is the best one
the network can provide, even if it currently may not be that one.


-- 
Aleksander
https://aleksander.es