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Current capabilities is the set of *active* radios that can be used
right now. Modem capabilities are the set of all radios the modem
could use, if some action were performed to enable them if they are
not enabled already (firmware reload, changing allowed mode, etc).
For QMI devices, the DMS Get Capabilities command represents all
radios, and thus "modem capabilities".
But to read *current* capabilities, ie active radios, we need to
query the NAS System Selection Preference and grab the "mode
preference" TLV. Unfortunately that is only available with NAS
>= 1.1, which means older Gobi devices (1K and 2K) don't support
it. So for older devices, we try to get the Technology Preference
(which takes into account user-requested limitations) and then
mask that with the DMS Get Capabilities result for a best-effort
current capabilities.
For example, the Pantech UML290VW reports DMS Get Capabilities
of "cdma, evdo, gsm, umts, lte", but a more limited SSP mode
preference according to what modes are actually enabled. Gobi
1K devices don't support SSP, and the DMS Get Capabilities
reports cdma/evdo or gsm/umts depending on the currently loaded
firmware. Previous to this patch, ModemManager reported all
modes as available on the UML290, ignoring what modes were
actually enabled.
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