How to tweak sim atom

[Guillaume Zajac <guillaume.zajac@linux.intel.com>]

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Hi all,

As the thread concerning SIM tweaking was growing fast, I summarized it 
in a new one.

We want to use existing oFono sim atom with CSIM (CDMA SIM) to support 
PIN management and get the IMSI at first place.
So far we have to distinguish CSIM and (U)SIM in order into the atom to 
use PIN management and get the IMSI, as other operations won't be 
possible as explained below.

1) 1st solution is to precise at sim atom creation the modem type, 
however Denis denied this solution. Modem type is used by external 
application and not by oFono core.

2) 2nd solution is to get sim_type by deduction of modem type into 
Huawei plugin. Then we precise this sim_type during atom creation.

3) Another method would be to implement a new entry point into 
ofono_sim_driver, for instance ->GetSimType().
However this method will require to access to the file system:
         - for GSM, that can be done using AT+CRSM (EFdir) or AT+CUAD.
         - for CDMA, we don't have any AT commands to do it.

To complete this solution, we might need for CSIM file system access 
some specific Qualcomm commands.
But for the moment, we have no information/documentation from 
manufacturer regarding CSIM file system access.
Therefore, we will not be able to populate following properties:
- MobileCountryCode
- MobileNetworkCode
- SubscriberNumbers
- PreferredLanguages
- ServiceNumbers
- CardIdentifier
- FixedDialing
- BarredDialing

4) Having 2 drivers can be a solution to make difference between CSIM 
and (U)SIM:
         - "atmodem/sim.c" drivers
         - "cdmamodem/sim.c" drivers
There can be a lib simutil for PIN management and IMSI retrieval whose 
APIs would be called by "atmodem" and "cdmamodem" drivers to avoid 
duplicated code.

Thus we don't implement all file system access entry points for 
"cdmamodem/sim.c", but we can keep suggested GetSimType() for both 
drivers and return CSIM type for CDMA without asking modem (as we can't).
Later this will help us to precise right file id (which is different 
from (U)SIM) while reading CSIM file system, once we have the procedures 
from manufacturer to do it.

Kind regards,
Guillaume