Allow selecting SIM slot using environment variable in gbinder driver

[juanro49]

Hi!

Several SailfishOS users are adapting and testing lpac for this system and also creating a graphical interface to manage eSIMs using lpac (you can follow this thread on the forum https://forum.sailfishos.org/t/esim-on-xperia-10-iii-and-other-sfos-devices/14962/23?u=juanro49).

We have seen that currently the gbinder driver automatically selects the SIM slot in which it detects an eSIM. This is fine, but if you have two eSIMs (integrated eSIM + eSIM with physical SIM card, or two eSIMs with physical SIM cards), it would only detect the one in the first slot, ignoring the one in the second.

In order to manage both slots, we have made a modification to the gbinder driver juanro49@971580e based on what has already been done in #97, so that the slot can be selected using an environment variable (and if it is not specified or -1 is specified, it is done automatically as before).

I have created an issue instead of directly a PR because there is a comment in the code that says “we don't want to force the user to choose in this case” and therefore, I suppose it is necessary to discuss whether you want the change (and check that the code style is correct, as I don't usually program in C) before creating the PR.

[CoelacanthusHex]

cc @PeterCxy, you write those lines before, which kind of opinions on this change?

[septs]

https://github.com/estkme-group/lpac/pull/291/changes

if possible, I would like you to completely refactor and test the gbinder driver.

[PeterCxy]

I have no objections against what's done by the current gbinder driver changes, and there doesn't seem to be a reason to include the refactoring effort with this simple change -- though it would be good to have someone do that and maintain that driver since I do not currently have a device running libhybris at the moment.

[juanro49]

https://github.com/estkme-group/lpac/pull/291/changes

if possible, I would like you to completely refactor and test the gbinder driver.

If it helps, I have tested that refactored code from gbinder on my SailfishOS mobile with libhybris, and with a few modifications to adapt it to the current tree and adding the option to manually select the slot, everything seems to work correctly. I have tested listing, activating, deactivating, downloading, and deleting profiles, listing notifications, and obtaining chip information, and all operations have been successful.