GREENTEA: init trace if trace is enabled in json

[jeromecoutant]

Description

Hi

I was interested to enable mbed trace feature.

I can read that someone has to call the trace initialization function.
https://github.com/ARMmbed/mbed-os/blame/master/features/frameworks/mbed-trace/README.md#L56

Proposition is to init trace within GREENTEA_SETUP call.

Thx

Example of mbed_app.json:

{
    "target_overrides": {
        "*": {
            "mbed-trace.enable": "1",
            "mbed-trace.max-level": "TRACE_LEVEL_INFO"
        },
    }
}

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Reviewers

Release Notes

[ciarmcom]

@jeromecoutant, thank you for your changes.
@ARMmbed/mbed-os-maintainers please review.

[0xc0170]

It might be seen as nice to have but not certain enabling trace would add also this call by default to greentea. It is known that this call needs to come from an app if tracing is used.

cc @SeppoTakalo

[SeppoTakalo]

Mbed Trace API is a bit odd, as it does not automatically initialize itself.
Having application to call it, is a bit annoying, but acceptable.

However, test cases are a bit different. There is common boilerplate that everyone follows. Pushing trace_init() there is just annoyance that I would happily avoid, and therefore I would accept this as a good workaround.

I think there is value on allowing traces to be turned on easily from test config.

[0xc0170]

I'll run CI meanwhile (@jamesbeyond Please review)

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

[jamesbeyond]

Look Good