Implementing support for a new RTOS

[Spivoxity]

Is there a written guide anywhere to the steps needed to add support for a new RTOS to pyocd? Code for several existing RTOS's is available, but I haven't found documentation for the interface it is implementing.

A simplified OS (tentatively called micro:bian) for the BBC micro:bit, based on message passing and reminiscent of Andy Tanenbaum's MINIX kernel, will be covered in my book "Bare Metal micro:bit". I'd like to include debugger support if possible.

Best wishes,
-- Mike Spivey

[newbrain]

Having recently added the support for Azure RTOS/ThreadX (#1064), I can confidently say that there is no written guide.

The whole thing can be summed up in the following steps (if I find the time, I might try to make a PR with an expanded version of this:

• The structure is based on the specialization of a number of base classes
  • Plugin
    Simply defines the name, description and entry point (ThreadProvider) of the plug-in
  • ThreadProvider
    This class is responsible to make sure we are looking at an actual RTOS instance (in the init method) by cecking for RTOS specific symbols in the elf file.
    It also must be able to enumerate the threads, by walking the RTOS data structures (_build_thread_list, get_thread, get_threads)
  • TargetThread
    Represent a thread in the RTOS, knows about its state and how to get to its registers, using the specialized DebugContext
  • DebugContext
    The derived class understands the structure of a thread stack frame, and can return any register in it (on in the base context) with the read_register_raw method.
• The plug-in needs to be registered in the top level setup.py file in order to be loaded (search for the entry_points dictionary)

I started mostly from the freeRTOS and argon plug-ins, taking liberal inspiration (AKA CtrlC Ctrl-V), then simplifying as much as possible.

[flit]

micro:bian sounds very cool! I'm a fan of small OSes and OS architecture, and I help out the micro:bit Foundation (for DAPLink) so it's fantastic to hear it being used for such work and educational resources.

As @newbrain stated, there's not a guide for writing an RTOS plugin, sorry about that. If you have any questions, feel free to ask here. I will try to extract a guide from what he's already written and anything I add here, with some details filled in.