Initiator classes

[penguali]

I have a question regarding the generated SystemVerilog header file hdl_call_if_api.svh in the call_sv_bfm example provided.

In this header file there are three classes, the interface initiator class which extends the API base class, the virtual Initiator, and the virtual wrapper class.
I am kinda confused about the last two because they are somehow identical. Why are both needed?

The second question is why do these two classes inherit from an empty base class, why not directly from the interface class ICallApi

[mballance]

The short asnwer is that the _wrap class's intended use is to create a SystemVerilog class around a pre-existing Python object, while the non-_wrap class's intended use is to create both a SystemVerilog class and a peer Python object. Another use of the the _wrap class is when you want to create a Python object that is derived from the class used to define the API -- for example, you have a family of test classes in Python that all derive from a common base class that defines the Python <-> SystemVerilog API.

You're correct that the code is nearly identical. Perhaps some factory methods defined on a single class would provide an alternative.

Inheritance from a type parameter (which defaults to an empty class) is done to allow wrapping existing classes. It's quite common in UVM environments to have an environment-specific base class for certain sequences. I wanted to ensure that these could easily be accessed.

Let's assume we have a sequence base class:

class my_seq_base extends uvm_sequence;
endclass

We can create a new sequence that can interact with Python as follows:

class my_my_seq extends WishboneInitiator #(my_seq_base);
    virtual task write();
        // Implement write for our environment
    endtask
endclass

[penguali]

Ok. Currently, only the initiator class is used in the example. If I understand correctly, a SV object from the implementation class (_InitiatorImpl) is created. It inherits from the initiator, which creates a new PyObject and links it to the created _InitiatorImpl object.
The initiator class kinda takes care of the Python <-> SV API. right?

Could you maybe provide an example where the _wrap class is used?

As always, thanks for your answers!