[BUG] External Register Missing Field Generation

[Zeeshan88c]

Problem

When a register is defined using the external keyword, the tool does not generate field structures (field struct / field combo), while normal registers work as expected.
This behavior is inconsistent and unclear, especially since defining the register inside the RDL does not change the outcome.

Expected Behavior

External registers should either:

• Generate field structures like normal registers
• Have clearly defined and documented behavior explaining why field generation is skipped

The external keyword lacks proper documentation. It is unclear what its intended functionality is and how it should affect field generation

[amykyta3]

This issue list is generally for the top-level PeakRDL command-line tool. Since you mention "field struct" and "field combo" components, I assume you are referring to PeakRDL-regblock. Is that correct?

If so, please see the documentation on how external components work here: https://peakrdl-regblock.readthedocs.io/en/latest/rdl_features/external.html
If you find something in that document unclear, or lacking in detail, please let me know and I'd be happy to improve the documentation text!

[Zeeshan88c]

Yes, I am referring to PeakRDL-regblock.

I reviewed the external component documentation. It explains hwif behavior clearly, but it does not explicitly state the impact on field-level RTL generation (field struct / field combo).

My concern is specifically that this relationship is not documented — fields still influence interface signals, but do not result in generated field-level structures when external is used.

Clarifying this distinction in the documentation would prevent confusion.

[amykyta3]

Currently in the docs:

When generating the RTL for a regblock, the implementations of external components are omitted and instead a user-interface is presented on the hwif_in/hwif_out i/o structs.

Is there something else I should add that is missing?

[Zeeshan88c]

Yes, I saw that part about implementations being omitted and hwif_in/hwif_out being used instead.

What’s still unclear (and not explicitly stated) is the effect on internal field-level RTL artifacts:

Specifically:

• Whether field-level structures (field structs / field comb logic) are intentionally not generated at all for external registers
• Or whether they are still part of the internal model but simply not exposed in hwif because the implementation is external

Right now it reads like a behavior gap: fields exist in the RDL definition and still drive interface signals, but no field-level RTL representation is produced, without that being explicitly stated as a rule.

I think a short clarification like:
“External components do not generate internal field-level RTL structures; only hwif interface signals are produced”

would make the behavior unambiguous.

[amykyta3]

Gotchya that makes sense. I had assumed that was self-evident, but of course I have the usual "maintainer's perspective" blindspot. Will update the text!