doc(reg): improve README and add examples

[Maijin]

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• I've added tests that prove my changes are effective (required for changes to RZ_API).
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Gemini 3 Flash / Antigravity

Detailed description
This PR improves the documentation and provides a practical example for the librz/reg module.

Key Changes:

• Enhanced librz/reg/README.md:
• **New Example

[Rot127]

I struggle to see how the example covers a common use case.
Because the reg profile on its own is not that important I think?
Could you elaborate on this?

[Maijin]

I struggle to see how the example covers a common use case.
Because the reg profile on its own is not that important I think?
Could you elaborate on this?

@Rot127 Thanks for the review - Yes I thought of this flow mostly because that way I can then show the whole chain from ingestion of the profile to the manipulation. Most Reg Profiles are actually hardcoded in different part of Rizin code instead of being defined here - perhaps that's something that could be improved in future.

Open for ideas though if you think of a better chain to showcase this library.

[Rot127]

Open for ideas though if you think of a better chain to showcase this library.

For RzReg idk tbh. Don't have an immediate good use case.
But what would be great IMHO are examples which show basic analysis and how to get the results of it.

Something like:

• Open file
• Set some configs
• Analyze it
• Get all xrefs or similar.

Although this should wait until we have the new analysis ready in a few months.

But what would be useful is an example how to get the RzIL for an instruction.
Because it can be used easily from outside libraries.

[Maijin]

@Rot127 - Yes I'm tackling each librz/* libs one by one 👍 I'll keep that in mind when working on librz/analysis and friends

[codecov]

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[Rot127]

This is not true as far as I can see. The files in reg/d/ map register names to memory addresses.
The register profile is only defined in analysis_ARCH.c as far as I know.

[wargio]

this is related to mmio registers, where for example in AVR the registers are also memory mapped, maybe it should be specified.

[Rot127]

Yes, and the docs here say

Use the format described in the "Register Profile Format" section.

Which is not the correct syntax for those files.

[Maijin]

Yes actually the LLM had it right in the first place and then I got carried away when I was reviewing it and I changed this by mistake. I'll update this section and separate both.

When I was looking at these I was even thinking that registry profiles should all be moved away from the analysis_ARCH files and moved over here instead of being hardcoded in but that's a different discussion.

[Rot127]

Yes actually the LLM had it right in the first place and then I got carried away when I was reviewing it and I changed this by mistake.

This is why I think documentation is written in the best case, while you are actively doing something with the module. So you not just read the code, but interact with it.