[rixnobis]

Host side of pcsx-redux/nugget#196 (System 573 / GV monitor).

run --features N sends RUN's optional features word; bit 0 is the watchdog kick, and leaving the flag off keeps the monitor's default. ping reports the new watchdog cap (0x10).

LOAD now falls back to a raw transfer when the monitor answers the first LZ4 frame with EBADCMD, and stays raw for the rest of the session. The 573 build refuses LZ4 above 518400 baud: with RTS looped back to CTS it has no receive throttle, and at 691200 LZ4 decode overruns the SIO1 FIFO on hardware while a raw LOAD passes. A refusal later in the stream is still an error. A monitor built without LZ4 gives the same EBADCMD, so this also helps there.

Both halves do nothing on a monitor that never uses them, so this goes in ahead of nugget#196. The real 691200 refusal on a 573 is still to run; that check stays on nugget#196, which holds the cap.

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📝 Summary

Summary by CodeRabbit

• New Features
  • The run command accepts an optional --features word to configure RUN behavior, including watchdog handling during program execution. Omitting the option preserves the monitor’s default behavior.
• Bug Fixes
  • If a monitor refuses the first LZ4 upload slice, the upload retries in plain LOAD mode and uses that mode for later uploads in the session.
• Documentation
  • Updated command and LZ4 guidance to explain the features option, watchdog behavior, and fallback when LZ4 is refused.

The RUN command now accepts an optional features word. Session handling falls back to raw LOAD when the first LZ4 slice receives EBADCMD and uses raw LOAD for later loads in that session.

Changes: LZ4 refusal fallback

Layer / File(s)	Summary
LZ4 refusal and raw LOAD fallback src/session.rs, tests/session/sim.rs, tests/session/main.rs, README.md	A refusal on the first LZ4 slice triggers a full raw LOAD and records that LZ4 was refused for the session. Later loads use raw LOAD. A refusal after an accepted slice still returns an error. The simulator and tests cover these cases. The README documents the fallback.

RUN watchdog feature word

Layer / File(s)	Summary
Watchdog feature-word support src/proto.rs, src/main.rs, src/session.rs, tests/session/main.rs, tests/session/sim.rs, README.md	The CLI accepts an optional RUN features word and passes it to run_with_features. The session appends the word to the RUN payload when supplied. Capability reporting includes watchdog when CAP_WATCHDOG is set. Tests cover payload encoding, and the README documents the option.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Session
  participant Transport
  participant Monitor
  Session->>Transport: Send first LZ4 LOAD slice
  Transport->>Monitor: Forward LZ4 LOAD
  Monitor-->>Transport: Return EBADCMD
  Transport-->>Session: Report refusal
  Session->>Transport: Send full data with raw LOAD

Loading

sequenceDiagram
  participant CLI as psxmon CLI
  participant Session
  participant Monitor
  CLI->>Session: Call run_with_features with optional features
  Session->>Monitor: Send RUN payload with optional features word

Loading

Possibly related PRs

• pcsx-redux/psxmon#51: It reports Session::load results, which may differ when this change falls back from LZ4 to raw LOAD.
• pcsx-redux/psxmon#49: It adds bulk LOAD retry and settlement logic that intersects with this change’s LZ4 refusal handling.

Merge Risk: Minimal · up to 8ef2d

The previously flagged import has been corrected. No remaining issue identified here blocks merging, subject to normal CI checks.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 47.37% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely identifies both main changes: the run features option and the raw LOAD fallback when LZ4 is refused.
Description check		The description directly explains the watchdog feature-word behavior, the LZ4 refusal fallback, the affected hardware conditions, and the remaining validation scope.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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