fix(vader5): map M1..M4 to BTN_TRIGGER_HAPPY1..4 (Steam Elite paddle slots)

[BANANASJIM]

Summary

• Xbox Elite Series 2 evdev spec reserves BTN_TRIGGER_HAPPY1..4 for back paddles P1..P4. padctl masquerades Vader 5 Pro as Xbox Elite Series 2 (vid=0x045e pid=0x0b00), so the same slot reservation applies.
• PR uhid: emit per-button Usage items instead of Usage Min/Max range #235 (1535d8a) enabled C/Z/LM/RM in [output.buttons] and placed them at HAPPY1..4, displacing the real back paddles M1..M4 to HAPPY5..8 which Steam/games do not recognize as paddles.
• User-observed regression on Flydigi Vader 5 Pro hardware: pressing the extra face buttons (C/Z) appeared as back-paddle input; pressing the actual back paddles produced no input.
• Move M1..M4 to HAPPY1..4 (preserving the M2/M3 swap so Vader M2 lands at the Steam Elite P3 slot per PR fix: restore Vader 5 M2 Steam paddle label #323's intent). Push C/Z/LM/RM/O to HAPPY9..13 — they keep stable evdev codes but no longer collide with the paddle reserved range.
• Update src/io/uhid_descriptor.zig companion test that asserted the old hard-coded HAPPY values and propagated USAGE-number offsets (HAPPY1=usage 17, HAPPY9=usage 25, etc.).
• Add regression test in src/test/validate_e2e_test.zig:
  1. M1..M4 occupy BTN_TRIGGER_HAPPY1..4 (positive lock, including M2/M3 swap)
  2. None of C/Z/LM/RM/O fall in BTN_TRIGGER_HAPPY1..4 (structural invariant — catches the PR uhid: emit per-button Usage items instead of Usage Min/Max range #235 class of regression)

Test plan

• zig build test green in canonical Docker image (1558 tests, 7 skipped) — pre-push hook
• Falsifiability: setting M1 = BTN_TRIGGER_HAPPY5 in TOML fires the new positive-lock test and the existing uhid_descriptor test (2 failures, both reverted)
• User local hardware verification with evtest /dev/input/event26 — physical M1..M4 → HAPPY1..4 confirmed; physical C/Z/LM/RM → HAPPY9..12 confirmed
• CI matrix: check / coverage / lean / e2e / install / pkg / systemd hardening / distro-check / tsan

Refs #235

Summary by CodeRabbit

• Bug Fixes

  • Corrected button mappings for the Flydigi Vader 5 Pro controller to ensure proper Steam and console button label recognition.

• Tests

  • Added validation tests for paddle button assignments to prevent regressions.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f77b12e4-17e4-4abc-8992-54a9578c6e89

📥 Commits

Reviewing files that changed from the base of the PR and between cb990be and 271d917.

📒 Files selected for processing (3)

• devices/flydigi/vader5.toml
• src/io/uhid_descriptor.zig
• src/test/validate_e2e_test.zig

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📝 Walkthrough

Walkthrough

This PR updates the Flydigi Vader 5 controller button mappings in the device configuration, reassigning M1–M4 paddle slots and face buttons to different trigger-happy codes. Unit and E2E test expectations are updated and expanded to validate the new button-to-HID-usage relationships.

Changes

Vader 5 Button Mapping Update

Layer / File(s)	Summary
Vader 5 button mapping configuration devices/flydigi/vader5.toml	M1–M4 paddle slots and C, Z, LM, RM, O face/extra buttons are reassigned to new BTN_TRIGGER_HAPPY codes; M2/M3 swap slots, C/Z/LM/RM move to BTN_TRIGGER_HAPPY9–12, and O maps to BTN_TRIGGER_HAPPY13.
Unit test expectations for button ordering src/io/uhid_descriptor.zig	Vader 5 button-mapping assertions updated to match the new M1–M4 trigger-happy codes and the expected HID Usage byte sequence in the generated descriptor.
E2E regression test for paddle slots src/test/validate_e2e_test.zig	New regression test section validates that paddle slots M1–M4 correspond exactly to BTN_TRIGGER_HAPPY1–4, and that face/extra buttons do not collide with paddle-slot codes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• BANANASJIM/padctl#235: The PR aligns with the per-button HID Usage(N) emission logic that drives correct evdev↔HID mapping.
• BANANASJIM/padctl#323: Both PRs adjust the Vader 5 M2/M3 trigger-happy ordering and related test expectations.
• BANANASJIM/padctl#58: Both modify the Vader 5 [output.buttons] evdev button mapping table.

Poem

🐰 In Zig and TOML, buttons dance anew,
M1 through M4 find slots bright and true,
With tests to guide them, from E2E's care,
The Vader 5 now maps with buttons fair! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and accurately describes the main change: remapping Vader 5 Pro paddle buttons M1..M4 to BTN_TRIGGER_HAPPY1..4 for Xbox Elite Series 2 compatibility.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/vader5-paddle-mapping-regression

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