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third_party/tinyusb/AGENTS.md

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+# TinyUSB Agent Instructions
+
+TinyUSB is a cross-platform USB Host/Device stack for embedded systems: memory-safe (no dynamic allocation) and thread-safe (ISR events deferred to task context).
+
+Reference these instructions first; fall back to search/bash only when reality diverges.
+
+## Behavioral Guidelines
+
+Bias toward caution over speed. For trivial tasks, use judgment.
+
+- **Think first** — state assumptions; ask if unclear; present alternatives instead of picking silently.
+- **Simplicity** — no features, abstractions, flexibility, or error handling beyond what was asked. If 200 lines could be 50, rewrite.
+- **Surgical changes** — touch only what the task requires; match existing style; don't refactor working code; mention unrelated dead code rather than deleting it. Remove only orphans *your* changes created.
+- **Goal-driven** — turn tasks into verifiable goals ("write failing test, make it pass"). For multi-step work, state a brief `step → verify` plan.
+
+## Ground Rules
+
+- **Language/style:** C99, 2-space indent (no tabs), snake_case helpers, `UPPER_CASE` macros. Public APIs use `tud_`/`tuh_`; macros use `TU_`. Headers self-contained with `#if CFG_TUSB_MCU` guards.
+- **Safety:** no dynamic allocation; defer ISR work to task context; use `TU_ASSERT()` for error checks; always check return values; include order: C stdlib → tusb common → drivers → classes.
+- **Layout:** `src/` core, `hw/{mcu,bsp}/` MCU+BSP, `examples/{device,host,dual}/`, `test/{unit-test,fuzz,hil}/`, `docs/`, `tools/`.
+- **Commits/PRs:** imperative mood, scoped changes, link issues, include test/build evidence. After opening a PR, monitor it and drive it to green: address automated review comments (Copilot/Codex/Claude) and fix any failing CI builds, pushing follow-up commits until checks pass and review threads are resolved. Useful: `gh pr checks <num> --watch`, `gh pr view <num> --comments`.
+- **Formatting/lint:** `clang-format` (`.clang-format`), `codespell` (`.codespellrc`), run `pre-commit run --all-files` before submitting.
+
+## Bootstrap
+
+```bash
+sudo apt-get install -y gcc-arm-none-eabi          # ARM toolchain (2-5 min, one-time)
+python3 tools/get_deps.py [FAMILY|-b BOARD]        # fetch deps into lib/, hw/mcu/ (<1 s)
+. $HOME/code/esp-idf/export.sh                     # Espressif only: before any build/flash/monitor
+```
+
+## Build
+
+Single example (CMake+Ninja, recommended, 1-3 s):
+```bash
+cd examples/device/cdc_msc && mkdir -p build && cd build
+cmake -DBOARD=raspberry_pi_pico -G Ninja -DCMAKE_BUILD_TYPE=MinSizeRel ..
+cmake --build .
+```
+
+All examples for a board (15-20 s; some objcopy failures are non-critical). Use `cmake-build-<board>` as the build dir — HIL tests expect that exact name:
+```bash
+cd examples
+cmake -B cmake-build-raspberry_pi_pico -DBOARD=raspberry_pi_pico -G Ninja -DCMAKE_BUILD_TYPE=MinSizeRel .
+cmake --build cmake-build-raspberry_pi_pico
+```
+
+Single example with Make:
+```bash
+cd examples/device/cdc_msc && make BOARD=raspberry_pi_pico all
+```
+
+Espressif (only ESP-IDF examples like `cdc_msc_freertos`):
+```bash
+. $HOME/code/esp-idf/export.sh
+cd examples/device/cdc_msc_freertos
+idf.py -DBOARD=espressif_s3_devkitc build
+```
+
+**Build options** (CMake `-D…` / Make `…=…`):
+- Debug: `CMAKE_BUILD_TYPE=Debug` / `DEBUG=1`
+- Logging: `LOG=2` (add `LOGGER=rtt` for RTT)
+- Root hub port: `RHPORT_DEVICE=1`
+- Speed: `RHPORT_DEVICE_SPEED=OPT_MODE_FULL_SPEED`
+
+## Flash
+
+```bash
+# JLink
+ninja cdc_msc-jlink                                       # CMake
+make BOARD=<board> flash-jlink                            # Make
+
+# OpenOCD
+ninja cdc_msc-openocd                                     # CMake
+make BOARD=<board> flash-openocd                          # Make
+
+# UF2
+ninja cdc_msc-uf2                                         # CMake
+make BOARD=<board> all uf2                                # Make
+
+ninja -t targets                                          # list CMake targets
+
+# Espressif (after . $HOME/code/esp-idf/export.sh)
+idf.py -DBOARD=<board> flash
+idf.py -DBOARD=<board> monitor
+```
+
+## GDB Debugging
+
+Look up `JLINK_DEVICE` / `OPENOCD_OPTION` in `hw/bsp/*/boards/*/board.cmake` (CMake builds) or `board.mk` (Make builds).
+
+**JLink — Terminal 1:**
+```bash
+JLinkGDBServer -device stm32h743xi -if SWD -speed 4000 -port 2331 -swoport 2332 -telnetport 2333 -nogui
+```
+
+**OpenOCD — Terminal 1:**
+```bash
+openocd -f interface/stlink.cfg -f target/stm32h7x.cfg
+# or with a J-Link interface:
+openocd -f interface/jlink.cfg -f target/stm32h7x.cfg
+# rp2040/rp2350 via CMSIS-DAP:
+openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c "adapter speed 5000"
+```
+
+**Terminal 2 — connect GDB** (replace `<port>` with `2331` for JLinkGDBServer or `3333` for OpenOCD):
+```bash
+arm-none-eabi-gdb /tmp/build/firmware.elf
+(gdb) target remote :<port>
+(gdb) monitor reset halt
+(gdb) load
+(gdb) break main         # optional, to stop at entry
+(gdb) continue
+```
+
+**RTT logging:** build with `LOG=2 LOGGER=rtt`, flash, then run JLinkGDBServer with `-RTTTelnetPort 19021`, and in another terminal `JLinkRTTClient` (pipe to `tee rtt.log` or use `timeout 20s JLinkRTTClient > rtt.log` for non-interactive capture).
+
+## Testing
+
+**Unit (Ceedling, Unity+CMock, ~4 s):**
+```bash
+sudo gem install ceedling
+cd test/unit-test && ceedling test:all        # or ceedling test:test_fifo
+```
+
+**HIL (2-5 min):** invoke the `hil` skill (`.claude/skills/hil/SKILL.md`) for the full procedure (local vs remote mode, config selection, SSH copy steps, debugging tips). Requires pre-built examples — see Build → "All examples for a board".
+
+## Documentation
+
+Sphinx docs in `docs/` (reStructuredText `.rst` or Markdown `.md` via MyST). Use the `build-doc` skill (`.claude/skills/build-doc/SKILL.md`) to build/preview locally (`sphinx-build`) and to regenerate auto-generated files (`tools/gen_doc.py` + `tools/gen_presets.py`) after adding a board or dependency.
+
+## Code Size Metrics
+
+Verify size impact before committing. Invoke the `code-size` skill (`.claude/skills/code-size/SKILL.md`) — it wraps `tools/metrics_compare_base.py` to handle the base-vs-branch worktree + build + compare flow.
+
+Quick reference:
+```bash
+# Single example, one board:
+python3 tools/metrics_compare_base.py -b raspberry_pi_pico -e device/cdc_msc
+# Add --bloaty for section/symbol breakdown.
+
+# All examples, one board:
+python3 tools/metrics_compare_base.py -b raspberry_pi_pico
+
+# All arm-gcc CI families combined (pre-merge sweep, 4-8 min):
+python3 tools/metrics_compare_base.py --ci
+```
+
+Reports land in `cmake-metrics/<board>/metrics_compare.md` (per-board) and `cmake-metrics/_combined/metrics_compare.md` (with `--combined`/`--ci`).
+
+## Static Analysis (PVS-Studio)
+
+Requires `compile_commands.json`, which the examples build exports by default
+(`hw/bsp/family_support.cmake` sets `CMAKE_EXPORT_COMPILE_COMMANDS ON`). The
+`pvs` skill (`.claude/skills/pvs/SKILL.md`) wraps the build + analyze flow for a
+board; the commands below are the underlying steps.
+
+```bash
+# Whole project:
+pvs-studio-analyzer analyze \
+  -f examples/cmake-build-raspberry_pi_pico/compile_commands.json \
+  -R .PVS-Studio/.pvsconfig \
+  -o pvs-report.log -j12 \
+  --security-related-issues \
+  --misra-c-version 2023 --misra-cpp-version 2008 --use-old-parser
+
+# Specific files: -S takes a plaintext list (one path per line), not paths directly:
+printf 'src/foo.c\nsrc/bar.c\n' > files.txt
+pvs-studio-analyzer analyze \
+  -f examples/cmake-build-raspberry_pi_pico/compile_commands.json \
+  -R .PVS-Studio/.pvsconfig \
+  -S files.txt \
+  -o pvs-report.log -j12 \
+  --security-related-issues \
+  --misra-c-version 2023 --misra-cpp-version 2008 --use-old-parser
+
+plog-converter -a GA:1,2 -t errorfile pvs-report.log     # view results
+```
+
+Takes ~10-30 s. (`--dump-files` adds preprocessed `.PVS-Studio.i/.cfg` dumps next
+to every source for false-positive debugging — omit it for normal runs.)
+
+## Validation After Changes
+
+1. `pre-commit run --all-files` — format, spell, unit tests (10-15 s).
+2. Build at least one board's full example set (Build → "All examples for a board") for modules you touched.
+3. Run relevant unit tests; add fuzz/HIL coverage for parsers or protocol state machines.
+
+**Boards good for local testing:**
+- `stm32f407disco` — no external SDK
+- `raspberry_pi_pico` — Pico SDK required
+- Others: see `hw/bsp/FAMILY/boards/`
+
+Device examples need real hardware to validate runtime behavior; must at least build.
+
+## Release
+
+Cutting a release — version bump, regenerated files, the per-release changelog, validation, and the maintainer's commit/tag/GitHub-release — is handled by the `make-release` skill (`.claude/skills/make-release/SKILL.md`).
+
+## References
+
+- MCU reference manuals, datasheets, schematics: `$HOME/Documents/calibre-library`.
+- Supported MCUs/boards: `hw/bsp/` and `docs/reference/boards.rst`.
+- USB classes: `src/class/{cdc,hid,msc,audio,…}/` — each has `*_device.c` and `*_host.c`.
+- Key files: `src/tusb.h`, `src/tusb_config.h`, `tools/get_deps.py`, `tools/build.py`, `test/unit-test/project.yml`.
+
+## Common Build Issues
+
+- Missing compiler → install `gcc-arm-none-eabi`.
+- Missing deps → `python3 tools/get_deps.py FAMILY`.
+- Unknown board → check `hw/bsp/FAMILY/boards/`.
+- `objcopy` errors in full builds are often non-critical; retry the single example.