[makermelissa-ai-assistant]

Fixes #165 by implementing a vendor- and generation-independent Linux board-ID file for custom boards and SoM carriers.

Changes

• On Linux, optionally read /etc/blinka-board before ordinary board detection to select a known public constant from adafruit_platformdetect.constants.boards.
• Preserve BLINKA_FORCEBOARD precedence and existing per-Detector caching. Chip detection remains independent; non-Linux platforms do not consult the file.
• Keep ordinary board detection if the file is missing, unreadable, invalid UTF-8, empty, or does not select a known public string constant.
• Document configuration and support boundaries, and run hardware-free regression tests in CI using the standard library.

This is an explicit system-wide administrator-selected override, like a persistent BLINKA_FORCEBOARD, not automatic carrier identification or an electrical-compatibility check. BLINKA_FORCEBOARD can override the file for an individual process, including USB-adapter use. It does not configure peripherals, change device trees, add chip support, or add a particular carrier's pin mapping. A new carrier still needs its PlatformDetect constant/family memberships and corresponding Blinka board definition/routing. Connector-compatible modules with different SoCs still require appropriate mappings.

The file is deliberately not limited to Raspberry Pi CM4: it also applies to other Raspberry Pi Compute Module generations, third-party compatible modules, and other Linux SoM designs. The initial, unmerged /etc/cm4-board path has been replaced rather than retained as an alias.

Verification

• All 22 hardware-free tests pass (python -m unittest discover -s tests -v). They cover all seven supported Raspberry Pi Compute Module types, non-Broadcom chip identities, independent chip/board selection, non-Linux isolation, revision decoding and model fallback without a valid override, explicit environment precedence, caching, and failure fallback.
• GitHub's Linux Build CI passes at e5fcb77.
• Black, the repository's Pylint rules, REUSE licensing checks, and git diff --check pass.
• README reStructuredText parsing and Python 3.7 syntax checks pass.
• Approved fresh-context re-review of e5fcb77 found no issues. Beyond passing the 22 committed tests, the reviewer used real Detector/Chip objects, actual UTF-8 decoding, and in-memory BCM2711/RK3566/A311D device-tree fixtures to verify chip independence and cached selection. The reviewer also checked Blinka's chip-first initialization and first-match board routing, including the documented system-wide effect on USB-adapter processes and per-process BLINKA_FORCEBOARD precedence.
• Sphinx renders the updated documentation; a strict build with the available Sphinx 8 environment still reports the existing theme configuration's get_html_theme_path deprecation warning. No documentation configuration is changed here.

Local tests and review ran on macOS with hardware-path reads intercepted, not native Linux or MicroPython hardware. No physical GPIOs, USB devices, or board configuration were accessed or changed.

[makermelissa]

This can also apply to Pi CM5, CM3 boards, etc.

[makermelissa-ai-assistant]

Updated in e5fcb77: the file is now /etc/blinka-board and is not gated by Raspberry Pi model or module vendor. It is a Linux-wide, persistent board override below BLINKA_FORCEBOARD, with chip detection remaining independent. This covers other Pi Compute Module generations and third-party or other SoM designs without maintaining a module allowlist. Non-Linux platforms do not read it. The README explains that connector compatibility does not imply interchangeable GPIO mappings. All 22 hardware-free tests and local lint checks pass. The approved fresh-context re-review of the broader revision is complete with no findings, and GitHub Linux CI passes. The PR description records verification and limitations; no hardware was accessed.

[makermelissa]

Looks good.