Libraries

lib/ holds portable code: device-class contracts and pure algorithms. No registers, no part numbers, no pins. A lib crate may depend only on other lib crates — tools/check-layers.sh enforces it — which is what lets the same code run on any MCU FlintOS supports, and on the host under test.

Crate	What it is
led-strip	The LedStrip contract an addressable strip promises, plus effects written against it. A driver like ws2812 implements it.
led-matrix	Chained panels: turns (x, y) into a position along the strip. Depends on nothing, not even api.
crypto	First-party no_std primitives — SHA-1/256, HMAC, PBKDF2, AES, CMAC, CCM, key-wrap. Exists for WPA2/WPA3, not as a general crypto lib.
wpa	A first-party WPA2/WPA3-Personal supplicant: the 4-way handshake, over crypto. Replaces the vendored C one.
kvstore	A key/value store that survives an interrupted write — for calibration and config that must outlive a reboot.
heap	A free-list allocator over caller-supplied regions. FlintOS has no global allocator by default; this is opt-in.

Why this is a separate tier

A driver knows a part number and its output is destined for a pin. A lib knows neither. Filing led-matrix under drivers/ would be a false statement about what it is — it turns coordinates into an integer and touches no hardware, so it is testable on the host with no board at all.

Device-class contracts live here so a driver and the code that uses it never name each other directly: an application written against LedStrip swaps a ws2812 panel for another chip by changing one line. make device-matrix shows which drivers keep which contract.

See Architecture for how lib/ sits against the driver layers, and Writing a Driver for implementing a contract.