Module keys 

The bytes a keyboard driver puts on the console stream for a chord that is not a keystroke - outside ASCII, so no typed key produces one - and that the program reading the console acts on: Ctrl+Alt+Del (CTRL_ALT_DEL_SIGNAL, the shell reboots), and the audio shortcuts Ctrl+Alt+Up, Ctrl+Alt+Down and Ctrl+Alt+M (docs/audio.md); and a USB host’s word that it just printed a device notice (NOTICE_SIGNAL, the shell redraws its prompt). The drivers write them from the SDK’s hid module; this is the same definition, so the two ends cannot drift.

Constants

CTRL_ALT_DEL_SIGNAL

Console-stream signal for the Ctrl+Alt+Del secure-attention chord (the SEC-2 follow-up).

MUTE_TOGGLE_SIGNAL

NOTICE_SIGNAL

Console-stream signal from a USB host: it has just printed a device notice (USB: WiFi dongle connected (xhci)) over whatever the console showed, and the program reading the console may want to put its own line back. The shell redraws its prompt with the half-typed line under the notice; anything else ignores it, because it is not a key. The hosts pushed a real Enter (\n) for this until 2026-10-24, and an Enter is an ANSWER: a plug while godspeed install asked [y/N] answered it N, and at the prompt it ran the half-typed line (the VisionFive card). Outside ASCII, so no typed key produces it, and read from here by both ends.

VOLUME_DOWN_SIGNAL

VOLUME_UP_SIGNAL

Console-stream signals for the audio shortcuts (docs/audio.md, “Keyboard shortcuts”): Ctrl+Alt+Up, Ctrl+Alt+Down and Ctrl+Alt+M. The Ctrl+Alt+Del pattern exactly: the keyboard driver only SAYS the chord happened, on the console stream, and the SHELL - which asks the audio driver - acts. The keyboard drivers gain no capability and never speak to the audio driver. Outside ASCII, so no typed key produces them, and read from here by both ends.