# Protocols

Some subsystems (and in the case of KEY and EMIT, the core) re-
quire drivers to implement certain words in a certain way. For
example, the core requires drivers to implement (key) and (emit)
or else it won't know how to provide a console.

These protocols are described here.

# TTY protocol

(key)      -- c    Returns the next typed key on the console.
                   If none, block until there is one.
(emit)     c --    Spit a character on the console.

# PS/2 protocol

This protocol enables communication with a device that spits
PS/2 keycodes.

(ps2kc)   -- kc    Returns the next typed PS/2 keycode from the
                   console. Blocking.

# SPI Relay protocol

This protocol enables communication with a SPI relay. This
protocol is designed to support devices with multiple endpoints.
To that end, (spie) takes a device ID argument, with a meaning
that is up to the device itself. To disable all devices, supply
0 to (spie).

We expect relay devices to support only one enabled device at
once. Enabling a specific device is expected to disable the
previously enabled one.

(spie)    n --     Enable SPI device
(spix)    n -- n   Perform SPI exchange (push a number, get a
                   number back)