boot/misc: Add script to generate linux input event codes

boot/misc/generate_evdev_data.rb

@@ -0,0 +1,53 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --packages linuxHeaders ruby -i ruby
+
+# This script can be used to update the input_event_codes ruby file.
+# The file is intended to be committed and updated as needed.
+# At worst, an outdated file will lack *newly introduced* identifiers.
+# This is not much of an issue when most of the kernels for this
+# project are of older vintage!
+# On the same idea, using newer headers is never an issue with "kernel
+# header files". In this particular instance, at worst you're looking
+# for an identifier the kernel does not know about, so it will never
+# return it.
+
+HEADERS = ENV["buildInputs"].split(/\s+/).grep(/linux-headers/).first
+INPUT_CODES = File.join(HEADERS, "/include/linux/input-event-codes.h")
+
+parsed = File.read(INPUT_CODES).lines.grep(/^#define/).map do |line|
+  line.split("/*").first.sub(/^#define/, "").strip.split(/\s+/, 2)
+end.reject { |pair| pair.first.match(/^_/) }
+
+mod = <<~EOF
+# This is generated by `generate_evdev_data.rb`.
+# If an update is needed, simply run the script.
+module Linux
+  module InputEventCodes
+#{
+  parsed.map do |pair|
+    name, value = pair
+    %Q{    #{name} = #{value}}
+  end.join("\n")
+}
+  end
+end
+EOF
+
+# Verify it works
+eval mod
+
+# A bit of additional checks
+{
+  EV_KEY: 1,
+  KEY_Q: 16,
+  KEY_VOLUMEUP: 115,
+}.each do |k, v|
+  actual = Linux::InputEventCodes.const_get(k)
+  unless actual == v
+    raise "The module probably is not right. #{k} != #{v} // #{k} = #{actual}"
+  end
+end
+
+path = File.join(__dir__(), "..", "lib/linux/input_event_codes.rb")
+File.write(path, mod)
+puts "Wrote '#{path}'."