modules/hardware-eink: Add module for eink-friendlier config

As of right now, it mostly makes things black on white.

Why make enabling the theme a discrete option? That's because it can be
useful for people like me who would like to live with a flicker-free
boot using a black on white fbcon!

modules/hardware-eink.nix

@@ -0,0 +1,58 @@
+{ config, lib, pkgs, ... }:
+
+let
+  inherit (lib)
+    mkIf
+    mkOption
+    types
+  ;
+  cfg = config.mobile.hardware.eink;
+in
+{
+  options.mobile.hardware.eink = {
+    enable = mkOption {
+      default = false;
+      description = lib.mdDoc ''
+        Enable to change some defaults so they work better on an eink display.
+      '';
+    };
+    enableEinkTheme = mkOption {
+      default = cfg.enable;
+      description = lib.mdDoc ''
+        Enable only the eink changes affecting the theme.
+      '';
+    };
+  };
+  config = mkIf cfg.enableEinkTheme {
+    boot.kernelParams = [
+      # Black on white fbcon
+      "vt.default_red=0xFF,0xBC,0x4F,0xB4,0x56,0xBC,0x4F,0x00,0xA1,0xCF,0x84,0xCA,0x8D,0xB4,0x84,0x68"
+      "vt.default_grn=0xFF,0x55,0xBA,0xBA,0x4D,0x4D,0xB3,0x00,0xA0,0x8F,0xB3,0xCA,0x88,0x93,0xA4,0x68"
+      "vt.default_blu=0xFF,0x58,0x5F,0x58,0xC5,0xBD,0xC5,0x00,0xA8,0xBB,0xAB,0x97,0xBD,0xC7,0xC5,0x68"
+    ];
+
+    # Why not use `logo.svg`?
+    # It's because it's not pure black, it has blue.
+    # Let's use a pure black logo for eink!
+    mobile.boot.stage-1.gui.logo = pkgs.runCommand "logo.eink.svg" {} ''
+      sed -e 's/#ffffff/#000000/g' ${../artwork/logo/logo.white.svg} > $out
+    '';
+
+    # With this one, we have to switch colours around!
+    mobile.boot.stage-1.kernel.logo.logo = pkgs.runCommand "kernel-logo.eink.svg" {} ''
+      sed \
+        -e 's/#ffffff/#xxxxxx/g' \
+        -e 's/#000000/#ffffff/g' \
+        -e 's/#xxxxxx/#000000/g' \
+        ${../artwork/boot-logo.svg} > $out
+    '';
+
+    mobile.boot.stage-1.bootConfig = {
+      splash = {
+        theme = "mono";
+        background = "0xFFFFFFFF";
+        foreground = "0xFF000000";
+      };
+    };
+  };
+}

modules/module-list.nix

@@ -10,6 +10,7 @@
   ./cross-workarounds.nix
   ./devices-metadata.nix
   ./documentation.nix
+  ./hardware-eink.nix
   ./generated-filesystems.nix
   ./hardware-allwinner.nix
   ./hardware-exynos.nix