nixos/hardware.deviceTree: new module

Add support for custom device-tree files, and applying overlays to them.
This is useful for supporting non-discoverable hardware, such as sensors
attached to GPIO pins on a Raspberry Pi.

1 files changed, 56 insertions, 0 deletions

diff --git a/nixos/modules/hardware/device-tree.nix b/nixos/modules/hardware/device-tree.nix
new file mode 100644
index 00000000000..20066939572
--- /dev/null
+++ b/nixos/modules/hardware/device-tree.nix
@@ -0,0 +1,56 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.hardware.deviceTree;
+in {
+  options = {
+      hardware.deviceTree = {
+        enable = mkOption {
+          default = pkgs.stdenv.hostPlatform.platform.kernelDTB or false;
+          type = types.bool;
+          description = ''
+            Build device tree files. These are used to describe the
+            non-discoverable hardware of a system.
+          '';
+        };
+
+        base = mkOption {
+          default = "${config.boot.kernelPackages.kernel}/dtbs";
+          defaultText = "\${config.boot.kernelPackages.kernel}/dtbs";
+          example = literalExample "pkgs.deviceTree.raspberryPiDtbs";
+          type = types.nullOr types.path;
+          description = ''
+            The package containing the base device-tree (.dtb) to boot. Contains
+            device trees bundled with the Linux kernel by default.
+          '';
+        };
+
+        overlays = mkOption {
+          default = [];
+          example = literalExample
+            "[\"\${pkgs.deviceTree.raspberryPiOverlays}/w1-gpio.dtbo\"]";
+          type = types.listOf types.path;
+          description = ''
+            A path containing device tree overlays (.dtbo) to be applied to all
+            base device-trees.
+          '';
+        };
+
+        package = mkOption {
+          default = null;
+          type = types.nullOr types.path;
+          description = ''
+            A path containing device tree overlays (.dtbo) to be applied to all
+            base device-trees. Overrides `base` and `overlays`.
+          '';
+        };
+      };
+  };
+
+  config = mkIf (cfg.enable) {
+    hardware.deviceTree.package = if (cfg.overlays != [])
+      then pkgs.deviceTree.applyOverlays cfg.base cfg.overlays else cfg.base;
+  };
+}