From b52133a28bfc8bd7e264a9a3b9ea0cce7e64224a Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Tue, 17 Dec 2024 20:36:14 +0000
Subject: [PATCH] add hardware.dts.includes option

---
 NEWS                 | 11 ++++++++---
 modules/hardware.nix |  5 +++++
 modules/outputs.nix  |  2 +-
 pkgs/kernel/dtb.nix  | 12 ++++++++++--
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/NEWS b/NEWS
index 6aaca64..11cd306 100644
--- a/NEWS
+++ b/NEWS
@@ -134,6 +134,11 @@ and then run the generated `install.sh` script
 
 2024-12-16
 
-config option rename: config.hardware.dts.includes is now
-hardware.dts.includePaths, which is a better name and  also
-means I can use hardware.dts.includes for a different purpose
\ No newline at end of file
+Config options changed: if you had set config.hardware.dts.includes
+(maybe in an out-of-tree device port) to specify the search paths
+in which dtc finds include files, you will need to change this to 
+hardware.dts.includePaths.
+
+The "new" hardware.dts.includes option is now for dtsi files which
+should be merged into the device tree.
+
diff --git a/modules/hardware.nix b/modules/hardware.nix
index 27c4e97..056cd04 100644
--- a/modules/hardware.nix
+++ b/modules/hardware.nix
@@ -29,6 +29,11 @@ in
           description = "List of directories to search for DTS includes (.dtsi files)";
           type = types.listOf types.path;
         };
+        includes = mkOption {
+          default = [ ];
+          description = "\"dtsi\" fragments to include in the generated device tree";
+          type = types.listOf types.path;
+        };
       };
       defaultOutput = mkOption {
         description = "\"Default\" output: what gets built for this device when outputs.default is requested. Typically this is \"mtdimage\" or \"vmroot\"";
diff --git a/modules/outputs.nix b/modules/outputs.nix
index 5ab12b7..84f6f45 100644
--- a/modules/outputs.nix
+++ b/modules/outputs.nix
@@ -104,7 +104,7 @@ in
     system.outputs = rec {
       dtb = liminix.builders.dtb {
         inherit (config.boot) commandLine;
-        dts = config.hardware.dts.src;
+        dts = config.hardware.dts.includes ++ [config.hardware.dts.src];
         includes = config.hardware.dts.includePaths ++ [
           "${o.kernel.headers}/include"
         ];
diff --git a/pkgs/kernel/dtb.nix b/pkgs/kernel/dtb.nix
index f971cec..505c4a6 100644
--- a/pkgs/kernel/dtb.nix
+++ b/pkgs/kernel/dtb.nix
@@ -2,6 +2,8 @@
   stdenv
 , dtc
 , lib
+, runCommand
+, writeText
 }:
 { dts
 , includes
@@ -10,14 +12,20 @@
   cppDtSearchFlags = builtins.concatStringsSep " " (map (f: "-I${f}") includes);
   dtcSearchFlags = builtins.concatStringsSep " " (map (f: "-i${f}") includes);
   cmdline = lib.concatStringsSep " " commandLine;
+  chosen = writeText "chosen.dtsi" "/{ chosen { bootargs = ${builtins.toJSON cmdline}; }; };";
+  combined = writeText "combined-dts-fragments"
+    (lib.concatStrings
+      (builtins.map
+        (f: "#include \"${f}\"\n")
+        (dts ++ [ chosen ])));
 in stdenv.mkDerivation {
   name = "dtb";
   phases = [ "buildPhase" ];
   nativeBuildInputs = [ dtc ];
   buildPhase = ''
-    ${stdenv.cc.targetPrefix}cpp -nostdinc -x assembler-with-cpp ${cppDtSearchFlags} -undef -D__DTS__  -o dtb.tmp ${dts}
-    echo '/{ chosen { bootargs = ${builtins.toJSON cmdline}; }; };'  >> dtb.tmp
+    ${stdenv.cc.targetPrefix}cpp -nostdinc -x assembler-with-cpp ${cppDtSearchFlags} -undef -D__DTS__  -o dtb.tmp ${combined}
     dtc ${dtcSearchFlags} -I dts  -O dtb -o $out dtb.tmp
+    # dtc -I dtb  -O dts  $out
     test -e $out
   '';
 }