fix: use P3767-0001 nvpmodel conf for Orin NX 8GB

note: nvpmodel.service is failing on 8GB variants of this board since it
has 2 less cores than the 16GB variant (supported already) and since the
nvpmodel configuration file was being recycled for all Orin NX variants.
So, `nvpmodel.service` would try to change settings for 8 CPUs when only
6 exist. cf.
  https://docs.nvidia.com/jetson/archives/r35.3.1/DeveloperGuide/index.html
for the mapping between Orin NX variant and Nvidia "P-number".

modules/default.nix

@@ -57,6 +57,19 @@ in
         description = "Jetson SoM (System-on-Module) to target. Can be null to target a generic jetson device, but some things may not work.";
       };
 
+      sku = mkOption {
+        default = null;
+        # "Extensible option types" in the NixOS manual
+        type = types.nullOr types.string;
+        example = "0001";
+        description = "Specific SKU of a given SOM. This can be
+        helpful to fine-tune configuration of a given device. For
+        example, Orin NX devices come in 8GB and 16GB flavors which
+        differ in the number of supported cores. Configuring the SKU
+        for this SOM would ensure things like nvpmodel work
+        correctly.";
+      };
+
       carrierBoard = mkOption {
         default = null;
         type = types.nullOr (types.enum [ "devkit" ]);

modules/devices.nix

@@ -1,6 +1,6 @@
 { pkgs, config, lib, ... }:
 
-# Configuration specific to particular SoM or carrier boardsl
+# Configuration specific to particular SoM or carrier boards
 let
   inherit (lib)
     mkDefault
@@ -11,7 +11,9 @@ let
 
   nvpModelConf = {
     orin-agx = "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_p3701_0000.conf";
-    orin-nx = "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_p3767_0000.conf";
+    orin-nx = if (cfg.sku == "0001")
+      then "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_p3767_0001.conf"
+      else "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_p3767_0000.conf";
     orin-nano = "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_p3767_0003.conf";
     xavier-agx = "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_t194.conf";
     xavier-nx = "${pkgs.nvidia-jetpack.l4t-nvpmodel}/etc/nvpmodel/nvpmodel_t194_p3668.conf";