Refactor USB network card patch a bit

* Rename the module to ax88179_178a, which is the kernel module name.
* Enable manually based on option instead of condition based on
  config.boot.kernelPackages.kernel.version, which started to cause
  infinite recursion when evaluating against nixos-unstable.
* Enable manually only for platforms knwon having affected 6.1.x kernel.

Signed-off-by: Mika Tammi <mika.tammi@unikie.com>

modules/common/hardware/ax88179_178a.nix

@@ -0,0 +1,29 @@
+# Copyright 2024 TII (SSRC) and the Ghaf contributors
+# SPDX-License-Identifier: Apache-2.0
+#
+# Fix for ax88179_178a USB network card kernel driver MAC-address issue.
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}: let
+  cfg = config.ghaf.hardware.ax88179_178a;
+in {
+  options.ghaf.hardware.ax88179_178a = {
+    enable = lib.mkEnableOption "fix for ax88179_178a USB network card kernel driver MAC-address";
+  };
+
+  config = lib.mkIf cfg.enable {
+    boot.kernelPatches = [
+      # Fix MAC-address randomized on USB network cards because of kernel bug.
+      # This specifically affects network cards used in testing.
+      {
+        patch = pkgs.fetchpatch2 {
+          url = "https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/patch/?id=2e91bb99b9d4f756e92e83c4453f894dda220f09";
+          hash = "sha256-fX7yBsXW1oFt1Nfns42oZnCXf36qehXijvCNEmqBGsE=";
+        };
+      }
+    ];
+  };
+}

modules/common/hardware/default.nix

@@ -6,6 +6,6 @@
     ./x86_64-generic
     ./definition.nix
 
-    ./usb-network-kernel-patch.nix
+    ./ax88179_178a.nix
   ];
 }

targets/generic-x86_64/flake-module.nix

@@ -45,6 +45,7 @@
           {
             ghaf = {
               hardware.x86_64.common.enable = true;
+              hardware.ax88179_178a.enable = true;
 
               virtualization.microvm-host.enable = true;
               virtualization.microvm-host.networkSupport = true;

targets/lenovo-x1-installer/flake-module.nix

@@ -25,8 +25,11 @@
         in {
           imports = [
             "${toString modulesPath}/installer/cd-dvd/installation-cd-minimal.nix"
+            ../../modules/common/hardware/ax88179_178a.nix
           ];
 
+          ghaf.hardware.ax88179_178a.enable = true;
+
           # SSH key to installer for test automation.
           users.users.nixos.openssh.authorizedKeys.keys = lib.mkIf (variant == "debug") [
             "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIAolaKCuIUBQSBFGFZI1taNX+JTAr8edqUts7A6k2Kv7"

targets/lenovo-x1/everything.nix

@@ -78,6 +78,7 @@
               host.kernel.hardening.hypervisor.enable = false;
 
               hardware.x86_64.common.enable = true;
+              hardware.ax88179_178a.enable = true;
 
               security.tpm2.enable = true;