fix a380 ???

configuration.nix

@@ -120,7 +120,15 @@
     };
   };
 
+  # Arc A380 (56a5) is not in xe's default probe list on kernel 6.12.
+  # Without force_probe, xe refuses to bind and i915 claims the device
+  # instead -- producing broken MMIO (forcewake 0xFFFFFFFF) and crashing
+  # every VAAPI transcode.
   hardware.intelgpu.driver = "xe";
+  boot.kernelParams = [
+    "xe.force_probe=56a5"
+    "i915.force_probe=!56a5"
+  ];
 
   # Per-service 2MB hugepage budget calculated in service-configs.nix.
   boot.kernel.sysctl."vm.nr_hugepages" = service_configs.hugepages_2m.total_pages;