native: Add preferred-primary GPU selection via udev tag

src/backends/native/meta-backend-native.c

@@ -526,6 +526,9 @@ create_gpu_from_udev_device (MetaBackendNative  *native,
   if (meta_is_udev_device_requires_modifiers (device))
     flags |= META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS;
 
+  if (meta_is_udev_device_preferred_primary (device))
+    flags |= META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY;
+
   device_path = g_udev_device_get_device_file (device);
 
   kms_device = meta_kms_create_device (native->kms, device_path, flags,

src/backends/native/meta-gpu-kms.c

@@ -283,6 +283,15 @@ meta_gpu_kms_requires_modifiers (MetaGpuKms *gpu_kms)
   return !!(flags & META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS);
 }
 
+gboolean
+meta_gpu_kms_is_preferred_primary (MetaGpuKms *gpu_kms)
+{
+  MetaKmsDeviceFlag flags;
+
+  flags = meta_kms_device_get_flags (gpu_kms->kms_device);
+  return !!(flags & META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY);
+}
+
 static int
 compare_outputs (gconstpointer one,
                  gconstpointer two)

src/backends/native/meta-gpu-kms.h

@@ -48,6 +48,7 @@ gboolean meta_gpu_kms_is_crtc_active (MetaGpuKms *gpu_kms,
 gboolean meta_gpu_kms_is_boot_vga (MetaGpuKms *gpu_kms);
 gboolean meta_gpu_kms_is_platform_device (MetaGpuKms *gpu_kms);
 gboolean meta_gpu_kms_requires_modifiers (MetaGpuKms *gpu_kms);
+gboolean meta_gpu_kms_is_preferred_primary (MetaGpuKms *gpu_kms);
 
 gboolean meta_gpu_kms_wait_for_flip (MetaGpuKms *gpu_kms,
                                      GError    **error);

src/backends/native/meta-kms-types.h

@@ -57,6 +57,7 @@ typedef enum _MetaKmsDeviceFlag
   META_KMS_DEVICE_FLAG_BOOT_VGA = 1 << 0,
   META_KMS_DEVICE_FLAG_PLATFORM_DEVICE = 1 << 1,
   META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS = 1 << 2,
+  META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY = 1 << 3,
 } MetaKmsDeviceFlag;
 
 typedef enum _MetaKmsPlaneType MetaKmsPlaneType;

src/backends/native/meta-renderer-native.c

@@ -3940,6 +3940,17 @@ choose_primary_gpu_unchecked (MetaBackend        *backend,
    */
   for (allow_sw = 0; allow_sw < 2; allow_sw++)
   {
+    /* Prefer a device tagged as preferred primary via udev */
+    for (l = gpus; l; l = l->next)
+      {
+        MetaGpuKms *gpu_kms = META_GPU_KMS (l->data);
+
+        if (meta_gpu_kms_is_preferred_primary (gpu_kms) &&
+            (allow_sw == 1 ||
+             gpu_kms_is_hardware_rendering (renderer_native, gpu_kms)))
+          return gpu_kms;
+      }
+
     /* Prefer a platform device */
     for (l = gpus; l; l = l->next)
       {

src/backends/native/meta-udev.c

@@ -74,6 +74,18 @@ meta_is_udev_device_boot_vga (GUdevDevice *device)
   return g_udev_device_get_sysfs_attr_as_int (pci_device, "boot_vga") == 1;
 }
 
+gboolean
+meta_is_udev_device_preferred_primary (GUdevDevice *device)
+{
+  const char * const * tags;
+
+  tags = g_udev_device_get_tags (device);
+  if (!tags)
+    return FALSE;
+
+  return g_strv_contains (tags, "muffin-device-preferred-primary");
+}
+
 gboolean
 meta_is_udev_device_requires_modifiers (GUdevDevice *device)
 {

src/backends/native/meta-udev.h

@@ -32,6 +32,8 @@ gboolean meta_is_udev_device_platform_device (GUdevDevice *device);
 
 gboolean meta_is_udev_device_boot_vga (GUdevDevice *device);
 
+gboolean meta_is_udev_device_preferred_primary (GUdevDevice *device);
+
 gboolean meta_is_udev_device_requires_modifiers (GUdevDevice *device);
 
 gboolean meta_udev_is_drm_device (MetaUdev    *udev,