kms: Only force legacy mode setting when using EGLStream

EGLStream is incompatible with atomic mode setting, but nvidia-drm when
using libgbm is not, so lets only deny using atomic mode setting when
the render device is an EGLStream based one.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2578>

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

@@ -604,6 +604,11 @@ add_drm_device (MetaBackendNative  *backend_native,
   if (!render_device)
     return FALSE;
 
+#ifdef HAVE_EGL_DEVICE
+  if (META_IS_RENDER_DEVICE_EGL_STREAM (render_device))
+    flags |= META_KMS_DEVICE_FLAG_FORCE_LEGACY;
+#endif
+
   kms_device = meta_kms_create_device (backend_native->kms, device_path, flags,
                                        error);
   if (!kms_device)

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

@@ -411,6 +411,8 @@ meta_create_kms_impl_device (MetaKmsDevice      *device,
     {
       if (flags & META_KMS_DEVICE_FLAG_NO_MODE_SETTING)
         kms_mode = KMS_MODE_HEADLESS;
+      else if (flags & META_KMS_DEVICE_FLAG_FORCE_LEGACY)
+        kms_mode = KMS_MODE_SIMPLE;
       else
         kms_mode = KMS_MODE_AUTO;
     }

src/backends/native/meta-kms-impl-device-atomic.c

@@ -1214,7 +1214,6 @@ is_atomic_allowed (const char *driver_name)
     "qxl",
     "vmwgfx",
     "vboxvideo",
-    "nvidia-drm",
     "virtio_gpu",
     "xlnx",
     NULL,

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

@@ -63,6 +63,7 @@ typedef enum _MetaKmsDeviceFlag
   META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY = 1 << 3,
   META_KMS_DEVICE_FLAG_NO_MODE_SETTING = 1 << 4,
   META_KMS_DEVICE_FLAG_HAS_ADDFB2 = 1 << 5,
+  META_KMS_DEVICE_FLAG_FORCE_LEGACY = 1 << 6,
 } MetaKmsDeviceFlag;
 
 typedef enum _MetaKmsResourceChanges