[mutter] onscreen/native: Fall back if COPY_MODE_SECONDARY_GPU fails to init

[Marge Bot <marge-bot src gnome org>]

commit 8354289650aa3ae0c531820d3a95251b627f9eb4
Author: Daniel van Vugt <daniel van vugt canonical com>
Date:   Fri Mar 11 17:23:55 2022 +0800

    onscreen/native: Fall back if COPY_MODE_SECONDARY_GPU fails to init
    
    This can happen if we've got a GBM driver that is incomplete or
    buggy for any reason. Currently this includes the Nvidia driver
    when used as a secondary GPU, and as soon as they fix that it will
    use the fast path instead.
    
    Falling back means we can still use it as a KMS device with all rendering
    done on the primary GPU instead. Just like a DisplayLink.
    
    It's slow, but at least the screens all light up now and you get a
    usable desktop. Surprisingly it's still a better experience than using
    Xorg, maybe because we can flip the outputs independently with the
    native backend.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2166,
           https://gitlab.gnome.org/GNOME/mutter/-/issues/2182,
           https://launchpad.net/bugs/1959888,
           https://launchpad.net/bugs/1964037
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2341>

 src/backends/native/meta-onscreen-native.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)
---
diff --git a/src/backends/native/meta-onscreen-native.c b/src/backends/native/meta-onscreen-native.c
index f2c2090dd1..43b95490a0 100644
--- a/src/backends/native/meta-onscreen-native.c
+++ b/src/backends/native/meta-onscreen-native.c
@@ -2063,6 +2063,7 @@ init_secondary_gpu_state (MetaRendererNative  *renderer_native,
   MetaOnscreenNative *onscreen_native = META_ONSCREEN_NATIVE (onscreen);
   MetaGpu *gpu = meta_crtc_get_gpu (onscreen_native->crtc);
   MetaRendererNativeGpuData *renderer_gpu_data;
+  g_autoptr (GError) local_error = NULL;
 
   renderer_gpu_data = meta_renderer_native_get_gpu_data (renderer_native,
                                                          META_GPU_KMS (gpu));
@@ -2070,12 +2071,21 @@ init_secondary_gpu_state (MetaRendererNative  *renderer_native,
   switch (renderer_gpu_data->secondary.copy_mode)
     {
     case META_SHARED_FRAMEBUFFER_COPY_MODE_SECONDARY_GPU:
-      if (!init_secondary_gpu_state_gpu_copy_mode (renderer_native,
-                                                   onscreen,
-                                                   renderer_gpu_data,
-                                                   error))
-        return FALSE;
-      break;
+      if (init_secondary_gpu_state_gpu_copy_mode (renderer_native,
+                                                  onscreen,
+                                                  renderer_gpu_data,
+                                                  &local_error))
+        return TRUE;
+
+      g_warning ("Secondary GPU initialization failed (%s). "
+                 "Falling back to GPU-less mode instead, so the "
+                 "the secondary monitor may be slow to update.",
+                 local_error->message);
+
+      renderer_gpu_data->secondary.copy_mode =
+        META_SHARED_FRAMEBUFFER_COPY_MODE_ZERO;
+
+      G_GNUC_FALLTHROUGH;
     case META_SHARED_FRAMEBUFFER_COPY_MODE_ZERO:
       /*
        * Initialize also the primary copy mode, so that if zero-copy