[mutter] drm-buffer: Don't always generate fb_id on construction

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

commit b3dffb43b3845d40d0463966b5ed836e1ae571df
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed May 5 14:35:48 2021 +0200

    drm-buffer: Don't always generate fb_id on construction
    
    It might not be needed by the user of the buffer, so don't always
    require it up front. Instead make sure that any user that needs it first
    calls "meta_drm_buffer_ensure_fb_id()" to create the ID.
    
    Only the plain gbm implementation creates the ID lazilly, the other
    still does it on construction due to the objects used to create them
    only existing during construction.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1854>

 src/backends/native/meta-drm-buffer-dumb.c        |  2 +-
 src/backends/native/meta-drm-buffer-gbm.c         | 21 ++++++++-------------
 src/backends/native/meta-drm-buffer-import.c      |  6 +++---
 src/backends/native/meta-drm-buffer-private.h     |  9 ++++++---
 src/backends/native/meta-drm-buffer.c             | 18 +++++++++++++++---
 src/backends/native/meta-drm-buffer.h             |  3 +++
 src/backends/native/meta-kms-impl-device-atomic.c |  3 +++
 src/backends/native/meta-kms-impl-device-simple.c | 10 ++++++++++
 8 files changed, 49 insertions(+), 23 deletions(-)
---
diff --git a/src/backends/native/meta-drm-buffer-dumb.c b/src/backends/native/meta-drm-buffer-dumb.c
index b0c713decf..87ed4c9cee 100644
--- a/src/backends/native/meta-drm-buffer-dumb.c
+++ b/src/backends/native/meta-drm-buffer-dumb.c
@@ -251,7 +251,7 @@ init_dumb_buffer (MetaDrmBufferDumb  *buffer_dumb,
     .handles = { create_arg.handle },
     .strides = { create_arg.pitch },
   };
-  if (!meta_drm_buffer_ensure_fb_id (buffer, &fb_args, error))
+  if (!meta_drm_buffer_do_ensure_fb_id (buffer, &fb_args, error))
     goto err_add_fb;
 
   map_arg = (struct drm_mode_map_dumb) {
diff --git a/src/backends/native/meta-drm-buffer-gbm.c b/src/backends/native/meta-drm-buffer-gbm.c
index 7a3abaa6bd..30a8f5cbcd 100644
--- a/src/backends/native/meta-drm-buffer-gbm.c
+++ b/src/backends/native/meta-drm-buffer-gbm.c
@@ -133,11 +133,12 @@ meta_drm_buffer_gbm_get_modifier (MetaDrmBuffer *buffer)
 }
 
 static gboolean
-init_fb_id (MetaDrmBufferGbm  *buffer_gbm,
-            struct gbm_bo     *bo,
-            GError           **error)
+meta_drm_buffer_gbm_ensure_fb_id (MetaDrmBuffer  *buffer,
+                                  GError        **error)
 {
+  MetaDrmBufferGbm *buffer_gbm = META_DRM_BUFFER_GBM (buffer);
   MetaDrmFbArgs fb_args = { 0, };
+  struct gbm_bo *bo = buffer_gbm->bo;
 
   if (gbm_bo_get_handle_for_plane (bo, 0).s32 == -1)
     {
@@ -164,8 +165,8 @@ init_fb_id (MetaDrmBufferGbm  *buffer_gbm,
   fb_args.height = gbm_bo_get_height (bo);
   fb_args.format = gbm_bo_get_format (bo);
 
-  if (!meta_drm_buffer_ensure_fb_id (META_DRM_BUFFER (buffer_gbm),
-                                     &fb_args, error))
+  if (!meta_drm_buffer_do_ensure_fb_id (META_DRM_BUFFER (buffer_gbm),
+                                        &fb_args, error))
     return FALSE;
 
   return TRUE;
@@ -185,7 +186,7 @@ lock_front_buffer (MetaDrmBufferGbm  *buffer_gbm,
       return FALSE;
     }
 
-  return init_fb_id (buffer_gbm, buffer_gbm->bo, error);
+  return meta_drm_buffer_gbm_ensure_fb_id (META_DRM_BUFFER (buffer_gbm), error);
 }
 
 MetaDrmBufferGbm *
@@ -223,13 +224,6 @@ meta_drm_buffer_gbm_new_take (MetaDeviceFile      *device_file,
                              "device-file", device_file,
                              "flags", flags,
                              NULL);
-
-  if (!init_fb_id (buffer_gbm, bo, error))
-    {
-      g_object_unref (buffer_gbm);
-      return NULL;
-    }
-
   buffer_gbm->bo = bo;
 
   return buffer_gbm;
@@ -510,6 +504,7 @@ meta_drm_buffer_gbm_class_init (MetaDrmBufferGbmClass *klass)
   object_class->finalize = meta_drm_buffer_gbm_finalize;
 
   buffer_class->export_fd = meta_drm_buffer_gbm_export_fd;
+  buffer_class->ensure_fb_id = meta_drm_buffer_gbm_ensure_fb_id;
   buffer_class->get_width = meta_drm_buffer_gbm_get_width;
   buffer_class->get_height = meta_drm_buffer_gbm_get_height;
   buffer_class->get_stride = meta_drm_buffer_gbm_get_stride;
diff --git a/src/backends/native/meta-drm-buffer-import.c b/src/backends/native/meta-drm-buffer-import.c
index 4769e5326b..698bbda088 100644
--- a/src/backends/native/meta-drm-buffer-import.c
+++ b/src/backends/native/meta-drm-buffer-import.c
@@ -181,9 +181,9 @@ import_gbm_buffer (MetaDrmBufferImport  *buffer_import,
 
   fb_args.handles[0] = gbm_bo_get_handle (imported_bo).u32;
 
-  ret = meta_drm_buffer_ensure_fb_id (META_DRM_BUFFER (buffer_import),
-                                      &fb_args,
-                                      error);
+  ret = meta_drm_buffer_do_ensure_fb_id (META_DRM_BUFFER (buffer_import),
+                                         &fb_args,
+                                         error);
 
   gbm_bo_destroy (imported_bo);
 
diff --git a/src/backends/native/meta-drm-buffer-private.h b/src/backends/native/meta-drm-buffer-private.h
index 08d8ae88e0..9b41379f14 100644
--- a/src/backends/native/meta-drm-buffer-private.h
+++ b/src/backends/native/meta-drm-buffer-private.h
@@ -42,6 +42,9 @@ struct _MetaDrmBufferClass
   int (* export_fd) (MetaDrmBuffer  *buffer,
                      GError        **error);
 
+  gboolean (* ensure_fb_id) (MetaDrmBuffer  *buffer,
+                             GError        **error);
+
   int (* get_width) (MetaDrmBuffer *buffer);
   int (* get_height) (MetaDrmBuffer *buffer);
   int (* get_stride) (MetaDrmBuffer *buffer);
@@ -58,8 +61,8 @@ struct _MetaDrmBufferClass
 
 MetaDeviceFile * meta_drm_buffer_get_device_file (MetaDrmBuffer *buffer);
 
-gboolean meta_drm_buffer_ensure_fb_id (MetaDrmBuffer        *buffer,
-                                       const MetaDrmFbArgs  *fb_args,
-                                       GError              **error);
+gboolean meta_drm_buffer_do_ensure_fb_id (MetaDrmBuffer        *buffer,
+                                          const MetaDrmFbArgs  *fb_args,
+                                          GError              **error);
 
 #endif /* META_DRM_BUFFER_PRIVATE_H */
diff --git a/src/backends/native/meta-drm-buffer.c b/src/backends/native/meta-drm-buffer.c
index 09e07b61de..c526263f7c 100644
--- a/src/backends/native/meta-drm-buffer.c
+++ b/src/backends/native/meta-drm-buffer.c
@@ -67,9 +67,21 @@ meta_drm_buffer_get_device_file (MetaDrmBuffer *buffer)
 }
 
 gboolean
-meta_drm_buffer_ensure_fb_id (MetaDrmBuffer        *buffer,
-                              const MetaDrmFbArgs  *fb_args,
-                              GError              **error)
+meta_drm_buffer_ensure_fb_id (MetaDrmBuffer  *buffer,
+                              GError        **error)
+{
+  MetaDrmBufferPrivate *priv = meta_drm_buffer_get_instance_private (buffer);
+
+  if (priv->fb_id)
+    return TRUE;
+
+  return META_DRM_BUFFER_GET_CLASS (buffer)->ensure_fb_id (buffer, error);
+}
+
+gboolean
+meta_drm_buffer_do_ensure_fb_id (MetaDrmBuffer        *buffer,
+                                 const MetaDrmFbArgs  *fb_args,
+                                 GError              **error)
 {
   MetaDrmBufferPrivate *priv = meta_drm_buffer_get_instance_private (buffer);
   int fd;
diff --git a/src/backends/native/meta-drm-buffer.h b/src/backends/native/meta-drm-buffer.h
index 2a8035d8d3..441473aca1 100644
--- a/src/backends/native/meta-drm-buffer.h
+++ b/src/backends/native/meta-drm-buffer.h
@@ -43,6 +43,9 @@ G_DECLARE_DERIVABLE_TYPE (MetaDrmBuffer,
 int meta_drm_buffer_export_fd (MetaDrmBuffer  *buffer,
                                GError        **error);
 
+gboolean meta_drm_buffer_ensure_fb_id (MetaDrmBuffer  *buffer,
+                                       GError        **error);
+
 uint32_t meta_drm_buffer_get_fb_id (MetaDrmBuffer *buffer);
 
 int meta_drm_buffer_get_width (MetaDrmBuffer *buffer);
diff --git a/src/backends/native/meta-kms-impl-device-atomic.c 
b/src/backends/native/meta-kms-impl-device-atomic.c
index e1adf20b3c..7e14cff014 100644
--- a/src/backends/native/meta-kms-impl-device-atomic.c
+++ b/src/backends/native/meta-kms-impl-device-atomic.c
@@ -421,6 +421,9 @@ process_plane_assignment (MetaKmsImplDevice  *impl_device,
 
   buffer = plane_assignment->buffer;
 
+  if (buffer && !meta_drm_buffer_ensure_fb_id (buffer, error))
+    return FALSE;
+
   meta_topic (META_DEBUG_KMS,
               "[atomic] Assigning %s plane (%u, %s) to %u, "
               "%hdx%hd+%hd+%hd -> %dx%d+%d+%d",
diff --git a/src/backends/native/meta-kms-impl-device-simple.c 
b/src/backends/native/meta-kms-impl-device-simple.c
index 28d5127208..4391ebaeca 100644
--- a/src/backends/native/meta-kms-impl-device-simple.c
+++ b/src/backends/native/meta-kms-impl-device-simple.c
@@ -396,6 +396,9 @@ process_mode_set (MetaKmsImplDevice  *impl_device,
         }
 
       buffer = plane_assignment->buffer;
+      if (!meta_drm_buffer_ensure_fb_id (buffer, error))
+        return FALSE;
+
       fb_id = meta_drm_buffer_get_fb_id (buffer);
 
       for (l = mode_set->connectors; l; l = l->next)
@@ -822,6 +825,9 @@ mode_set_fallback (MetaKmsImplDeviceSimple  *impl_device_simple,
       return FALSE;
     }
 
+  if (!meta_drm_buffer_ensure_fb_id (plane_assignment->buffer, error))
+    return FALSE;
+
   fill_connector_ids_array (cached_mode_set->connectors,
                             &connectors,
                             &n_connectors);
@@ -926,6 +932,10 @@ dispatch_page_flip (MetaKmsImplDevice    *impl_device,
       return TRUE;
     }
 
+  if (plane_assignment && plane_assignment->buffer &&
+      !meta_drm_buffer_ensure_fb_id (plane_assignment->buffer, error))
+    return FALSE;
+
   fd = meta_kms_impl_device_get_fd (impl_device);
   if (custom_page_flip)
     {