[mutter/gbsneto/dmabuf-screencast: 2/6] renderer-native: Implement DMA buffer creation

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit d366fb335de68a04c16fd54e545f9177e7e999af
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Dec 9 10:05:37 2019 -0300

    renderer-native: Implement DMA buffer creation
    
    Create a new gbm_bo using the same given geometry, and export the new
    bo's DMA buffer fd. The new bo lives as long as necessary to be used,
    and reused, by PipeWire.
    
    Unfortunately, PipeWire doesn't support modifiers properly, so use the
    linear format for now. For now, a hardcoded format of DRM_FORMAT_XRGB8888
    is set, so we don't need to negotiate the format with PipeWire early.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/1086

 src/backends/native/meta-renderer-native.c | 68 ++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
---
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 92f5a28bb..6d9243716 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -2132,6 +2132,73 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen *onscreen,
   COGL_TRACE_END (MetaRendererNativePostKmsUpdate);
 }
 
+static CoglDmaBufHandle *
+meta_renderer_native_create_dma_buf (CoglRenderer  *cogl_renderer,
+                                     int            width,
+                                     int            height,
+                                     GError       **error)
+{
+  CoglRendererEGL *cogl_renderer_egl = cogl_renderer->winsys;
+  MetaRendererNativeGpuData *renderer_gpu_data = cogl_renderer_egl->platform;
+  MetaRendererNative *renderer_native = renderer_gpu_data->renderer_native;
+
+  switch (renderer_gpu_data->mode)
+    {
+    case META_RENDERER_NATIVE_MODE_GBM:
+      {
+        CoglFramebuffer *dmabuf_fb;
+        struct gbm_bo *new_bo;
+        int dmabuf_fd = -1;
+
+        new_bo = gbm_bo_create (renderer_gpu_data->gbm.device,
+                                width, height, DRM_FORMAT_XRGB8888,
+                                GBM_BO_USE_RENDERING | GBM_BO_USE_LINEAR);
+
+        if (!new_bo)
+          {
+            g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                         "Failed to allocate buffer");
+            return NULL;
+          }
+
+        dmabuf_fd = gbm_bo_get_fd (new_bo);
+
+        if (dmabuf_fd == -1)
+          {
+            g_set_error (error, G_IO_ERROR, G_IO_ERROR_EXISTS,
+                         "Failed to export buffer's DMA fd: %s",
+                         g_strerror (errno));
+            return NULL;
+          }
+
+        dmabuf_fb = create_dma_buf_framebuffer (renderer_native,
+                                                dmabuf_fd,
+                                                width, height,
+                                                gbm_bo_get_stride (new_bo),
+                                                gbm_bo_get_offset (new_bo, 0),
+                                                DRM_FORMAT_MOD_LINEAR,
+                                                DRM_FORMAT_XRGB8888,
+                                                error);
+
+        if (!dmabuf_fb)
+          return NULL;
+
+        return cogl_dma_buf_handle_new (dmabuf_fb, dmabuf_fd, new_bo,
+                                        (GDestroyNotify) gbm_bo_destroy);
+      }
+      break;
+#ifdef HAVE_EGL_DEVICE
+    case META_RENDERER_NATIVE_MODE_EGL_DEVICE:
+      break;
+#endif
+    }
+
+  g_set_error (error, G_IO_ERROR, G_IO_ERROR_UNKNOWN,
+               "Current mode does not support exporting DMA buffers");
+
+  return NULL;
+}
+
 static gboolean
 meta_renderer_native_init_egl_context (CoglContext *cogl_context,
                                        GError     **error)
@@ -2874,6 +2941,7 @@ get_native_cogl_winsys_vtable (CoglRenderer *cogl_renderer)
 
       vtable.renderer_connect = meta_renderer_native_connect;
       vtable.renderer_disconnect = meta_renderer_native_disconnect;
+      vtable.renderer_create_dma_buf = meta_renderer_native_create_dma_buf;
 
       vtable.onscreen_init = meta_renderer_native_init_onscreen;
       vtable.onscreen_deinit = meta_renderer_native_release_onscreen;