[mutter/gbsneto/dmabuf-screencast: 3/7] renderer-native: Implement DMA buffer allocation

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

commit f79f9288363a3792583601dd9409d426d80bde9b
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Dec 9 10:05:37 2019 -0300

    renderer-native: Implement DMA buffer allocation
    
    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 d1b064ead..1c2e2f9ef 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_allocate_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;
+  int dmabuf_fd = -1;
+
+  switch (renderer_gpu_data->mode)
+    {
+    case META_RENDERER_NATIVE_MODE_GBM:
+      {
+        CoglFramebuffer *dmabuf_fb;
+        struct gbm_bo *new_bo;
+
+        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_dmabuf_image (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_allocate_dma_buf = meta_renderer_native_allocate_dma_buf;
 
       vtable.onscreen_init = meta_renderer_native_init_onscreen;
       vtable.onscreen_deinit = meta_renderer_native_release_onscreen;