From d366fb335de68a04c16fd54e545f9177e7e999af Mon Sep 17 00:00:00 2001
From: Georges Basile Stavracas Neto <georges.stavracas@gmail.com>
Date: Mon, 9 Dec 2019 10:05:37 -0300
Subject: [PATCH] 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;