wip: test download of dmabuf textures

Do the necessary GL gymnastics ourselves.

For testing this, there is currently an
env var to select:

DMABUF_DOWNLOAD_METHOD=gl

gdk/gdkdisplay.c

@@ -1770,6 +1770,10 @@ gdk_display_init_egl (GdkDisplay  *self,
     epoxy_has_egl_extension (priv->egl_display, "EGL_KHR_no_config_context");
   self->have_egl_pixel_format_float =
     epoxy_has_egl_extension (priv->egl_display, "EGL_EXT_pixel_format_float");
+  self->have_egl_dma_buf_import =
+    epoxy_has_egl_extension (priv->egl_display, "EGL_EXT_image_dma_buf_import_modifiers");
+  self->have_egl_dma_buf_export =
+    epoxy_has_egl_extension (priv->egl_display, "EGL_MESA_image_dma_buf_export");
 
   if (self->have_egl_no_config_context)
     priv->egl_config_high_depth = gdk_display_create_egl_config (self,
@@ -1846,6 +1850,7 @@ gdk_display_get_egl_display (GdkDisplay *self)
 static void
 init_dmabuf_formats (GdkDisplay *display)
 {
+  GdkDisplayPrivate *priv = gdk_display_get_instance_private (display);
   GdkDmabufFormatsBuilder *builder;
 
   if (display->dmabuf_formats != NULL)
@@ -1858,6 +1863,9 @@ init_dmabuf_formats (GdkDisplay *display)
       gdk_display_prepare_gl (display, NULL);
 
       gdk_dmabuf_texture_add_supported_formats (builder);
+
+      if (priv->gl_context)
+        gdk_gl_context_add_dmabuf_formats (priv->gl_context, builder);
     }
 
   display->dmabuf_formats = gdk_dmabuf_formats_builder_free_to_formats (builder);

gdk/gdkdisplayprivate.h

@@ -114,6 +114,8 @@ struct _GdkDisplay
   guint have_egl_buffer_age : 1;
   guint have_egl_no_config_context : 1;
   guint have_egl_pixel_format_float : 1;
+  guint have_egl_dma_buf_import : 1;
+  guint have_egl_dma_buf_export : 1;
 
   GdkDmabufFormats *dmabuf_formats;
 };

gdk/gdkdmabuftexture.c

@@ -24,7 +24,7 @@
 #include "gdkdmabufformatsbuilderprivate.h"
 #include "gdkmemoryformatprivate.h"
 #include "gdkmemorytextureprivate.h"
-#include <gdk/gdkglcontext.h>
+#include <gdk/gdkglcontextprivate.h>
 #include <gdk/gdkgltexturebuilder.h>
 #include <gdk/gdktexturedownloader.h>
 
@@ -36,6 +36,8 @@
 #include <epoxy/egl.h>
 #endif
 
+#include <graphene.h>
+
 /**
  * GdkDmabufTexture:
  *
@@ -155,6 +157,9 @@ struct _GdkDrmFormatInfo
   GdkMemoryFormat unpremultiplied_memory_format;
 };
 
+/* These are the dma-buf formats that we can support just with memcpy,
+ * as long as they are combined with DRM_FORMAT_MOD_LINEAR
+ */
 static GdkDrmFormatInfo supported_formats[] = {
   { DRM_FORMAT_ARGB8888, GDK_MEMORY_A8R8G8B8_PREMULTIPLIED, GDK_MEMORY_A8R8G8B8 },
   { DRM_FORMAT_RGBA8888, GDK_MEMORY_R8G8B8A8_PREMULTIPLIED, GDK_MEMORY_R8G8B8A8 },
@@ -176,6 +181,410 @@ get_drm_format_info (guint32 fourcc)
   return NULL;
 }
 
+/* Hack. We don't include gsk/gsk.h here to avoid a build order problem
+ * with the generated header gskenumtypes.h, so we need to hack around
+ * a bit to access the gsk api we need.
+ */
+
+typedef gpointer GskRenderer;
+typedef gpointer GskRenderNode;
+
+extern GskRenderer *   gsk_gl_renderer_new         (void);
+extern gboolean        gsk_renderer_realize        (GskRenderer            *renderer,
+                                                    GdkSurface             *surface,
+                                                    GError                **error);
+extern void            gsk_renderer_unrealize      (GskRenderer            *renderer);
+extern GdkTexture *    gsk_renderer_render_texture (GskRenderer            *renderer,
+                                                    GskRenderNode          *node,
+                                                    const graphene_rect_t  *bounds);
+extern GskRenderNode * gsk_texture_node_new        (GdkTexture             *texture,
+                                                    const graphene_rect_t  *viewport);
+extern void            gsk_render_node_unref       (GskRenderNode          *node);
+
+static int
+gl_format_for_memory_format (GdkMemoryFormat format)
+{
+  switch (gdk_memory_format_get_depth (format))
+    {
+    case GDK_MEMORY_U8:
+      return GL_RGBA8;
+    case GDK_MEMORY_U16:
+      return GL_RGBA16;
+    case GDK_MEMORY_FLOAT16:
+      return GL_RGBA16F;
+    case GDK_MEMORY_FLOAT32:
+      return GL_RGBA32F;
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static int
+gl_type_for_gl_format (int format)
+{
+  switch (format)
+    {
+    case GL_RGBA8:
+      return GL_UNSIGNED_BYTE;
+    case GL_RGBA16:
+      return GL_UNSIGNED_SHORT;
+    case GL_RGBA16F:
+      return GL_HALF_FLOAT;
+    case GL_RGBA32F:
+      return GL_FLOAT;
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+create_render_target (int           width,
+                      int           height,
+                      int           format,
+                      unsigned int *fbo_id,
+                      unsigned int *texture_id)
+{
+  int type;
+  unsigned int texture, fbo;
+
+  type = gl_type_for_gl_format (format);
+
+  glGenTextures (1, &texture);
+
+  glActiveTexture (GL_TEXTURE0);
+  glBindTexture (GL_TEXTURE_2D, texture);
+
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+  glTexImage2D (GL_TEXTURE_2D, 0, format, width, height, 0, GL_RGBA, type, NULL);
+
+  glGenFramebuffers (1, &fbo);
+  glBindFramebuffer (GL_FRAMEBUFFER, fbo);
+  glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
+  g_assert (glCheckFramebufferStatus (GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
+
+  *fbo_id = fbo;
+  *texture_id = texture;
+}
+
+static const char vertex_shader_source[] = ""
+"#version 150\n"
+"in vec2 in_position;\n"
+"void main() {\n"
+"  gl_Position = vec4(in_position, 0.0, 1.0);\n"
+"}";
+
+static const char fragment_shader_source[] = ""
+"#version 150\n"
+"uniform sampler2D source;\n"
+"uniform vec2 size;\n"
+"out vec4 out_color;\n"
+"void main() {\n"
+"  vec4 in_color = texture(source, gl_FragCoord.xy / size);\n"
+"  out_color = in_color;\n"
+"}";
+
+static unsigned int
+create_shader (int         type,
+               const char *src)
+{
+  unsigned int shader;
+  int status;
+
+  shader = glCreateShader (type);
+  glShaderSource (shader, 1, &src, NULL);
+  glCompileShader (shader);
+
+  glGetShaderiv (shader, GL_COMPILE_STATUS, &status);
+  if (status == GL_FALSE)
+    {
+      int log_len;
+      char *buffer;
+
+      glGetShaderiv (shader, GL_INFO_LOG_LENGTH, &log_len);
+
+      buffer = g_malloc (log_len + 1);
+      glGetShaderInfoLog (shader, log_len, NULL, buffer);
+
+      g_warning ("Compile failure in %s shader:\n%s",
+                 type == GL_VERTEX_SHADER ? "vertex" : "fragment",
+                 buffer);
+
+      g_free (buffer);
+
+      glDeleteShader (shader);
+
+      return 0;
+    }
+
+  return shader;
+}
+
+static unsigned int
+compile_program (const char *vs,
+                 const char *fs,
+                 unsigned int *source_location,
+                 unsigned int *size_location)
+{
+  unsigned int vertex, fragment, program;
+  int status;
+
+  vertex = create_shader (GL_VERTEX_SHADER, vs);
+  if (vertex == 0)
+    return 0;
+
+  fragment = create_shader (GL_FRAGMENT_SHADER, fs);
+  if (fragment == 0)
+    {
+      glDeleteShader (vertex);
+      return 0;
+    }
+
+  program = glCreateProgram ();
+
+  glAttachShader (program, vertex);
+  glAttachShader (program, fragment);
+
+  glLinkProgram (program);
+
+  glGetProgramiv (program, GL_LINK_STATUS, &status);
+  if (status == GL_FALSE)
+    {
+      int log_len;
+      char *buffer;
+
+      glGetProgramiv (program, GL_INFO_LOG_LENGTH, &log_len);
+
+      buffer = g_malloc (log_len + 1);
+      glGetProgramInfoLog (program, log_len, NULL, buffer);
+
+      g_warning ("Linking failure:\n%s", buffer);
+
+      g_free (buffer);
+
+      glDeleteProgram (program);
+      program = 0;
+
+      goto out;
+    }
+
+  *source_location = glGetUniformLocation (program, "source");
+  *size_location = glGetUniformLocation (program, "size");
+
+  glDetachShader (program, vertex);
+  glDetachShader (program, fragment);
+
+out:
+  glDeleteShader (vertex);
+  glDeleteShader (fragment);
+
+  return program;
+}
+
+typedef struct {
+  unsigned int program;
+  unsigned int source_location;
+  unsigned int size_location;
+} ProgramData;
+
+static unsigned int
+get_blit_program (GdkGLContext *context,
+                  unsigned int *source_location,
+                  unsigned int *size_location)
+{
+  ProgramData *data;
+
+  data = g_object_get_data (G_OBJECT (context), "dmabuf-blit-program-data");
+  if (!data)
+    {
+      data = g_new0 (ProgramData, 1);
+      data->program = compile_program (vertex_shader_source,
+                                       fragment_shader_source,
+                                       &data->source_location,
+                                       &data->size_location);
+      g_object_set_data (G_OBJECT (context), "dmabuf-blit-program-data", data);
+    }
+
+  *source_location = data->source_location;
+  *size_location = data->size_location;
+
+  return data->program;
+}
+
+static void
+blit_texture (GdkGLContext *context,
+              int           width,
+              int           height,
+              unsigned int  texture,
+              unsigned int  fbo)
+{
+  unsigned int program;
+  unsigned int source_location;
+  unsigned int size_location;
+  unsigned int vao;
+  unsigned int buffer;
+  const float vertices[] = {
+    -1.0f, 1.0f,
+    -1.0f, -1.0f,
+    1.0f, 1.0f,
+    1.0f, -1.0f
+  };
+
+  program = get_blit_program (context, &source_location, &size_location);
+
+  glGenVertexArrays (1, &vao);
+  glBindVertexArray (vao);
+
+  glGenBuffers (1, &buffer);
+  glBindBuffer (GL_ARRAY_BUFFER, buffer);
+  glBufferData (GL_ARRAY_BUFFER, sizeof (vertices), vertices, GL_STATIC_DRAW);
+
+  glVertexAttribPointer (0, 2, GL_FLOAT, GL_FALSE, 0, NULL);
+  glEnableVertexAttribArray (0);
+
+  glActiveTexture (GL_TEXTURE0);
+  glBindTexture (GL_TEXTURE_2D, texture);
+  glBindFramebuffer (GL_FRAMEBUFFER, fbo);
+
+  glUseProgram (program);
+  glUniform1i (source_location, texture);
+  glUniform2f (size_location, width, height);
+
+  glDrawArrays (GL_TRIANGLE_STRIP, 0, 4);
+
+  glUseProgram (0);
+  glDisableVertexAttribArray (0);
+  glBindBuffer (GL_ARRAY_BUFFER, 0);
+
+  glDeleteBuffers (1, &buffer);
+  glDeleteVertexArrays (1, &vao);
+}
+
+static void
+do_indirect_download_gl (GdkDmabufTexture *self,
+                         GdkMemoryFormat   format,
+                         guchar           *data,
+                         gsize             stride)
+{
+  GdkGLContext *context;
+  unsigned int texture_id;
+  unsigned int texture_id2;
+  unsigned int fbo;
+  int width, height;
+  int gl_format;
+  GdkGLTextureBuilder *builder;
+  GdkTexture *gl_texture;
+  gpointer sync;
+  GdkTextureDownloader *downloader;
+
+  GDK_DEBUG (DMABUF, "Using gl for downloading a dmabuf");
+
+  context = gdk_display_get_gl_context (self->display);
+
+  gdk_gl_context_make_current (context);
+
+  gl_format = gl_format_for_memory_format (format),
+
+  width = gdk_texture_get_width (GDK_TEXTURE (self));
+  height = gdk_texture_get_height (GDK_TEXTURE (self));
+
+  /* 1. import the dmabuf as GL texture */
+  texture_id = gdk_gl_context_import_dmabuf (context, width, height,
+                                             self->fourcc,
+                                             self->modifier,
+                                             self->n_planes,
+                                             self->fds,
+                                             self->strides,
+                                             self->offsets);
+
+  /* 2. create a texture to render into */
+  create_render_target (width, height, gl_format, &fbo, &texture_id2);
+
+  /* 3. copy from texture_id1 to texture_id2, using a blit shader */
+  glClear (GL_COLOR_BUFFER_BIT);
+  blit_texture (context, width, height, texture_id, fbo);
+  sync = glFenceSync (GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
+
+  /* 4. create a GdkGLTexture from the rendered texture */
+  builder = gdk_gl_texture_builder_new ();
+  gdk_gl_texture_builder_set_context (builder, context);
+  gdk_gl_texture_builder_set_id (builder, texture_id2);
+  gdk_gl_texture_builder_set_width (builder, width);
+  gdk_gl_texture_builder_set_height (builder, height);
+  gdk_gl_texture_builder_set_format (builder, format);
+  gdk_gl_texture_builder_set_sync (builder, sync);
+  gl_texture = gdk_gl_texture_builder_build (builder, NULL, NULL);
+
+  /* 5. download it */
+  downloader = gdk_texture_downloader_new (gl_texture);
+  gdk_texture_downloader_set_format (downloader, format);
+  gdk_texture_downloader_download_into (downloader, data, stride);
+  gdk_texture_downloader_free (downloader);
+  g_object_unref (gl_texture);
+
+  /* 6. cleanup */
+  glDeleteFramebuffers (1, &fbo);
+  glDeleteTextures (1, &texture_id);
+  glDeleteTextures (1, &texture_id2);
+}
+
+static void
+do_indirect_download_gsk (GdkDmabufTexture *self,
+                          GdkMemoryFormat  format,
+                          guchar          *data,
+                          gsize            stride)
+{
+  GskRenderer *renderer;
+  int width, height;
+  GskRenderNode *node;
+  GdkTexture *gl_texture;
+  GdkTextureDownloader *downloader;
+  GError *error = NULL;
+
+  GDK_DEBUG (DMABUF, "Using gsk for downloading a dmabuf");
+
+  g_assert (GDK_IS_DISPLAY (self->display));
+  g_assert (GDK_IS_GL_CONTEXT (gdk_display_get_gl_context (self->display)));
+
+  renderer = g_object_get_data (G_OBJECT (self->display), "dmabuf-gl-renderer");
+  if (!renderer)
+    {
+      renderer = gsk_gl_renderer_new ();
+      if (!gsk_renderer_realize (renderer, NULL, &error))
+        {
+          g_warning ("Failed to realize GL renderer: %s", error->message);
+          g_error_free (error);
+          g_object_unref (renderer);
+          return;
+        }
+
+      g_object_set_data_full (G_OBJECT (self->display), "dmabuf-gl-renderer",
+                              renderer, g_object_unref);
+    }
+
+  width = gdk_texture_get_width (GDK_TEXTURE (self));
+  height = gdk_texture_get_height (GDK_TEXTURE (self));
+
+  node = gsk_texture_node_new (GDK_TEXTURE (self), &GRAPHENE_RECT_INIT (0, 0, width, height));
+  gl_texture = gsk_renderer_render_texture (renderer, node, &GRAPHENE_RECT_INIT (0, 0, width, height));
+  gsk_render_node_unref (node);
+
+  gsk_renderer_unrealize (renderer);
+  g_object_unref (renderer);
+
+  downloader = gdk_texture_downloader_new (gl_texture);
+
+  gdk_texture_downloader_set_format (downloader, format);
+
+  gdk_texture_downloader_download_into (downloader, data, stride);
+
+  gdk_texture_downloader_free (downloader);
+  g_object_unref (gl_texture);
+}
+
 static void
 do_direct_download (GdkDmabufTexture *self,
                     guchar           *data,
@@ -187,7 +596,7 @@ do_direct_download (GdkDmabufTexture *self,
   guchar *src_data;
   int bpp;
 
-  GDK_DEBUG (DMABUF, "Using mmap() and memcpy() for downloading a dmabuf");
+  GDK_DEBUG (DMABUF, "Using mmap for downloading a dmabuf");
 
   height = gdk_texture_get_height (GDK_TEXTURE (self));
   bpp = gdk_memory_format_bytes_per_pixel (gdk_texture_get_format (GDK_TEXTURE (self)));
@@ -196,7 +605,7 @@ do_direct_download (GdkDmabufTexture *self,
   size = self->strides[0] * height;
 
   if (ioctl (self->fds[0], DMA_BUF_IOCTL_SYNC, &(struct dma_buf_sync) { DMA_BUF_SYNC_START|DMA_BUF_SYNC_READ }) < 0)
-    g_warning ("Failed to sync dma-buf: %s", g_strerror (errno));
+    g_warning ("Failed to sync dmabuf: %s", g_strerror (errno));
 
   src_data = mmap (NULL, size, PROT_READ, MAP_SHARED, self->fds[0], self->offsets[0]);
 
@@ -211,7 +620,76 @@ do_direct_download (GdkDmabufTexture *self,
   munmap (src_data, size);
 
   if (ioctl (self->fds[0], DMA_BUF_IOCTL_SYNC, &(struct dma_buf_sync) { DMA_BUF_SYNC_END|DMA_BUF_SYNC_READ }) < 0)
-    g_warning ("Failed to sync dma-buf: %s", g_strerror (errno));
+    g_warning ("Failed to sync dmabuf: %s", g_strerror (errno));
+}
+
+/* A helper to determine suitable download memory formats for drm formats */
+static GdkMemoryFormat
+compute_memory_format (guint32  fourcc,
+                       gboolean premultiplied)
+{
+  switch (fourcc)
+    {
+    case DRM_FORMAT_ARGB8888:
+    case DRM_FORMAT_ABGR8888:
+    case DRM_FORMAT_XRGB8888_A8:
+    case DRM_FORMAT_XBGR8888_A8:
+      return premultiplied ? GDK_MEMORY_A8R8G8B8_PREMULTIPLIED : GDK_MEMORY_A8R8G8B8;
+
+    case DRM_FORMAT_RGBA8888:
+    case DRM_FORMAT_RGBX8888_A8:
+      return premultiplied ? GDK_MEMORY_R8G8B8A8_PREMULTIPLIED : GDK_MEMORY_R8G8B8A8;
+
+    case DRM_FORMAT_BGRA8888:
+      return premultiplied ? GDK_MEMORY_B8G8R8A8_PREMULTIPLIED : GDK_MEMORY_B8G8R8A8;
+
+    case DRM_FORMAT_RGB888:
+    case DRM_FORMAT_XRGB8888:
+    case DRM_FORMAT_XBGR8888:
+    case DRM_FORMAT_RGBX8888:
+    case DRM_FORMAT_BGRX8888:
+      return GDK_MEMORY_R8G8B8;
+
+    case DRM_FORMAT_BGR888:
+      return GDK_MEMORY_B8G8R8;
+
+    case DRM_FORMAT_XRGB2101010:
+    case DRM_FORMAT_XBGR2101010:
+    case DRM_FORMAT_RGBX1010102:
+    case DRM_FORMAT_BGRX1010102:
+    case DRM_FORMAT_XRGB16161616:
+    case DRM_FORMAT_XBGR16161616:
+      return GDK_MEMORY_R16G16B16;
+
+    case DRM_FORMAT_ARGB2101010:
+    case DRM_FORMAT_ABGR2101010:
+    case DRM_FORMAT_RGBA1010102:
+    case DRM_FORMAT_BGRA1010102:
+    case DRM_FORMAT_ARGB16161616:
+    case DRM_FORMAT_ABGR16161616:
+      return premultiplied ? GDK_MEMORY_R16G16B16A16_PREMULTIPLIED : GDK_MEMORY_R16G16B16A16;
+
+    case DRM_FORMAT_ARGB16161616F:
+    case DRM_FORMAT_ABGR16161616F:
+      return premultiplied ? GDK_MEMORY_R16G16B16A16_FLOAT_PREMULTIPLIED : GDK_MEMORY_R16G16B16A16_FLOAT;
+
+    case DRM_FORMAT_XRGB16161616F:
+    case DRM_FORMAT_XBGR16161616F:
+      return GDK_MEMORY_R16G16B16_FLOAT;
+
+    case DRM_FORMAT_YUYV:
+    case DRM_FORMAT_YVYU:
+    case DRM_FORMAT_UYVY:
+    case DRM_FORMAT_VYUY:
+    case DRM_FORMAT_XYUV8888:
+    case DRM_FORMAT_XVUY8888:
+    case DRM_FORMAT_VUY888:
+      return GDK_MEMORY_R8G8B8;
+
+    /* Add more formats here */
+    default:
+      return premultiplied ? GDK_MEMORY_A8R8G8B8_PREMULTIPLIED : GDK_MEMORY_A8R8G8B8;
+    }
 }
 
 #endif  /* HAVE_LINUX_DMA_BUF_H */
@@ -231,6 +709,20 @@ gdk_dmabuf_texture_add_supported_formats (GdkDmabufFormatsBuilder *builder)
 #endif
 }
 
+static void
+do_indirect_download (GdkDmabufTexture *self,
+                      GdkMemoryFormat   format,
+                      guchar           *data,
+                      gsize             stride)
+{
+  const char *method = g_getenv ("DMABUF_DOWNLOAD_METHOD");
+
+  if (g_strcmp0 (method, "gl") == 0)
+    do_indirect_download_gl (self, format, data, stride);
+  else
+    do_indirect_download_gsk (self, format, data, stride);
+}
+
 static void
 gdk_dmabuf_texture_download (GdkTexture      *texture,
                              GdkMemoryFormat  format,
@@ -240,8 +732,14 @@ gdk_dmabuf_texture_download (GdkTexture      *texture,
 #ifdef HAVE_LINUX_DMA_BUF_H
   GdkDmabufTexture *self = GDK_DMABUF_TEXTURE (texture);
   GdkMemoryFormat src_format = gdk_texture_get_format (texture);
+  GdkDrmFormatInfo *info;
 
-  if (format == src_format)
+  info = get_drm_format_info (self->fourcc);
+
+  if (!info || self->n_planes > 1 || self->modifier != DRM_FORMAT_MOD_LINEAR ||
+      g_getenv ("DMABUF_DOWNLOAD_METHOD") != NULL)
+    do_indirect_download (self, format, data, stride);
+  else if (format == src_format)
     do_direct_download (self, data, stride);
   else
     {
@@ -262,10 +760,25 @@ gdk_dmabuf_texture_download (GdkTexture      *texture,
                           width, height);
 
       g_free (src_data);
-    }
+     }
 #endif  /* HAVE_LINUX_DMA_BUF_H */
 }
 
+static gboolean
+display_supports_format (GdkDisplay *display,
+                         guint32     fourcc,
+                         guint64     modifier)
+{
+  GdkDmabufFormats *formats;
+
+  if (!display)
+    return FALSE;
+
+  formats = gdk_display_get_dmabuf_formats (display);
+
+  return gdk_dmabuf_formats_contains (formats, fourcc, modifier);
+}
+
 GdkTexture *
 gdk_dmabuf_texture_new_from_builder (GdkDmabufTextureBuilder *builder,
                                      GDestroyNotify           destroy,
@@ -281,26 +794,25 @@ gdk_dmabuf_texture_new_from_builder (GdkDmabufTextureBuilder *builder,
   gboolean premultiplied = gdk_dmabuf_texture_builder_get_premultiplied (builder);
   unsigned int n_planes = gdk_dmabuf_texture_builder_get_n_planes (builder);
   GdkDrmFormatInfo *info;
+  gboolean can_download_directly;
+  gboolean can_download_indirectly;
 
   info = get_drm_format_info (fourcc);
 
-  if (!info || modifier != DRM_FORMAT_MOD_LINEAR)
+  can_download_directly = info != NULL && n_planes == 1 && modifier == DRM_FORMAT_MOD_LINEAR;
+  can_download_indirectly = display_supports_format (display, fourcc, modifier);
+
+  if (!can_download_directly && !can_download_indirectly)
     {
       g_set_error (error, GDK_DMABUF_ERROR, GDK_DMABUF_ERROR_UNSUPPORTED_FORMAT,
-                   "Unsupported dmabuf format: %.4s:%#lx",
-                   (char *) &fourcc, modifier);
-      return NULL;
-    }
-  if (n_planes > 1)
-    {
-      g_set_error (error, GDK_DMABUF_ERROR, GDK_DMABUF_ERROR_CREATION_FAILED,
-                   "Cannot create multiplanar textures for dmabuf format: %.4s:%#lx",
-                   (char *) &fourcc, modifier);
+                   "Unsupported dmabuf format: %.4s:%#lx, planes: %u",
+                   (char *) &fourcc, modifier, n_planes);
       return NULL;
     }
 
-  GDK_DEBUG (DMABUF, "Create dmabuf texture (format %.4s:%#lx)",
-             (char *) &fourcc, modifier);
+  GDK_DEBUG (DMABUF,
+             "Create dmabuf texture (format: %.4s:%#lx, planes: %u)",
+             (char *) &fourcc, modifier, n_planes);
 
   self = g_object_new (GDK_TYPE_DMABUF_TEXTURE,
                        "width", gdk_dmabuf_texture_builder_get_width (builder),
@@ -310,8 +822,11 @@ gdk_dmabuf_texture_new_from_builder (GdkDmabufTextureBuilder *builder,
   self->destroy = destroy;
   self->data = data;
 
-  GDK_TEXTURE (self)->format = premultiplied ? info->premultiplied_memory_format
-                                             : info->unpremultiplied_memory_format;
+  if (can_download_directly)
+    GDK_TEXTURE (self)->format = premultiplied ? info->premultiplied_memory_format
+                                               : info->unpremultiplied_memory_format;
+  else
+    GDK_TEXTURE (self)->format = compute_memory_format (fourcc, premultiplied);
 
   g_set_object (&self->display, display);
 

gdk/gdkglcontext.c

@@ -83,6 +83,7 @@
 #include "gdkmemorytextureprivate.h"
 #include "gdkprofilerprivate.h"
 #include "gdkglversionprivate.h"
+#include "gdkdmabufformatsprivate.h"
 
 #include "gdkprivate.h"
 
@@ -95,6 +96,10 @@
 #include <epoxy/egl.h>
 #endif
 
+#ifdef HAVE_LINUX_DMA_BUF_H
+#include <drm/drm_fourcc.h>
+#endif
+
 #include <math.h>
 
 #define DEFAULT_ALLOWED_APIS GDK_GL_API_GL | GDK_GL_API_GLES
@@ -109,6 +114,7 @@ typedef struct {
   guint has_sync : 1;
   guint has_unpack_subimage : 1;
   guint has_debug_output : 1;
+  guint has_image_storage : 1;
   guint extensions_checked : 1;
   guint debug_enabled : 1;
   guint forward_compatible : 1;
@@ -1555,6 +1561,8 @@ gdk_gl_context_check_extensions (GdkGLContext *context)
                    epoxy_has_gl_extension ("GL_ARB_sync") ||
                    epoxy_has_gl_extension ("GL_APPLE_sync");
 
+  priv->has_image_storage = epoxy_has_gl_extension ("GL_EXT_EGL_image_storage");
+
 #ifdef G_ENABLE_DEBUG
   {
     int max_texture_size;
@@ -1942,3 +1950,226 @@ gdk_gl_backend_use (GdkGLBackend backend_type)
 
   g_assert (the_gl_backend_type == backend_type);
 }
+
+void
+gdk_gl_context_add_dmabuf_formats (GdkGLContext            *self,
+                                   GdkDmabufFormatsBuilder *builder)
+{
+#if defined(HAVE_EGL) && defined(HAVE_LINUX_DMA_BUF_H)
+  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (self);
+  GdkDisplay *display = gdk_gl_context_get_display (self);
+  EGLDisplay egl_display = gdk_display_get_egl_display (display);
+
+  gdk_gl_context_make_current (self);
+
+  if (egl_display != EGL_NO_DISPLAY &&
+      display->have_egl_dma_buf_import &&
+      priv->has_image_storage)
+    {
+      int num_fourccs;
+      int *fourccs;
+
+      eglQueryDmaBufFormatsEXT (egl_display, 0, NULL, &num_fourccs);
+      fourccs = g_new (int, num_fourccs);
+      eglQueryDmaBufFormatsEXT (egl_display, num_fourccs, fourccs, &num_fourccs);
+
+      for (int i = 0; i < num_fourccs; i++)
+        {
+          int num_modifiers;
+          uint64_t *modifiers;
+          unsigned int *external_only;
+
+          eglQueryDmaBufModifiersEXT (egl_display, fourccs[i], 0, NULL, NULL, &num_modifiers);
+          modifiers = g_new (uint64_t, num_modifiers);
+          external_only = g_new (unsigned int, num_modifiers);
+          eglQueryDmaBufModifiersEXT (egl_display, fourccs[i], num_modifiers, modifiers, external_only, &num_modifiers);
+
+          for (int j = 0; j < num_modifiers; j++)
+            {
+              GDK_DEBUG (DMABUF, "%ssupported EGL dmabuf format %.4s:%#lx %s",
+                         external_only[j] ? "un" : "",
+                         (char *) &fourccs[i],
+                         modifiers[j],
+                         external_only[j] ? "EXT" : "");
+              if (!external_only[j])
+                gdk_dmabuf_formats_builder_add_format (builder, fourccs[i], modifiers[j]);
+            }
+
+          g_free (modifiers);
+       }
+
+      g_free (fourccs);
+    }
+#endif
+}
+
+guint
+gdk_gl_context_import_dmabuf (GdkGLContext *self,
+                              int           width,
+                              int           height,
+                              unsigned int  fourcc,
+                              guint64       modifier,
+                              unsigned int  n_planes,
+                              int          *fds,
+                              unsigned int *strides,
+                              unsigned int *offsets)
+{
+#if defined(HAVE_EGL) && defined(HAVE_LINUX_DMA_BUF_H)
+  GdkDisplay *display = gdk_gl_context_get_display (self);
+  EGLDisplay egl_display = gdk_display_get_egl_display (display);
+  EGLint attribs[64];
+  int i;
+  EGLImage image;
+  guint texture_id;
+
+  g_return_val_if_fail (GDK_IS_GL_CONTEXT (self), 0);
+  g_return_val_if_fail (width > 0, 0);
+  g_return_val_if_fail (height > 0, 0);
+  g_return_val_if_fail (1 <= n_planes && n_planes <= 4, 0);
+  g_return_val_if_fail (fds != NULL, 0);
+  g_return_val_if_fail (strides != NULL, 0);
+  g_return_val_if_fail (offsets != NULL, 0);
+
+  if (egl_display == EGL_NO_DISPLAY || !display->have_egl_dma_buf_import)
+    return 0;
+
+  GDK_DEBUG (DMABUF,
+             "Importing dmabuf (format: %.4s:%#lx, planes: %u) into GL",
+             (char *) &fourcc, modifier, n_planes);
+
+  i = 0;
+  attribs[i++] = EGL_WIDTH;
+  attribs[i++] = width;
+  attribs[i++] = EGL_HEIGHT;
+  attribs[i++] = height;
+  attribs[i++] = EGL_LINUX_DRM_FOURCC_EXT;
+  attribs[i++] = fourcc;
+
+#define ADD_PLANE(plane) \
+  { \
+    if (modifier != DRM_FORMAT_MOD_INVALID) \
+      { \
+        attribs[i++] = EGL_DMA_BUF_PLANE## plane ##_MODIFIER_LO_EXT; \
+        attribs[i++] = modifier & 0xFFFFFFFF; \
+        attribs[i++] = EGL_DMA_BUF_PLANE## plane ## _MODIFIER_HI_EXT; \
+        attribs[i++] = modifier >> 32; \
+      } \
+    attribs[i++] = EGL_DMA_BUF_PLANE## plane ##_FD_EXT; \
+    attribs[i++] = fds[plane]; \
+    attribs[i++] = EGL_DMA_BUF_PLANE## plane ##_PITCH_EXT; \
+    attribs[i++] = strides[plane]; \
+    attribs[i++] = EGL_DMA_BUF_PLANE## plane ##_OFFSET_EXT; \
+    attribs[i++] = offsets[plane]; \
+  }
+
+  ADD_PLANE (0);
+
+  if (n_planes > 1) ADD_PLANE (1);
+  if (n_planes > 2) ADD_PLANE (2);
+  if (n_planes > 3) ADD_PLANE (3);
+
+  attribs[i++] = EGL_NONE;
+
+  image = eglCreateImageKHR (egl_display,
+                             EGL_NO_CONTEXT,
+                             EGL_LINUX_DMA_BUF_EXT,
+                             (EGLClientBuffer)NULL,
+                             attribs);
+
+  if (image == EGL_NO_IMAGE)
+    {
+      g_warning ("Creating EGLImage for dmabuf failed: %#x", eglGetError ());
+      return 0;
+    }
+
+  glGenTextures (1, &texture_id);
+  glBindTexture (GL_TEXTURE_2D, texture_id);
+  glEGLImageTargetTexture2DOES (GL_TEXTURE_2D, image);
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+  glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+  eglDestroyImageKHR (egl_display, image);
+
+  return texture_id;
+#else
+  return 0;
+#endif
+}
+
+gboolean
+gdk_gl_context_export_dmabuf (GdkGLContext *self,
+                              unsigned int  texture_id,
+                              int          *fourcc,
+                              int          *n_planes,
+                              guint64      *modifier,
+                              int          *fds,
+                              int          *strides,
+                              int          *offsets)
+{
+#if defined(HAVE_EGL) && defined(HAVE_LINUX_DMA_BUF_H)
+  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (self);
+  GdkDisplay *display = gdk_gl_context_get_display (self);
+  EGLDisplay egl_display = gdk_display_get_egl_display (display);
+  EGLContext egl_context = priv->egl_context;
+  EGLint attribs[10];
+  int i;
+  EGLImage image;
+  gboolean result = FALSE;
+
+  g_return_val_if_fail (GDK_IS_GL_CONTEXT (self), FALSE);
+  g_return_val_if_fail (texture_id > 0, FALSE);
+  g_return_val_if_fail (fourcc != NULL, FALSE);
+  g_return_val_if_fail (n_planes != NULL, FALSE);
+  g_return_val_if_fail (modifier != NULL, FALSE);
+  g_return_val_if_fail (fds != NULL, FALSE);
+  g_return_val_if_fail (strides != NULL, FALSE);
+  g_return_val_if_fail (offsets != NULL, FALSE);
+
+  if (egl_display == EGL_NO_DISPLAY || !display->have_egl_dma_buf_export)
+    return 0;
+
+  GDK_DEBUG (DMABUF, "Exporting GL texture to dmabuf");
+
+  i = 0;
+  attribs[i++] = EGL_IMAGE_PRESERVED_KHR;
+  attribs[i++] = EGL_TRUE;
+
+  attribs[i++] = EGL_NONE;
+
+  image = eglCreateImageKHR (egl_display,
+                             egl_context,
+                             EGL_GL_TEXTURE_2D_KHR,
+                             (EGLClientBuffer)GUINT_TO_POINTER (texture_id),
+                             attribs);
+
+  if (image == EGL_NO_IMAGE)
+    return FALSE;
+
+  if (!eglExportDMABUFImageQueryMESA (egl_display,
+                                      image,
+                                      fourcc,
+                                      n_planes,
+                                      modifier))
+    goto out;
+
+  if (!eglExportDMABUFImageMESA (egl_display,
+                                 image,
+                                 fds,
+                                 strides,
+                                 offsets))
+    goto out;
+
+  GDK_DEBUG (DMABUF,
+             "Exported GL texture to dmabuf (format: %.4s:%#lx, planes: %d)",
+             (char *)fourcc, *modifier, *n_planes);
+
+  result = TRUE;
+
+out:
+  eglDestroyImageKHR (egl_display, image);
+
+  return result;
+#else
+  return FALSE:
+#endif
+}

gdk/gdkglcontextprivate.h

@@ -23,6 +23,7 @@
 #include "gdkglcontext.h"
 #include "gdkdrawcontextprivate.h"
 #include "gdkglversionprivate.h"
+#include "gdkdmabufformatsbuilderprivate.h"
 
 G_BEGIN_DECLS
 
@@ -159,5 +160,28 @@ gboolean                gdk_gl_context_has_sync                 (GdkGLContext
 
 double                  gdk_gl_context_get_scale                (GdkGLContext    *self);
 
-G_END_DECLS
+void                    gdk_gl_context_add_dmabuf_formats       (GdkGLContext            *self,
+                                                                 GdkDmabufFormatsBuilder *builder);
 
+guint                   gdk_gl_context_import_dmabuf            (GdkGLContext    *self,
+                                                                 int              width,
+                                                                 int              height,
+                                                                 unsigned int     fourcc,
+                                                                 guint64          modifier,
+                                                                 unsigned int     n_planes,
+                                                                 int             *fds,
+                                                                 unsigned int    *strides,
+                                                                 unsigned int    *offsets);
+
+gboolean                gdk_gl_context_export_dmabuf            (GdkGLContext    *self,
+                                                                 unsigned int     texture_id,
+                                                                 int             *fourcc,
+                                                                 int             *n_planes,
+                                                                 guint64         *modifier,
+                                                                 int             *fds,
+                                                                 int             *strides,
+                                                                 int             *offsets);
+
+
+
+G_END_DECLS

gsk/gl/gskgldriver.c

@@ -44,6 +44,8 @@
 #include <gdk/gdktextureprivate.h>
 
 #include <gdk/gdkmemoryformatprivate.h>
+#include <gdk/gdkdmabuftextureprivate.h>
+
 
 G_DEFINE_TYPE (GskGLDriver, gsk_gl_driver, G_TYPE_OBJECT)
 
@@ -399,7 +401,6 @@ gsk_gl_driver_load_programs (GskGLDriver  *self,
          g_steal_pointer (&program);                                                            \
   } G_STMT_END;
 # include "gskglprograms.defs"
-#undef GSK_GL_DEFINE_PROGRAM_CLIP
 #undef GSK_GL_DEFINE_PROGRAM
 #undef GSK_GL_ADD_UNIFORM
 #undef GSK_GL_SHADER_SINGLE
@@ -759,7 +760,19 @@ gsk_gl_driver_load_texture (GskGLDriver *self,
       return t->texture_id;
     }
 
-  if (GDK_IS_GL_TEXTURE (texture))
+  if (GDK_IS_DMABUF_TEXTURE (texture))
+    {
+      texture_id = gdk_gl_context_import_dmabuf (context,
+                                                 gdk_texture_get_width (texture),
+                                                 gdk_texture_get_height (texture),
+                                                 gdk_dmabuf_texture_get_fourcc (GDK_DMABUF_TEXTURE (texture)),
+                                                 gdk_dmabuf_texture_get_modifier (GDK_DMABUF_TEXTURE (texture)),
+                                                 gdk_dmabuf_texture_get_n_planes (GDK_DMABUF_TEXTURE (texture)),
+                                                 gdk_dmabuf_texture_get_fds (GDK_DMABUF_TEXTURE (texture)),
+                                                 gdk_dmabuf_texture_get_strides (GDK_DMABUF_TEXTURE (texture)),
+                                                 gdk_dmabuf_texture_get_offsets (GDK_DMABUF_TEXTURE (texture)));
+    }
+  else if (GDK_IS_GL_TEXTURE (texture))
     {
       GdkGLTexture *gl_texture = (GdkGLTexture *) texture;
       GdkGLContext *texture_context = gdk_gl_texture_get_context (gl_texture);
@@ -1004,9 +1017,9 @@ gsk_gl_driver_release_render_target (GskGLDriver       *self,
       texture_id = render_target->texture_id;
 
       texture = gsk_gl_texture_new (render_target->texture_id,
-                                     render_target->width,
-                                     render_target->height,
-                                     self->current_frame_id);
+                                    render_target->width,
+                                    render_target->height,
+                                    self->current_frame_id);
       g_hash_table_insert (self->textures,
                            GUINT_TO_POINTER (texture_id),
                            g_steal_pointer (&texture));

gsk/gl/gskglrenderjob.c

@@ -30,6 +30,7 @@
 #include <gsk/gskglshaderprivate.h>
 #include <gdk/gdktextureprivate.h>
 #include <gdk/gdkmemorytextureprivate.h>
+#include <gdk/gdkdmabuftexture.h>
 #include <gsk/gsktransformprivate.h>
 #include <gsk/gskroundedrectprivate.h>
 #include <gsk/gskrectprivate.h>
@@ -47,6 +48,7 @@
 #include "ninesliceprivate.h"
 #include "fp16private.h"
 
+
 #define ORTHO_NEAR_PLANE   -10000
 #define ORTHO_FAR_PLANE     10000
 #define MAX_GRADIENT_STOPS  6
@@ -3630,16 +3632,12 @@ gsk_gl_render_job_upload_texture (GskGLRenderJob       *job,
                                   gboolean              ensure_mipmap,
                                   GskGLRenderOffscreen *offscreen)
 {
-  GdkGLTexture *gl_texture = NULL;
-
-  if (GDK_IS_GL_TEXTURE (texture))
-    gl_texture = GDK_GL_TEXTURE (texture);
-
+  /* Don't put GL or dma-buf textures into icon caches, they are already on the GPU side */
   if (!ensure_mipmap &&
       gsk_gl_texture_library_can_cache ((GskGLTextureLibrary *)job->driver->icons_library,
                                         texture->width,
                                         texture->height) &&
-      !gl_texture)
+      !(GDK_IS_GL_TEXTURE (texture) || GDK_IS_DMABUF_TEXTURE (texture)))
     {
       const GskGLIconData *icon_data;
 
@@ -3653,16 +3651,18 @@ gsk_gl_render_job_upload_texture (GskGLRenderJob       *job,
       /* Only generate a mipmap if it does not make use reupload
        * a GL texture which we could otherwise use directly.
        */
-      if (gl_texture &&
-          gdk_gl_context_is_shared (gdk_gl_texture_get_context (gl_texture), job->command_queue->context))
-        ensure_mipmap = gdk_gl_texture_has_mipmap (gl_texture);
+      if (GDK_IS_GL_TEXTURE (texture) &&
+          gdk_gl_context_is_shared (gdk_gl_texture_get_context (GDK_GL_TEXTURE (texture)),
+                                    job->command_queue->context))
+        ensure_mipmap = gdk_gl_texture_has_mipmap (GDK_GL_TEXTURE (texture));
 
       offscreen->texture_id = gsk_gl_driver_load_texture (job->driver, texture, ensure_mipmap);
       init_full_texture_region (offscreen);
       offscreen->has_mipmap = ensure_mipmap;
 
-      if (gl_texture && offscreen->texture_id == gdk_gl_texture_get_id (gl_texture))
-        offscreen->sync = gdk_gl_texture_get_sync (gl_texture);
+      if (GDK_IS_GL_TEXTURE (texture) &&
+          offscreen->texture_id == gdk_gl_texture_get_id (GDK_GL_TEXTURE (texture)))
+        offscreen->sync = gdk_gl_texture_get_sync (GDK_GL_TEXTURE (texture));
     }
 }
 

tests/meson.build

@@ -1,5 +1,6 @@
 gtk_tests = [
   # testname, optional extra sources
+  ['testdmabuf'],
   ['testsections'],
   ['testfilelauncher'],
   ['input'],

tests/testdmabuf.c

@@ -0,0 +1,442 @@
+#include <gtk/gtk.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <linux/dma-heap.h>
+#include <drm/drm_fourcc.h>
+
+/* For this to work, you may need to give /dev/dma_heap/system
+ * lax permissions.
+ */
+
+static int
+allocate_dma_buf (gsize size)
+{
+  static int fd = -1;
+  struct dma_heap_allocation_data heap_data;
+  int ret;
+
+  if (fd == -1)
+    {
+      fd = open ("/dev/dma_heap/system", O_RDONLY | O_CLOEXEC);
+      if (fd == -1)
+        g_error ("Failed to open /dev/dma_heap/system");
+    }
+
+  heap_data.len = size;
+  heap_data.fd = 0;
+  heap_data.fd_flags = O_RDWR | O_CLOEXEC;
+  heap_data.heap_flags = 0;
+
+  ret = ioctl (fd, DMA_HEAP_IOCTL_ALLOC, &heap_data);
+  if (ret)
+    g_error ("dma-buf allocation failed");
+
+  return heap_data.fd;
+}
+
+static void
+populate_dma_buf (int     fd,
+                  guchar *data,
+                  gsize   size)
+{
+  guchar *buf;
+
+  buf = mmap (NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
+  memcpy (buf, data, size);
+  munmap (buf, size);
+}
+
+
+/* The YUV conversion code is adapted from weston/tests/yuv-buffer-test.c */
+
+/*
+ * Based on Rec. ITU-R BT.601-7
+ *
+ * This is intended to be obvious and accurate, not fast.
+ */
+static void
+x8r8g8b8_to_ycbcr8_bt601 (guint32 xrgb,
+                          guchar *y_out,
+                          guchar *cb_out,
+                          guchar *cr_out)
+{
+  double y, cb, cr;
+  double r = (xrgb >> 16) & 0xff;
+  double g = (xrgb >> 8) & 0xff;
+  double b = (xrgb >> 0) & 0xff;
+
+  /* normalize to [0.0, 1.0] */
+  r /= 255.0;
+  g /= 255.0;
+  b /= 255.0;
+
+  /* Y normalized to [0.0, 1.0], Cb and Cr [-0.5, 0.5] */
+  y = 0.299 * r + 0.587 * g + 0.114 * b;
+  cr = (r - y) / 1.402;
+  cb = (b - y) / 1.772;
+
+  /* limited range quantization to 8 bit */
+  *y_out = round(219.0 * y + 16.0);
+  if (cr_out)
+    *cr_out = round(224.0 * cr + 128.0);
+  if (cb_out)
+    *cb_out = round(224.0 * cb + 128.0);
+}
+
+/*
+ * 3 plane YCbCr
+ * plane 0: Y plane, [7:0] Y
+ * plane 1: Cb plane, [7:0] Cb
+ * plane 2: Cr plane, [7:0] Cr
+ * YUV420: 2x2 subsampled Cb (1) and Cr (2) planes
+ * YUV444: no subsampling
+ */
+static guchar *
+y_u_v_create_buffer (uint32_t  drm_format,
+                     guchar   *rgb_data,
+                     int       rgb_width,
+                     int       rgb_height,
+                     int      *size,
+                     int      *u_offset,
+                     int      *v_offset)
+{
+  gsize bytes;
+  int x, y;
+  guint32 *rgb_row;
+  guchar *y_base;
+  guchar *u_base;
+  guchar *v_base;
+  guchar *y_row;
+  guchar *u_row;
+  guchar *v_row;
+  guint32 argb;
+  int sub = (drm_format == DRM_FORMAT_YUV420) ? 2 : 1;
+  guchar *buf;
+
+  g_assert (drm_format == DRM_FORMAT_YUV420 ||
+            drm_format == DRM_FORMAT_YUV444);
+
+  /* Full size Y plus quarter U and V */
+  bytes = rgb_width * rgb_height +
+          (rgb_width / sub) * (rgb_height / sub) * 2;
+
+  buf = g_new (guchar, bytes);
+
+  *size = bytes;
+  *u_offset = rgb_width * rgb_height;
+  *v_offset = *u_offset + (rgb_width / sub) * (rgb_height / sub);
+
+  y_base = buf;
+  u_base = y_base + rgb_width * rgb_height;
+  v_base = u_base + (rgb_width / sub) * (rgb_height / sub);
+
+  for (y = 0; y < rgb_height; y++)
+    {
+      rgb_row = (guint32 *) (rgb_data + y * 4 * rgb_width);
+      y_row = y_base + y * rgb_width;
+      u_row = u_base + (y / sub) * (rgb_width / sub);
+      v_row = v_base + (y / sub) * (rgb_width / sub);
+
+      for (x = 0; x < rgb_width; x++)
+        {
+          /*
+           * Sub-sample the source image instead, so that U and V
+           * sub-sampling does not require proper
+           * filtering/averaging/siting.
+           */
+          argb = *(rgb_row + x / 2 * 2);
+
+          /*
+           * A stupid way of "sub-sampling" chroma. This does not
+           * do the necessary filtering/averaging/siting or
+           * alternate Cb/Cr rows.
+           */
+          if ((y & (sub - 1)) == 0 && (x & (sub - 1)) == 0)
+            x8r8g8b8_to_ycbcr8_bt601 (argb, y_row + x, u_row + x / sub, v_row + x / sub);
+          else
+            x8r8g8b8_to_ycbcr8_bt601 (argb, y_row + x, NULL, NULL);
+        }
+    }
+
+  return buf;
+}
+
+/*
+ * 2 plane YCbCr
+ * plane 0 = Y plane, [7:0] Y
+ * plane 1 = Cr:Cb plane, [15:0] Cr:Cb little endian
+ * 2x2 subsampled Cr:Cb plane
+ */
+static guchar *
+nv12_create_buffer (uint32_t drm_format,
+                    guchar   *rgb_data,
+                    int       rgb_width,
+                    int       rgb_height,
+                    int      *size,
+                    int      *uv_offset)
+{
+  size_t bytes;
+  int x, y;
+  uint32_t *rgb_row;
+  uint8_t *y_base;
+  uint16_t *uv_base;
+  uint8_t *y_row;
+  uint16_t *uv_row;
+  uint32_t argb;
+  uint8_t cr;
+  uint8_t cb;
+  guchar *buf;
+
+  g_assert (drm_format == DRM_FORMAT_NV12);
+
+  /* Full size Y, quarter UV */
+  bytes = rgb_width * rgb_height +
+          (rgb_width / 2) * (rgb_height / 2) * sizeof (uint16_t);
+
+  buf = g_new0 (guchar, bytes);
+
+  *uv_offset = rgb_width * rgb_height;
+  y_base = buf;
+  uv_base = (uint16_t *)(y_base + rgb_width * rgb_height);
+
+  for (y = 0; y < rgb_height; y++)
+    {
+      rgb_row = (uint32_t *) (rgb_data + y * 4 * rgb_width);
+      y_row = y_base + y * rgb_width;
+      uv_row = (uint16_t *) (uv_base + (y / 2) * (rgb_width / 2));
+
+      for (x = 0; x < rgb_width; x++)
+        {
+          /*
+           * Sub-sample the source image instead, so that U and V
+           * sub-sampling does not require proper
+           * filtering/averaging/siting.
+           */
+          argb = *(rgb_row + x / 2 * 2);
+
+          /*
+           * A stupid way of "sub-sampling" chroma. This does not
+           * do the necessary filtering/averaging/siting.
+           */
+          if ((y & 1) == 0 && (x & 1) == 0)
+            {
+              x8r8g8b8_to_ycbcr8_bt601(argb, y_row + x, &cb, &cr);
+              *(uv_row + x / 2) = ((uint16_t)cr << 8) | cb;
+            }
+          else
+            {
+              x8r8g8b8_to_ycbcr8_bt601(argb, y_row + x, NULL, NULL);
+            }
+        }
+    }
+
+  return buf;
+}
+
+static GdkTexture *
+make_dmabuf_texture (const char *filename,
+                     guint32     format)
+{
+  GdkTexture *texture;
+  int width, height;
+  gsize rgb_stride, rgb_size;
+  guchar *rgb_data;
+  int fd;
+  GdkDmabufTextureBuilder *builder;
+  GError *error = NULL;
+
+  texture = gdk_texture_new_from_filename (filename, NULL);
+
+  width = gdk_texture_get_width (texture);
+  height = gdk_texture_get_height (texture);
+  rgb_stride = 4 * width;
+  rgb_size = rgb_stride * height;
+
+  rgb_data = g_new0 (guchar, rgb_size);
+
+  gdk_texture_download (texture, rgb_data, rgb_stride);
+
+  g_object_unref (texture);
+
+  builder = gdk_dmabuf_texture_builder_new ();
+
+  gdk_dmabuf_texture_builder_set_display (builder, gdk_display_get_default ());
+  gdk_dmabuf_texture_builder_set_width (builder, width);
+  gdk_dmabuf_texture_builder_set_height (builder, height);
+  gdk_dmabuf_texture_builder_set_fourcc (builder, format);
+  gdk_dmabuf_texture_builder_set_modifier (builder, DRM_FORMAT_MOD_LINEAR);
+
+  if (format == DRM_FORMAT_XRGB8888)
+    {
+      gdk_dmabuf_texture_builder_set_n_planes (builder, 1);
+
+      fd = allocate_dma_buf (rgb_size);
+      populate_dma_buf (fd, rgb_data, rgb_size);
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 0, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 0, rgb_stride);
+    }
+  else if (format == DRM_FORMAT_YUV420)
+    {
+      guchar *buf;
+      int size, u_offset, v_offset;
+
+      gdk_dmabuf_texture_builder_set_n_planes (builder, 3);
+
+      buf = y_u_v_create_buffer (format, rgb_data, width, height, &size, &u_offset, &v_offset);
+
+      fd = allocate_dma_buf (width * height);
+      populate_dma_buf (fd, buf, width * height);
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 0, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 0, width);
+      gdk_dmabuf_texture_builder_set_offset (builder, 0, 0);
+
+      fd = allocate_dma_buf ((width / 2) * (height / 2));
+      populate_dma_buf (fd, buf + u_offset, (width / 2) * (height / 2));
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 1, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 1, width / 2);
+      gdk_dmabuf_texture_builder_set_offset (builder, 1, 0);
+
+      fd = allocate_dma_buf ((width / 2) * (height / 2));
+      populate_dma_buf (fd, buf + v_offset, (width / 2) * (height / 2));
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 2, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 2, width / 2);
+      gdk_dmabuf_texture_builder_set_offset (builder, 2, 0);
+
+      g_free (buf);
+    }
+  else if (format == DRM_FORMAT_NV12)
+    {
+      guchar *buf;
+      int size, uv_offset;
+
+      gdk_dmabuf_texture_builder_set_n_planes (builder, 2);
+
+      buf = nv12_create_buffer (format, rgb_data, width, height, &size, &uv_offset);
+
+      fd = allocate_dma_buf (width * height);
+      populate_dma_buf (fd, buf, width * height);
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 0, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 0, width);
+      gdk_dmabuf_texture_builder_set_offset (builder, 0, 0);
+
+      fd = allocate_dma_buf ((width / 2) * (height / 2) * sizeof (uint16_t));
+      populate_dma_buf (fd, buf + uv_offset, (width / 2) * (height / 2) * sizeof (uint16_t));
+
+      gdk_dmabuf_texture_builder_set_fd (builder, 1, fd);
+      gdk_dmabuf_texture_builder_set_stride (builder, 1, width);
+      gdk_dmabuf_texture_builder_set_offset (builder, 1, 0);
+
+      g_free (buf);
+    }
+
+  g_free (rgb_data);
+
+  texture = gdk_dmabuf_texture_builder_build (builder, NULL, NULL, &error);
+  if (!texture)
+    g_error ("Failed to create dmabuf texture: %s", error->message);
+
+  g_object_unref (builder);
+
+  return texture;
+}
+
+static guint32 supported_formats[] = {
+  DRM_FORMAT_XRGB8888,
+  DRM_FORMAT_YUV420,
+  DRM_FORMAT_NV12,
+};
+
+static gboolean
+format_is_supported (guint32 fmt)
+{
+  for (int i = 0; i < G_N_ELEMENTS (supported_formats); i++)
+    {
+      if (supported_formats[i] == fmt)
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
+static char *
+supported_formats_to_string (void)
+{
+  GString *s;
+
+  s = g_string_new ("");
+  for (int i = 0; i < G_N_ELEMENTS (supported_formats); i++)
+    {
+      if (s->len)
+        g_string_append (s, ", ");
+      g_string_append_printf (s, "%.4s", (char *)&supported_formats[i]);
+    }
+
+  return g_string_free (s, FALSE);
+}
+
+static void
+usage (void)
+{
+  char *formats = supported_formats_to_string ();
+  g_print ("Usage: testdmabuf FORMAT FILE\n"
+           "Supported formats: %s\n", formats);
+  g_free (formats);
+  exit (1);
+}
+
+static guint32
+parse_format (const char *a)
+{
+  if (strlen (a) == 4)
+    {
+      guint32 format = fourcc_code (a[0], a[1], a[2], a[3]);
+      if (format_is_supported (format))
+        return format;
+    }
+
+  usage ();
+  return 0;
+}
+
+int
+main (int argc, char *argv[])
+{
+  GdkTexture *texture;
+  GtkWidget *window, *picture;
+  char *filename;
+  guint32 format;
+
+  if (argc != 3)
+  g_assert (argc == 3);
+
+  format = parse_format (argv[1]);
+  filename = argv[2];
+
+  gtk_init ();
+
+  /* Get the list of supported formats with GDK_DEBUG=opengl */
+  gdk_display_get_dmabuf_formats (gdk_display_get_default ());
+
+  texture = make_dmabuf_texture (filename, format);
+
+  gdk_texture_save_to_png (texture, "testdmabuf.out.png");
+
+  window = gtk_window_new ();
+
+  picture = gtk_picture_new_for_paintable (GDK_PAINTABLE (texture));
+
+  gtk_window_set_child (GTK_WINDOW (window), picture);
+
+  gtk_window_present (GTK_WINDOW (window));
+
+  while (g_list_model_get_n_items (gtk_window_get_toplevels ()) > 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  return 0;
+}