drm/dumb-buffers: Add defaults for .dumb_map_offset and .dumb_destroy

Almost everyone did end up using GEM as bo, so this adds defaults
for the drm_driver.dumb_destroy and drm_driver.dumb_map_offset
callbacks.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1500837417-40580-3-git-send-email-noralf@tronnes.org

drivers/gpu/drm/drm_dumb_buffers.c

@@ -24,6 +24,7 @@
  */
 
 #include <drm/drmP.h>
+#include <drm/drm_gem.h>
 
 #include "drm_crtc_internal.h"
 
@@ -42,9 +43,10 @@
  * create dumb buffers suitable for scanout, which can then be used to create
  * KMS frame buffers.
  *
- * To support dumb objects drivers must implement the &drm_driver.dumb_create,
- * &drm_driver.dumb_destroy and &drm_driver.dumb_map_offset operations. See
- * there for further details.
+ * To support dumb objects drivers must implement the &drm_driver.dumb_create
+ * operation. &drm_driver.dumb_destroy defaults to drm_gem_dumb_destroy() if
+ * not set and &drm_driver.dumb_map_offset defaults to
+ * drm_gem_dumb_map_offset(). See the callbacks for further details.
  *
  * Note that dumb objects may not be used for gpu acceleration, as has been
  * attempted on some ARM embedded platforms. Such drivers really must have
@@ -108,11 +110,16 @@ int drm_mode_mmap_dumb_ioctl(struct drm_device *dev,
 {
 	struct drm_mode_map_dumb *args = data;
 
-	/* call driver ioctl to get mmap offset */
-	if (!dev->driver->dumb_map_offset)
+	if (!dev->driver->dumb_create)
 		return -ENOSYS;
 
-	return dev->driver->dumb_map_offset(file_priv, dev, args->handle, &args->offset);
+	if (dev->driver->dumb_map_offset)
+		return dev->driver->dumb_map_offset(file_priv, dev,
+						    args->handle,
+						    &args->offset);
+	else
+		return drm_gem_dumb_map_offset(file_priv, dev, args->handle,
+					       &args->offset);
 }
 
 int drm_mode_destroy_dumb_ioctl(struct drm_device *dev,
@@ -120,9 +127,12 @@ int drm_mode_destroy_dumb_ioctl(struct drm_device *dev,
 {
 	struct drm_mode_destroy_dumb *args = data;
 
-	if (!dev->driver->dumb_destroy)
+	if (!dev->driver->dumb_create)
 		return -ENOSYS;
 
+	if (dev->driver->dumb_destroy)
 		return dev->driver->dumb_destroy(file_priv, dev, args->handle);
+	else
+		return drm_gem_dumb_destroy(file_priv, dev, args->handle);
 }