1 files changed, 42 insertions, 4 deletions

diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
index 15fb516ae2d8..74946690aba4 100644
--- a/drivers/gpu/drm/drm_simple_kms_helper.c
+++ b/drivers/gpu/drm/drm_simple_kms_helper.c
@@ -26,12 +26,51 @@
  * entity. Some flexibility for code reuse is provided through a separately
  * allocated &drm_connector object and supporting optional &drm_bridge
  * encoder drivers.
+ *
+ * Many drivers require only a very simple encoder that fulfills the minimum
+ * requirements of the display pipeline and does not add additional
+ * functionality. The function drm_simple_encoder_init() provides an
+ * implementation of such an encoder.
  */
 
-static const struct drm_encoder_funcs drm_simple_kms_encoder_funcs = {
+static const struct drm_encoder_funcs drm_simple_encoder_funcs_cleanup = {
 	.destroy = drm_encoder_cleanup,
 };
 
+/**
+ * drm_simple_encoder_init - Initialize a preallocated encoder with
+ *                           basic functionality.
+ * @dev: drm device
+ * @encoder: the encoder to initialize
+ * @encoder_type: user visible type of the encoder
+ *
+ * Initialises a preallocated encoder that has no further functionality.
+ * Settings for possible CRTC and clones are left to their initial values.
+ * The encoder will be cleaned up automatically as part of the mode-setting
+ * cleanup.
+ *
+ * The caller of drm_simple_encoder_init() is responsible for freeing
+ * the encoder's memory after the encoder has been cleaned up. At the
+ * moment this only works reliably if the encoder data structure is
+ * stored in the device structure. Free the encoder's memory as part of
+ * the device release function.
+ *
+ * FIXME: Later improvements to DRM's resource management may allow for
+ *        an automated kfree() of the encoder's memory.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_simple_encoder_init(struct drm_device *dev,
+			    struct drm_encoder *encoder,
+			    int encoder_type)
+{
+	return drm_encoder_init(dev, encoder,
+				&drm_simple_encoder_funcs_cleanup,
+				encoder_type, NULL);
+}
+EXPORT_SYMBOL(drm_simple_encoder_init);
+
 static enum drm_mode_status
 drm_simple_kms_crtc_mode_valid(struct drm_crtc *crtc,
 			       const struct drm_display_mode *mode)
@@ -229,7 +268,7 @@ static const struct drm_plane_funcs drm_simple_kms_plane_funcs = {
 int drm_simple_display_pipe_attach_bridge(struct drm_simple_display_pipe *pipe,
 					  struct drm_bridge *bridge)
 {
-	return drm_bridge_attach(&pipe->encoder, bridge, NULL);
+	return drm_bridge_attach(&pipe->encoder, bridge, NULL, 0);
 }
 EXPORT_SYMBOL(drm_simple_display_pipe_attach_bridge);
 
@@ -288,8 +327,7 @@ int drm_simple_display_pipe_init(struct drm_device *dev,
 		return ret;
 
 	encoder->possible_crtcs = drm_crtc_mask(crtc);
-	ret = drm_encoder_init(dev, encoder, &drm_simple_kms_encoder_funcs,
-			       DRM_MODE_ENCODER_NONE, NULL);
+	ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_NONE);
 	if (ret || !connector)
 		return ret;