drm: allow passing a real encoder object for wb connector

Instead of creating an internal encoder for the writeback
connector to satisfy DRM requirements, allow the clients
to pass a real encoder to it by changing the drm_writeback's
encoder to a pointer.

If a real encoder is not passed, drm_writeback_connector_init
will internally allocate one.

This will help the clients to manage the real encoder states
better as they will allocate and maintain the encoder.

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

drivers/gpu/drm/drm_writeback.c

@@ -189,8 +189,11 @@ int drm_writeback_connector_init(struct drm_device *dev,
 	if (IS_ERR(blob))
 		return PTR_ERR(blob);
 
-	drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
-	ret = drm_encoder_init(dev, &wb_connector->encoder,
+	/* allocate the internal drm encoder if a real one wasnt passed */
+	if (!wb_connector->encoder)
+		wb_connector->encoder = devm_kzalloc(dev->dev, sizeof(struct drm_encoder), GFP_KERNEL);
+	drm_encoder_helper_add(wb_connector->encoder, enc_helper_funcs);
+	ret = drm_encoder_init(dev, wb_connector->encoder,
 			       &drm_writeback_encoder_funcs,
 			       DRM_MODE_ENCODER_VIRTUAL, NULL);
 	if (ret)
@@ -204,7 +207,7 @@ int drm_writeback_connector_init(struct drm_device *dev,
 		goto connector_fail;
 
 	ret = drm_connector_attach_encoder(connector,
-						&wb_connector->encoder);
+						wb_connector->encoder);
 	if (ret)
 		goto attach_fail;
 
@@ -233,7 +236,7 @@ int drm_writeback_connector_init(struct drm_device *dev,
 attach_fail:
 	drm_connector_cleanup(connector);
 connector_fail:
-	drm_encoder_cleanup(&wb_connector->encoder);
+	drm_encoder_cleanup(wb_connector->encoder);
 fail:
 	drm_property_blob_put(blob);
 	return ret;

include/drm/drm_writeback.h

@@ -31,7 +31,7 @@ struct drm_writeback_connector {
 	 * by passing the @enc_funcs parameter to drm_writeback_connector_init()
 	 * function.
 	 */
-	struct drm_encoder encoder;
+	struct drm_encoder *encoder;
 
 	/**
 	 * @pixel_formats_blob_ptr: