diff --git a/drivers/gpu/drm/drm_encoder_slave.c b/drivers/gpu/drm/drm_encoder_slave.c
index d18b88b..e862907 100644
--- a/drivers/gpu/drm/drm_encoder_slave.c
+++ b/drivers/gpu/drm/drm_encoder_slave.c
@@ -124,7 +124,7 @@ EXPORT_SYMBOL(drm_i2c_encoder_destroy);
  * Wrapper fxns which can be plugged in to drm_encoder_helper_funcs:
  */
 
-static inline struct drm_encoder_slave_funcs *
+static inline const struct drm_encoder_slave_funcs *
 get_slave_funcs(struct drm_encoder *enc)
 {
 	return to_encoder_slave(enc)->slave_funcs;
diff --git a/drivers/gpu/drm/nouveau/nouveau_encoder.h b/drivers/gpu/drm/nouveau/nouveau_encoder.h
index c38a864..ee6a6d3 100644
--- a/drivers/gpu/drm/nouveau/nouveau_encoder.h
+++ b/drivers/gpu/drm/nouveau/nouveau_encoder.h
@@ -83,7 +83,7 @@ static inline struct drm_encoder *to_drm_encoder(struct nouveau_encoder *enc)
 	return &enc->base.base;
 }
 
-static inline struct drm_encoder_slave_funcs *
+static inline const struct drm_encoder_slave_funcs *
 get_slave_funcs(struct drm_encoder *enc)
 {
 	return to_encoder_slave(enc)->slave_funcs;
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_hdmicon.c b/drivers/gpu/drm/rcar-du/rcar_du_hdmicon.c
index 96f2eb4..a37b6e2 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_hdmicon.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_hdmicon.c
@@ -28,7 +28,7 @@ static int rcar_du_hdmi_connector_get_modes(struct drm_connector *connector)
 {
 	struct rcar_du_connector *con = to_rcar_connector(connector);
 	struct drm_encoder *encoder = rcar_encoder_to_drm_encoder(con->encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (sfuncs->get_modes == NULL)
 		return 0;
@@ -41,7 +41,7 @@ static int rcar_du_hdmi_connector_mode_valid(struct drm_connector *connector,
 {
 	struct rcar_du_connector *con = to_rcar_connector(connector);
 	struct drm_encoder *encoder = rcar_encoder_to_drm_encoder(con->encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (sfuncs->mode_valid == NULL)
 		return MODE_OK;
@@ -66,7 +66,7 @@ rcar_du_hdmi_connector_detect(struct drm_connector *connector, bool force)
 {
 	struct rcar_du_connector *con = to_rcar_connector(connector);
 	struct drm_encoder *encoder = rcar_encoder_to_drm_encoder(con->encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (sfuncs->detect == NULL)
 		return connector_status_unknown;
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_hdmienc.c b/drivers/gpu/drm/rcar-du/rcar_du_hdmienc.c
index 11267de..2567efc 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_hdmienc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_hdmienc.c
@@ -35,7 +35,7 @@ struct rcar_du_hdmienc {
 static void rcar_du_hdmienc_disable(struct drm_encoder *encoder)
 {
 	struct rcar_du_hdmienc *hdmienc = to_rcar_hdmienc(encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (sfuncs->dpms)
 		sfuncs->dpms(encoder, DRM_MODE_DPMS_OFF);
@@ -50,7 +50,7 @@ static void rcar_du_hdmienc_disable(struct drm_encoder *encoder)
 static void rcar_du_hdmienc_enable(struct drm_encoder *encoder)
 {
 	struct rcar_du_hdmienc *hdmienc = to_rcar_hdmienc(encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (hdmienc->renc->lvds)
 		rcar_du_lvdsenc_enable(hdmienc->renc->lvds, encoder->crtc,
@@ -67,7 +67,7 @@ static int rcar_du_hdmienc_atomic_check(struct drm_encoder *encoder,
 					struct drm_connector_state *conn_state)
 {
 	struct rcar_du_hdmienc *hdmienc = to_rcar_hdmienc(encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 	struct drm_display_mode *adjusted_mode = &crtc_state->adjusted_mode;
 	const struct drm_display_mode *mode = &crtc_state->mode;
 
@@ -89,7 +89,7 @@ static void rcar_du_hdmienc_mode_set(struct drm_encoder *encoder,
 				     struct drm_display_mode *adjusted_mode)
 {
 	struct rcar_du_hdmienc *hdmienc = to_rcar_hdmienc(encoder);
-	struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
+	const struct drm_encoder_slave_funcs *sfuncs = to_slave_funcs(encoder);
 
 	if (sfuncs->mode_set)
 		sfuncs->mode_set(encoder, mode, adjusted_mode);
diff --git a/include/drm/drm_encoder_slave.h b/include/drm/drm_encoder_slave.h
index 8b9cc36..82cdf61 100644
--- a/include/drm/drm_encoder_slave.h
+++ b/include/drm/drm_encoder_slave.h
@@ -95,7 +95,7 @@ struct drm_encoder_slave_funcs {
 struct drm_encoder_slave {
 	struct drm_encoder base;
 
-	struct drm_encoder_slave_funcs *slave_funcs;
+	const struct drm_encoder_slave_funcs *slave_funcs;
 	void *slave_priv;
 	void *bus_priv;
 };
