diff --git a/drivers/staging/greybus/audio_codec.h b/drivers/staging/greybus/audio_codec.h
index d36f8cd35e06..9ba09ea9c2fc 100644
--- a/drivers/staging/greybus/audio_codec.h
+++ b/drivers/staging/greybus/audio_codec.h
@@ -173,66 +173,66 @@ int gbaudio_register_module(struct gbaudio_module_info *module);
 void gbaudio_unregister_module(struct gbaudio_module_info *module);
 
 /* protocol related */
-extern int gb_audio_gb_get_topology(struct gb_connection *connection,
-				    struct gb_audio_topology **topology);
-extern int gb_audio_gb_get_control(struct gb_connection *connection,
-				   u8 control_id, u8 index,
-				   struct gb_audio_ctl_elem_value *value);
-extern int gb_audio_gb_set_control(struct gb_connection *connection,
-				   u8 control_id, u8 index,
-				   struct gb_audio_ctl_elem_value *value);
-extern int gb_audio_gb_enable_widget(struct gb_connection *connection,
-				     u8 widget_id);
-extern int gb_audio_gb_disable_widget(struct gb_connection *connection,
-				      u8 widget_id);
-extern int gb_audio_gb_get_pcm(struct gb_connection *connection,
-			       u16 data_cport, u32 *format,
-			       u32 *rate, u8 *channels,
-			       u8 *sig_bits);
-extern int gb_audio_gb_set_pcm(struct gb_connection *connection,
-			       u16 data_cport, u32 format,
-			       u32 rate, u8 channels,
-			       u8 sig_bits);
-extern int gb_audio_gb_set_tx_data_size(struct gb_connection *connection,
-					u16 data_cport, u16 size);
-extern int gb_audio_gb_activate_tx(struct gb_connection *connection,
-				   u16 data_cport);
-extern int gb_audio_gb_deactivate_tx(struct gb_connection *connection,
-				     u16 data_cport);
-extern int gb_audio_gb_set_rx_data_size(struct gb_connection *connection,
-					u16 data_cport, u16 size);
-extern int gb_audio_gb_activate_rx(struct gb_connection *connection,
-				   u16 data_cport);
-extern int gb_audio_gb_deactivate_rx(struct gb_connection *connection,
-				     u16 data_cport);
-extern int gb_audio_apbridgea_set_config(struct gb_connection *connection,
-					 __u16 i2s_port, __u32 format,
-					 __u32 rate, __u32 mclk_freq);
-extern int gb_audio_apbridgea_register_cport(struct gb_connection *connection,
-					     __u16 i2s_port, __u16 cportid,
-					     __u8 direction);
-extern int gb_audio_apbridgea_unregister_cport(struct gb_connection *connection,
-					       __u16 i2s_port, __u16 cportid,
-					       __u8 direction);
-extern int gb_audio_apbridgea_set_tx_data_size(struct gb_connection *connection,
-					       __u16 i2s_port, __u16 size);
-extern int gb_audio_apbridgea_prepare_tx(struct gb_connection *connection,
-					 __u16 i2s_port);
-extern int gb_audio_apbridgea_start_tx(struct gb_connection *connection,
-				       __u16 i2s_port, __u64 timestamp);
-extern int gb_audio_apbridgea_stop_tx(struct gb_connection *connection,
-				      __u16 i2s_port);
-extern int gb_audio_apbridgea_shutdown_tx(struct gb_connection *connection,
-					  __u16 i2s_port);
-extern int gb_audio_apbridgea_set_rx_data_size(struct gb_connection *connection,
-					       __u16 i2s_port, __u16 size);
-extern int gb_audio_apbridgea_prepare_rx(struct gb_connection *connection,
-					 __u16 i2s_port);
-extern int gb_audio_apbridgea_start_rx(struct gb_connection *connection,
-				       __u16 i2s_port);
-extern int gb_audio_apbridgea_stop_rx(struct gb_connection *connection,
-				      __u16 i2s_port);
-extern int gb_audio_apbridgea_shutdown_rx(struct gb_connection *connection,
-					  __u16 i2s_port);
+int gb_audio_gb_get_topology(struct gb_connection *connection,
+			     struct gb_audio_topology **topology);
+int gb_audio_gb_get_control(struct gb_connection *connection,
+			    u8 control_id, u8 index,
+			    struct gb_audio_ctl_elem_value *value);
+int gb_audio_gb_set_control(struct gb_connection *connection,
+			    u8 control_id, u8 index,
+			    struct gb_audio_ctl_elem_value *value);
+int gb_audio_gb_enable_widget(struct gb_connection *connection,
+			      u8 widget_id);
+int gb_audio_gb_disable_widget(struct gb_connection *connection,
+			       u8 widget_id);
+int gb_audio_gb_get_pcm(struct gb_connection *connection,
+			u16 data_cport, u32 *format,
+			u32 *rate, u8 *channels,
+			u8 *sig_bits);
+int gb_audio_gb_set_pcm(struct gb_connection *connection,
+			u16 data_cport, u32 format,
+			u32 rate, u8 channels,
+			u8 sig_bits);
+int gb_audio_gb_set_tx_data_size(struct gb_connection *connection,
+				 u16 data_cport, u16 size);
+int gb_audio_gb_activate_tx(struct gb_connection *connection,
+			    u16 data_cport);
+int gb_audio_gb_deactivate_tx(struct gb_connection *connection,
+			      u16 data_cport);
+int gb_audio_gb_set_rx_data_size(struct gb_connection *connection,
+				 u16 data_cport, u16 size);
+int gb_audio_gb_activate_rx(struct gb_connection *connection,
+			    u16 data_cport);
+int gb_audio_gb_deactivate_rx(struct gb_connection *connection,
+			      u16 data_cport);
+int gb_audio_apbridgea_set_config(struct gb_connection *connection,
+				  __u16 i2s_port, __u32 format,
+				  __u32 rate, __u32 mclk_freq);
+int gb_audio_apbridgea_register_cport(struct gb_connection *connection,
+				      __u16 i2s_port, __u16 cportid,
+				      __u8 direction);
+int gb_audio_apbridgea_unregister_cport(struct gb_connection *connection,
+					__u16 i2s_port, __u16 cportid,
+					__u8 direction);
+int gb_audio_apbridgea_set_tx_data_size(struct gb_connection *connection,
+					__u16 i2s_port, __u16 size);
+int gb_audio_apbridgea_prepare_tx(struct gb_connection *connection,
+				  __u16 i2s_port);
+int gb_audio_apbridgea_start_tx(struct gb_connection *connection,
+				__u16 i2s_port, __u64 timestamp);
+int gb_audio_apbridgea_stop_tx(struct gb_connection *connection,
+			       __u16 i2s_port);
+int gb_audio_apbridgea_shutdown_tx(struct gb_connection *connection,
+				   __u16 i2s_port);
+int gb_audio_apbridgea_set_rx_data_size(struct gb_connection *connection,
+					__u16 i2s_port, __u16 size);
+int gb_audio_apbridgea_prepare_rx(struct gb_connection *connection,
+				  __u16 i2s_port);
+int gb_audio_apbridgea_start_rx(struct gb_connection *connection,
+				__u16 i2s_port);
+int gb_audio_apbridgea_stop_rx(struct gb_connection *connection,
+			       __u16 i2s_port);
+int gb_audio_apbridgea_shutdown_rx(struct gb_connection *connection,
+				   __u16 i2s_port);
 
 #endif /* __LINUX_GBAUDIO_CODEC_H */