diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h
index 13d98e6e0db1a86f46cc7d77b5652bef0c8682d2..74e520fb944f7dbdf6426e75b5db5312a80b05ee 100644
--- a/include/uapi/linux/usb/audio.h
+++ b/include/uapi/linux/usb/audio.h
@@ -230,6 +230,14 @@ struct uac1_output_terminal_descriptor {
 #define UAC_OUTPUT_TERMINAL_COMMUNICATION_SPEAKER	0x306
 #define UAC_OUTPUT_TERMINAL_LOW_FREQ_EFFECTS_SPEAKER	0x307
 
+/* Terminals - 2.4 Bi-directional Terminal Types */
+#define UAC_BIDIR_TERMINAL_UNDEFINED			0x400
+#define UAC_BIDIR_TERMINAL_HANDSET			0x401
+#define UAC_BIDIR_TERMINAL_HEADSET			0x402
+#define UAC_BIDIR_TERMINAL_SPEAKER_PHONE		0x403
+#define UAC_BIDIR_TERMINAL_ECHO_SUPPRESSING		0x404
+#define UAC_BIDIR_TERMINAL_ECHO_CANCELING		0x405
+
 /* Set bControlSize = 2 as default setting */
 #define UAC_DT_FEATURE_UNIT_SIZE(ch)		(7 + ((ch) + 1) * 2)