diff --git a/include/sound/dmaengine_pcm.h b/include/sound/dmaengine_pcm.h
index b1d1150..f11c35c 100644
--- a/include/sound/dmaengine_pcm.h
+++ b/include/sound/dmaengine_pcm.h
@@ -91,6 +91,11 @@
  * bytes that are still left to transfer.
  */
 #define SND_DMAENGINE_PCM_FLAG_NO_RESIDUE BIT(2)
+/*
+ * The PCM is half duplex and the DMA channel is shared between capture and
+ * playback.
+ */
+#define SND_DMAENGINE_PCM_FLAG_HALF_DUPLEX BIT(3)
 
 /**
  * struct snd_dmaengine_pcm_config - Configuration data for dmaengine based PCM