diff --git a/include/tpm-common.h b/include/tpm-common.h
index 1ca5d28242679199f7fab4e1057f54abf990ab8e..e0ba696f1c9505fdff47e87dee5ffd75e492ea5b 100644
--- a/include/tpm-common.h
+++ b/include/tpm-common.h
@@ -35,6 +35,7 @@ enum tpm_duration {
  *
  * @duration_ms:	Length of each duration type in milliseconds
  * @retry_time_ms:	Time to wait before retrying receive
+ * @buf:		Buffer used during the exchanges with the chip
  */
 struct tpm_chip_priv {
 	uint duration_ms[TPM_DURATION_COUNT];