diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index fcb627f..9a9051b 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -22,6 +22,8 @@
 #ifndef __LINUX_TPM_H__
 #define __LINUX_TPM_H__
 
+#define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
+
 /*
  * Chip num is this value or a valid tpm idx
  */