diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h
index f7e75e1e71f3..0717a53ae732 100644
--- a/include/crypto/internal/ecc.h
+++ b/include/crypto/internal/ecc.h
@@ -63,6 +63,9 @@ static inline void ecc_swap_digits(const void *in, u64 *out, unsigned int ndigit
  * @nbytes    Size of input byte array
  * @out       Output digits array
  * @ndigits:  Number of digits to create from byte array
+ *
+ * The first byte in the input byte array is expected to hold the most
+ * significant bits of the large integer.
  */
 void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes,
 			   u64 *out, unsigned int ndigits);