cmak: improve documentation on parameter constraints
diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index c196793..7f989a0 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -77,7 +77,7 @@
* as one of the following types: MBEDTLS_CIPHER_AES_128_ECB,
* MBEDTLS_CIPHER_AES_192_ECB, MBEDTLS_CIPHER_AES_256_ECB,
* or MBEDTLS_CIPHER_DES_EDE3_ECB.
- * \param key The CMAC key.
+ * \param key The CMAC key. This must not be \c NULL.
* \param keybits The length of the CMAC key in bits.
* Must be supported by the cipher.
*
@@ -96,7 +96,8 @@
* Can be called repeatedly.
*
* \param ctx The cipher context used for the CMAC operation.
- * \param input The buffer holding the input data.
+ * This must be initialized.
+ * \param input The buffer holding the input data. This must not be \c NULL.
* \param ilen The length of the input data.
*
* \return \c 0 on success.
@@ -115,7 +116,9 @@
* mbedtls_cipher_cmac_update(), or mbedtls_cipher_free().
*
* \param ctx The cipher context used for the CMAC operation.
+ * This must be initialized.
* \param output The output buffer for the CMAC checksum result.
+ * This must not be \c NULL.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA
@@ -133,6 +136,7 @@
* and before mbedtls_cipher_cmac_update().
*
* \param ctx The cipher context used for the CMAC operation.
+ * This must be initialized.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA
@@ -151,12 +155,12 @@
* output = generic CMAC(cmac key, input buffer).
*
*
- * \param cipher_info The cipher information.
- * \param key The CMAC key.
+ * \param cipher_info The cipher information. This must not be \c NULL.
+ * \param key The CMAC key. This must not be \c NULL.
* \param keylen The length of the CMAC key in bits.
- * \param input The buffer holding the input data.
+ * \param input The buffer holding the input data. This must not be \c NULL.
* \param ilen The length of the input data.
- * \param output The buffer for the generic CMAC result.
+ * \param output The buffer for the generic CMAC result. This must not be \c NULL.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA
@@ -176,12 +180,12 @@
* (AES-CMAC-PRF-128) Algorithm for the Internet Key
* Exchange Protocol (IKE).</em>
*
- * \param key The key to use.
+ * \param key The key to use. This must not be \c NULL.
* \param key_len The key length in Bytes.
- * \param input The buffer holding the input data.
+ * \param input The buffer holding the input data. This must not be \c NULL.
* \param in_len The length of the input data in Bytes.
* \param output The buffer holding the generated 16 Bytes of
- * pseudorandom output.
+ * pseudorandom output. This must not be \c NULL.
*
* \return \c 0 on success.
*/