Doxygen comments improvement
diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index b2c57a4..3f3a25d 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -84,7 +84,7 @@
* to make references valid, and prepare the context
* for mbedtls_ccm_setkey() or mbedtls_ccm_free().
*
- * \param ctx The CCM context to initialize. Must not be \c NULL.
+ * \param ctx The CCM context to initialize. This must not be \c NULL.
*/
void mbedtls_ccm_init( mbedtls_ccm_context *ctx );
@@ -92,10 +92,10 @@
* \brief This function initializes the CCM context set in the
* \p ctx parameter and sets the encryption key.
*
- * \param ctx The CCM context to initialize. Must be an initialized
+ * \param ctx The CCM context to initialize. This must be an initialized
* context.
* \param cipher The 128-bit block cipher to use.
- * \param key The encryption key. Must not be \c NULL.
+ * \param key The encryption key. This must not be \c NULL.
* \param keybits The key size in bits. This must be acceptable by the cipher.
*
* \return \c 0 on success.
@@ -110,7 +110,8 @@
* \brief This function releases and clears the specified CCM context
* and underlying cipher sub-context.
*
- * \param ctx The CCM context to clear. Must be an initialized context.
+ * \param ctx The CCM context to clear. This must be an initialized
+ * context.
*
* \note If ctx is \c NULL, the function has no effect.
*/
@@ -125,26 +126,26 @@
* \p tag = \p output + \p length, and make sure that the
* output buffer is at least \p length + \p tag_len wide.
*
- * \param ctx The CCM context to use for encryption. Must be an
+ * \param ctx The CCM context to use for encryption. This must be an
* initialized context.
* \param length The length of the input data in Bytes.
- * \param iv Initialization vector (nonce). Must be a readable buffer of
- * at least \p iv_len Bytes.
+ * \param iv Initialization vector (nonce). This must be a readable
+ * buffer of at least \p iv_len Bytes.
* \param iv_len The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
* or 13. The length L of the message length field is
* 15 - \p iv_len.
* \param add The additional data field. If \p add_len is greater than
* zero, \p add must be a readable buffer of at least that
- * length.
+ * length. If `pad_len == 0`, this may be \c NULL.
* \param add_len The length of additional data in Bytes.
- * Must be less than 2^16 - 2^8.
+ * This must be less than 2^16 - 2^8.
* \param input The buffer holding the input data. If \p length is greater
* than zero, \p input must be a readable buffer of at least
* that length.
* \param output The buffer holding the output data. If \p length is greater
* than zero, \p output must be a writable buffer of at least
* that length.
- * \param tag The buffer holding the authentication field. Must be a
+ * \param tag The buffer holding the authentication field. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the authentication field to generate in Bytes:
* 4, 6, 8, 10, 12, 14 or 16.
@@ -171,31 +172,31 @@
* the tag length has to be encoded into the \p iv passed to
* this function.
*
- * \param ctx The CCM context to use for encryption. Must be an
+ * \param ctx The CCM context to use for encryption. This must be an
* initialized context.
* \param length The length of the input data in Bytes.
- * \param iv Initialization vector (nonce). Must be a readable buffer of
- * at least \p iv_len Bytes.
+ * \param iv Initialization vector (nonce). This must be a readable
+ * buffer of at least \p iv_len Bytes.
* \param iv_len The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
* or 13. The length L of the message length field is
* 15 - \p iv_len.
* \param add The additional data field. If \p add_len is greater than
* zero, \p add must be a readable buffer of at least that
- * length.
+ * length. If `pad_len == 0`, this may be \c NULL.
* \param add_len The length of additional data in Bytes.
- * Must be less than 2^16 - 2^8.
+ * This must be less than 2^16 - 2^8.
* \param input The buffer holding the input data. If \p length is greater
* than zero, \p input must be a readable buffer of at least
* that length.
* \param output The buffer holding the output data. If \p length is greater
* than zero, \p output must be a writable buffer of at least
* that length.
- * \param tag The buffer holding the authentication field. Must be a
+ * \param tag The buffer holding the authentication field. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the authentication field to generate in Bytes:
* 0, 4, 6, 8, 10, 12, 14 or 16.
*
- * \warning Passing 0 as \p tag_len means that the message is no
+ * \warning Passing \c 0 as \p tag_len means that the message is no
* longer authenticated.
*
* \return \c 0 on success.
@@ -211,26 +212,26 @@
* \brief This function performs a CCM authenticated decryption of a
* buffer.
*
- * \param ctx The CCM context to use for decryption. Must be an
+ * \param ctx The CCM context to use for decryption. This must be an
* initialized context.
* \param length The length of the input data in Bytes.
- * \param iv Initialization vector (nonce). Must be a readable buffer of
- * at least \p iv_len Bytes.
+ * \param iv Initialization vector (nonce). This must be a readable
+ * buffer of at least \p iv_len Bytes.
* \param iv_len The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
* or 13. The length L of the message length field is
* 15 - \p iv_len.
* \param add The additional data field. If \p add_len is greater than
* zero, \p add must be a readable buffer of at least that
- * length.
+ * length. If `pad_len == 0`, this may be \c NULL.
* \param add_len The length of additional data in Bytes.
- * Must be less than 2^16 - 2^8.
+ * This must be less than 2^16 - 2^8.
* \param input The buffer holding the input data. If \p length is greater
* than zero, \p input must be a readable buffer of at least
* that length.
* \param output The buffer holding the output data. If \p length is greater
* than zero, \p output must be a writable buffer of at least
* that length.
- * \param tag The buffer holding the authentication field. Must be a
+ * \param tag The buffer holding the authentication field. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the authentication field to generate in Bytes:
* 4, 6, 8, 10, 12, 14 or 16.
@@ -254,31 +255,31 @@
* this function as \p tag_len. (\p tag needs to be adjusted
* accordingly.)
*
- * \param ctx The CCM context to use for decryption. Must be an
+ * \param ctx The CCM context to use for decryption. This must be an
* initialized context.
* \param length The length of the input data in Bytes.
- * \param iv Initialization vector (nonce). Must be a readable buffer of
- * at least \p iv_len Bytes.
+ * \param iv Initialization vector (nonce). This must be a readable
+ * buffer of at least \p iv_len Bytes.
* \param iv_len The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
* or 13. The length L of the message length field is
* 15 - \p iv_len.
* \param add The additional data field. If \p add_len is greater than
* zero, \p add must be a readable buffer of at least that
- * length.
+ * length. If `pad_len == 0`, this may be \c NULL.
* \param add_len The length of additional data in Bytes.
- * Must be less than 2^16 - 2^8.
+ * This must be less than 2^16 - 2^8.
* \param input The buffer holding the input data. If \p length is greater
* than zero, \p input must be a readable buffer of at least
* that length.
* \param output The buffer holding the output data. If \p length is greater
* than zero, \p output must be a writable buffer of at least
* that length.
- * \param tag The buffer holding the authentication field. Must be a
+ * \param tag The buffer holding the authentication field. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the authentication field in Bytes.
* 0, 4, 6, 8, 10, 12, 14 or 16.
*
- * \warning Passing 0 as \p tag_len means that the message is no
+ * \warning Passing \c 0 as \p tag_len means that the message is nos
* longer authenticated.
*
* \return \c 0 on success.