diff --git a/include/mbedtls/sha512.h b/include/mbedtls/sha512.h
index 28b4998..93f9646 100644
--- a/include/mbedtls/sha512.h
+++ b/include/mbedtls/sha512.h
@@ -71,25 +71,26 @@
 /**
  * \brief          This function initializes a SHA-512 context.
  *
- * \param ctx      The SHA-512 context to initialize.
- *                 Must not be \c NULL.
+ * \param ctx      The SHA-512 context to initialize. This must
+ *                 not be \c NULL.
  */
 void mbedtls_sha512_init( mbedtls_sha512_context *ctx );
 
 /**
  * \brief          This function clears a SHA-512 context.
  *
- * \param ctx      The SHA-512 context to clear.
+ * \param ctx      The SHA-512 context to clear. This may be \c NULL,
+ *                 in which case this function does nothing. If it
+ *                 is not \c NULL, it must point to an initialized
+ *                 SHA-512 context.
  */
 void mbedtls_sha512_free( mbedtls_sha512_context *ctx );
 
 /**
  * \brief          This function clones the state of a SHA-512 context.
  *
- * \param dst      The destination context.
- *                 Must not be \c NULL.
- * \param src      The context to clone.
- *                 Must not be \c NULL.
+ * \param dst      The destination context. This must be initialized.
+ * \param src      The context to clone. This must be initialized.
  */
 void mbedtls_sha512_clone( mbedtls_sha512_context *dst,
                            const mbedtls_sha512_context *src );
@@ -98,12 +99,12 @@
  * \brief          This function starts a SHA-384 or SHA-512 checksum
  *                 calculation.
  *
- * \param ctx      The SHA-512 context to initialize.
- *                 Must not be \c NULL.
- * \param is384    Determines which function to use:
- *                 0: Use SHA-512, or 1: Use SHA-384.
+ * \param ctx      The SHA-512 context to use. This must be initialized.
+ * \param is384    Determines which function to use. This must be
+ *                 either \c for SHA-512, or \c 1 for SHA-384.
  *
  * \return         \c 0 on success.
+ * \return         A negative error code on failure.
  */
 int mbedtls_sha512_starts_ret( mbedtls_sha512_context *ctx, int is384 );
 
@@ -111,13 +112,15 @@
  * \brief          This function feeds an input buffer into an ongoing
  *                 SHA-512 checksum calculation.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
- * \param input    The buffer holding the input data.
- *                 Must not be \c NULL if \p ilen is greater than 0.
- * \param ilen     The length of the input data.
+ * \param ctx      The SHA-512 context. This must be initialized
+ *                 and have a hash operation started.
+ * \param input    The buffer holding the input data. This must
+ *                 be a readable buffer of length \p ilen Bytes.
+ *                 It must not be \c NULL.
+ * \param ilen     The length of the input data \p input in Bytes.
  *
  * \return         \c 0 on success.
+ * \return         A negative error code on failure.
  */
 int mbedtls_sha512_update_ret( mbedtls_sha512_context *ctx,
                     const unsigned char *input,
@@ -128,12 +131,13 @@
  *                 the result to the output buffer. This function is for
  *                 internal use only.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
+ * \param ctx      The SHA-512 context. This must be initialized
+ *                 and have a hash operation started.
  * \param output   The SHA-384 or SHA-512 checksum result.
- *                 Must not be \c NULL.
+ *                 This must be a writable buffer of length \c 64 Bytes.
  *
  * \return         \c 0 on success.
+ * \return         A negative error code on failure.
  */
 int mbedtls_sha512_finish_ret( mbedtls_sha512_context *ctx,
                                unsigned char output[64] );
@@ -142,12 +146,13 @@
  * \brief          This function processes a single data block within
  *                 the ongoing SHA-512 computation.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
- * \param data     The buffer holding one block of data.
- *                 Must not be \c NULL.
+ * \param ctx      The SHA-512 context. This must be initialized
+ *                 and have a hash operation started.
+ * \param data     The buffer holding one block of data. This
+ *                 must be a readable buffer of length \c 128 Bytes.
  *
  * \return         \c 0 on success.
+ * \return         A negative error code on failure.
  */
 int mbedtls_internal_sha512_process( mbedtls_sha512_context *ctx,
                                      const unsigned char data[128] );
@@ -163,10 +168,9 @@
  *
  * \deprecated     Superseded by mbedtls_sha512_starts_ret() in 2.7.0
  *
- * \param ctx      The SHA-512 context to initialize.
- *                 Must not be \c NULL.
- * \param is384    Determines which function to use:
- *                 0: Use SHA-512, or 1: Use SHA-384.
+ * \param ctx      The SHA-512 context to use. This must be initialized.
+ * \param is384    Determines which function to use. This must be either
+ *                 \c 0 for SHA-512 or \c 1 for SHA-384.
  */
 MBEDTLS_DEPRECATED void mbedtls_sha512_starts( mbedtls_sha512_context *ctx,
                                                int is384 );
@@ -177,11 +181,11 @@
  *
  * \deprecated     Superseded by mbedtls_sha512_update_ret() in 2.7.0.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
- * \param input    The buffer holding the data.
- *                 Must not be \c NULL if \p ilen is greater than 0.
- * \param ilen     The length of the input data.
+ * \param ctx      The SHA-512 context. This must be initialized
+ *                 and have a hash operation started.
+ * \param input    The buffer holding the data. This must be a readable
+ *                 buffer of length \p ilen Bytes. It must not be \c NULL.
+ * \param ilen     The length of the input data \p input in Bytes.
  */
 MBEDTLS_DEPRECATED void mbedtls_sha512_update( mbedtls_sha512_context *ctx,
                                                const unsigned char *input,
@@ -193,10 +197,10 @@
  *
  * \deprecated     Superseded by mbedtls_sha512_finish_ret() in 2.7.0.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
- * \param output   The SHA-384 or SHA-512 checksum result.
- *                 Must not be \c NULL.
+ * \param ctx      The SHA-512 context. This must be initialized
+ *                 and have a hash operation started.
+ * \param output   The SHA-384 or SHA-512 checksum result. This must
+ *                 be a writable buffer of size \c 64 Bytes.
  */
 MBEDTLS_DEPRECATED void mbedtls_sha512_finish( mbedtls_sha512_context *ctx,
                                                unsigned char output[64] );
@@ -208,10 +212,10 @@
  *
  * \deprecated     Superseded by mbedtls_internal_sha512_process() in 2.7.0.
  *
- * \param ctx      The SHA-512 context.
- *                 Must not be \c NULL.
- * \param data     The buffer holding one block of data.
- *                 Must not be \c NULL.
+ * \param ctx      The SHA-512 context. This must be initialized and
+ *                 have a hash operation started.
+ * \param data     The buffer holding one block of data. This must be
+ *                 a readable buffer of length \c 128 Bytes.
  */
 MBEDTLS_DEPRECATED void mbedtls_sha512_process(
                                             mbedtls_sha512_context *ctx,
@@ -230,15 +234,17 @@
  *                 The SHA-512 result is calculated as
  *                 output = SHA-512(input buffer).
  *
- * \param input    The buffer holding the input data.
- *                 Must not be \c NULL if \p ilen is greater than 0.
- * \param ilen     The length of the input data.
+ * \param input    The buffer holding the input data. This must be
+ *                 a readable buffer of length \p ilen Bytes. It
+ *                 must not be \c NULL.
+ * \param ilen     The length of the input data \p input in Bytes.
  * \param output   The SHA-384 or SHA-512 checksum result.
- *                 Must not be \c NULL.
- * \param is384    Determines which function to use:
- *                 0: Use SHA-512, or 1: Use SHA-384.
+ *                 This must be a writable buffer of length \c 64 Bytes.
+ * \param is384    Determines which function to use. This must be either
+ *                 \c 0 for SHA-512, or \c 1 for SHA-384.
  *
  * \return         \c 0 on success.
+ * \return         A negative error code on failure.
  */
 int mbedtls_sha512_ret( const unsigned char *input,
                         size_t ilen,
@@ -263,13 +269,14 @@
  *
  * \deprecated     Superseded by mbedtls_sha512_ret() in 2.7.0
  *
- * \param input    The buffer holding the data.
- *                 Must not be \c NULL if \p ilen is greater than 0.
- * \param ilen     The length of the input data.
- * \param output   The SHA-384 or SHA-512 checksum result.
- *                 Must not be \c NULL.
- * \param is384    Determines which function to use:
- *                 0: Use SHA-512, or 1: Use SHA-384.
+ * \param input    The buffer holding the data. This must be a
+ *                 readable buffer of length \p ilen Bytes. It
+ *                 must not be \c NULL.
+ * \param ilen     The length of the input data \p input in Bytes.
+ * \param output   The SHA-384 or SHA-512 checksum result. This must
+ *                 be a writable buffer of length \c 64 Bytes.
+ * \param is384    Determines which function to use. This must be eiher
+ *                 \c 0 for SHA-512, or \c 1 for SHA-384.
  */
 MBEDTLS_DEPRECATED void mbedtls_sha512( const unsigned char *input,
                                         size_t ilen,