diff --git a/ChangeLog b/ChangeLog
index 214b414..dea8bfd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -33,6 +33,16 @@
      hash and signature sizes that comply with FIPS 186-4, including SHA-512
      with a 1024-bit key.
 
+API Changes
+   * Add a common error code for a feature that is not supported by the
+     underlying alternative implementations.
+
+New deprecations
+   * All the current module specific errors that mean a feature is not available
+     are deprecated, so the platform error should be used.
+   * All the module specific generic hardware accelaration errors that existed
+     are deprecated, so the platform error should be used.
+
 Bugfix
    * Fix wrong order of freeing in programs/ssl/ssl_server2 example
      application leading to a memory leak in case both
diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index 4c8dab3..cfb20c4 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -60,7 +60,11 @@
 
 /* Error codes in range 0x0021-0x0025 */
 #define MBEDTLS_ERR_AES_BAD_INPUT_DATA                    -0x0021  /**< Invalid input data. */
+
+/* MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE is deprecated and should not be used. */
 #define MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE               -0x0023  /**< Feature not available. For example, an unsupported AES key size. */
+
+/* MBEDTLS_ERR_AES_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_AES_HW_ACCEL_FAILED                   -0x0025  /**< AES hardware accelerator failed. */
 
 #if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
diff --git a/include/mbedtls/arc4.h b/include/mbedtls/arc4.h
index 83a7461..c43f406 100644
--- a/include/mbedtls/arc4.h
+++ b/include/mbedtls/arc4.h
@@ -36,6 +36,7 @@
 
 #include <stddef.h>
 
+/* MBEDTLS_ERR_ARC4_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_ARC4_HW_ACCEL_FAILED                  -0x0019  /**< ARC4 hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/aria.h b/include/mbedtls/aria.h
index 4a79c13..483d4c2 100644
--- a/include/mbedtls/aria.h
+++ b/include/mbedtls/aria.h
@@ -48,7 +48,12 @@
 
 #define MBEDTLS_ERR_ARIA_INVALID_KEY_LENGTH   -0x005C  /**< Invalid key length. */
 #define MBEDTLS_ERR_ARIA_INVALID_INPUT_LENGTH -0x005E  /**< Invalid data input length. */
+
+/* MBEDTLS_ERR_ARIA_FEATURE_UNAVAILABLE is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_ARIA_FEATURE_UNAVAILABLE  -0x005A  /**< Feature not available. For example, an unsupported ARIA key size. */
+
+/* MBEDTLS_ERR_ARIA_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_ARIA_HW_ACCEL_FAILED      -0x0058  /**< ARIA hardware accelerator failed. */
 
 #if !defined(MBEDTLS_ARIA_ALT)
diff --git a/include/mbedtls/blowfish.h b/include/mbedtls/blowfish.h
index eea6882..82b772a 100644
--- a/include/mbedtls/blowfish.h
+++ b/include/mbedtls/blowfish.h
@@ -41,7 +41,11 @@
 #define MBEDTLS_BLOWFISH_BLOCKSIZE   8          /* Blowfish uses 64 bit blocks */
 
 #define MBEDTLS_ERR_BLOWFISH_INVALID_KEY_LENGTH                -0x0016  /**< Invalid key length. */
+
+/* MBEDTLS_ERR_BLOWFISH_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_BLOWFISH_HW_ACCEL_FAILED                   -0x0017  /**< Blowfish hardware accelerator failed. */
+
 #define MBEDTLS_ERR_BLOWFISH_INVALID_INPUT_LENGTH              -0x0018  /**< Invalid data input length. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/camellia.h b/include/mbedtls/camellia.h
index fa1e05e..1555867 100644
--- a/include/mbedtls/camellia.h
+++ b/include/mbedtls/camellia.h
@@ -38,6 +38,9 @@
 
 #define MBEDTLS_ERR_CAMELLIA_INVALID_KEY_LENGTH           -0x0024  /**< Invalid key length. */
 #define MBEDTLS_ERR_CAMELLIA_INVALID_INPUT_LENGTH         -0x0026  /**< Invalid data input length. */
+
+/* MBEDTLS_ERR_CAMELLIA_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_CAMELLIA_HW_ACCEL_FAILED              -0x0027  /**< Camellia hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index e1dc124..dfb1b5e 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -53,6 +53,8 @@
 
 #define MBEDTLS_ERR_CCM_BAD_INPUT       -0x000D /**< Bad input parameters to the function. */
 #define MBEDTLS_ERR_CCM_AUTH_FAILED     -0x000F /**< Authenticated decryption failed. */
+
+/* MBEDTLS_ERR_CCM_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_CCM_HW_ACCEL_FAILED -0x0011 /**< CCM hardware accelerator failed. */
 
 
diff --git a/include/mbedtls/chacha20.h b/include/mbedtls/chacha20.h
index cfea40a..529f22d 100644
--- a/include/mbedtls/chacha20.h
+++ b/include/mbedtls/chacha20.h
@@ -43,7 +43,13 @@
 #include <stddef.h>
 
 #define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA         -0x0051 /**< Invalid input parameter(s). */
+
+/* MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE is deprecated and should not be
+ * used. */
 #define MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE    -0x0053 /**< Feature not available. For example, s part of the API is not implemented. */
+
+/* MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED        -0x0055  /**< Chacha20 hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index dfb1541..58a5d63 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -62,6 +62,8 @@
 #define MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED  -0x6280  /**< Decryption of block requires a full block. */
 #define MBEDTLS_ERR_CIPHER_AUTH_FAILED          -0x6300  /**< Authentication failed (for AEAD modes). */
 #define MBEDTLS_ERR_CIPHER_INVALID_CONTEXT      -0x6380  /**< The context is invalid. For example, because it was freed. */
+
+/* MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED      -0x6400  /**< Cipher hardware accelerator failed. */
 
 #define MBEDTLS_CIPHER_VARIABLE_IV_LEN     0x01    /**< Cipher accepts IVs of variable length. */
diff --git a/include/mbedtls/cmac.h b/include/mbedtls/cmac.h
index a4fd552..c196793 100644
--- a/include/mbedtls/cmac.h
+++ b/include/mbedtls/cmac.h
@@ -34,6 +34,7 @@
 extern "C" {
 #endif
 
+/* MBEDTLS_ERR_CMAC_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_CMAC_HW_ACCEL_FAILED -0x007A  /**< CMAC hardware accelerator failed. */
 
 #define MBEDTLS_AES_BLOCK_SIZE          16
diff --git a/include/mbedtls/des.h b/include/mbedtls/des.h
index 91d16b6..d62042d 100644
--- a/include/mbedtls/des.h
+++ b/include/mbedtls/des.h
@@ -42,6 +42,8 @@
 #define MBEDTLS_DES_DECRYPT     0
 
 #define MBEDTLS_ERR_DES_INVALID_INPUT_LENGTH              -0x0032  /**< The data input has an invalid length. */
+
+/* MBEDTLS_ERR_DES_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_DES_HW_ACCEL_FAILED                   -0x0033  /**< DES hardware accelerator failed. */
 
 #define MBEDTLS_DES_KEY_SIZE    8
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 3e11789..8e2d020 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -84,7 +84,10 @@
 #define MBEDTLS_ERR_DHM_INVALID_FORMAT                    -0x3380  /**< The ASN.1 data is not formatted correctly. */
 #define MBEDTLS_ERR_DHM_ALLOC_FAILED                      -0x3400  /**< Allocation of memory failed. */
 #define MBEDTLS_ERR_DHM_FILE_IO_ERROR                     -0x3480  /**< Read or write of file failed. */
+
+/* MBEDTLS_ERR_DHM_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_DHM_HW_ACCEL_FAILED                   -0x3500  /**< DHM hardware accelerator failed. */
+
 #define MBEDTLS_ERR_DHM_SET_GROUP_FAILED                  -0x3580  /**< Setting the modulus and generator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 5db8752..2fb1af4 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -49,7 +49,10 @@
 #define MBEDTLS_ERR_ECP_RANDOM_FAILED                     -0x4D00  /**< Generation of random value, such as ephemeral key, failed. */
 #define MBEDTLS_ERR_ECP_INVALID_KEY                       -0x4C80  /**< Invalid private or public key. */
 #define MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH                  -0x4C00  /**< The buffer contains a valid signature followed by more data. */
+
+/* MBEDTLS_ERR_ECP_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_ECP_HW_ACCEL_FAILED                   -0x4B80  /**< The ECP hardware accelerator failed. */
+
 #define MBEDTLS_ERR_ECP_IN_PROGRESS                       -0x4B00  /**< Operation in progress, call again with the same parameters to continue. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 39cd67f..0c38889 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -80,7 +80,7 @@
  * CHACHA20  3                  0x0051-0x0055
  * POLY1305  3                  0x0057-0x005B
  * CHACHAPOLY 2 0x0054-0x0056
- * PLATFORM  1  0x0070-0x0070
+ * PLATFORM  1  0x0070-0x0072
  *
  * High-level module nr (3 bits - 0x0...-0x7...)
  * Name      ID  Nr of Errors
diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index d2098eb..93d15ee 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -41,7 +41,10 @@
 #define MBEDTLS_GCM_DECRYPT     0
 
 #define MBEDTLS_ERR_GCM_AUTH_FAILED                       -0x0012  /**< Authenticated decryption failed. */
+
+/* MBEDTLS_ERR_GCM_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED                   -0x0013  /**< GCM hardware accelerator failed. */
+
 #define MBEDTLS_ERR_GCM_BAD_INPUT                         -0x0014  /**< Bad input parameters to function. */
 
 #ifdef __cplusplus
@@ -146,9 +149,9 @@
  * \return          \c 0 if the encryption or decryption was performed
  *                  successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
  *                  this does not indicate that the data is authentic.
- * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid.
- * \return          #MBEDTLS_ERR_GCM_HW_ACCEL_FAILED or a cipher-specific
- *                  error code if the encryption or decryption failed.
+ * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid or
+ *                  a cipher-specific error code if the encryption
+ *                  or decryption failed.
  */
 int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
                        int mode,
@@ -185,9 +188,8 @@
  *
  * \return          \c 0 if successful and authenticated.
  * \return          #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
- * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid.
- * \return          #MBEDTLS_ERR_GCM_HW_ACCEL_FAILED or a cipher-specific
- *                  error code if the decryption failed.
+ * \return          #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths are not valid or
+ *                  a cipher-specific error code if the decryption failed.
  */
 int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
                       size_t length,
diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index bf29524..8bcf766 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -39,6 +39,8 @@
 #define MBEDTLS_ERR_MD_BAD_INPUT_DATA                     -0x5100  /**< Bad input parameters to function. */
 #define MBEDTLS_ERR_MD_ALLOC_FAILED                       -0x5180  /**< Failed to allocate memory. */
 #define MBEDTLS_ERR_MD_FILE_IO_ERROR                      -0x5200  /**< Opening or reading of file failed. */
+
+/* MBEDTLS_ERR_MD_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_MD_HW_ACCEL_FAILED                    -0x5280  /**< MD hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/md2.h b/include/mbedtls/md2.h
index a46bddb..f9bd98f 100644
--- a/include/mbedtls/md2.h
+++ b/include/mbedtls/md2.h
@@ -37,6 +37,7 @@
 
 #include <stddef.h>
 
+/* MBEDTLS_ERR_MD2_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_MD2_HW_ACCEL_FAILED                   -0x002B  /**< MD2 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/md4.h b/include/mbedtls/md4.h
index 1672e90..dc3c048 100644
--- a/include/mbedtls/md4.h
+++ b/include/mbedtls/md4.h
@@ -38,6 +38,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_MD4_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_MD4_HW_ACCEL_FAILED                   -0x002D  /**< MD4 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/md5.h b/include/mbedtls/md5.h
index 4c95090..6c3354f 100644
--- a/include/mbedtls/md5.h
+++ b/include/mbedtls/md5.h
@@ -37,6 +37,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_MD5_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_MD5_HW_ACCEL_FAILED                   -0x002F  /**< MD5 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 9ec33da..df3a03c 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -64,6 +64,8 @@
 #define MBEDTLS_ERR_PK_UNKNOWN_NAMED_CURVE -0x3A00  /**< Elliptic curve is unsupported (only NIST curves are supported). */
 #define MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE -0x3980  /**< Unavailable feature, e.g. RSA disabled for RSA key. */
 #define MBEDTLS_ERR_PK_SIG_LEN_MISMATCH    -0x3900  /**< The buffer contains a valid signature followed by more data. */
+
+/* MBEDTLS_ERR_PK_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_PK_HW_ACCEL_FAILED     -0x3880  /**< PK hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/platform.h b/include/mbedtls/platform.h
index 5cd143c..89fe8a7 100644
--- a/include/mbedtls/platform.h
+++ b/include/mbedtls/platform.h
@@ -43,7 +43,8 @@
 #include "platform_time.h"
 #endif
 
-#define MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED       -0x0070 /**< Hardware accelerator failed */
+#define MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED     -0x0070 /**< Hardware accelerator failed */
+#define MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED -0x0072 /**< The requested feature is not supported by the platform */
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/include/mbedtls/poly1305.h b/include/mbedtls/poly1305.h
index c490cdf..b02f968 100644
--- a/include/mbedtls/poly1305.h
+++ b/include/mbedtls/poly1305.h
@@ -43,7 +43,13 @@
 #include <stddef.h>
 
 #define MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA         -0x0057 /**< Invalid input parameter(s). */
+
+/* MBEDTLS_ERR_POLY1305_FEATURE_UNAVAILABLE is deprecated and should not be
+ * used. */
 #define MBEDTLS_ERR_POLY1305_FEATURE_UNAVAILABLE    -0x0059 /**< Feature not available. For example, s part of the API is not implemented. */
+
+/* MBEDTLS_ERR_POLY1305_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_POLY1305_HW_ACCEL_FAILED        -0x005B  /**< Poly1305 hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/ripemd160.h b/include/mbedtls/ripemd160.h
index 0c8e568..c74b7d2 100644
--- a/include/mbedtls/ripemd160.h
+++ b/include/mbedtls/ripemd160.h
@@ -33,6 +33,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_RIPEMD160_HW_ACCEL_FAILED is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_RIPEMD160_HW_ACCEL_FAILED             -0x0031  /**< RIPEMD160 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index b348299..406a317 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -55,7 +55,12 @@
 #define MBEDTLS_ERR_RSA_VERIFY_FAILED                     -0x4380  /**< The PKCS#1 verification failed. */
 #define MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE                  -0x4400  /**< The output buffer for decryption is not large enough. */
 #define MBEDTLS_ERR_RSA_RNG_FAILED                        -0x4480  /**< The random generator failed to generate non-zeros. */
+
+/* MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION is deprecated and should not be used.
+ */
 #define MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION             -0x4500  /**< The implementation does not offer the requested operation, for example, because of security violations or lack of functionality. */
+
+/* MBEDTLS_ERR_RSA_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_RSA_HW_ACCEL_FAILED                   -0x4580  /**< RSA hardware accelerator failed. */
 
 /*
@@ -281,7 +286,7 @@
  *                 zero Bytes.
  *
  *                 Possible reasons for returning
- *                 #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION:<ul>
+ *                 #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED:<ul>
  *                 <li>An alternative RSA implementation is in use, which
  *                 stores the key externally, and either cannot or should
  *                 not export it into RAM.</li>
@@ -301,7 +306,7 @@
  * \param E        The MPI to hold the public exponent, or NULL.
  *
  * \return         \c 0 on success.
- * \return         #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION if exporting the
+ * \return         #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED if exporting the
  *                 requested parameters cannot be done due to missing
  *                 functionality or because of security policies.
  * \return         A non-zero return code on any other failure.
@@ -321,7 +326,7 @@
  *                 zero Bytes.
  *
  *                 Possible reasons for returning
- *                 #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION:<ul>
+ *                 #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED:<ul>
  *                 <li>An alternative RSA implementation is in use, which
  *                 stores the key externally, and either cannot or should
  *                 not export it into RAM.</li>
@@ -350,7 +355,7 @@
  * \param E_len    The size of the buffer for the public exponent.
  *
  * \return         \c 0 on success.
- * \return         #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION if exporting the
+ * \return         #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED if exporting the
  *                 requested parameters cannot be done due to missing
  *                 functionality or because of security policies.
  * \return         A non-zero return code on any other failure.
@@ -563,7 +568,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Needed for padding, PKCS#1 v2.1
@@ -598,7 +603,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Needed for padding and
@@ -633,7 +638,7 @@
  *
  * \note             Alternative implementations of RSA need not support
  *                   mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                   return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                   return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx        The RSA context.
  * \param f_rng      The RNG function. Needed for padding and PKCS#1 v2.1
@@ -682,7 +687,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -725,7 +730,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -770,7 +775,7 @@
  *
  * \note             Alternative implementations of RSA need not support
  *                   mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                   return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                   return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx        The RSA context.
  * \param f_rng      The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -817,7 +822,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Needed for PKCS#1 v2.1 encoding and for
@@ -856,7 +861,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -911,7 +916,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PUBLIC and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA context.
  * \param f_rng    The RNG function. Needed for PKCS#1 v2.1 encoding and for
@@ -957,7 +962,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA public key context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -995,7 +1000,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA public key context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
@@ -1044,7 +1049,7 @@
  *
  * \note           Alternative implementations of RSA need not support
  *                 mode being set to #MBEDTLS_RSA_PRIVATE and might instead
- *                 return #MBEDTLS_ERR_RSA_UNSUPPORTED_OPERATION.
+ *                 return #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED.
  *
  * \param ctx      The RSA public key context.
  * \param f_rng    The RNG function. Only needed for #MBEDTLS_RSA_PRIVATE.
diff --git a/include/mbedtls/sha1.h b/include/mbedtls/sha1.h
index 7a19da0..bcaeab5 100644
--- a/include/mbedtls/sha1.h
+++ b/include/mbedtls/sha1.h
@@ -40,6 +40,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_SHA1_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_SHA1_HW_ACCEL_FAILED                  -0x0035  /**< SHA-1 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/sha256.h b/include/mbedtls/sha256.h
index 33aff28..47a31e8 100644
--- a/include/mbedtls/sha256.h
+++ b/include/mbedtls/sha256.h
@@ -36,6 +36,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_SHA256_HW_ACCEL_FAILED                -0x0037  /**< SHA-256 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/sha512.h b/include/mbedtls/sha512.h
index 0145890..020f95d 100644
--- a/include/mbedtls/sha512.h
+++ b/include/mbedtls/sha512.h
@@ -35,6 +35,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+/* MBEDTLS_ERR_SHA512_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_SHA512_HW_ACCEL_FAILED                -0x0039  /**< SHA-512 hardware accelerator failed */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/threading.h b/include/mbedtls/threading.h
index 75298bf..92e6e6b 100644
--- a/include/mbedtls/threading.h
+++ b/include/mbedtls/threading.h
@@ -36,7 +36,10 @@
 extern "C" {
 #endif
 
+/* MBEDTLS_ERR_THREADING_FEATURE_UNAVAILABLE is deprecated and should not be
+ * used. */
 #define MBEDTLS_ERR_THREADING_FEATURE_UNAVAILABLE         -0x001A  /**< The selected feature is not available. */
+
 #define MBEDTLS_ERR_THREADING_BAD_INPUT_DATA              -0x001C  /**< Bad input parameters to function. */
 #define MBEDTLS_ERR_THREADING_MUTEX_ERROR                 -0x001E  /**< Locking / unlocking / free failed with error code. */
 
diff --git a/include/mbedtls/xtea.h b/include/mbedtls/xtea.h
index c70c3fe..6430c13 100644
--- a/include/mbedtls/xtea.h
+++ b/include/mbedtls/xtea.h
@@ -37,6 +37,8 @@
 #define MBEDTLS_XTEA_DECRYPT     0
 
 #define MBEDTLS_ERR_XTEA_INVALID_INPUT_LENGTH             -0x0028  /**< The data input has an invalid length. */
+
+/* MBEDTLS_ERR_XTEA_HW_ACCEL_FAILED is deprecated and should not be used. */
 #define MBEDTLS_ERR_XTEA_HW_ACCEL_FAILED                  -0x0029  /**< XTEA hardware accelerator failed. */
 
 #ifdef __cplusplus
diff --git a/library/aes.c b/library/aes.c
index fce32ce..3de571e 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -36,6 +36,7 @@
 #include <string.h>
 
 #include "mbedtls/aes.h"
+#include "mbedtls/platform.h"
 #include "mbedtls/platform_util.h"
 #if defined(MBEDTLS_PADLOCK_C)
 #include "mbedtls/padlock.h"
@@ -1757,7 +1758,7 @@
          * there is an alternative underlying implementation i.e. when
          * MBEDTLS_AES_ALT is defined.
          */
-        if( ret == MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE && keybits == 192 )
+        if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED && keybits == 192 )
         {
             mbedtls_printf( "skipped\n" );
             continue;
@@ -1821,7 +1822,7 @@
          * there is an alternative underlying implementation i.e. when
          * MBEDTLS_AES_ALT is defined.
          */
-        if( ret == MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE && keybits == 192 )
+        if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED && keybits == 192 )
         {
             mbedtls_printf( "skipped\n" );
             continue;
@@ -1886,7 +1887,7 @@
          * there is an alternative underlying implementation i.e. when
          * MBEDTLS_AES_ALT is defined.
          */
-        if( ret == MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE && keybits == 192 )
+        if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED && keybits == 192 )
         {
             mbedtls_printf( "skipped\n" );
             continue;
@@ -1949,7 +1950,7 @@
          * there is an alternative underlying implementation i.e. when
          * MBEDTLS_AES_ALT is defined.
          */
-        if( ret == MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE && keybits == 192 )
+        if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED && keybits == 192 )
         {
             mbedtls_printf( "skipped\n" );
             continue;
diff --git a/library/error.c b/library/error.c
index 27692db..eabee9e 100644
--- a/library/error.c
+++ b/library/error.c
@@ -834,6 +834,8 @@
 #if defined(MBEDTLS_PLATFORM_C)
     if( use_ret == -(MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED) )
         mbedtls_snprintf( buf, buflen, "PLATFORM - Hardware accelerator failed" );
+    if( use_ret == -(MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED) )
+        mbedtls_snprintf( buf, buflen, "PLATFORM - The requested feature is not supported by the platform" );
 #endif /* MBEDTLS_PLATFORM_C */
 
 #if defined(MBEDTLS_POLY1305_C)
diff --git a/library/gcm.c b/library/gcm.c
index 57b0279..c486ef7 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -48,9 +48,8 @@
 
 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
 #include "mbedtls/aes.h"
-#if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
-#else
+#if !defined(MBEDTLS_PLATFORM_C)
 #include <stdio.h>
 #define mbedtls_printf printf
 #endif /* MBEDTLS_PLATFORM_C */
@@ -764,7 +763,7 @@
              * there is an alternative underlying implementation i.e. when
              * MBEDTLS_AES_ALT is defined.
              */
-            if( ret == MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE && key_len == 192 )
+            if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED && key_len == 192 )
             {
                 mbedtls_printf( "skipped\n" );
                 break;