Add ChangeLog and migration guide for MBEDTLS_ECP_FIXED_POINT_OPTIM
Signed-off-by: kXuan <kxuanobj@gmail.com>
diff --git a/ChangeLog.d/issue4128.txt b/ChangeLog.d/issue4128.txt
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+API changes
+ * The option `MBEDTLS_ECP_FIXED_POINT_OPTIM` use pre-computed comb tables
+ instead of computing tables in runtime. Thus, this option now use more
+ ROM, and it does not increase RAM usage in runtime anymore.
diff --git a/docs/3.0-migration-guide.d/modify_MBEDTLS_ECP_FIXED_POINT_OPTIM_behaviour.md b/docs/3.0-migration-guide.d/modify_MBEDTLS_ECP_FIXED_POINT_OPTIM_behaviour.md
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+++ b/docs/3.0-migration-guide.d/modify_MBEDTLS_ECP_FIXED_POINT_OPTIM_behaviour.md
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+Change MBEDTLS_ECP_FIXED_POINT_OPTIM behaviour
+------------------------------------------------------
+
+The option MBEDTLS_ECP_FIXED_POINT_OPTIM now use more ROM and does not increase
+peak RAM usage anymore.
+
+If you are limited by ROM space, you can define MBEDTLS_ECP_FIXED_POINT_OPTIM
+to `0` in your config file. This will save about 50 KiB ROM space.