The shared Mbed TLS heap feature has a default implementation (weak function) that will soon be removed: plat_get_mbedtls_heap(). This is part of the general effort to avoid using weak functions in generic code. As a result, the implementation of this function becomes mandatory when supporting Trusted Board Boot.
The corresponding patch can be found here: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/841
The fact that the implementation of plat_get_mbedtls_heap() becomes mandatory will break compatibility with platforms not implementing a strong version of the function.
Upstream platforms are taken care of in the above patch.
Downstream platforms will break, but it is easy to fix.
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