3.2. Platform Ports Policy
This document clarifies a couple of policy points around platform ports management.
3.2.1. Platform compatibility policy
Platform compatibility is mainly affected by changes to Platform APIs (as documented in the Porting Guide), driver APIs (like the GICv3 drivers) or library interfaces (like xlat_table library). The project will try to maintain compatibility for upstream platforms.
Due to evolving requirements and enhancements, there might be changes affecting platform compatibility, which means the previous interface needs to be deprecated and a new interface introduced to replace it. In case the migration to the new interface is trivial, the contributor of the change is expected to make good effort to migrate the upstream platforms to the new interface.
The project will generally not take into account downstream platforms. If those are affected by a deprecation / removal decision, we encourage their maintainers to upstream their platform code or copy the latest version of the code being deprecated into their downstream tree.
The deprecated interfaces are listed inside Release Processes as well as the release after which each one will be removed. When an interface is deprecated, the page must be updated to indicate the release after which the interface will be removed. This must be at least 1 full release cycle in future. For non-trivial interface changes, an email should be sent out to the TF-A public mailing list to notify platforms that they should migrate away from the deprecated interfaces. Platforms are expected to migrate before the removal of the deprecated interface.
3.2.2. Deprecation policy
If a platform, driver or library interface is no longer maintained, it is best to deprecate it to keep the projects’ source tree clean and healthy. Deprecation can be a 1-stage or 2-stage process (up to the maintainers).
2-stage: The source code can be kept in the repository for a cooling off period before deleting it (typically 2 release cycles). In this case, we keep track of the Deprecated version separately from the Deleted version.
1-stage: The source code can be deleted straight away. In this case, both versions are the same.
The Platform Ports page provides a list of all deprecated/deleted platform ports (or soon to be) to this day.
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