OptoHybrid slow-control transmission error detection
As observed in #50 (comment 6214366), the current mechanism to detect transmission errors in the OptoHybrid slow-control path is not strong enough. Many transactions return arbitrary data without any reliable way to detect something went wrong.
After a quick look into the code, it seems that no CRC/checksum/FEC is implemented on the slow-control communication path between the GEM backend and the OptoHybrid. Such a mechanism should be added in order to improve the trustworthiness of the communication. I would propose adding a simple CRC check on both the downstream and upstream links and avoid correcting errors on the fly (CRC instead FEC). Would an error be detected, the register access would fail and the software would react accordingly. Since slow-control transactions can already fail, the software is ready to handle such cases.
Additionally, the various OH slow-control status and counters should be connected to register in the backend address table for enhanced monitoring.