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I'm aware of that, but that's not my question. Oftentimes there is a reason why they choose to ignore standards. They added a simple C++ (not full C++) layer on

I'm aware of that, but that's not my question. Oftentimes there is a reason why they choose to ignore standards. They added a simple C++ (not full C++) layer on top of their driver code when they took FreeBSD drivers and integrated them into their OS. But there was a benefit to doing so, making the drivers arguably easier to compose. In this case the answer might be just that they were too time constrained to design something better. But I was just curious if the RPMsg framework has too many issues that would make it unsuitable.

gok 5y ago
RPMsg isn't really a standard, is it? I think it was added in Linux 4.11, in April 2017, way after this stuff was introduced in Apple devices.
marcan_42 5y ago
Taking a quick look at RPmsg, it seems it's from 2016. Apple have been doing coprocessors longer than that; Apple had their Secure Enclave in 2013 and that was already using their mailbox system, which is fundamentally different from the IRQs-only RPmsg that keeps all message passing entirely in shared memory. In general, this kind of message passing thing is easy to reinvent and everyone does it differently. You'll find tons of mailbox drivers in Linux already, all different.