IIRC TESTSET is usable: IIRC it just sends a message that causes that to happen, but you don't learn if the test succeeded. I was talking about the DMA mode in

IIRC TESTSET is usable: IIRC it just sends a message that causes that to happen, but you don't learn if the test succeeded. I was talking about the DMA mode in which every write to special register (that may be coming from a different core) gets "redirected" to subsequent byte of the DMA target region. This can work as a queue with multiple enqueuers, but has bounded size (after the size is exhausted, messages get lost) and operates on single byte messages.