This maybe something that just isn't available yet, but if I can help with the development I am happy to.   I have created the following patches as a starting point but they don't yet work.   Looking at the source code for the spidev module and comparing it to the H3 datasheet, it would appear that the H3 uses the sun6i spi register addresses. Though the datasheet lists the RX and TX buffers as 64 bytes whereas the sun6i spidev driver implements 128byte buffers. I'm assuming that this wont b