2991c7a831
Implement spi_prepare to fix the undefined behavior on SPI transaction start. Tested with the following command sequence: allocate_oids count=2 config_spi oid=0 bus=0 pin=PA8 mode=3 rate=1000000 shutdown_msg= config_spi oid=1 bus=0 pin=PA8 mode=1 rate=1000000 shutdown_msg= spi_send oid=0 data=30313233343536373839 spi_transfer oid=1 data=3031 Discussion about this here: https://github.com/KevinOConnor/klipper/pull/453#issuecomment-403131149 Signed-off-by: Grigori Goronzy <greg@chown.ath.cx>