The stm32 has a small queue for spi tx/rx. The current code only uses the
spi with a single byte buffer, effectively waiting for each byte to complete
before starting the next transfer.
This patch changes the structure of spi_transfer() to make use of the queue
and achieve back-to-back transfer of bytes on spi.
Signed-off-by: Arne Jansen <arne@die-jansens.de>
a2c309a2b0