Spi synchronous 8 bit write followed by 8 bit read
ssize_t spi_w8r8(struct spi_device * spi, u8 cmd);
spi
device with which data will be exchanged
cmd
command to be written before data is read back
can sleep
This returns the (unsigned) eight bit number returned by the device, or else a negative error code. Callable only from contexts that can sleep.