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