34.1.5.7 spi_m_async_set_char_size

Set SPI transfer character size in number of bits.

int32_t spi_m_async_set_char_size(
    struct spi_m_async_descriptor * spi,
    const enum spi_char_size char_size
)

The character size (spi_char_size) influence the way the data is sent/received. For char size <= 8-bit, data is stored byte by byte. For char size between 9-bit ~ 16-bit, data is stored in 2-byte length. Note that the default and recommended char size is 8-bit since it's supported by all system.