in adgs1408.c [25:34]
static int adgs1408_spi_reg_write(struct spi_device *spi, u8 reg_addr, u8 reg_data) { u8 tx_buf[2]; tx_buf[0] = reg_addr; tx_buf[1] = reg_data; return spi_write_then_read(spi, tx_buf, sizeof(tx_buf), NULL, 0); }