spi_send_byte
spi_send_byte(ice, dev & ~1); /* WRITE */
spi_send_byte(ice, reg); /* MAP */
spi_send_byte(ice, data); /* DATA */
spi_send_byte(ice, dev & ~1); /* WRITE */
spi_send_byte(ice, reg); /* MAP */
spi_send_byte(ice, dev | 1); /* READ */