I8254_CTRL_RW
#define I8254_CTRL_LATCH I8254_CTRL_RW(0)
#define I8254_CTRL_LSB_ONLY I8254_CTRL_RW(1)
#define I8254_CTRL_MSB_ONLY I8254_CTRL_RW(2)
#define I8254_CTRL_LSB_MSB I8254_CTRL_RW(3)
