speed       0 -> rc=-1 errno=22 (Invalid argument)
speed       1 -> rc=-1 errno=22 (Invalid argument)
speed      50 -> rc=-1 errno=22 (Invalid argument)
speed     177 -> rc=-1 errno=22 (Invalid argument)
speed     178 -> rc=0 errno=22 (ok)
speed     300 -> rc=0 errno=22 (ok)
speed    9600 -> rc=0 errno=22 (ok)
speed   57600 -> rc=0 errno=22 (ok)
speed  115200 -> rc=0 errno=22 (ok)
speed  309278 -> rc=0 errno=22 (ok)
speed  309279 -> rc=0 errno=22 (ok)
speed 4000000 -> rc=-1 errno=22 (Invalid argument)
speed 12000000 -> rc=-1 errno=22 (Invalid argument)