Kernel info
-----------
# uname -a
Linux buildroot 4.17.0-rc7-next-20180601 #1 SMP Mon Jun 4 09:31:05 BST 2018 x86_64 GNU/Linux

insert modules
--------------
# modprobe speakup
# modprobe speakup_dummy dev=ttyS1 ser=1 start=1
# modprobe speakup_soft
# lsmod
Module                  Size  Used by    Tainted: G  
speakup_soft           16384  0 
speakup_dummy          16384  0 
speakup               118784  2 speakup_soft,speakup_dummy

switching to soft
-----------------
# echo 'soft' > /sys/accessibility/speakup/synth
# cat /sys/accessibility/speakup/synth
soft

switching to dummy
------------------
# echo 'dummy' > /sys/accessibility/speakup/synth
# cat /sys/accessibility/speakup/synth
dummy

Removing modules
----------------
# rmmod speakup_dummy
# rmmod speakup_soft
# lsmod
Module                  Size  Used by    Tainted: G  
speakup               118784  0 

view message log
----------------
# tail -25 /var/log/messages
Jun  6 20:06:57 buildroot kern.notice kernel: random: ssh-keygen: uninitialized urandom read (32 bytes read)
Jun  6 20:06:57 buildroot kern.notice kernel: random: sshd: uninitialized urandom read (32 bytes read)
Jun  6 20:06:57 buildroot auth.info sshd[105]: Server listening on :: port 22.
Jun  6 20:06:57 buildroot auth.info sshd[105]: Server listening on 0.0.0.0 port 22.
Jun  6 20:06:57 buildroot daemon.info : starting pid 107, tty '/dev/tty1': '/sbin/getty -L  tty1 0 vt100 '
Jun  6 20:07:00 buildroot auth.info login[107]: root login on 'tty1'
Jun  6 20:07:08 buildroot kern.notice kernel: random: crng init done
Jun  6 20:07:12 buildroot kern.warn kernel: speakup: module is from the staging directory, the quality is unknown, you have been warned.
Jun  6 20:07:13 buildroot kern.info kernel: input: Speakup as /devices/virtual/input/input4
Jun  6 20:07:13 buildroot kern.info kernel: initialized device: /dev/synth, node (MAJOR 10, MINOR 25)
Jun  6 20:07:13 buildroot kern.info kernel: speakup 3.1.6: initialized
Jun  6 20:07:13 buildroot kern.info kernel: synth name on entry is: (null)
Jun  6 20:07:13 buildroot kern.warn kernel: speakup_dummy: module is from the staging directory, the quality is unknown, you have been warned.
Jun  6 20:07:13 buildroot kern.warn kernel: synth probe
Jun  6 20:07:13 buildroot kern.warn kernel: speakup_soft: module is from the staging directory, the quality is unknown, you have been warned.
Jun  6 20:07:13 buildroot kern.info kernel: releasing synth dummy
Jun  6 20:07:13 buildroot kern.warn kernel: synth probe
Jun  6 20:07:13 buildroot kern.info kernel: initialized device: /dev/softsynth, node (MAJOR 10, MINOR 26)
Jun  6 20:07:13 buildroot kern.info kernel: initialized device: /dev/softsynthu, node (MAJOR 10, MINOR 27)
Jun  6 20:07:13 buildroot kern.warn kernel: soft already in use
Jun  6 20:07:13 buildroot kern.info kernel: releasing synth soft
Jun  6 20:07:13 buildroot kern.info kernel: unregistered /dev/softsynth
Jun  6 20:07:13 buildroot kern.info kernel: unregistered /dev/softsynthu
Jun  6 20:07:13 buildroot kern.warn kernel: synth probe
Jun  6 20:07:13 buildroot kern.info kernel: releasing synth dummy