On Ubuntu 12.04 with Kernel 3.3.6, swinput 0.7.4 does not immediately produce the fake keyboard events when writing to /dev/swkeybd. Instead, the events seem to be buffered and only passed on when the module is unloaded.

The following shell snippet shall illustrate:

root@hostname:~# modprobe swkeybd
root@hostname:~# echo test > /dev/swkeybd
root@hostname:~# echo "Hello World" > /dev/swkeybd
root@hostname:~# sync
root@hostname:~# modprobe -r swkeybd
testHello orldroot@hostname:~# testHello orld

Note that nothing happens after the two echo commands (line 2 and 3). But when the module is unloaded (line 5), suddenly the strings are written to the terminal.

I also have no idea why the "W" from "Hello World" is missing.

Note: I had to alter the source code to compile swinput in the first place (see #36511). I do not know if this is related.