This is truly a hack. The idea is taken from the Linux ibcs2 emulator.
To use this feature, you must use the option,
options SPX_HACK
in your config.
Also, in /compat/ibcs2/dev, you must do:
lrwxr-xr-x 1 root wheel 9 Oct 15 22:20 X0R@ -> /dev/null
lrwxr-xr-x 1 root wheel 7 Oct 15 22:20 nfsd@ -> socksys
lrwxr-xr-x 1 root wheel 9 Oct 15 22:20 socksys@ -> /dev/null
crw-rw-rw- 1 root wheel 41, 1 Oct 15 22:14 spx
Do NOT use old socksys driver as that has been removed.
This hack needs /compat/ibcs2/dev/spx to be any device that does NOT
exist/configured (so the now non-existant spx major/minor works fine).
When an open() is called, the error ENXIO is checked and then the
path is checked. If spx open detected, then a unix socket is opened
to the hardcoded path "/tmp/.X11-unix/X0".
As the Linux hacker author mentioned, the real way would be to detect
the getmsg/putmsg through /dev/X0R and /dev/spx. Until this true
solution is implemented (if ever), I think this hack is important
enough to be put into the tree, even though I don't like it dirtying
up my clean code (which is what #ifdef SPX_HACK is for).