How to use the '-config' option of `setxkbmap`?

-config file
       Specifies the name of an XKB configuration
       file which describes the keyboard to be used.

I think this dates back from the time of xf86cfg. When starting X on multiple VTs one could have different keyboard configurations with per-server keyboard config files:

<Xroot>/lib/X11/xkb/X0-config.keyboard
<Xroot>/lib/X11/xkb/X1-config.keyboard

---

A keyboard configuration file consists of key = value pairs, one per line. Here is my rather simple test file, /home/don/my-config.keyboard:

Rules    =  "xorg"
Model    =  "pc104"
Layout   =  "fr"
Variant  =  "dvorak"
Options  =  "grp:caps_toggle,grp_led:caps" 

load it with setxkbmap:

setxkbmap -config /home/don/my-config.keyboard

and voilà:

setxkbmap -query

returns:

rules:      xorg
model:      pc104
layout:     fr
variant:    dvorak
options:    grp:caps_toggle,grp_led:caps