Logitech LX710 Keyboard support and keycodes > 255

Marco Chiappero marco at absence.it
Tue Nov 20 04:07:49 PST 2007

A few weeks ago I received a brend new Logitech Desktop LX710, incluing 
one single USB receiver, one mouse and one keyboard with many extra and 
multimedia keys. I immediately discovered that many extra keys were non 
functioning (using the "kbd" driver and "pc105" as XkbdModel). After 
some tests I realized that these keys have a keycode > 255 and so X 
ignores them. So I tryed modifing my xorg.conf in this way:

Section "InputDevice"
         Identifier      "Generic Keyboard"
         Driver          "evdev"
         Option          "Phys"          "usb-0000:00:02.0-1/input0"
         Option          "CoreKeyboard"
         Option          "XkbModel"      "evdev"
         Option          "XkbLayout"     "it"

Section "InputDevice"
         Identifier      "Extra Keyboard"
         Driver          "evdev"
         Option          "Phys"          "usb-0000:00:02.0-1/input1"
         Option          "SendCoreEvents"
         Option          "XkbModel"      "evdev"
         Option          "XkbLayout"     "it"

and now every single key is working. But unfortunately mapping keycodes 
 > 255 into a 8-255 range with the formula X keycode = ((kernel
keycode + 8) mod 256) makes different keys share the same X keycode. So 
all the keys are now working but still some of them are unusable. This 
seems to be a problem for a growing number of today's keyboards, such as 
the Microsoft Natural Ergonomic Keyboard 4000 (take a look here 
and many others.
So, since these keys can be really usefull, expecially under X, what 
about adding support for keycodes > 255?
Here is a kernel bug report too: 


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