Bug#535997: Can not assign arbitrary modifiers to the keyboard leds
The keyboard driver of Linux supports several modifiers: shift, altgr,
control, alt, shiftl, shiftr, ctrll, ctrlr and capsshift. Due to some
limitations of the method CapsLock is implemented in the kernel, for
several languages it is necessary some other modifier to be used instead
of CapsLock. For example console-setup often uses ctrll instead of
capslock and the whole purpose of capsshift is to be used as a
replacement for capslock. Unfortunately currently it is impossible to
tell the kernel to display the state of the ctrll or capsshift modifier
with the CapsLock led. As a result the CapsLock led doesn't work for
keyboard layouts that can not use the CapsLock modifier.
A related bug to this one is #514464.