xkb: Modifier key sends KeyRelease immediately

[xorg at henrik.synth.no]

samuel.thibault at ens-lyon.org wrote:
>> I am not able to map a specific key as a modifier key (AltGr).  Using 
>> xev, I can see that the key in question sends a KeyRelease immediately 
>> after KeyPress, even though I haven't released it yet.
> 
> Some keys act like this, yes.  IIRC there is nothing to do about it,
> it's done in hardware :/ You may want to check that by running
> showkey -s 
> on the text console, to see what the keyboard sends.

Thanks for the tip.

With showkey -s, the KeyRelease doesn't trigger automatically, it waits 
  until I release the key.  (0x79 is KeyPress, 0xf0 is KeyRelease).

So I guess there's something wrong in my xkb setup (or in the x keyboard 
driver?).  Any ideas?

Henrik