Thank you for comments.

From: "Zdenek Salvet" <salvet@ics.muni.cz>
> Use /dev/ttyE?  .

Well, I think so too...

From: "Nathan J. Williams" <nathanw@MIT.EDU>
> I just ran into this same problem with my Alpha X server today
> (the last time I worked on this was before wsmux).

Really ? That's too bad.
According to the cvsweb, the wsmux came to the wsdisplay 8 months
ago. I can't believe that Xalpha has been broken for such a long time.
Who is the architect of wscons? No one is taking care of it?

From: "Lennart Augustsson" <augustss@augustsson.net>
> I have a bunch of ws changes that are supposed to fix this, but I
> need a machine to test it on.

That's sounds good! How do you solve the problem? I think the
wskbd must keep two mux at once. One is display mux, which is
connected to wsdisplay and another is normal mux like
/dev/wsmux1. Key event should be routed as:

1. If /dev/wskbd is opened,  you can read the event from 
   /dev/wdkbd. 
   (You can open /dev/wdkbd whenever you want.)

2. If wsmux is configurared and /dev/wsmux1 is opened, 
   you can read the event from /dev/wsmux1.

3. If wsmux is configurared and the keyboard is conneted to display,
   the keyboard event is passwd to display mux 

4. If wsmux is not configurared and the keyboard is conneted to 
   display, the keyboard event is passwd to wsdisplya_kbdinput().

5. Drop the event.

How do you think about this?
Please I don't ask me how to implement that :-)

Takemura