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Subject: Re: Plugging out Microsoft Nano Tranceiver (USB mouse) causes PS2
 keyboard to cease functioning
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I found the cause of this problem.

Due to the bug in Xorg it unloads the keyboard driver when it gets 
signal from hald that keyboard is disconnected, even though there is 
still another keyboard that is hooked up to kbdmux.
Looks like Xorg code assumes that there can only be one keyboard and 
isn't aware of kbdmux.

This was when hald is enabled (by default), and ServerFlags section in 
xorg.conf looked like this:
Section "ServerFlags"
Option "AllowEmptyInput" "yes"
EndSection

When I changed this section to this:
Section "ServerFlags"
Option "AutoAddDevices" "False"
EndSection
keyboard doesn't get affected, but mouse disappears for good when 
unplugged and plugged back, since (I guess) Xorg ignores ums0 device errors.

I filed the following PRs with Xorg:
https://bugs.freedesktop.org/show_bug.cgi?id=60069
https://bugs.freedesktop.org/show_bug.cgi?id=60070

Yuri