I've recently upgraded Xorg from 7.3 to 7.4 (the version currently in testing), only to discover that mouse and keyboard were not recognized any more. Booting in single user mode and typing

# /etc/init.d/gdm start; sleep 10; /etc/init.d/gdm stop

was enough to get myself a useful log to inspect.

The issue showed up in two surprisingly innocent lines:

(II) Cannot locate a core pointer device.
(II) Cannot locate a core keyboard device.

You have read correctly: they are classified "(II)", merely informational.

I, like many other users, have done without a conf file for a long time, as Xorg is perfectly able to configure itself without the user's help. Or so I thought...

Apparently, the new Xorg put all the burden of detecting and supporting input devices on HAL's shoulders, unless you specify otherwise in the conf file. HAL is the Hardware Abstraction Level, a subsystem that is supposed to take care of the low-level management of the hardware and just exposes a common interface to the applications that use it.

The new version of Xorg trusts HAL so much that it has the option AllowEmptyInput enabled by default. This means that if HAL, for some reason, does not pass any valid input device over to Xorg, the latter will be happy nonetheless. Hence the (II) non-warnings.

Now, I still have to understand why HAL fails to detect my pretty standard keyboard and mouse, but, at least, I discovered how to make my Xorg work in spite of this.

As I said before, Xorg defaults to blindly rely on HAL, but the old, legacy mouse and keyboard modules still work, if properly configured in the conf file. Setting the option AutoAddDevices to off, prevents HAL from getting in the way. A minimal conf file like the following worked for me.

Section "InputDevice"
  Identifier  "My beloved keyboard"
  Driver      "kbd"
  Option      "CoreKeyboard"
EndSection
Section "InputDevice"
  Identifier  "My beloved mouse"
  Driver      "mouse"
  Option      "CorePointer"
  Option      "Device"        "/dev/input/mice"
EndSection
Section "ServerFlags"
  Option      "AutoAddDevices" "False"
EndSection

Of course, disabling the AutoAddDevices also drops the possibility to hotplug input devices. This is only a workaround while waiting to understand what HAL does not like in my mouse and keyboard.