Griffin Powermate evdev setup

Phil Endecott spam_from_xorg at
Mon Apr 27 15:55:23 PDT 2009

Dan Nicholson wrote:
> On Mon, Apr 27, 2009 at 3:00 AM, Phil Endecott
> <spam_from_xorg at> wrote:
>> Dan Nicholson wrote:
>>> On Sun, Apr 26, 2009 at 4:09 PM, Phil Endecott
>>> <spam_from_xorg at> wrote:
>>>> I have a Griffin Powermate; it's a USB "knob" that you can use for
>>>> scrolling etc.  This morning the computer that it was attached to
>>>> died.  I'm now having trouble getting to work with the substitute
>>>> machine.
>>>> (**) Griffin Powermate: always reports core events
>>>> (**) Griffin Powermate: Device:
>>>> "/dev/input/by-id/usb-Griffin_Technology__Inc._Griffin_PowerMate-event-misc"
>>>> (WW) Griffin Powermate: Don't know how to use device
>>>> (II) UnloadModule: "evdev"
>>>> (EE) PreInit returned NULL for "Griffin Powermate"
>>>> So, what does "Don't know how to use device" mean?
>>> This means that the evdev driver didn't recognize it to be either a
>>> pointer, a keyboard or a touchscreen during it's probing routine.
>>> Looking at a photo online, I can't really tell how you'd classify it,
>>> but there could certainly be bugs in the detection logic. If you have
>>> the source, take a look in src/evdev.c:EvdevProbe.

>> This seems like a regression since the previous version of this driver,
>> which was able to manage this device.  What can be done?

> Right, it's definitely a bug. The core of the xorg evdev driver was
> basically rewritten (simplified greatly) for evdev-2.x, so that's why
> it's regressed. Someone with more knowledge of axes, keys and buttons
> will need to look into this.

Let me know if there's anything else I can do to help.  These devices 
are not _that_ unusual...

> In the meantime, you can poke around in that function and see if you
> can get the detection to work for your device.

Thanks Dan, will do.  I guess it's not hard, but I don't think I've 
ever tried to build an X driver before so there's an obvious 
learning-curve obstacle to overcome...


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