Griffin Powermate evdev setup

[Dan Nicholson]

On Mon, Apr 27, 2009 at 3:00 AM, Phil Endecott
<spam_from_xorg at chezphil.org> wrote:
> Dan Nicholson wrote:
>>
>> On Sun, Apr 26, 2009 at 4:09 PM, Phil Endecott
>> <spam_from_xorg at chezphil.org> 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.
>
> http://cgit.freedesktop.org/xorg/driver/xf86-input-evdev/tree/src/evdev.c -
> Right?

Yep.

> This seems like a regression since the previous version of this driver,
> which was able to manage this device.  What can be done?
>
> (BTW the kernel driver is here:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=drivers/input/misc/powermate.c)

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.

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

--
Dan