Griffin Powermate evdev setup

[Dan Nicholson]

On Sun, Apr 26, 2009 at 4:09 PM, Phil Endecott
<spam_from_xorg at chezphil.org> wrote:
> Dear Experts,
>
> 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.
>
> It looks like I have the kernel stuff working OK:
>
> # od -x /dev/input/by-id/usb-Griffin_Technology__Inc._Griffin_PowerMate-event-misc
> 0000000 e5f3 49f4 6a00 000c 0002 0007 ffff ffff
> 0000020 e5f3 49f4 6a1d 000c 0000 0000 0000 0000
> 0000040 e5f3 49f4 dae9 000e 0002 0007 ffff ffff
> 0000060 e5f3 49f4 dafa 000e 0000 0000 0000 0000
> 0000100 e5f3 49f4 3897 000f 0002 0007 ffff ffff
> 0000120 e5f3 49f4 38aa 000f 0000 0000 0000 0000
> 0000140 e5f4 49f4 34e8 0000 0002 0007 ffff ffff
> 0000160 e5f4 49f4 34f6 0000 0000 0000 0000 0000
>
> I've extracted this from the backup of the dead machine's /etc/X11/xorg.conf:
>
> Section "InputDevice"
>        Identifier      "Griffin Powermate"
>        Driver          "evdev"
>        #Option         "Device"                "/dev/input/by-id/usb-Griffin_Technology__Inc._Griffin_PowerMate-event-misc"
>        Option          "Name"                  "Griffin PowerMate"
>        Option          "SendCoreEvents"        "true"
>        Option          "DIALRelativeAxisButtons" "4 5"
> EndSection
>
> Note the use of Option Name and the commented-out Option Device; I
> recall that it took me a while to get that stuff right.  I believe that
> was working with the Debian package xserver-xorg-input-evdev 1.1.2-1.
>
> On the substitute machine I have xserver-xorg-input-evdev 1:2.0.8-1.
> "man evdev" does not mention "Option Name" and I have the impression
> that it has gone; when I use that config fragment as-is I get an error
> in the log saying that I haven't specified a device [sorry, I can't get
> the exact message now without restarting X].  If I use the Option
> Device line (or Option Path) I instead get this:
>
> (**) 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.

--
Dan