[PATCH v2] dix: don't BUG_WARN for button events from button-only device

[Chase Douglas]

On 03/29/2012 06:12 PM, Daniel Kurtz wrote:
> Events from button-only devices still need coordinates, and they get them
> from scale_to_desktop().  Therefore, a dev without valuators is not a bug.
> However, a dev with valuators, but less than two of them still is a bug.
> 
> This was noticed when unplugging a "Creative Technology SB Arena Headset",
> which has some BTNs and some KEYs, but no REL or ABS valuators.
> It emits [BTN_3] = 0 on unplug, which would trigger the BUG_WARN.
> 
> Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>

Looks good now :).

Reviewed-by: Chase Douglas <chase.douglas at canonical.com>