ttributes so we can easily add other items in the future (and
it also happens to be just about the cleanest way to do this).

The patch is a nice addition to
commit 1ac02185dff3afac146d745ba220dc6672d1d162
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Aug 30 13:26:48 2012 +0200

    drm/i915: add a tracepoint for gpu frequency changes

Reading the GPU frequncy can be done by reading a file like:
/sys/class/drm/card0/render_frequency_mhz

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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