Where:		/sys/bus/event_source/devices/<dev>/format
Date:		January 2012
Kernel Version: 3.3
Contact:	Jiri Olsa <jolsa@redhat.com>
Description:
		Attribute group to describe the magic bits that go into
		perf_event_attr::config[012] for a particular pmu.
		Each attribute of this group defines the 'hardware' bitmask
		we want to export, so that userspace can deal with sane
		name/value pairs.

		Userspace must be prepared for the possibility that attributes
		define overlapping bit ranges. For example:
			attr1 = 'config:0-23'
			attr2 = 'config:0-7'
			attr3 = 'config:12-35'

		Example: 'config1:1,6-10,44'
		Defines contents of attribute that occupies bits 1,6-10,44 of
		perf_event_attr::config1.