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+What: /sys/bus/event_source/devices/<dev>/format
+Date: January 2012
+KernelVersion: 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.