linux/Documentation/block/capability.txt
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   1Generic Block Device Capability
   2===============================================================================
   3This file documents the sysfs file block/<disk>/capability
   4
   5capability is a hex word indicating which capabilities a specific disk
   6supports.  For more information on bits not listed here, see
   7include/linux/genhd.h
   8
   9Capability                              Value
  10-------------------------------------------------------------------------------
  11GENHD_FL_MEDIA_CHANGE_NOTIFY            4
  12        When this bit is set, the disk supports Asynchronous Notification
  13        of media change events.  These events will be broadcast to user
  14        space via kernel uevent.
  15
  16