genhd: expose AN to user space

Allow user space to determine if a disk supports Asynchronous Notification of
media changes.  This is done by adding a new sysfs file "capability_flags",
which is documented in (insert file name).  This sysfs file will export all
disk capabilities flags to user space.  We also define a new flag to define
the media change notification capability.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/Documentation/block/capability.txt b/Documentation/block/capability.txt
new file mode 100644
index 000000000000..2f1729424ef4
--- /dev/null
+++ b/Documentation/block/capability.txt
@@ -0,0 +1,15 @@
+Generic Block Device Capability
+===============================================================================
+This file documents the sysfs file block/<disk>/capability
+
+capability is a hex word indicating which capabilities a specific disk
+supports.  For more information on bits not listed here, see
+include/linux/genhd.h
+
+Capability                              Value
+-------------------------------------------------------------------------------
+GENHD_FL_MEDIA_CHANGE_NOTIFY            4
+        When this bit is set, the disk supports Asynchronous Notification
+        of media change events.  These events will be broadcast to user
+        space via kernel uevent.
+