2 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-dev b/Documentation/ABI/testing/sysfs-dev
new file mode 100644
index 000000000000..a9f2b8b0530f
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-dev
@@ -0,0 +1,20 @@
+What:           /sys/dev
+Date:           April 2008
+KernelVersion:  2.6.26
+Contact:        Dan Williams <dan.j.williams@intel.com>
+Description:    The /sys/dev tree provides a method to look up the sysfs
+                path for a device using the information returned from
+                stat(2).  There are two directories, 'block' and 'char',
+                beneath /sys/dev containing symbolic links with names of
+                the form "<major>:<minor>".  These links point to the
+                corresponding sysfs path for the given device.
+
+                Example:
+                $ readlink /sys/dev/block/8:32
+                ../../block/sdc
+
+                Entries in /sys/dev/char and /sys/dev/block will be
+                dynamically created and destroyed as devices enter and
+                leave the system.
+
+Users:          mdadm <linux-raid@vger.kernel.org>
diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt
index 7f27b8f840d0..9e9c348275a9 100644
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -248,6 +248,7 @@ The top level sysfs directory looks like:
 block/
 bus/
 class/
+dev/
 devices/
 firmware/
 net/
@@ -274,6 +275,11 @@ fs/ contains a directory for some filesystems.  Currently each
 filesystem wanting to export attributes must create its own hierarchy
 below fs/ (see ./fuse.txt for an example).
 
+dev/ contains two directories char/ and block/. Inside these two
+directories there are symlinks named <major>:<minor>.  These symlinks
+point to the sysfs directory for the given device.  /sys/dev provides a
+quick way to lookup the sysfs interface for a device from the result of
+a stat(2) operation.
 
 More information can driver-model specific features can be found in
 Documentation/driver-model/.