Merge commit 'v2.6.27-rc8' into x86/setup

[pandora-kernel.git] / Documentation / filesystems / sysfs.txt

diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt
index 4598ef7..9e9c348 100644 (file)
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -176,8 +176,10 @@ implementations:
   Recall that an attribute should only be exporting one value, or an
   array of similar values, so this shouldn't be that expensive. 
 
-  This allows userspace to do partial reads and seeks arbitrarily over
-  the entire file at will. 
+  This allows userspace to do partial reads and forward seeks
+  arbitrarily over the entire file at will. If userspace seeks back to
+  zero or does a pread(2) with an offset of '0' the show() method will
+  be called again, rearmed, to fill the buffer.
 
 - On write(2), sysfs expects the entire buffer to be passed during the
   first write. Sysfs then passes the entire buffer to the store()
@@ -192,6 +194,9 @@ implementations:
 
 Other notes:
 
+- Writing causes the show() method to be rearmed regardless of current
+  file position.
+
 - The buffer will always be PAGE_SIZE bytes in length. On i386, this
   is 4096. 
 
@@ -243,6 +248,7 @@ The top level sysfs directory looks like:
 block/
 bus/
 class/
+dev/
 devices/
 firmware/
 net/
@@ -269,6 +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/.