sysfs.txt: mention that store method buffers are null-terminated
Without knowing this, the use of sysfs_streq() becomes puzzling.
The termination happens in kernfs_fop_write().
Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
[jc: moved the new text to a different paragraph]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt
index 78170ed..24da7b3 100644
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -191,9 +191,10 @@
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()
- method.
-
+ first write. Sysfs then passes the entire buffer to the store() method.
+ A terminating null is added after the data on stores. This makes
+ functions like sysfs_streq() safe to use.
+
When writing sysfs files, userspace processes should first read the
entire file, modify the values it wishes to change, then write the
entire buffer back.