1 files changed, 33 insertions, 0 deletions

diff --git a/Documentation/filesystems/seq_file.txt b/Documentation/filesystems/seq_file.txt
index 1fe0ccb1af55..8ea3e90ace07 100644
--- a/Documentation/filesystems/seq_file.txt
+++ b/Documentation/filesystems/seq_file.txt
@@ -235,6 +235,39 @@ be used for more than one file, you can store an arbitrary pointer in the
 private field of the seq_file structure; that value can then be retrieved
 by the iterator functions.
 
+There is also a wrapper function to seq_open() called seq_open_private(). It
+kmallocs a zero filled block of memory and stores a pointer to it in the
+private field of the seq_file structure, returning 0 on success. The
+block size is specified in a third parameter to the function, e.g.:
+
+        static int ct_open(struct inode *inode, struct file *file)
+        {
+                return seq_open_private(file, &ct_seq_ops,
+                                        sizeof(struct mystruct));
+        }
+
+There is also a variant function, __seq_open_private(), which is functionally
+identical except that, if successful, it returns the pointer to the allocated
+memory block, allowing further initialisation e.g.:
+
+        static int ct_open(struct inode *inode, struct file *file)
+        {
+                struct mystruct *p =
+                        __seq_open_private(file, &ct_seq_ops, sizeof(*p));
+
+                if (!p)
+                        return -ENOMEM;
+
+                p->foo = bar; /* initialize my stuff */
+                        ...
+                p->baz = true;
+
+                return 0;
+        }
+
+A corresponding close function, seq_release_private() is available which
+frees the memory allocated in the corresponding open.
+
 The other operations of interest - read(), llseek(), and release() - are
 all implemented by the seq_file code itself. So a virtual file's
 file_operations structure will look like: