sysfs, kernfs: add kernfs_ops->seq_{start|next|stop}()

kernfs_ops currently only supports single_open() behavior which is
pretty restrictive.  Add optional callbacks ->seq_{start|next|stop}()
which, when implemented, are invoked for seq_file traversal.  This
allows full seq_file functionality for kernfs users.  This currently
doesn't have any user and doesn't change any behavior.

v2: Refreshed on top of the updated "sysfs, kernfs: prepare read path
    for kernfs".

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index d0912cf02087..ba993ebcd81e 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -37,8 +37,9 @@ struct kernfs_ops {
 	/*
 	 * Read is handled by either seq_file or raw_read().
 	 *
-	 * If seq_show() is present, seq_file path is active.  The behavior
-	 * is equivalent to single_open().  @sf->private points to the
+	 * If seq_show() is present, seq_file path is active.  Other seq
+	 * operations are optional and if not implemented, the behavior is
+	 * equivalent to single_open().  @sf->private points to the
 	 * associated sysfs_open_file.
 	 *
 	 * read() is bounced through kernel buffer and a read larger than
@@ -46,6 +47,10 @@ struct kernfs_ops {
 	 */
 	int (*seq_show)(struct seq_file *sf, void *v);
 
+	void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
+	void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
+	void (*seq_stop)(struct seq_file *sf, void *v);
+
 	ssize_t (*read)(struct sysfs_open_file *of, char *buf, size_t bytes,
 			loff_t off);