proc tty: add struct tty_operations::proc_fops

Used for gradual switch of TTY drivers from using ->read_proc which helps
with gradual switch from ->read_proc for the whole tree.

As side effect, fix possible race condition when ->data initialized after
PDE is hooked into proc tree.

->proc_fops takes precedence over ->read_proc.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 7 deletions

diff --git a/fs/proc/proc_tty.c b/fs/proc/proc_tty.c
index 4a9e0f65ae60..854827b1d463 100644
--- a/fs/proc/proc_tty.c
+++ b/fs/proc/proc_tty.c
@@ -144,16 +144,22 @@ void proc_tty_register_driver(struct tty_driver *driver)
 {
         struct proc_dir_entry *ent;
                 
-        if (!driver->ops->read_proc || !driver->driver_name ||
-            driver->proc_entry)
+        if (!driver->driver_name || driver->proc_entry)
                 return;
 
-        ent = create_proc_entry(driver->driver_name, 0, proc_tty_driver);
-        if (!ent)
+        if (driver->ops->proc_fops) {
+                ent = proc_create_data(driver->driver_name, 0, proc_tty_driver,
+                                       driver->ops->proc_fops, driver);
+                if (!ent)
+                        return;
+        } else if (driver->ops->read_proc) {
+                ent = create_proc_entry(driver->driver_name, 0, proc_tty_driver);
+                if (!ent)
+                        return;
+                ent->read_proc = driver->ops->read_proc;
+                ent->data = driver;
+        } else
                 return;
-        ent->read_proc = driver->ops->read_proc;
-        ent->data = driver;
-
         driver->proc_entry = ent;
 }