ldisc: new dcd_change() method for line disciplines

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/serial/tty.txt b/Documentation/serial/tty.txt
index 5e5349a4fcd2..7c900507279f 100644
--- a/Documentation/serial/tty.txt
+++ b/Documentation/serial/tty.txt
@@ -105,6 +105,10 @@ write_wakeup()	-	May be called at any point between open and close.
                         is permitted to call the driver write method from
                         this function. In such a situation defer it.
 
+dcd_change()    -       Report to the tty line the current DCD pin status
+                        changes and the relative timestamp. The timestamp
+                        can be NULL.
+
 
 Driver Access
 
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 0c4ee9b88f85..526d66f066a3 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -99,6 +99,12 @@
  *      cease I/O to the tty driver. Can sleep. The driver should
  *      seek to perform this action quickly but should wait until
  *      any pending driver I/O is completed.
+ *
+ * void (*dcd_change)(struct tty_struct *tty, unsigned int status,
+ *                      struct timespec *ts)
+ *
+ *      Tells the discipline that the DCD pin has changed its status and
+ *      the relative timestamp. Pointer ts can be NULL.
  */
 
 #include <linux/fs.h>
@@ -136,6 +142,8 @@ struct tty_ldisc_ops {
         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
                                char *fp, int count);
         void    (*write_wakeup)(struct tty_struct *);
+        void    (*dcd_change)(struct tty_struct *, unsigned int,
+                                struct timespec *);
 
         struct  module *owner;