2 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7269daf7632b..8323ee4f95b9 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -557,6 +557,19 @@ extern void tty_ldisc_init(struct tty_struct *tty);
 extern void tty_ldisc_deinit(struct tty_struct *tty);
 extern void tty_ldisc_begin(void);
 
+static inline int tty_ldisc_receive_buf(struct tty_ldisc *ld, unsigned char *p,
+					char *f, int count)
+{
+	if (ld->ops->receive_buf2)
+		count = ld->ops->receive_buf2(ld->tty, p, f, count);
+	else {
+		count = min_t(int, count, ld->tty->receive_room);
+		if (count)
+			ld->ops->receive_buf(ld->tty, p, f, count);
+	}
+	return count;
+}
+
 
 /* n_tty.c */
 extern struct tty_ldisc_ops tty_ldisc_N_TTY;
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index 23bdd9debb84..f15c898ff462 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -109,6 +109,17 @@
  *
  *	Tells the discipline that the DCD pin has changed its status.
  *	Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
+ *
+ * int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
+ *			char *fp, int count);
+ *
+ *	This function is called by the low-level tty driver to send
+ *	characters received by the hardware to the line discpline for
+ *	processing.  <cp> is a pointer to the buffer of input
+ *	character received by the device.  <fp> is a pointer to a
+ *	pointer of flag bytes which indicate whether a character was
+ *	received with a parity error, etc.
+ *	If assigned, prefer this function for automatic flow control.
  */
 
 #include <linux/fs.h>
@@ -195,6 +206,8 @@ struct tty_ldisc_ops {
 	void	(*write_wakeup)(struct tty_struct *);
 	void	(*dcd_change)(struct tty_struct *, unsigned int);
 	void	(*fasync)(struct tty_struct *tty, int on);
+	int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
+				char *fp, int count);
 
 	struct  module *owner;