tty: Always handle NULL flag ptr

Most line disciplines already handle the undocumented NULL flag
ptr in their .receive_buf method; however, several don't.

Document the NULL flag ptr, and correct handling in the
N_MOUSE, N_GSM0710 and N_R394 line disciplines.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h
index f15c898ff462..b8347c207cb8 100644
--- a/include/linux/tty_ldisc.h
+++ b/include/linux/tty_ldisc.h
@@ -84,7 +84,8 @@
  *      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.
+ *      received with a parity error, etc. <fp> may be NULL to indicate
+ *      all data received is TTY_NORMAL.
  *
  * void (*write_wakeup)(struct tty_struct *);
  *
@@ -118,7 +119,8 @@
  *      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.
+ *      received with a parity error, etc. <fp> may be NULL to indicate
+ *      all data received is TTY_NORMAL.
  *      If assigned, prefer this function for automatic flow control.
  */