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, 15 insertions, 13 deletions

diff --git a/drivers/input/serio/serport.c b/drivers/input/serio/serport.c
index 8755f5f3ad37..0cb7ef59071b 100644
--- a/drivers/input/serio/serport.c
+++ b/drivers/input/serio/serport.c
@@ -124,7 +124,7 @@ static void serport_ldisc_receive(struct tty_struct *tty, const unsigned char *c
 {
         struct serport *serport = (struct serport*) tty->disc_data;
         unsigned long flags;
-        unsigned int ch_flags;
+        unsigned int ch_flags = 0;
         int i;
 
         spin_lock_irqsave(&serport->lock, flags);
@@ -133,18 +133,20 @@ static void serport_ldisc_receive(struct tty_struct *tty, const unsigned char *c
                 goto out;
 
         for (i = 0; i < count; i++) {
-                switch (fp[i]) {
-                case TTY_FRAME:
-                        ch_flags = SERIO_FRAME;
-                        break;
-
-                case TTY_PARITY:
-                        ch_flags = SERIO_PARITY;
-                        break;
-
-                default:
-                        ch_flags = 0;
-                        break;
+                if (fp) {
+                        switch (fp[i]) {
+                        case TTY_FRAME:
+                                ch_flags = SERIO_FRAME;
+                                break;
+
+                        case TTY_PARITY:
+                                ch_flags = SERIO_PARITY;
+                                break;
+
+                        default:
+                                ch_flags = 0;
+                                break;
+                        }
                 }
 
                 serio_interrupt(serport->serio, cp[i], ch_flags);