uart_get_baud_rate: stop mangling termios

Russell King noticed this one: We have to avoid replacing B0 when we pick a
baud rate for a "hung up" port.  Ugly but the proper fix is in the tty layer
and means changing the tty<->serial interfaces so we will defer that for now.

[akpm@linux-foundation.org: fix uninitialised var]
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index a9ca03ead3e5..977ce820ce30 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -329,13 +329,15 @@ EXPORT_SYMBOL(uart_update_timeout);
  *      If it's still invalid, we try 9600 baud.
  *
  *      Update the @termios structure to reflect the baud rate
- *      we're actually going to be using.
+ *      we're actually going to be using. Don't do this for the case
+ *      where B0 is requested ("hang up").
  */
 unsigned int
 uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
                    struct ktermios *old, unsigned int min, unsigned int max)
 {
         unsigned int try, baud, altbaud = 38400;
+        int hung_up = 0;
         upf_t flags = port->flags & UPF_SPD_MASK;
 
         if (flags == UPF_SPD_HI)
@@ -360,8 +362,10 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
                 /*
                  * Special case: B0 rate.
                  */
-                if (baud == 0)
+                if (baud == 0) {
+                        hung_up = 1;
                         baud = 9600;
+                }
 
                 if (baud >= min && baud <= max)
                         return baud;
@@ -373,7 +377,9 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
                 termios->c_cflag &= ~CBAUD;
                 if (old) {
                         baud = tty_termios_baud_rate(old);
-                        tty_termios_encode_baud_rate(termios, baud, baud);
+                        if (!hung_up)
+                                tty_termios_encode_baud_rate(termios,
+                                                                baud, baud);
                         old = NULL;
                         continue;
                 }
@@ -382,7 +388,8 @@ uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
                  * As a last resort, if the quotient is zero,
                  * default to 9600 bps
                  */
-                tty_termios_encode_baud_rate(termios, 9600, 9600);
+                if (!hung_up)
+                        tty_termios_encode_baud_rate(termios, 9600, 9600);
         }
 
         return 0;