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>

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index a9ca03ead3e5dc0337b9b7a1eecdf8bb4ce1569a..977ce820ce303914dc7e998940cdf524dec52586 100644 (file)
--- 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;