[PATCH] uart_get_baud_rate: stop mangling termios

From: Alan Cox
Date: Wed Feb 20 2008 - 15:53:47 EST


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.

Signed-off-by: Alan Cox <alan@xxxxxxxxxx>

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.25-rc2-mm1/drivers/serial/serial_core.c linux-2.6.25-rc2-mm1/drivers/serial/serial_core.c
--- linux.vanilla-2.6.25-rc2-mm1/drivers/serial/serial_core.c 2008-02-19 11:03:01.000000000 +0000
+++ linux-2.6.25-rc2-mm1/drivers/serial/serial_core.c 2008-02-20 16:22:49.000000000 +0000
@@ -329,13 +329,15 @@
* 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;
upf_t flags = port->flags & UPF_SPD_MASK;

if (flags == UPF_SPD_HI)
@@ -360,8 +362,10 @@
/*
* 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 @@
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 @@
* 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;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/