lkml.org 
[lkml]   [2007]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[SERIAL] Don't optimise away baud rate changes when BOTHER is used (v2)
From
Date
The uart_set_termios() function will bail out early without bothering to
touch the hardware, if it decides that nothing "relevant" has changed.
Unfortunately, its idea of "relevant" doesn't include c_[io]speed. So if
the baud rate bits are BOTHER and you just change the speed, the change
gets optimised away.

This patch makes it ignore the old Bfoo bits in c_cflag and just check
whether c_ispeed and c_ospeed have changed. Those integers are always
set appropriately for us by set_termios().

This version of the patch lacks the debugging printk which I
accidentally left in the previous one.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index e8be3b5..4480990 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1146,11 +1146,19 @@ static void uart_set_termios(struct tty_struct *tty, struct ktermios *old_termio

/*
* These are the bits that are used to setup various
- * flags in the low level driver.
+ * flags in the low level driver. We can ignore the Bfoo
+ * bits in c_cflag; c_[io]speed will always be set
+ * appropriately by set_termios() in tty_ioctl.c
*/
+#ifdef CIBAUD
+#define RELEVANT_CFLAG(cflag) ((cflag) & ~(CIBAUD|CBAUD)
+#else
+#define RELEVANT_CFLAG(cflag) ((cflag) & ~(CIBAUD|CBAUD)
+#endif
#define RELEVANT_IFLAG(iflag) ((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))
-
if ((cflag ^ old_termios->c_cflag) == 0 &&
+ tty->termios->c_ospeed == old_termios->c_ospeed &&
+ tty->termios->c_ispeed == old_termios->c_ispeed &&
RELEVANT_IFLAG(tty->termios->c_iflag ^ old_termios->c_iflag) == 0)
return;

--
dwmw2

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-06-08 13:17    [from the cache]
©2003-2011 Jasper Spaans