Hello,
for the sake of completion, here are few more details why I have suggest to
add the TTY_DRIVER_RESET_TERMIOS flag:
On Tue, Oct 14, 2008 at 10:40:25AM +0100, Alan Cox wrote:
> On Tue, 14 Oct 2008 11:12:49 +0200
> Hendrik Brueckner <[EMAIL PROTECTED]> wrote:
>
> > After a tty hangup() or close() operation, processes might not reset the
> > termio settings to a sane state.
> That is the job of the getty task normally. pty is special as the reissue
> of the same pty is done as a new device (with new state).
During some testing, I have experienced that the bash alters few termios
settings before showing the bash prompt:
-
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, TCSETSW, {B38400 opost isig -icanon -echo ...}) = 0
write(2, "[EMAIL PROTECTED]:~# ", 17) = 17
-
If the tty gets a hangup, the bash gets terminated but the settings still
remains after init has respawned the getty process.
For my network-based hvc backend, a tty_hangup() is caused by a disconnect.
I looked into the tty_io.c source and found out that the termios settings
are stored in an array of the tty driver struct and they remains unchanged
if a tty device is released and initialized again.
At tty device initialization, the tty_init_termios() set tty->termios to the
tty->driver->termios[tty->index].
The idea is to ensure that when a tty is initialized it has the
default (initial) termio settings; and that is actually done if
TTY_DRIVER_RESET_TERMIOS is set.
Anyhow the other possibility might be to always set the initial termios
when the tty is initialized (see patch below).
But I am not sure if that case is the general behavior of ttys.
Please let me know if there is a reason not to re-initialize the termios
of a new tty.
Thanks.
Best regards
Hendrik
Signed-off-by: Hendrik Brueckner <[EMAIL PROTECTED]>
---
drivers/char/tty_io.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/drivers/char/tty_io.c 2008-10-16 09:48:00.000000000 +0200
+++ b/drivers/char/tty_io.c 2008-10-16 12:55:52.000000000 +0200
@@ -1243,10 +1243,9 @@ int tty_init_termios(struct tty_struct *
tp = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
if (tp == NULL)
return -ENOMEM;
- memcpy(tp, &tty->driver->init_termios,
- sizeof(struct ktermios));
tty->driver->termios[idx] = tp;
}
+ memcpy(tp, &tty->driver->init_termios, sizeof(struct ktermios));
tty->termios = tp;
tty->termios_locked = tp + 1;
--
Hendrik Brueckner
D/3303 Linux on System z Development
Tel: +49 7031 16-1073
Fax: +49 7031 16-3456
eMail: [EMAIL PROTECTED]
IBM Deutschland Research & Development GmbH, Schoenaicher Str. 220, 71032
Boeblingen
IBM Deutschland Research & Development GmbH
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