On 02/05/2015 02:11 PM, Nan Li wrote: > This will greatly enhance the usefulness of QEMU virtual serial ports, > because the Linux kernel interprets a break on the serial console as a SysRq, > but there is currently no way to pass this signal over a pseudo-terminal. > This patch will work for transmitting BREAK from master to slave through > pseudo-terminal.
pty is an IPC mechanism, not a virtualization driver. Those programs that know they're consuming from a slave pty may not have bothered to set termios for BREAKs, and may not be prepared for NULLs in the input stream. Regards, Peter Hurley > Signed-off-by: Nan Li <[email protected]> > --- > drivers/tty/pty.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c > index e72ee62..ac8893a 100644 > --- a/drivers/tty/pty.c > +++ b/drivers/tty/pty.c > @@ -31,6 +31,7 @@ > static struct tty_driver *ptm_driver; > static struct tty_driver *pts_driver; > static DEFINE_MUTEX(devpts_mutex); > +#define BREAK_STRING '\0' > #endif > > static void pty_close(struct tty_struct *tty, struct file *filp) > @@ -674,6 +675,23 @@ static void pty_unix98_shutdown(struct tty_struct *tty) > devpts_kill_index(tty->driver_data, tty->index); > } > > +static int pty_unix98_break_ctl(struct tty_struct *tty, int break_state) > +{ > + int c; > + struct tty_struct *to = tty->link; > + > + if (break_state) { > + /* Stuff the break data into the input queue of the other end */ > + c = tty_insert_flip_char(to->port, BREAK_STRING, TTY_BREAK); > + /* And shovel */ > + if (c) > + tty_flip_buffer_push(to->port); > + else > + return -ENOMEM; > + } > + return 0; > +} > + > static const struct tty_operations ptm_unix98_ops = { > .lookup = ptm_unix98_lookup, > .install = pty_unix98_install, > @@ -686,6 +704,7 @@ static const struct tty_operations ptm_unix98_ops = { > .chars_in_buffer = pty_chars_in_buffer, > .unthrottle = pty_unthrottle, > .ioctl = pty_unix98_ioctl, > + .break_ctl = pty_unix98_break_ctl, > .resize = pty_resize, > .shutdown = pty_unix98_shutdown, > .cleanup = pty_cleanup > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
