tty_port: If we are opened non blocking we still need to raise the carrier

Original discussion:
http://thread.gmane.org/gmane.linux.usb.general/23217/focus=23248
or
http://marc.info/?l=linux-usb&m=125553790714133&w=2

The tty_port code inherited a bug common to various drivers it was based
upon. If the tty is opened O_NONBLOCK we do not wait for the carrier to be
raised but we must still raise our modem lines if appropriate.

(There is a second question here about whether we should do so if CLOCAL is
 set but that can wait)

Signed-off-by: Alan Cox <alan@linux.intel.com>
Reported-by: Karl Hiramoto <karl@hiramoto.org>
Tested-by:  Karl Hiramoto <karl@hiramoto.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index a4bbb28f10be..2e8552dc5eda 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -221,6 +221,9 @@ int tty_port_block_til_ready(struct tty_port *port,
            the port has just hung up or is in another error state */
         if ((filp->f_flags & O_NONBLOCK) ||
                         (tty->flags & (1 << TTY_IO_ERROR))) {
+                /* Indicate we are open */
+                if (tty->termios->c_cflag & CBAUD)
+                        tty_port_raise_dtr_rts(port);
                 port->flags |= ASYNC_NORMAL_ACTIVE;
                 return 0;
         }