linux-kernel - [PATCH 2/2] tty_port: If we are opened non blocking we still need to raise the carrier

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Message-ID: <20091106113244.14699.17332.stgit@localhost.localdomain>
Date:	Fri, 06 Nov 2009 11:32:48 +0000
From:	Alan Cox <alan@...ux.intel.com>
To:	greg@...ah.com, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] tty_port: If we are opened non blocking we still need to
	raise the carrier

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@...ux.intel.com>
---

 drivers/char/tty_port.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)


diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index 0a35600..5e2ac57 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -241,8 +241,14 @@ int tty_port_block_til_ready(struct tty_port *port,
 
 	/* if non-blocking mode is set we can pass directly to open unless
 	   the port has just hung up or is in another error state */
-	if ((filp->f_flags & O_NONBLOCK) ||
-			(tty->flags & (1 << TTY_IO_ERROR))) {
+	if (tty->flags & (1 << TTY_IO_ERROR)) {
+		port->flags |= ASYNC_NORMAL_ACTIVE;
+		return 0;
+	}
+	if (filp->f_flags & O_NONBLOCK) {
+		/* Indicate we are open */
+		if (tty->termios->c_cflag & CBAUD)
+			tty_port_raise_dtr_rts(port);
 		port->flags |= ASYNC_NORMAL_ACTIVE;
 		return 0;
 	}

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