[ 3.5.y.z extended stable ] Patch "pps: Use pps_lookup_dev to reduce ldisc coupling" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Tue Feb 26 16:14:19 UTC 2013

This is a note to let you know that I have just added a patch titled

    pps: Use pps_lookup_dev to reduce ldisc coupling

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From 8fde127c5b9ee6db81ef5218cf9fefb13166ed96 Mon Sep 17 00:00:00 2001
From: George Spelvin <linux at horizon.com>
Date: Sun, 10 Feb 2013 04:41:56 -0500
Subject: [PATCH] pps: Use pps_lookup_dev to reduce ldisc coupling

commit 03a7ffe4e542310838bac70ef85acc17536b6d7c upstream.

Now that N_TTY uses tty->disc_data for its private data,
'subclass' ldiscs cannot use ->disc_data for their own private data.
(This is a regression is v3.8-rc1)

Use pps_lookup_dev to associate the tty with the pps source instead.

This fixes a crashing regression in 3.8-rc1.

Signed-off-by: George Spelvin <linux at horizon.com>
Acked-by: Rodolfo Giometti <giometti at enneenne.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/pps/clients/pps-ldisc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 79451f2..60cee9e 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -31,7 +31,7 @@
 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
 				struct pps_event_time *ts)
-	struct pps_device *pps = (struct pps_device *)tty->disc_data;
+	struct pps_device *pps = pps_lookup_dev(tty);

 	BUG_ON(pps == NULL);

@@ -67,9 +67,9 @@ static int pps_tty_open(struct tty_struct *tty)
 		pr_err("cannot register PPS source \"%s\"\n", info.path);
 		return -ENOMEM;
-	tty->disc_data = pps;
+	pps->lookup_cookie = tty;

-	/* Should open N_TTY ldisc too */
+	/* Now open the base class N_TTY ldisc */
 	ret = alias_n_tty_open(tty);
 	if (ret < 0) {
 		pr_err("cannot open tty ldisc \"%s\"\n", info.path);
@@ -81,7 +81,6 @@ static int pps_tty_open(struct tty_struct *tty)
 	return 0;

-	tty->disc_data = NULL;
 	return ret;
@@ -90,11 +89,10 @@ static void (*alias_n_tty_close)(struct tty_struct *tty);

 static void pps_tty_close(struct tty_struct *tty)
-	struct pps_device *pps = (struct pps_device *)tty->disc_data;
+	struct pps_device *pps = pps_lookup_dev(tty);


-	tty->disc_data = NULL;
 	dev_info(pps->dev, "removed\n");

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