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Subject[PATCH 3.4 011/134] pps: Use pps_lookup_dev to reduce ldisc coupling
Date
3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: George Spelvin <linux@horizon.com>

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@horizon.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Qiang Huang <h.huangqiang@huawei.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/pps/clients/pps-ldisc.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

--- 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_struc
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_struc
return 0;

err_unregister:
- tty->disc_data = NULL;
pps_unregister_source(pps);
return ret;
}
@@ -90,11 +89,10 @@ static void (*alias_n_tty_close)(struct

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);

alias_n_tty_close(tty);

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



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