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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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