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    SubjectRe: [PATCH net-next v6 2/5] net/lapb: support netdev events
    On Tue, 24 Nov 2020 10:39:35 +0100 Martin Schiller wrote:
    > This patch allows layer2 (LAPB) to react to netdev events itself and
    > avoids the detour via layer3 (X.25).
    >
    > 1. Establish layer2 on NETDEV_UP events, if the carrier is already up.
    >
    > 2. Call lapb_disconnect_request() on NETDEV_GOING_DOWN events to signal
    > the peer that the connection will go down.
    > (Only when the carrier is up.)
    >
    > 3. When a NETDEV_DOWN event occur, clear all queues, enter state
    > LAPB_STATE_0 and stop all timers.
    >
    > 4. The NETDEV_CHANGE event makes it possible to handle carrier loss and
    > detection.
    >
    > In case of Carrier Loss, clear all queues, enter state LAPB_STATE_0
    > and stop all timers.
    >
    > In case of Carrier Detection, we start timer t1 on a DCE interface,
    > and on a DTE interface we change to state LAPB_STATE_1 and start
    > sending SABM(E).
    >
    > Signed-off-by: Martin Schiller <ms@dev.tdt.de>

    > +/* Handle device status changes. */
    > +static int lapb_device_event(struct notifier_block *this, unsigned long event,
    > + void *ptr)
    > +{
    > + struct net_device *dev = netdev_notifier_info_to_dev(ptr);
    > + struct lapb_cb *lapb;
    > +
    > + if (!net_eq(dev_net(dev), &init_net))
    > + return NOTIFY_DONE;
    > +
    > + if (dev->type == ARPHRD_X25) {

    Flip condition, save indentation.

    if (dev->type != ARPHRD_X25)
    return NOTIFY_DONE;

    You can also pull out of all the cases:

    lapb = lapb_devtostruct(dev);
    if (!lapb)
    return NOTIFY_DONE;

    right?

    > + switch (event) {
    > + case NETDEV_UP:
    > + lapb_dbg(0, "(%p) Interface up: %s\n", dev,
    > + dev->name);
    > +
    > + if (netif_carrier_ok(dev)) {
    > + lapb = lapb_devtostruct(dev);
    > + if (!lapb)
    > + break;

    > static int __init lapb_init(void)
    > {
    > + register_netdevice_notifier(&lapb_dev_notifier);

    This can fail, so:

    return register_netdevice_notifier(&lapb_dev_notifier);

    > return 0;
    > }
    >
    > static void __exit lapb_exit(void)
    > {
    > WARN_ON(!list_empty(&lapb_list));
    > +
    > + unregister_netdevice_notifier(&lapb_dev_notifier);
    > }
    >
    > MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");

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