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Date:   Thu, 26 Nov 2020 06:57:44 +0100
From:   Martin Schiller <ms@....tdt.de>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     andrew.hendry@...il.com, davem@...emloft.net,
        xie.he.0141@...il.com, linux-x25@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 2/5] net/lapb: support netdev events

On 2020-11-25 22:49, Jakub Kicinski wrote:
> 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@....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@...lx.demon.co.uk>");

Thanks for your hints! I will send an update.

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