linux-kernel - Re: [PATCH v3] can: rename LED trigger name on netdev renames

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Message-ID: <504E3901.10901@hartkopp.net>
Date:	Mon, 10 Sep 2012 21:01:21 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Fabio Baltieri <fabio.baltieri@...il.com>,
	Kurt Van Dijck <kurt.van.dijck@....be>
CC:	Marc Kleine-Budde <mkl@...gutronix.de>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	linux-kernel@...r.kernel.org, linux-can@...r.kernel.org
Subject: Re: [PATCH v3] can: rename LED trigger name on netdev renames

On 10.09.2012 20:40, Fabio Baltieri wrote:

> On Mon, Sep 10, 2012 at 08:25:50PM +0200, Oliver Hartkopp wrote:
>> On 10.09.2012 16:28, Kurt Van Dijck wrote:
>>> Fabio,
>>>
>>> I followed all your contribution to this patch.
> 
> Thanks!
> 
>>> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
>>> index 6c1e704..55ad320 100644
>>> --- a/drivers/net/can/dev.c
>>> +++ b/drivers/net/can/dev.c
>>> @@ -25,6 +25,7 @@
>>>  #include <linux/can.h>
>>>  #include <linux/can/dev.h>
>>>  #include <linux/can/netlink.h>
>>> +#include <linux/can/led.h>
>>>  #include <net/rtnetlink.h>
>>>  
>>>  #define MOD_DESC "CAN device driver interface"
>>> @@ -811,6 +812,10 @@ static __init int can_dev_init(void)
>>>  {
>>>  	int err;
>>>  
>>> +	can_led_notifier_init();
>>> +
>>> +	can_led_notifier_init();
>>> +
>>
>>
>> two times?
>>
>>>  	err = rtnl_link_register(&can_link_ops);
>>>  	if (!err)
>>>  		printk(KERN_INFO MOD_DESC "\n");
>>> @@ -822,6 +827,8 @@ module_init(can_dev_init);
>>>  static __exit void can_dev_exit(void)
>>>  {
>>>  	rtnl_link_unregister(&can_link_ops);
>>> +
>>> +	can_led_notifier_exit();
>>>  }
>>>  module_exit(can_dev_exit);
>>>  
>>> diff --git a/drivers/net/can/led.c b/drivers/net/can/led.c
>>> index eaa14ac..1663b28 100644
>>> --- a/drivers/net/can/led.c
>>> +++ b/drivers/net/can/led.c
>>> @@ -1,5 +1,6 @@
>>>  /*
>>>   * Copyright 2012, Fabio Baltieri <fabio.baltieri@...il.com>
>>> + * Copyright 2012, Kurt Van Dijck <kurt.van.dijck@....be>
>>>   *
>>>   * This program is free software; you can redistribute it and/or modify
>>>   * it under the terms of the GNU General Public License version 2 as
>>> @@ -87,3 +88,39 @@ void devm_can_led_init(struct net_device *netdev)
>>>  	devres_add(&netdev->dev, res);
>>>  }
>>>  EXPORT_SYMBOL_GPL(devm_can_led_init);
>>> +
>>> +/*
>>> + * NETDEV rename notifier to rename the associated led triggers too
>>> + */
>>> +static int can_led_notifier(struct notifier_block *nb, unsigned long msg,
>>> +			void *data)
>>> +{
>>> +	struct net_device *netdev = data;
>>> +	struct can_priv *priv = safe_candev_priv(netdev);
>>> +	char name[CAN_LED_NAME_SZ];
>>> +
>>
>>
>> What about
>>
>> if (!priv)
>> 	return NOTIFY_DONE;
>>
>> :-)
>>
>> You created that nice function but you are accessing priv->tx_led_trig below
>> without checking the output of save_candev_priv() ...
> 
> Also, I noticed you removed the namespace check... wasn't it needed?
> (just asking, I have no idea).
> 
>>> +	if (msg == NETDEV_CHANGENAME) {


I do have a second remark.

What about always using the notifiers to name the LED triggers?

Looking into

http://lxr.linux.no/#linux+v3.5.3/include/linux/netdevice.h#L1526

we have NETDEV_CHANGENAME but what about

	NETDEV_REGISTER

???

When changing and updating the LED trigger name always inside the notifier, we
should never run into any locking or race conditions ...

What do you think about this idea?

Regards,
Oliver

>>> +		snprintf(name, sizeof(name), "%s-tx", netdev->name);
>>> +		led_trigger_rename_static(name, priv->tx_led_trig);
>>> +        
> 
> whitespaces here? (checkpatch)
> 
> Fabio
> 
>>> +		snprintf(name, sizeof(name), "%s-rx", netdev->name);
>>> +		led_trigger_rename_static(name, priv->rx_led_trig);
>>> +	}
>>> +
>>> +	return NOTIFY_DONE;
>>> +}
>>> +
>>> +/* notifier block for netdevice event */
>>> +static struct notifier_block can_netdev_notifier __read_mostly = {
>>> +	.notifier_call = can_led_notifier,
>>> +};
>>> +
>>> +int __init can_led_notifier_init(void)
>>> +{
>>> +	return register_netdevice_notifier(&can_netdev_notifier);
>>> +}
>>> +
>>> +void __exit can_led_notifier_exit(void)
>>> +{
>>> +	unregister_netdevice_notifier(&can_netdev_notifier);
>>> +}
>>> diff --git a/include/linux/can/led.h b/include/linux/can/led.h
>>> index 12d5549..9c1167b 100644
>>> --- a/include/linux/can/led.h
>>> +++ b/include/linux/can/led.h
>>> @@ -26,6 +26,8 @@ enum can_led_event {
>>>  
>>>  void can_led_event(struct net_device *netdev, enum can_led_event event);
>>>  void devm_can_led_init(struct net_device *netdev);
>>> +int __init can_led_notifier_init(void);
>>> +void __exit can_led_notifier_exit(void);
>>>  
>>>  #else
>>>  
>>> @@ -36,6 +38,13 @@ static inline void can_led_event(struct net_device *netdev,
>>>  static inline void devm_can_led_init(struct net_device *netdev)
>>>  {
>>>  }
>>> +static inline int can_led_notifier_init(void)
>>> +{
>>> +	return 0;
>>> +}
>>> +static inline void can_led_notifier_exit(void)
>>> +{
>>> +}
>>>  
>>>  #endif
> 


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