netdev - Re: [patch net-next 1/4] net: add change

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Date:	Wed, 19 Dec 2012 09:20:50 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Dan Williams <dcbw@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	bhutchings@...arflare.com, mirqus@...il.com, shemminger@...tta.com,
	greearb@...delatech.com, fbl@...hat.com, john.r.fastabend@...el.com
Subject: Re: [patch net-next 1/4] net: add change_carrier netdev op

Wed, Dec 19, 2012 at 12:02:51AM CET, dcbw@...hat.com wrote:
>On Tue, 2012-12-18 at 23:14 +0100, Jiri Pirko wrote:
>> This allows a driver to register change_carrier callback which will be
>> called whenever user will like to change carrier state. This is useful
>> for devices like dummy, gre, team and so on.
>> 
>> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>> ---
>>  include/linux/netdevice.h |  9 +++++++++
>>  net/core/dev.c            | 19 +++++++++++++++++++
>>  2 files changed, 28 insertions(+)
>> 
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 02e0f6b..8047330 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -891,6 +891,11 @@ struct netdev_fcoe_hbainfo {
>>   * int (*ndo_bridge_setlink)(struct net_device *dev, struct nlmsghdr *nlh)
>>   * int (*ndo_bridge_getlink)(struct sk_buff *skb, u32 pid, u32 seq,
>>   *			     struct net_device *dev)
>> + *
>> + * int (*ndo_change_carrier)(struct net_device *dev, bool new_carrier);
>> + *	Called to update device carrier. Soft-devices which do not manage
>> + *	real hardware like dummy, team, etc. can define this to provide
>> + *	possibility to set their carrier state.
>
>How about something like:
>
>---
>Called to change device carrier.  Virtual devices (like dummy, team,
>etc) which do not represent real hardware may define this to allow their
>userspace components to manage their virtual carrier state.  Devices
>that determine carrier state from physical hardware properties (eg
>network cables) or protocol-dependent mechanisms (eg
>USB_CDC_NOTIFY_NETWORK_CONNECTION) should NOT implement this function.
>---
>
>I'm just worried that without some clearer wording, somebody will end up
>implementing the function for an actual hardware driver down the road
>and expect things to work when they change the carrier to "on" but the
>protocol isn't set up or cable isn't plugged in.  I'm also worried that
>it might be used to simply work around bugs in the drivers that should
>be fixed in the drivers instead.

Okay - I'll repost this single patch with your text as comment.
Thanks.

>
>Dan
>
>>  struct net_device_ops {
>>  	int			(*ndo_init)(struct net_device *dev);
>> @@ -1008,6 +1013,8 @@ struct net_device_ops {
>>  	int			(*ndo_bridge_getlink)(struct sk_buff *skb,
>>  						      u32 pid, u32 seq,
>>  						      struct net_device *dev);
>> +	int			(*ndo_change_carrier)(struct net_device *dev,
>> +						      bool new_carrier);
>>  };
>>  
>>  /*
>> @@ -2194,6 +2201,8 @@ extern int		dev_set_mtu(struct net_device *, int);
>>  extern void		dev_set_group(struct net_device *, int);
>>  extern int		dev_set_mac_address(struct net_device *,
>>  					    struct sockaddr *);
>> +extern int		dev_change_carrier(struct net_device *,
>> +					   bool new_carrier);
>>  extern int		dev_hard_start_xmit(struct sk_buff *skb,
>>  					    struct net_device *dev,
>>  					    struct netdev_queue *txq);
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index d0cbc93..268a714 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -5027,6 +5027,25 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa)
>>  }
>>  EXPORT_SYMBOL(dev_set_mac_address);
>>  
>> +/**
>> + *	dev_change_carrier - Change device carrier
>> + *	@dev: device
>> + *	@new_carries: new value
>> + *
>> + *	Change device carrier
>> + */
>> +int dev_change_carrier(struct net_device *dev, bool new_carrier)
>> +{
>> +	const struct net_device_ops *ops = dev->netdev_ops;
>> +
>> +	if (!ops->ndo_change_carrier)
>> +		return -EOPNOTSUPP;
>> +	if (!netif_device_present(dev))
>> +		return -ENODEV;
>> +	return ops->ndo_change_carrier(dev, new_carrier);
>> +}
>> +EXPORT_SYMBOL(dev_change_carrier);
>> +
>>  /*
>>   *	Perform the SIOCxIFxxx calls, inside rcu_read_lock()
>>   */
>
>
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