netdev - Re: query : unregister/register netdev

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Date:	Fri, 18 Nov 2011 15:52:06 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Madhvapathi Sriram <sriram.madhvapathi@...il.com>
CC:	<netdev@...r.kernel.org>
Subject: Re: query : unregister/register netdev

On Fri, 2011-11-18 at 17:53 +0530, Madhvapathi Sriram wrote:
> Hi,
> 
> In register_netdevice(), BUG_ON(dev->reg_state != NETREG_UNINITIALIZED) is
> used to check if the device that is being registered is indeed a new one.
> 
> However, I see that this state is never moved to. It only happens when a
> netdevice is allocated (by default to 0 using kzalloc).
> 
> So, the cycle register-->unregister-->register would fail since in the
> unregister_netdevice the state is only moved to NETREG_UNREGISTERED (at max
> to NETREG_RELEASED using free_netdev)
> 
> So, I presume that to reinitialize a netdevice one has to free the
> netdevice, re allocate netdevice and only then re register.
> 
> Wondering why unregister and reregister is not allowed, rather than having
> go through the free/alloc cycle - I am not an expert though.

Why do you think that would be useful?

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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