netdev - query : unregister/register netdev

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Message-ID: <CAAvRe=jhfXEnLFkwbPmWEroDE-qHUpZ54TSSdw=WpmfPGZpsPQ@mail.gmail.com>
Date:	Fri, 18 Nov 2011 17:53:37 +0530
From:	Madhvapathi Sriram <sriram.madhvapathi@...il.com>
To:	netdev@...r.kernel.org
Subject: query : unregister/register netdev

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.

Thanks
-Sriram
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