linux-kernel - Re: [ 07/91] net/wireless: ipw2200: Fix WARN_ON occurring in wiphy_register called by ipw_pci

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Date:	Sun, 27 May 2012 20:50:00 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Stanislav Yakovlev <stas.yakovlev@...il.com>,
	Stefan Lippers-Hollmann <s.l-h@....de>,
	"John W. Linville" <linville@...driver.com>,
	Cesare Leonardi <celeonar@...il.com>
Subject: Re: [ 07/91] net/wireless: ipw2200: Fix WARN_ON occurring in
 wiphy_register called by ipw_pci_probe

On Sun, 2012-05-27 at 16:24 -0300, Herton Ronaldo Krzesinski wrote:
> On Sun, May 27, 2012 at 09:25:13AM +0900, Greg KH wrote:
> > 3.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> 
> As I see, this is not needed on 3.4.x or 3.3.x, since the commit
> "ipw2200: Fix order of device registration", wasn't included in 3.4 or
> any earlier kernels.
> 
> This is fixing an issue introduced on that commit ("ipw2200: Fix order of
> device registration"), that moved register_netdev after ipw_wdev_init,
> but ipw_wdev_init needs initialization made on ndo_init callback.
> 
> Unless there is any plan to include any of the "... Fix order of device
> registration" commits on 3.4 stable, I don't see any reason to include
> the fix for them.
>
> Besides that, I noted that ipw2100 seems to need a similar fix as below
> after the change "ipw2100: Fix order of device registration". ipw2100
> will have the same issue I expect: because ipw2100_wdev_init was moved
> before register_netdev, the ndo_init callback that runs ipw2100_up will
> only execute later with required initialization, after wiphy_register
> inside ipw2100_wdev_init runs.
[...]

Right.

As it happens, ipw2100 also has a comment explaining why .ndo_init is
used now:

	 * If we called ipw2100_up before we registered the device, then the
	 * device name wasn't registered.  So, we instead use the net_dev->init
	 * member to call a function that then just turns and calls ipw2100_up.
	 * net_dev->init is called after name allocation but before the
	 * notifier chain is called */

So this can result in log messages referring to "wlan%d" rather than the
yet-to-be-determined device name.  (That can be avoided by using
netdev_printk, which will log the PCI address.)

If userland depends on the "phy80211" symlinks for wireless net devices
in sysfs then all 4 fixes would be worth applying to stable.  Otherwise,
none of them should be applied.

Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption] would be
development of an easy way to factor large prime numbers. - Bill Gates

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