Date: Wed, 5 Aug 2009 14:07:59 -0700
From: Greg KH <greg@kroah.com>
To: "John W. Linville" <linville@tuxdriver.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>, Zhu Yi <yi.zhu@intel.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
	linux-wireless@vger.kernel.org, stable@kernel.org
Subject: Re: [stable] [PATCH 2.6.30] iwl3945: fix rfkill switch
Message-ID: <20090805210759.GA21086@kroah.com>
References: <1249389350-4158-1-git-send-email-sgruszka@redhat.com>
 <20090804124951.GA3988@tuxdriver.com>
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On Tue, Aug 04, 2009 at 08:49:51AM -0400, John W. Linville wrote:
> On Tue, Aug 04, 2009 at 02:35:50PM +0200, Stanislaw Gruszka wrote:
> > Due to rfkill and iwlwifi mishmash of SW / HW killswitch representation,
> > we have race conditions which make unable turn wifi radio on, after enable
> > and disable again killswitch. I can observe this problem on my laptop
> > with iwl3945 device.
> > 
> > In rfkill core HW switch and SW switch are separate 'states'. Device can
> > be only in one of 3 states: RFKILL_STATE_SOFT_BLOCKED, RFKILL_STATE_UNBLOCKED,
> > RFKILL_STATE_HARD_BLOCKED. Whereas in iwlwifi driver we have separate bits
> > STATUS_RF_KILL_HW and STATUS_RF_KILL_SW for HW and SW switches - radio can be
> > turned on, only if both bits are cleared.
> > 
> > In this particular race conditions, radio can not be turned on if in driver
> > STATUS_RF_KILL_SW bit is set, and rfkill core is in state
> > RFKILL_STATE_HARD_BLOCKED, because rfkill core is unable to call
> > rfkill->toggle_radio(). This situation can be entered in case:
> > 
> > - killswitch is turned on
> > - rfkill core 'see' button change first and move to RFKILL_STATE_SOFT_BLOCKED
> >   also call ->toggle_radio() and STATE_RF_KILL_SW in driver is set
> > - iwl3945 get info about button from hardware to set STATUS_RF_KILL_HW bit and
> >   force rfkill to move to RFKILL_STATE_HARD_BLOCKED
> > - killsiwtch is turend off
> > - driver clear STATUS_RF_KILL_HW
> > - rfkill core is unable to clear STATUS_RF_KILL_SW in driver
> > 
> > Additionally call to rfkill_epo() when STATUS_RF_KILL_HW in driver is set
> > cause move to the same situation.
> > 
> > In 2.6.31 this problem is fixed due to _total_ rewrite of rfkill subsystem.
> > This is a quite small fix for 2.6.30.x in iwl3945 driver. We disable
> > STATUS_RF_KILL_SW bit regardless of HW bit state. Also report to rfkill
> > subsystem SW switch bit before HW switch bit to move rfkill subsystem
> > to SOFT_BLOCK rather than HARD_BLOCK.
> > 
> > Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> > ---
> > I'm not sure if this is good candidate for stable as this is not backport
> > of upstream commit. Also I did not test this patch with other iwlwifi devices,
> > only with iwl3945.
> 
> stable is about the only place it can go, since it fixes a problem
> that doesn't exist in 2.6.31...

Do you ack this for inclusion in 2.6.30-stable?

thanks,

greg k-h