Subject: Re: [ipw3945-devel] [BUG] iwlwifi 3945 works only with
	disable_hw_scan=1
From: Dan Williams <dcbw@redhat.com>
To: Zhu Yi <yi.zhu@intel.com>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>,
	linux-wireless@vger.kernel.org, ipw3945-devel@lists.sourceforge.net
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Content-Type: text/plain
Date: Fri, 13 Jun 2008 10:45:50 -0400
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On Fri, 2008-06-13 at 10:00 +0800, Zhu Yi wrote:
> On Thu, 2008-06-12 at 11:02 -0400, Dan Williams wrote:
> > > I guess that the right solution is to listen to the wireless button
> > (via 
> > > input layer), and turn card on manually.
> > > 
> > > If I remember correctly there is something like that in kernel, I
> > try to 
> > > enable this.
> > > 
> > > Otherwise this can be implemented in userspace.
> > 
> > The right solution is for NM to not take the device down (essentially
> > doing SIOCSIFFLAGS with !IFF_UP), but to set the TX power off.
> > However,
> > that's not possible right now, because HAL doesn't provide enough
> > information about the killswitches to distinguish between a software
> > rfkill (which means we can turn the power back on) and a hardware
> > rfkill
> > (which means the user has to flip something).  On ipw2100, 2200, and
> > 2915, setting the TX power off looks exactly like a hardware kill to
> > HAL, so if you chose unchecked "Enable Wireless" in the nm applet,
> > you'd never be able to turn wireless back on, because HAL and NM think
> > there's a hardware kill active.
> 
> I think who takes the interface down is responsible to bring it up. Even
> if the driver receives a rf_kill switch disabled interrupt, it should
> keep the current IFF_UP status. It should never bring it up or down
> itself. (Think about the carrier on/off in ethernet).
> 
> I wonder why NM need to ifdown or "txpower off" when rf_kill switch
> (both for SW and HW) is enabled. The driver already handles it. Could it
> save more power?

SW rfkill doesn't necessarily kill the device.  Input-only switches
(like Fn+F5 on thinkpads for exampel) aren't handled by the kernel
rfkill system and thus something in userspace needs to handle them
instead.  It's probably worth checking the radio state when the event
comes in and only if the radio isn't already disabled, then set tx power
off.

Dan