Subject: Re: [PATCH] mac80211: trigger ieee80211_sta_work after opening
	interface
From: Dan Williams <dcbw@redhat.com>
To: Tomas Winkler <tomasw@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
	Jan Niehusmann <jan@gondor.com>,
	"John W. Linville" <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org,
	Michael Wu <flamingice@sourmilk.net>, Jiri Benc <jbenc@suse.cz>
In-Reply-To: <1ba2fa240803231528i4fc38343ifb49d44f5072c882@mail.gmail.com>
References: <20080323192355.GA5773@x61s.gondor.com>
	 <1206310595.16475.190.camel@johannes.berg>
	 <1ba2fa240803231528i4fc38343ifb49d44f5072c882@mail.gmail.com>
Content-Type: text/plain
Date: Mon, 24 Mar 2008 10:32:34 -0400
Message-Id: <1206369154.23379.4.camel@localhost.localdomain> (sfid-20080324_143442_162067_9BCAADA5)
Mime-Version: 1.0
Sender: linux-wireless-owner@vger.kernel.org

On Mon, 2008-03-24 at 00:28 +0200, Tomas Winkler wrote:
> On Mon, Mar 24, 2008 at 12:16 AM, Johannes Berg
> <johannes@sipsolutions.net> wrote:
> >
> >  On Sun, 2008-03-23 at 20:23 +0100, Jan Niehusmann wrote:
> >  > ieee80211_sta_work is disabled while network interface
> >  > is down. Therefore, if you configure wireless parameters
> >  > before bringing the interface up, these configurations are
> >  > not yet effective and association fails.
> >  >
> >  > A workaround from userspace is calling a command like
> >  > 'iwconfig wlan0 ap any' after the interface is brought up.
> >  >
> >  > To fix this behaviour, trigger execution of ieee80211_sta_work from
> >  > ieee80211_open when in STA or IBSS mode.
> >
> >  What happens with this patch when you haven't set any configuration
> >  items before bringing the interface up? We want it to do nothing, if
> >  that behaviour is kept the patch should be fine.
> 
> Why should be possible to configure device when it's not up. Shouldn't
> be there some order in which things are happening?

This was the way that wireless-tools/WEXT worked with older fullmac type
cards; the driver would usually cache the value until the device came up
(and then blast all cached values to the card and try to associate) or
the firmware would still accept commands while the interface was down
because the firmware was already on the card and didn't have to be
loaded at runtime.

These days, of course, with cards that load firmware on open() (ex iwl
to save power, and others) this isn't possible unless the driver caches
the values until the device is brought up.

Personally, I don't really think this is an issue.  Things change, some
cards don't allow scanning when they are down, etc.  It's a lot of code
to cache the values in the driver that isn't really needed if people
just start setting the device up before configuring it.  I think the
tradeoff of having to modify userspace tool behavior versus having to
maintain more code in the drivers/stack is quite clear: less code in
mac80211/drivers.

Dan

> Thanks
> Tomas
> 
> >  johannes
> >
> --
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