Date: Wed, 12 Dec 2012 11:18:45 -0500
From: Solomon Peachy <pizza@shaftnet.org>
To: Christian Lamparter <chunkeey@googlemail.com>
Cc: "John W. Linville" <linville@tuxdriver.com>,
	Steev Klimaszewski <steev@genesi-usa.com>,
	Janusz Dziedzic <janusz.dziedzic@gmail.com>,
	Dmitry Tarnyagin <abi.dmitryt@gmail.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-wireless@vger.kernel.org
Subject: Re: [PATCHv2 00/21] cw1200: ST-Ericsson cw1200 wlan device driver
Message-ID: <20121212161845.GA21461@shaftnet.org> (sfid-20121212_171852_926037_880C2532)
References: <1330720003-15866-1-git-send-email-dmitry.tarnyagin@stericsson.com>
 <20120706201839.GE1879@tuxdriver.com>
 <20121211232311.GA9080@shaftnet.org>
 <201212121613.12750.chunkeey@googlemail.com>
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On Wed, Dec 12, 2012 at 04:13:12PM +0100, Christian Lamparter wrote:
> Mac80211 already reserves at least 18 bytes tailroom [which can be
> allocated by a simple skb_put]. In fact p54 uses this tailroom to
> pass the MIC (8 bytes) + ICV (4 bytes) to the firmware. Do you need
> more than 18 bytes?

I just went back and had a look at the code -- There were two related=20
workarounds: One made room for the MIC, but as you said, that hasn't=20
been necessary for a while so the code was disabled.

The other workaround is still in place, however -- cw1200 also needs a=20
gap in the frame payload for the IV, even though it's generated by the=20
firmware. I worked around this by telling setting the=20
IEEE80211_KEY_FLAG_GENERATE_IV flag on the mac80211 keys, and then=20
zeroing that part of the payload when the frame went out to the harware.

I figured it was a less costly approach than memmoving the whole payload=20
over by sizeof(ICV).

Is there a better way to handle this now?

 - Solomon
--=20
Solomon Peachy        		       pizza at shaftnet dot org	=20
Melbourne, FL                          ^^ (mail/jabber/gtalk) ^^
Quidquid latine dictum sit, altum viditur.

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