Subject: Re: [PATCH 1/2] mac80211: Adding HW flag
 IEEE80211_HW_CRYPTO_ENABLED
From: Johannes Berg <johannes@sipsolutions.net>
To: Yogesh Ashok Powar <yogeshp@marvell.com>
Cc: "John W. Linville" <linville@tuxdriver.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Lennert Buytenhek <buytenh@wantstofly.org>
In-Reply-To: <20110415105140.GD11576@hertz.marvell.com>
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Date: Fri, 15 Apr 2011 13:01:44 +0200
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On Fri, 2011-04-15 at 16:21 +0530, Yogesh Ashok Powar wrote:

> > > Then Skip the code which expands the skb iff
> > > IEEE80211_CRYPTO_NO_TAILROOM_NEEDED is set and the key is programmed
> > > into the hardware (checking KEY_FLAG_UPLOADED_TO_HARDWARE).
> > 
> > You don't know the key at this point, so you have to keep track of
> > whether this is true for all keys, which depends on whether or not
> > they're already programmed into the HW (since for SW crypto we need the
> > tailroom)
> From this it seems that we do not reserve tailroom iff
> IEEE80211_KEY_FLAG_GENERATE_MMIC flag is unset for all keys and all the keys
> are programmed into the hardware.
> 
> Also, say in mixed mode if TKIP and CCMP keys are configured and this
> flag is set for TKIP MMIC, we will end up reserving tailroom even for
> CCMP.  Is my understanding correct?

Yes, correct.

> Also, though I have not looked into this part of the code very closely,
> how about deriving key information at this place? Will that be feasible?

No, we can't do it here. I suppose we could postpone it for per key
stuff, but that's more complex and probably good for a separate patch.

johannes