Subject: Re: [PATCH] Re: atheros hardware needs padding for QoS data
From: Johannes Berg <johannes@sipsolutions.net>
To: bruno randolf <bruno@thinktube.com>
Cc: linux-wireless@vger.kernel.org
In-Reply-To: <200710151634.33480.bruno@thinktube.com>
References: <200710121946.30024.bruno@thinktube.com>
	 <1192194578.4770.55.camel@johannes.berg>
	 <200710151241.17651.bruno@thinktube.com>
	 <200710151634.33480.bruno@thinktube.com>
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Date: Mon, 15 Oct 2007 10:31:56 +0200
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On Mon, 2007-10-15 at 16:34 +0900, bruno randolf wrote:
> what do you think about the following solution?

I don't like it. If we wanted to implement this in mac80211 we should do
a zero-copy solution with pointers to header/data portion which is very
hard right now because mac80211 has much assumptions that it's all
contiguous. Secondly, this adds overhead for all hardware to mac80211
for something that can be *trivially* solved in the driver, and only a
single driver so far requires it. I think the driver is a *much* better
place to do this.

> Atheros hardware requires the header to be padded to 4 byte (32 bit)
> boundaries. It expects the payload data to start at multiples of 4 byte f=
or TX
> frames and will add the padding for received frames. For most headers the=
re is
> no need for padding, since they are multiples of 4 already - except QoS a=
nd 4
> address headers.
>=20
> This adds a new hw flag IEEE80211_HW_HEADER_PADDING to tell mac80211 that=
 such
> a padding is needed.

[patch snipped]

johannes

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