Return-path: Received: from xc.sipsolutions.net ([83.246.72.84]:40658 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752824AbZK0JU6 (ORCPT ); Fri, 27 Nov 2009 04:20:58 -0500 Subject: Re: [RFC 1/2] wireless: add ieee80211_asmdu_to_8023s From: Johannes Berg To: Zhu Yi Cc: "linville@tuxdriver.com" , "linux-wireless@vger.kernel.org" In-Reply-To: <1259290376.13126.219.camel@debian> References: <1259215413-16753-1-git-send-email-yi.zhu@intel.com> <1259229943.32372.50.camel@johannes.local> <1259290376.13126.219.camel@debian> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-5jSaHKyn3w6O/zXVsiU5" Date: Fri, 27 Nov 2009 10:20:53 +0100 Message-ID: <1259313653.5428.5.camel@johannes.local> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: --=-5jSaHKyn3w6O/zXVsiU5 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2009-11-27 at 10:52 +0800, Zhu Yi wrote: > > Also -- you lost the extra TX headroom which I think mac80211 as an AP > > requires since it could forward these frames? Or does that not happen? > > Not sure right now why that was there to start with.=20 >=20 > Yes, I'd like to hear more feedback on this. I think it's a trade off > between performance optimization and clean interface. As we already use > dev_alloc_skb to reserve 32 bytes headroom, it should be enough for most > of the current drivers.=20 Is it? I don't think so. Many drivers go up beyond that as far as I know. Then some do different things like putting it in a different DMA block. > While for those drivers really need a bigger > extra headroom and support Rx aggregation, this probably means > ieee80211_skb_resize. But the resize should always happen for every > packet from the IP stack, right? No, davem and I optimised that away a long time ago via using netdev->needed_headroom and netdev->needed_tailroom. It even works for bridges and their slave devices, iirc. johannes --=-5jSaHKyn3w6O/zXVsiU5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQIcBAABAgAGBQJLD5nxAAoJEODzc/N7+QmaMXMP/ivFxRvFOrliLavKs28FbOld 9gs8fitGvGrardeGbAE6lVTkBwR467FptG445kbv6wU/Vbs+SqcBnf9c+qFVrpxT PutuhaCzRBdR2NHV/eNOr/sh2SPU/tRLVX3fJCt5RVhsU/jmaK0L+ZZlNka3FwsV 9+5mjQ56WHTWvE0qrs2YUMMvfoZDdipKjUIYNKPHZ8kLugSk6ayjpyU9EUPTwTo2 +tr51GSsPXxO5pEHkYVhxkCAJTR5xg+vN5jGIoZy3GbKd+Ck0LydJnBkZyIfV/Vb UYZV4aaWa37LI0ajLK2fgHmoNv4+Z0eA145gJS6Nam/0367TZm7XjIc7zemrnqmy HRie8CWUrnPpYdeAEXVby6zeGFP6bFMdwnX5wYyv0Rosv8OHXLW+sPueT0flEpLL QFkyX76fl8JuAz4q7HJQRzzoTAco5e0EDNLv/CuN7W4EuInhDJRINpi3kToxFwJG WVCA9sgJK4LS2vqdegH3iZFjW0N96/IadVwhaTLESxT0K7iK+nQ5vjnnWYthLXQ0 4JWtuYXw2f8PpjVVX2FcIqEXT0my+3cDuTMmEmo8N0nSCV+liLLzMT7PIra8X9O2 BCyFAvq7K5G7wHpN4ODR6tOzo2rV93+X3Pw9G0O16h8V7Kxy510J0DW9Zz9bvpAJ /cHZm69Ss9Og6woB88oV =85wr -----END PGP SIGNATURE----- --=-5jSaHKyn3w6O/zXVsiU5--