From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennert Buytenhek Subject: Re: [PATCH v2] net: add Fast Ethernet driver for PXA168. Date: Tue, 10 Aug 2010 19:30:52 +0200 Message-ID: <20100810173052.GB25474@mail.wantstofly.org> References: <1281429004.17990.2.camel@pe-lt522.marvell.com> <20100810123329.GR8876@mail.wantstofly.org> <7B1965FC-E61F-4BFD-86B1-F9D390A012CC@marvell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sachin Sanap , "netdev@vger.kernel.org" , Ashish Karkare , Prabhanjan Sarnaik , "eric.y.miao@gmail.com" , Mark Brown To: Philip Rakity Return-path: Received: from fw.wantstofly.org ([80.101.37.227]:35936 "EHLO mail.wantstofly.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932446Ab0HJRay (ORCPT ); Tue, 10 Aug 2010 13:30:54 -0400 Content-Disposition: inline In-Reply-To: <7B1965FC-E61F-4BFD-86B1-F9D390A012CC@marvell.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Aug 10, 2010 at 09:24:23AM -0700, Philip Rakity wrote: > >> * Headroom in SKB for 802.11 not included in the patch since that > >> varies based on 802.11 a/b/g/n. > > > > I don't think this is true? > > > > (The 11a/b/n on-the-air preambles are of different lengths (and are > > sent at different rates), but that isn't visible to software.) > > 802.11b/g headers are larger and if not handled by firmware in an > offload engine are programmed by the driver. There needs to be room > for > > a) Frame Control (2 bytes) > b) AID (2 bytes) > c) address-1 (6 bytes) > d) address-2 (6 bytes) > e) address-3 (6 bytes) > f) seqfrag (2 bytes) > g) address-4 (6 bytes) > > or 30 bytes. Depends on the driver and/or whether you are doing WDS. mwl8k always needs 30 bytes due to hardware pecularities (while the 4-address-with-QoS header is 32 bytes, the QoS field is always passed in the TX descriptor), but other drivers might need 32 bytes (and not 30 bytes) for 4-address-with-QoS headers, or might not need 30 or 32 bytes for transmitting 3-address or 2-address frames. > 11n needs more. Really? Pointer? > Some of these fields ARE visible to s/w. Where did I say that they are not? What I said was that the _preambles_ are not visible to software.