From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Keyur Chudgar" Subject: Fwd: skbuff data pointer alignment requirement Date: Fri, 28 Dec 2007 16:54:23 -0800 Message-ID: References: <476CEE69.20902@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from hs-out-0708.google.com ([64.233.178.246]:15434 "EHLO hs-out-2122.google.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751579AbXL2AyZ (ORCPT ); Fri, 28 Dec 2007 19:54:25 -0500 Received: by hs-out-2122.google.com with SMTP id 54so2522899hsz.5 for ; Fri, 28 Dec 2007 16:54:23 -0800 (PST) In-Reply-To: Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: ---------- Forwarded message ---------- From: Keyur Chudgar Date: Dec 28, 2007 4:53 PM Subject: Re: skbuff data pointer alignment requirement To: Jarek Poplawski Hi Jarek, > Do you mean hardware requirements of an architecture or a specific driver? I meant any hardware requirements of an architecture. > So, if you have more than one network card, is it needed by all of them, > while other (not network) drivers are happy with default allocations? Yes. So, anything related to skbuff data block, will need specific alignment requirements, while others (non-network drivers) will work as default. Thanks, - Keyur On Dec 22, 2007 3:00 AM, Jarek Poplawski wrote: > Keyur Chudgar wrote, On 12/21/2007 02:12 AM: > ... > > > If some hardware requirements, for example is, they need to have 256 > > bytes aligned address for them to do the DMA, no matter what the > > packet size is. In this kind of cases, can you guide me what should I > > do? Is there any way already in Linux I can do this? > > ... > > > In the above specified situation, I can define SKB_ADDR_MIN_ALIGN = > > 256 in my Makefile or I don't define it at all if I am okay with > > default alignment size. > > Do you mean hardware requirements of an architecture or a specific driver? > So, if you have more than one network card, is it needed by all of them, > while other (not network) drivers are happy with default allocations? > > Regards, > Jarek P. >