From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754275Ab0CZDdV (ORCPT ); Thu, 25 Mar 2010 23:33:21 -0400 Received: from sh.osrg.net ([192.16.179.4]:46836 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753914Ab0CZDdT (ORCPT ); Thu, 25 Mar 2010 23:33:19 -0400 Date: Fri, 26 Mar 2010 12:33:12 +0900 To: hancockrwd@gmail.com Cc: fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org, davem@davemloft.net, bzolnier@gmail.com Subject: Re: [PATCH RFC] fix problems with NETIF_F_HIGHDMA in networking drivers v2 From: FUJITA Tomonori In-Reply-To: <51f3faa71003251803q7ccec5d5x82bc277c590e2848@mail.gmail.com> References: <4B8F213B.40603@gmail.com> <20100304135738C.fujita.tomonori@lab.ntt.co.jp> <51f3faa71003251803q7ccec5d5x82bc277c590e2848@mail.gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20100326123250A.fujita.tomonori@lab.ntt.co.jp> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (sh.osrg.net [192.16.179.4]); Fri, 26 Mar 2010 12:33:12 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Mar 2010 19:03:37 -0600 Robert Hancock wrote: > This seems like it could be a reasonable approach. The only thing is > that in this code you're returning 1 if the parent device has no DMA > mask set. Wouldn't it make more sense to return 0 in this case? I'm > assuming that in that situation it's a virtual device not backed by > any hardware and there should be no DMA mask restriction... I chose the safer option because I don't know enough how net_device structure is used. If returning zero in such case is always safe, it's fine by me. any example of such virtual device driver?