From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759636AbXJaQYl (ORCPT ); Wed, 31 Oct 2007 12:24:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756604AbXJaQYd (ORCPT ); Wed, 31 Oct 2007 12:24:33 -0400 Received: from rgminet01.oracle.com ([148.87.113.118]:33735 "EHLO rgminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755929AbXJaQYc (ORCPT ); Wed, 31 Oct 2007 12:24:32 -0400 Date: Wed, 31 Oct 2007 09:23:50 -0700 From: Randy Dunlap To: Trent Piepho Cc: lkml , v4l-dvb-maintainer@linuxtv.org Subject: Re: [v4l-dvb-maintainer] bttv build error (CONFIG_NET=n) Message-Id: <20071031092350.91eae067.randy.dunlap@oracle.com> In-Reply-To: References: <20071030221508.3139ea5c.randy.dunlap@oracle.com> Organization: Oracle Linux Eng. X-Mailer: Sylpheed 2.4.6 (GTK+ 2.8.10; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAQAAAAI= X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 31 Oct 2007 04:51:45 -0700 (PDT) Trent Piepho wrote: > On Tue, 30 Oct 2007, Randy Dunlap wrote: > > drivers/media/video/bt8xx/bttv-cards.c calls ip_compute_csum(). > > However, when CONFIG_NET=n, that produces: > > > > ERROR: "ip_compute_csum" [drivers/media/video/bt8xx/bttv.ko] undefined! > > > > Config symbol VIDEO_BT848 can be made to depend on NET, or the > > osprey_eeprom() function can be built depending on some new config > > symbol, or bttv could have its own checksum function... > > The real problem here is that ip_compute_csum is part of lib-y, but is also > exported for modules. This problem has come up before, for instance your > patch for csum_partial() > http://lkml.org/lkml/2007/4/3/209 > > Or the problem with kasprintf and the lg module: > http://lkml.org/lkml/2007/9/24/15 > > The general lib-y vs EXPORT_SYMBOL problem: > http://lkml.org/lkml/2007/9/25/17 > > The only reason the net stuff works, is because CONFIG_NET includes igmp.c, > which can't be compiled as a module. That means ip_compute_csum() will get > pulled out of the lib.a file for igmp, and thus be present for the net modules > that use it too. If igmp could be turned off, made a module, or stopped using > ip_compute_csum(), then the users of ip_compute_csum() that do depend on > CONFIG_NET would have the same problem as bttv does. Thanks for the analysis and summary. (I'm still waiting for those lkml.org links to load... timed out) > It seems a shame to create a new ip checksum function in the bttv driver when > a perfectly good one already exists and will already be present in just about > every kernel out there. Honestly, how common is NET=n and VIDEO_BT848=m > outside of randconfig? so just adding "depends on NET" should be OK then? --- ~Randy