From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762984AbYENR5m (ORCPT ); Wed, 14 May 2008 13:57:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756645AbYENR5b (ORCPT ); Wed, 14 May 2008 13:57:31 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:57878 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755773AbYENR5a (ORCPT ); Wed, 14 May 2008 13:57:30 -0400 Date: Wed, 14 May 2008 14:55:54 -0300 From: Mauro Carvalho Chehab To: Adrian Bunk Cc: Linus Torvalds , Andrew Morton , linux-dvb-maintainer@linuxtv.org, video4linux-list@redhat.com, linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: [GIT PATCHES] V4L/DVB fixes for 2.6.26 Message-ID: <20080514145554.10e3385c@gaivota> In-Reply-To: <20080514165434.GC22115@cs181133002.pp.htv.fi> References: <20080514114910.4bcfd220@gaivota> <20080514165434.GC22115@cs181133002.pp.htv.fi> X-Mailer: Claws Mail 3.4.0 (GTK+ 2.12.9; x86_64-mandriva-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 14 May 2008 19:54:34 +0300 Adrian Bunk wrote: > On Wed, May 14, 2008 at 11:49:10AM -0300, Mauro Carvalho Chehab wrote: > >... > > PS.: There are yet a number of other Kconfig potential breakages at V4L/DVB. I'm > > currently working on fixing those issues. Basically, what users do is to select > > I2C, DVB and V4L as module. This works fine, but more complex scenarios where > > you mix 'M' and 'Y' inside the subsystem generally cause compilation breakage. > > Those scenarios are more theorical, since there's not much practical sense on > > having a DVB driver foo as module, and V4L driver bar as in-kernel. However, > > the better is to not allow compilation of the scenarios that don't work. > > > > The main trouble at drivers/media Kbuild is that several rules there assumed that > > "select" would check the "depends on" dependencies of the selected drivers. > > However, this feature doesn't exist at the current Kbuild implementation. Even > > if implemented, I suspect that this will generate circular dependency errors on > > some cases. > >... > > The basic problem is that drivers/media/ does the most fancy kconfig > stuff in the kernel since it tries to both have very fine grained > dependencies and offer a usable kconfig UI to the user, which results > in very complicated dependencies. True. > We are not getting this solved by any changes in the kconfig > implementation. > > Thinking about reasonable ways to reduce the problem space: > > Where could we reduce the complexity without big disadvantages? > > Could we e.g. let VIDEO_DEV select I2C which would remove all the > fiddling with I2C dependencies (which is a bigger part of recent > problems)? This seems to be reasonable. However, there are quite a few devices that don't need I2C (for example, some legacy ISA radio modules - also, some webcam drivers don't use i2c layer to communicate with their i2c sensor - so - they don't need I2C. The same also applies to some DVB drivers). So, I'm not sure if this would be a good idea, since it will force I2C even for devices that don't need. This is bad, for example, on embedded devices like set-top-boxes and maybe on cellular phones with non-i2c webcams. > I can make a patch for it after this pull went into Linus' tree if it is > considered an acceptable option. It would be nice if you could help on fixing those issues. One dependency that will probably solve is to add "depends on VIDEO_MEDIA && I2C" to all devices that are hybrid (bttv, saa7134, cx88, pvrusb, em28xx). Cheers, Mauro