Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760094Ab0LNVMc (ORCPT ); Tue, 14 Dec 2010 16:12:32 -0500 Received: from mail-fx0-f43.google.com ([209.85.161.43]:57581 "EHLO mail-fx0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758540Ab0LNVMb convert rfc822-to-8bit (ORCPT ); Tue, 14 Dec 2010 16:12:31 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=bEtu3JhdqWOD1fJsWa340E9pvmorN6fMXgRJ2cV0iA8TaDbSeojRj//AvBgVP/p9xA 2gex82AGM3Hv1p+xdKUsc+hfCWLHJzrhOSab8CM/9wx2787tynZ6SJI5Ot7gZ9EOp5N+ sUmaP9gOBgYaqBwyTG9PJfYQgPBNC00Bw59TE= MIME-Version: 1.0 In-Reply-To: <1292356893.29257.1.camel@koala> References: <22c797d00709272118i33d32b9dy93d5f5ec8f8edd30@mail.gmail.com> <20071024011712.GA3762@falooley.org> <1193208689.26096.48.camel@pmac.infradead.org> <20071227181524.GA19051@falooley.org> <20071228174853.GA4252@uranus.ravnborg.org> <20101207072919.GA8511@falooley.org> <20101207182012.GA10546@falooley.org> <1292343878.2538.80.camel@localhost> <20101214195124.GA6010@falooley.org> <1292356893.29257.1.camel@koala> Date: Tue, 14 Dec 2010 22:12:28 +0100 X-Google-Sender-Auth: N69dsufX8BqrsruJXep4sk6Za0s Message-ID: Subject: Re: [PATCH] mtd: allow mtd and jffs2 when ARCH=um From: Geert Uytterhoeven To: dedekind1@gmail.com Cc: Jason Lunz , richard -rw- weinberger , Sam Ravnborg , David Woodhouse , atom ota , user-mode-linux-devel@lists.sourceforge.net, Jeff Dike , lkml , linux-mtd@lists.infradead.org, Rob Landley Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2680 Lines: 55 On Tue, Dec 14, 2010 at 21:01, Artem Bityutskiy wrote: > On Tue, 2010-12-14 at 11:51 -0800, Jason Lunz wrote: >> On Tue, Dec 14, 2010 at 06:24:38PM +0200, Artem Bityutskiy wrote: >> > But I think your solution is a bit dirty, because it adds a great deal >> > of little 'if HAS_IOMEM' and '#ifdef CONFIG_HAS_IOMEM' to many places. >> > This is error-prone. >> >> The intent of that patch was to allow as much of the mtd subsystem to >> compile as possible. My thinking was to try and rectify the fact that >> uml has gone without mtd (and hence jffs2) support for years even though >> much of it works just fine. I think the entire subsystem being marked >> BROKEN in kconfig kept anyone from experimenting with it. >> >> The patch I sent was actually a reaction to feedback I got from Sam >> Ravnborg on my last attempt (um, three years ago :/ ) in which he >> suggested pushing down the ifdefs closer to their points of use. But I >> agree, the minimal version has a much smaller footprint. >> >> The version below still meets the goal of allowing jffs2-on-block2mtd >> usage under uml but is much smaller because only the mtd core is >> included. Compile-tested on i386, x86_64, um/i386, and um/x86_64. >> >> > Instead, you should solve this problem in UML code. I do not know how, >> > but may be you can add readb/writeb there which actually do nothing or >> > print a scary warning, or do BUG(), and let things which use them just >> > fail run-time. >> >> Something like this could work, but it would be error-prone for anyone >> else who attempts using iomem-requiring drivers on uml. Instead of >> getting obvious compile failures we'd have broken drivers that BUG() or >> emit scary warnings. That doesn't seem to me like an improvement. > > This problem does not seem to be mtd-specific, right? So my point was > that it would be nicer to come up with a general solution. The generic solution for stuff that needs I/O operations is to mark it "depends on HAS_IOMEM". I used a similar patch in the past, IIRC to try axfs on UML. Gr{oetje,eeting}s,                         Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.                                 -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/