From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ew0-f43.google.com ([209.85.215.43]) by canuck.infradead.org with esmtp (Exim 4.72 #1 (Red Hat Linux)) id 1PSb47-0006og-TW for linux-mtd@lists.infradead.org; Tue, 14 Dec 2010 20:01:40 +0000 Received: by ewy22 with SMTP id 22so663100ewy.30 for ; Tue, 14 Dec 2010 12:01:38 -0800 (PST) Subject: Re: [PATCH] mtd: allow mtd and jffs2 when ARCH=um From: Artem Bityutskiy To: Jason Lunz In-Reply-To: <20101214195124.GA6010@falooley.org> 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> Content-Type: text/plain; charset="UTF-8" Date: Tue, 14 Dec 2010 22:01:33 +0200 Message-ID: <1292356893.29257.1.camel@koala> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: atom ota , user-mode-linux-devel@lists.sourceforge.net, richard -rw- weinberger , Sam Ravnborg , Jeff Dike , lkml , linux-mtd@lists.infradead.org, Rob Landley , David Woodhouse Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. -- Best Regards, Artem Bityutskiy (Битюцкий Артём)