Return-Path: From: Rob Landley Subject: Re: [PATCH] mtd: allow mtd and jffs2 when ARCH=um Date: Tue, 14 Dec 2010 18:40:25 -0600 References: <20071024011712.GA3762@falooley.org> <1292356893.29257.1.camel@koala> <20101214212349.GA6937@falooley.org> In-Reply-To: <20101214212349.GA6937@falooley.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <201012141840.27529.rob@landley.net> Sender: linux-kernel-owner@vger.kernel.org To: Jason Lunz Cc: Artem Bityutskiy , richard -rw- weinberger , Sam Ravnborg , David Woodhouse , atom ota , user-mode-linux-devel@lists.sourceforge.net, Jeff Dike , lkml , linux-mtd@lists.infradead.org List-ID: On Tuesday 14 December 2010 15:23:49 Jason Lunz wrote: > On one hand you've got uml, which simply doesn't have mmio. On the other > there's mtd, which began as a method for accessing hardware devices that > are often accessed using mmio. But then the mtd subsystem developed > emulations of that hardware that are software based and thus don't > require mmio. It's mainly these emulated backends I'm interested in > exposing. > > Nothing is going to change so that it makes sense to have any real > mmio-using hardware driver run on uml. The question you raise is, are > there other classes of driver with a software-only subset that can be > exposed on uml? And if so, would adding stub implementations of > readb/writeb and friends actually be enough to make those work? I'm not > aware of any, so at present I don't think the argument for implementing > this in uml arch code is very strong. Or in other words, I don't think a > "general solution" would be very general. For what it's worth, QEMU had replaced all my use cases for UML in the past few years. If I wanted to play with loopback mounting jffs2 I'd build a kernel to run under QEMU, and have that emulate the flash. Rob -- GPLv3: as worthy a successor as The Phantom Menace, as timely as Duke Nukem Forever, and as welcome as New Coke.