From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751681Ab2BZM0O (ORCPT ); Sun, 26 Feb 2012 07:26:14 -0500 Received: from edge1.cs.stonybrook.edu ([130.245.9.210]:31262 "EHLO edge1.cs.stonybrook.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223Ab2BZM0N (ORCPT ); Sun, 26 Feb 2012 07:26:13 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of ryao@cs.stonybrook.edu designates 10.50.155.231 as permitted sender) smtp.mail=ryao@cs.stonybrook.edu MIME-Version: 1.0 In-Reply-To: <20120226104701.GA18152@polaris.bitmath.org> References: <20120224191535.GA4505@polaris.bitmath.org> <20120224192643.GB24120@kroah.com> <20120224201027.GA4859@polaris.bitmath.org> <20120224201655.GA5994@kroah.com> <20120224203715.GA4995@polaris.bitmath.org> <20120224205651.GA13333@kroah.com> <20120224212238.GA5178@polaris.bitmath.org> <20120224213027.GB15735@thunk.org> <20120224221459.GA5254@polaris.bitmath.org> <20120226104701.GA18152@polaris.bitmath.org> Date: Sun, 26 Feb 2012 07:26:10 -0500 Message-ID: Subject: Re: Can we move device drivers into user-space? From: Richard Yao To: Henrik Rydberg CC: Bobby Powers , "Ted Ts'o" , Greg KH , Guenter Roeck , Jidong Xiao , Kernel development list Content-Type: text/plain; charset="ISO-8859-1" X-Originating-IP: [209.85.210.174] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 26, 2012 at 5:47 AM, Henrik Rydberg wrote: >> > The main issue that set me off has been sufficiently diluted in the >> > (selective) discussion so as to no longer make sense as a reply: At >> > some point, in-tree or out-of-tree will no longer be distinguishable, >> >> Please explain how you would be unable to distinguish between a driver >> that lives in the kernel source tree, and one that does not. > > The SUD pointed to in the beginning of the thread is an example of > this, but I was not thinking of it in quite so literal terms. Rather, > I was imagining that as the kernel grows and the in-kernel interfaces > matures, the amount of actual communication between different portions > of the code diminishes. Code on opposite sides of a stable interface > is, for all practical purposes, separated. Whether that code lives > in-tree or out-of tree is then of little consequence. > > To try to prevent another flame war, let's make it clear that I am not > saying that the most powerful in-kernel argument, that code can be > changed, is unimportant. Maybe code, like so many other things, > arranges itself in a scale-free critical fashion, which would forever > warrant a monolithic approach. Maybe it would even make sense to have > userspace join the same tree as well. There is however a frofoundly > political aspect here, which cannot be expressed in terms of > code. Also, in practise, breaking things down into manageable chunks > is usually a good idea in the end. I do not see what prevents an in-kernel context switch into a ring 3 context with a different process address space. Is it necessary to remove the code from the kernel tree before someone can do this?