From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Sat, 03 Mar 2007 21:13:06 +0000 (GMT) Received: from localhost.localdomain ([127.0.0.1]:29859 "EHLO dl5rb.ham-radio-op.net") by ftp.linux-mips.org with ESMTP id S20037687AbXCCVNE (ORCPT ); Sat, 3 Mar 2007 21:13:04 +0000 Received: from denk.linux-mips.net (denk.linux-mips.net [127.0.0.1]) by dl5rb.ham-radio-op.net (8.13.8/8.13.8) with ESMTP id l23FVpp0017951 for ; Sat, 3 Mar 2007 15:31:51 GMT Received: (from ralf@localhost) by denk.linux-mips.net (8.13.8/8.13.8/Submit) id l23F3ExR005359; Sat, 3 Mar 2007 15:03:14 GMT Date: Sat, 3 Mar 2007 15:03:14 +0000 From: Ralf Baechle To: Martin Michlmayr Cc: linux-mips@linux-mips.org Subject: Re: Creating infrastructure to allow one kernel for multiple machines Message-ID: <20070303150314.GE16562@linux-mips.org> References: <20070227144818.GA25883@deprecation.cyrius.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070227144818.GA25883@deprecation.cyrius.com> User-Agent: Mutt/1.4.2.2i Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 14337 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Tue, Feb 27, 2007 at 02:48:18PM +0000, Martin Michlmayr wrote: > On ARM and PowerPC, you can compile one kernel that will support > multiple machines, as long as they all belong to the same group (e.g. > have a compatible CPU). On ARM, each machine needs to register a > machine id at http://www.arm.linux.org.uk/developer/machines/ and then > the boot loader passes this value to the kernel via a register. On > PowerPC, information about the machine can be found in OF's > device-tree. > > On MIPS, you need a separate kernel for each machine, which makes it > hard for distros to support many machines. For example, it would be > nice if you could compile one kernel for vr41xx devices since they > only differ slightly, e.g. in their PCI mappings. I'm therefore > wondering if there are any plans to introduce a scheme on MIPS that > would allow one kernel for several machines. In some cases that works but in many case it would simply be painful or even impossible to implement due to conflicting load addresses, different word sizes or endianess. Probing for the system type would be required and that would turn out to be about as fun as ISA probing. So there are limitations and within those I'm not so sure if the pain would be justifyable. As usual, I however will consider patches :-9 Ralf