Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753373Ab1FTHcB (ORCPT ); Mon, 20 Jun 2011 03:32:01 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:36505 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753283Ab1FTHb7 (ORCPT ); Mon, 20 Jun 2011 03:31:59 -0400 Date: Mon, 20 Jun 2011 09:31:22 +0200 From: Ingo Molnar To: Ryan Mallon Cc: Petr Tesarik , Andrew Morton , Fenghua Yu , "H. Peter Anvin" , Ingo Molnar , Paul Mundt , Russell King , Thomas Gleixner , Tony Luck , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Arjan van de Ven , Dave Jones , Linus Torvalds Subject: Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary physical addresses Message-ID: <20110620073122.GA24716@elte.hu> References: <201106171038.25988.ptesarik@suse.cz> <20110617093032.GA19235@elte.hu> <4DFE7FF9.9070406@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DFE7FF9.9070406@gmail.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1527 Lines: 43 * Ryan Mallon wrote: > On 17/06/11 19:30, Ingo Molnar wrote: > >* Petr Tesarik wrote: > > > >>This patch series enhances /dev/mem, so that read and write is > >>possible at any address. The patchset includes actual > >>implementation for x86. > >This series lacks a description of why this is desired. > > > >My strong opinion is that it's not desired at all: /dev/mem never > >worked beyond 4G addresses so by today it has become largely obsolete > >and is on the way out really. > > > >I'm aware of these current /dev/mem uses: > > > > - Xorg maps below 4G non-RAM addresses and the video BIOS > > > > - It used to have some debugging role but these days kexec and kgdb > > has largely taken over that role - partly due to the 4G limit. > > > > - there's some really horrible out-of-tree drivers that do mmap()s > > via /dev/mem, those should be fixed if they want to move beyond > > 4G: their char device should be mmap()able. > > There are drivers where this makes sense. For example an FPGA > device with a proprietary register layout on the memory bus can be > done this way. [...] So you want us to help vendors screw users with insane, proprietary, user-space drivers with sekrit binary blobs? Wow. Thanks, Ingo -- 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/