From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932911AbaE2NjF (ORCPT ); Thu, 29 May 2014 09:39:05 -0400 Received: from terminus.zytor.com ([198.137.202.10]:52167 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757079AbaE2NjD (ORCPT ); Thu, 29 May 2014 09:39:03 -0400 Message-ID: <5387385B.1030203@zytor.com> Date: Thu, 29 May 2014 06:38:35 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Arnd Bergmann CC: josh@joshtriplett.org, Greg Kroah-Hartman , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports References: <20140509191914.GA7286@jtriplet-mobl1> <63645237.lSKEVJUKkQ@wuerfel> <53865820.7010309@zytor.com> <16228376.RHijyT1ZPk@wuerfel> In-Reply-To: <16228376.RHijyT1ZPk@wuerfel> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/29/2014 02:26 AM, Arnd Bergmann wrote: > On Wednesday 28 May 2014 14:41:52 H. Peter Anvin wrote: >> On 05/19/2014 05:36 AM, Arnd Bergmann wrote: >>> >>> My feeling is that all devices we can think of fall into at least one >>> of these categories: >>> >>> * legacy PC stuff that needs only byte access >>> * PCI devices that can be accessed through sysfs >>> * devices on x86 that can be accessed using iopl >>> >> >> I don't believe PCI I/O space devices can be accessed through sysfs, but >> perhaps I'm wrong? (mmapping I/O space is not portable.) > > The interface is there, both a read/write and mmap on the resource > bin_attribute. But it seems you're right, neither of them is implemented > on all architectures. > > Only powerpc, microblaze, alpha, sparc and xtensa allow users to mmap > I/O space, even though a lot of others could. The read-write interface > is only defined for alpha, ia64, microblaze and powerpc. > And how is that read/write interface defined? Does it have the same silly handling of data sizes? -hpa