From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269256AbUIYHou (ORCPT ); Sat, 25 Sep 2004 03:44:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269260AbUIYHou (ORCPT ); Sat, 25 Sep 2004 03:44:50 -0400 Received: from holomorphy.com ([207.189.100.168]:59877 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S269256AbUIYHos (ORCPT ); Sat, 25 Sep 2004 03:44:48 -0400 Date: Sat, 25 Sep 2004 00:44:45 -0700 From: William Lee Irwin III To: Andrew Morton Cc: linux-kernel@vger.kernel.org Subject: [vm 0/6] convert remap_page_range() to remap_pfn_range() in a patch series shorter than 76 patches Message-ID: <20040925074445.GD9106@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.6+20040722i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Resolve physical address overflow issue in the remap_page_range() API by replacing it with remap_pfn_range(), which accepts its physical address argument as a pfn, hence allowing the use of a single-precision physical address argument without the risk of overflow at the API boundary. The above issue has hobbled support for various 32-bit architectures, including some embedded systems (ppc440 IIRC), caused persistent portability issues for sound drivers for legacy systems (sparc32; unfortunately this patch alone does not fully resolve those), and according to John Fusco's reports, made drivers for some PCI-X hardware infeasible to port to recent ia32 PAE enterprise systems. With this patch series applied, physical address overflows on 32-bit systems caused directly by remap_page_range() are gone forever, and ca. 100LOC of cut-and-waste driver code are swept out of existence alongside them. -- wli P.S.: The existing solution to the sparc32 issue was to pass a double precision representation of the physical address as 2 single- precision arguments in an API (io_remap_page_range()) whose argument corresponding to those two was a single single- precision argument on most/all other architectures. The sparc32-specific issue requires more work beyond these patches to rectify. The most apparent consequence of the API skew is that drivers don't compile on sparc32 when they use io_remap_page_range() due to passing insufficient arguments, or vice-versa for drivers originally written for sparc32.