From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762703Ab2DLUcp (ORCPT ); Thu, 12 Apr 2012 16:32:45 -0400 Received: from mail2.gnudd.com ([213.203.150.91]:63957 "EHLO mail.gnudd.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756075Ab2DLUcn (ORCPT ); Thu, 12 Apr 2012 16:32:43 -0400 Date: Thu, 12 Apr 2012 22:32:20 +0200 From: Alessandro Rubini To: hpa@zytor.com Cc: mingo@elte.hu, akpm@linux-foundation.org, jbarnes@virtuousgeek.org, fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, giancarlo.asnaghi@st.com, alan@linux.intel.com Subject: Re: [PATCH V4 1/3] x86: introduce CONFIG_X86_DEV_DMA_OPS Message-ID: <20120412203220.GA27629@mail.gnudd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Organization: GnuDD, Device Drivers, Embedded Systems, Courses In-Reply-To: <4F87388C.300@zytor.com> References: <4F87388C.300@zytor.com> <4F87186B.9010303@zytor.com> <5965c5b1f828732b3599131fb21070aba6f1a386.1331622735.git.rubini@gnudd.com> <20120314065614.GB27480@elte.hu> <20120412201533.GA26533@mail.gnudd.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> config MAX_DMA_PADDR >> int >> default 536870912 if MAX_DMA_PADDR_512M >> default 16777216 >> >> config MAX_DMA_PADDR_512M >> bool >> >> (actually, we'd benefit from being able to use hex in defaults) >> >> Is this worth exploring, to possibly submit a patch in this direction? >> > > Not as a compile-time patch. Why not? CONFIG_ISA is a compile-time choice. I thought that if you compile for non-ISA systems you may reuse the zone mechanism with a different split. But if not a compile-time thing, would you accept it at run time? I feel it's not a beautiful approach, because it must clearly be masked by #ifndef CONFIG_ISA or such. Worse, you must know the zone split at the beginning, before you scan the PCI bus and find your devices. thanks /alessandro