Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751976Ab3FZJeH (ORCPT ); Wed, 26 Jun 2013 05:34:07 -0400 Received: from intranet.asianux.com ([58.214.24.6]:13339 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751631Ab3FZJeE (ORCPT ); Wed, 26 Jun 2013 05:34:04 -0400 X-Spam-Score: -100.8 Message-ID: <51CAB556.4070700@asianux.com> Date: Wed, 26 Jun 2013 17:33:10 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Richard Weinberger CC: Jeff Dike , Arnd Bergmann , dhsharp@google.com, Mark Brown , "sfr@canb.auug.org.au" , Steven Rostedt , Ingo Molnar , uml-devel , uml-user , "linux-kernel@vger.kernel.org" , Linux-Arch Subject: Re: [PATCH] include/asm-generic/io.h: add 'UML' case just like 'no-MMU' References: <51CA8AB8.7080504@asianux.com> <51CA900E.9020407@nod.at> <51CA9E92.4000107@asianux.com> <51CAA0C6.60007@nod.at> <51CAA78C.5040900@asianux.com> <51CAA8D6.9000505@nod.at> <51CAAD1D.8050801@asianux.com> <51CAAE7C.9090003@nod.at> In-Reply-To: <51CAAE7C.9090003@nod.at> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2759 Lines: 70 On 06/26/2013 05:03 PM, Richard Weinberger wrote: > Am 26.06.2013 10:58, schrieb Chen Gang: >> > On 06/26/2013 04:39 PM, Richard Weinberger wrote: >>>>>>>>>>> >>>>>>>>>> The drivers internal code has already check the related return value, >>>>>>>>>>> >>>>>>>>>> so it is the architecture's duty to 'tell' the driver whether support >>>>>>>>>>> >>>>>>>>>> io memory (e.g. define ioremap, but return NULL). >>>>>>> >>>>>> It does so already by setting CONFIG_HAS_IOMEM=n >>>>> >>>> >>>>> >>>> Excuse me, I use "grep -rn ioremap *" under "include/" and "arch/um/" >>>>> >>>> directory, but can not find the related definition for 'ioremap'. >>>>> >>>> >>>>> >>>> Is there another declaration or definition way which I don't know ? >>>>> >>>> (maybe it is). >>> >> Both UML and s390 (in the !CONFIG_PCI) do not define ioremap() because >>> >> without io memory you cannot have a ioremap(). >>> >> >> > >> > I assume if ioremap() return NULL, it means "without io memory", is it >> > correct ? >> > >> > If it is correct, "define a dummy ioremap(), and return NULL" is just >> > the meaning that you mentioned above. >> > >> > If so, for UML, it is not requirement, but recommend to define a dummy >> > ioremap() which return NULL, so can be generic enough to mach all cases. > No. > Not setting CONFIG_HAS_IOMEM=y means "This arch has no io memory and therefore no > functions to mess with it". > Since the API itself already contents the meaning: "return NULL means the arch has no related io memory", Why not define a generic dummy one in "include/asm-generic/io.h" instead of "HAS_IOMEM" (which has already spread many various places, and also, most of new drivers have to know about it). e.g: in "include/asm-generic/io.h", if "CONFIG_HAS_IOMEM=n", define a dummy ioremap() which return NULL ... (also need consider more details). All together, I think: it is the duty of "asm-generic/io.h" to process this issue, not the duty of many drivers and some architectures. > Let's get back to the real problem, > drivers/ptp/ptp_pch.c does not build on UML (and I'm very sure also not on S390). > Fix the issue by making it depend on HAS_IOMEM. > At least now, it seems it is the only suitable way to fix this issue. :-( > Btw: Did you actually look at this driver? There is *zero* reason to have it on UML. > ..like 99.9% of all other drivers which use io memory. Excuse me, I did not look at the details of this driver. Maybe it just like you said above. Thanks. -- Chen Gang Asianux Corporation -- 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/